INTERNET-DRAFT
Document: draft-ietf-ipo-carrier-requirements-00.txt
Yong Xue
Category: Informational
(Editor)
Expiration Date: January, 2002
UUNET/Worldcom
Monica Lazer
John Strand
Jennifer Yates
Dongmei Wang
AT&T
Ananth Nagarajan
Lynn Neir
Wesam Alanqar
Tammy Ferris
Sprint
Hirokazu Ishimatsu
Japan Telecom Co., LTD
Steven Wright
Bellsouth
Olga Aparicio
Cable & Wireless Global
Carrier Optical Services Requirements
Status of this Memo
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draft-ietf-ipo-carrier-requirements-00.txt [Page 1]
The list of Internet-Draft Shadow Directories can be accessed at
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Abstract
This contribution describes a carriers optical services framework
and associated requirements for the optical network. As such, this
document concentrates on the requirements driving the work towards
realization of ASON. This document is intended to be protocol-
neutral.
Table of Contents
1. Introduction....................................................3
1.1 Justification................................................3
1.2 Conventions used in this document............................3
1.3 Background...................................................3
1.4 Value Statement..............................................4
1.5 Scope of This Document.......................................5
2. Definitions and Terminology.....................................5
3. General Requirements............................................6
3.1 Separation of Networking Functions...........................6
3.2 Network and Service Scalability..............................7
3.3 Transport Network Technology.................................7
3.4 Service Building Blocks......................................8
4. Service Model and Applications..................................8
5. Network Reference Model........................................11
5.1 Optical Networks and Subnetworks............................11
5.2 Network Interfaces..........................................11
5.3 Intra-Carrier Network Model.................................15
5.4 Inter-Carrier Network Model.................................16
6. Optical Service User Requirements..............................17
6.1 Connection Management.......................................17
6.2 Optical Services............................................20
6.3 Levels of Transparency......................................21
6.4 Optical Connection granularity..............................21
6.5 Other Service Parameters and Requirements...................23
7. Optical Service Provider Requirements..........................25
7.1 Access Methods to Optical Networks..........................25
7.2 Bearer Interface Types ....................................26
7.3 Names and Address Management................................26
7.4 Link Identification.........................................29
7.5 Policy-Based Service Management Framework...................29
7.6 Multiple Hierarchies........................................32
8. Control Plane Functional Requirements for Optical Services.....32
8.1 Control Plane Capabilities and Functions....................32
8.2 Signaling Network...........................................34
8.3 Control Plane Interface to Data Plane.......................36
8.4 Control Plane Interface to Management Plane.................36
draft-ietf-ipo-carrier-requirements-00.txt [page 2]
8.5 Control Plane Interconnection...............................41
9. Requirements for Signaling, Routing and Discovery .............43
9.1 Signaling Functions ........................................44
9.2 Routing Functions...........................................46
9.3 Automatic Discovery Functions...............................49
10. Requirements for service and control plane resiliency........54
10.1 Service resiliency.......................................54
10.2 Control plane resiliency........ ........... ...............58
11. Security concerns and requirements............................58
11.1 Data Plane Security and Control Plane Security.............58
11.2 Service Access Control.....................................59
11.3 Optical Network Security Concerns..........................62
1. Introduction
1.1 Justification
The charter of the IPO WG calls for a document on "Carrier Optical
Services Requirements" for IP/Optical networks. This document addresses
that aspect of the IPO WG charter. Furthermore, this document was
accepted as an IPO WG document by unanimous agreement at the IPO WG
meeting held on March 19, 2001, in Minneapolis, MN, USA. It presents a
carrier and end-user perspective on optical network services and
requirements.
1.2 Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
1.3 Background
Next generation optical transport network (OTN) will consist of optical
crossconnects (OXC), DWDM optical line systems (OLS) and optical add-
drop multiplexers (OADM) based on the architecture defined by the ITU
standards G.872 in [G.872]. The OTN network is an optical transport
network bounded by a set of optical channel access points and has a
layered structure consisting of optical channel, multiplex section and
transmission section sub-layer networks. Optical networking encompasses
the functionality for establishment, transmission, multiplexing,
switching, protection, and restoration of optical connections carrying
a wide range of user signals of varying formats and bit rate.
It is an emerging trend to enhance the OTN network with an intelligent
optical layer control plane to dynamically provision network resources
and to provide network survivability using mesh-based protection and
restoration techniques. The resulting intelligent networks are called
automatic switched optical networks or ASON.
draft-ietf-ipo-carrier-requirements-00.txt [page 3]
The emerging and rapidly evolving automatic switched optical networking
(ASON) technologies [G.ASON] are aimed at providing optical networks
with intelligent networking functions and capabilities in its control
plane to enable wavelength switching, rapid optical connection
provisioning and dynamic rerouting. This new networking platform will
create tremendous business opportunities for the network operators and
service providers to offer new services to the market.
1.4 Value Statement
By deploying ASON technology, a carrier expects to achieve the
following benefits from both technical and business perspectives:
Rapid Circuit Provisioning: ASON technology will enable the dynamic
end-to-end provisioning of the optical connections across the optical
network by using standard routing and signaling protocols.
Enhanced Survivability: ASON technology will enable the network to
dynamically reroute an optical connection in case of a failure using
mesh-based network protection and restoration techniques, which greatly
improves the cost-effectiveness compared to the current line and ring
protection schemes in the SONET/SDH network.
Cost-Reduction: ASON networks will enable the carrier to better utilize
the optical network , thus achieving significant unit cost reduction
per Megabit due to the cost-effective nature of the optical
transmission technology, simplified network architecture and reduced
operation cost.
Service Flexibility: ASON technology will support provisioning of an
assortment of existing and new services such as protocol and bit-rate
independent transparent network services, and bandwidth-on-demand
services.
Editor's Note: The next revision will make this more explicit with
respect to the relationship with the ASON control plane.
Enhanced Interoperability: ASON technology will be using a control
plane utilizing the industry and international standards architecture
and protocols, which facilitate the interoperability of the optical
network equipment from different vendors.
In addition, the introduction of a standards-based control plane offers
the following potential benefits:
- Reactive traffic engineering at optical layer that allows network
resources to be dynamically allocated to traffic flow.
- Reduce the need for service providers to develop new operational
support systems software for the network control and new service
provisioning on the optical network, thus speeding up the deployment
draft-ietf-ipo-carrier-requirements-00.txt [page 4]
of the optical network technology and reducing the software
development and maintenance cost.
- Potential development of a unified control plane that can be used for
different transport technologies including ONT, SONET/SDH, ATM and
PDH.
1.5 Scope of This Document
This IPO working group (WG) document is aimed at providing, from the
carrier's perspective, a service framework and associated requirements
in relation to the optical services to be offered in the next
generation optical networking environment and the service control and
management functions.
As such, this document concentrates on the requirements driving the
work towards realization of ASON. This document is intended to be
protocol-neutral.
Note: It is recognized by carriers writing this document that some
features and requirements are not supported by protocols being
developed in the IETF. However, the purpose of this document is to
specify generic carrier functional requirements.
Editor's Note - We may add a statement that these are not all
inclusive requirements, and keep it until future revision make it an
all inclusive list of requirements.
Every carrier's needs are different. The objective of this document is
NOT to define some specific service models. Instead, some major service
building blocks are identified that will enable the carriers to mix and
match in order to create the best service platform most suitable to
their business model. These building blocks include generic service
types, service enabling control mechanisms and service control and
management functions. The ultimate goal is to provide the requirements
to guide the control protocol developments within IETF in terms of IP
over optical technology.
In this document, we consider IP a major client to the optical network,
but the same requirements and principles should be equally applicable
to non-IP clients such as SONET/SDH, ATM, ITU G.709, etc.
2. Definitions and Terminology
Optical Transport Network (OTN)
SONET/SDH Network
Automatic Switched Transport Network (ASTN)
Optical Service Carriers
Transparent and Opaque Network
Other Terminology
Bearer channels
Abbreviations
draft-ietf-ipo-carrier-requirements-00.txt [page 5]
ASON Automatic Switched Optical Networking
ASTN Automatic Switched Transport Network
AD Administrative Domain
AND Automatic Neighbor Discovery
ASD Automatic Service Discovery
CAC Connection Admission Control
DCM Distributed Connection Management
E-NNI Exterior NNI
IWF InterWorking Function
I-NNI Interior NNI
IrDI Inter-Domain Interface
IaDI Intra-Domain Interface
INC Intra-network Connection
NNI Node-to-Node Interface
NE Network Element
OTN Optical Transport Network
OLS Optical Line System
OCC Optical Connection Controller
PI Physical Interface
SLA Service Level Agreement
UNI User-to-Network Interface
3. General Requirements
In this section, a number of generic requirements related to the
service control and management functions are discussed.
3.1 Separation of Networking Functions
It makes logical sense to segregate the networking functions within
each layer network into three logical functional network planes:
control plane, data plane and management plane. They are responsible
for providing network control functions, data transmission functions
and network element management functions respectively.
Control Plane: includes the functions related to networking control
capabilities such as routing, signaling, and policy control, as well as
resource and service discovery.
Data Plane (transport plane): includes the functions related to bearer
channels and transmission.
Management Plane: includes the functions related to the management
functions of network element, networks and network services.
Each plane consists of a set of interconnected functional or control
entities responsible for providing the networking or control functions
defined for that network layer.
The crux of the ASON network is the networking intelligence that
contains automatic routing, signaling and discovery functions to
automate the network control functions and these automatic control
functions are collectively called the control plane functions.
draft-ietf-ipo-carrier-requirements-00.txt [page 6]
The separation of the control plane from both the data and management
plane is beneficial to the carriers in that:
. Allow equipment vendors to have a modular system design that will be
more reliable and maintainable thus reducing the overall systems
ownership and operation cost.
. Allow carriers to have the flexibility to choose a third party vendor
control plane software systems as its control plane solution for its
switched optical network.
. Allow carriers to deploy a unified control plane and OSS systems to
manage and control different types of transport networks it owes.
. Allow carriers to use a separate control network specially designed
and engineered for the control plane communications.
Requirement 1. The control traffic and user data traffic shall not be
assumed to be congruently routed under the same topology because the
control transport network topology may very well be different from
that of the data transport network.
Note: This is in contrast to the IP network where the control messages
and user traffic are routed and switched based on the same network
topology due to the associated in-band signaling nature of the IP
network.
3.2 Network and Service Scalability
In terms of the scale and complexity of the future optical network, the
following assumption can be made when considering the scalability and
performance requirements of the optical control and management
functions.
Within one operator subnetwork:
- There may be hundreds of OXC nodes
- There may be thousands of terminating ports/wavelength per OXC node
- There may be hundreds of parallel fibers between a pair of OXC nodes
- There may be hundreds of wavelength channels transmitted on each
fiber.
The number of optical connections on a network varies depending upon
the size of the network.
Requirement 2. Although specific applications may be on a small scale,
the protocol itself shall not limit large-scale networks.
3.3 Transport Network Technology
Optical services can be offered over different types of underlying
optical technologies. The service characteristic in certain degree will
determine the features and constraints of the services.
draft-ietf-ipo-carrier-requirements-00.txt [page 7]
This document assumes standards-based transport technologies such as
SONET/SDH and OTN - G.709
3.4 Service Building Blocks
The ultimate goal of this document is to identify a set of basic
service building blocks the carriers can mix and match to create the
best suitable service models that serve their business needs.
Editor's Note: May need list of building blocks in view of document
content.
4. Service Model and Applications
A carrier's optical network supports multiple types of service models.
Each service model may have its own service operations, target markets,
and service management requirements.
4.1 Static Provisioned Bandwidth Service (SPB)
Static Provisioned Bandwidth Service creates Soft Permanent
Connections. Soft Permanent Connections are those connections initiated
from the management plane, but completed through the control plane and
its interactions with the management plane. These connections
traditionally fall within the category of circuit provisioning and are
characterized by very long holding times.
Requirement 3. The control plane shall allow the management plane
control of network resources for network management including, but
not limited to management of soft permanent connections.
Service Concept: The SPB supports enhanced leased line and private line
services. The network operator provides connection provisioning at the
customer request through carrier network operation center. The
provisioning time could take some time and provisioning process could
be manual or semi-manual. The specific functionalities of SPB offered
by a carrier may be carrier specific. But any network capability that
can be invoked by, say, signaling across the UNI shall also be directly
accessible by the network operator's network provisioning and network
management work centers. This is basically the "point and click" type
of provisioning services currently proposed by many vendors. The
connections established in this way are so-called permanent or soft-
permanent connections.
Service Operation: During the provision process multiple network
resources are reserved and dedicated to the specific path. The control
interface is either human (e.g. a customer calls a customer service
representative) or via a customer network management system (e.g.,
customer may make its request over a secure web site or by logging into
a specialized OSS). Any provisioned bandwidth service facility is
draft-ietf-ipo-carrier-requirements-00.txt [page 8]
tracked. The path is data based as an object (or structure) containing
information relating to the connection attributes and the physical
entities used in creating the path (e.g., ingress and egress, NE ports,
cross-office and inter-office facilities). This information is used to
reserve network resources at provisioning time, to track performance
parameters, and to perform maintenance functions. An end-to-end managed
service may involve multiple networks, e.g., both access networks and
an intercity network. In this case provisioning may be initiated by
whichever network has primary service responsibility.
Target Market: SPB service focuses on customers unable to request
connections using direct signaling to the network, customers with
complex engineering requirements that cannot be handled autonomously by
the operator's optical layer control plane, customers requiring
connections to off-net locations, and customers who need end-to-end
managed service offered by (or out-sourced to) carriers.
Service Management: SPB service involves carrier management system. The
connections provided by SPB may be under the control of value-added
network management services, such as specific path selection, complex
engineering requirements, or customer required monitor functions. The
connection should be deleted only at customer's request. Billing of SPB
will be based on the bandwidth, service during, quality-of-service, and
other characteristics of the connection. In SPB model, the user shall
not have any information about the optical network, however,
information on the health of the provisioned connection and other
technical aspects of this connection may be provided to the user as a
part of the service agreement.
4.2 Bandwidth-on-Demand Service (BOD)
Bandwidth on Demand Service supports management of switched
connections. Switched connections are those connections initiated by
the user edge device over the UNI and completed through the control
plane. These connections may be more dynamic than the soft permanent
connections and have much shorter holding times than soft permanent
connections.
Service Concept: In SPB model, user is required to pay the cost of the
connection independent of the usage of the connection. In current data
private line services, the average utilization rate is very low and
most of the bits are unused. This is mainly due to time of day and day
of week reasons. Even though businesses close down at night and over
the weekend, user still needs to pay for the SPB connections. In BOD
model, there shall be the potential of tearing down a user's connection
when he is closed and giving it back to the user again when his
business day begins. This is the service model of bandwidth on demand.
In BOD service model, connections are established and reconfigured in
real time, and are so-called switched optical connections. Signaling
between the user NE and the optical layer control plane initiates all
necessary network activities. A real-time commitment for a future
connection may also be established. A standard set of "branded"
draft-ietf-ipo-carrier-requirements-00.txt [page 9]
service options is available. The functionality available is a proper
subset of that available to SPB Service users and is constrained by the
requirement for real-time provisioning, among other things.
Availability of the requested connection is contingent on resource
availability.
Service Operation: This service provides support of real-time creation
of bandwidth between two end-points. The time needed to set up
bandwidth on demand shall be on the order of seconds, preferably sub-
seconds. To support connections establishment dynamically, the end
terminals shall be already physically connected to the network with
adequate capacity. Ingress into the network needs to be pre-provisioned
for point-to-point ingress facilities. Also, necessary cross-connects
throughout the network shall be set up automatically upon service
request. To provide BOD services, the UNI signaling between user edge
device and network edge device is required for all connection end-
points. The BOD service request shall be completed if and only if the
request is consistent with the relevant SLAs, the network can support
the requested connection, and the user edge device at the other end
point accepts connection.
Target Market: BOD service focuses on customers, such as ISP's, large
intranet, and other data and SDH/SONET networks, requiring large point-
to-point capacities and having very dynamic demands, customers
supporting UNI functions in their edge devices.
Service Management: BOD service provides customers the possibility of
rapid provisioning and high service utilization. Since connection
establishment is not part of the functions of the network management
system, the connection management may be some value-added services
according to LSAs. Also, connection admission control shall be provided
at the connection request on time. The connection shall be deleted from
customer's request at either the source endpoint or the destination
endpoint. Billing of BOD shall be based on the bandwidth, service
during, quality-of-service, and other characteristics of the
connection. In BOD model, the user shall not have any information about
the optical network, however, information on the health of the
provisioned connection and other technical aspects of this connection
may be provided to the user via UNI connection request.
4.3 Optical Virtual Private Network (OVPN)
Service Concept: The customer may contract for some specific network
resources (capacity between OXCs, OXC ports, OXC switching resources)
such that the customer is able to control these resources to
reconfigure the optical cross-connections and establish, delete,
maintain connections. In effect they would have a dedicated optical
sub-network under the customer's control.
Service Operations: For future study.
draft-ietf-ipo-carrier-requirements-00.txt [page 10]
Target market: OVPN service focuses on customers, such as ISP, large
intranets, carriers, and other networks requiring large point-to-point
capacities and having variable demands who wish to integrate the
control of their service and optical layers, business-to-business
broadband solution assemblers.
Service Management: OVPN service provides the customer the possibility
of loaning some optical network resources such that the customer is
able to maintain its own sub-network. Since the OVPN connections
maintenance is no longer part of the functions of the network
management system, the connection management may provide some value-
added services according to LSAs. In OVPN model, there is no connection
admission control from the carrier and the customer is free to
reconfigure its network resources. Billing of OVPN shall be based on
the network resources contracted. Network connection acceptance shall
involve only a simple check to ensure that the request is in
conformance with capacities and constraints specified in the OVPN
service agreement.
Requirement 4. In OVPN model, real-time information about the state of
all resources contracted for shall be made available to the customer.
Depending on the service agreement, this may include information on
both in-effects and spare resources accessible to the customer.
5. Network Reference Model
This Section discusses major architectural and functional components of
a generic carrier optical network, which should provide a reference
model for describing the requirements for the carrier optical services.
5.1 Optical Networks and Subnetworks
There are two main types of optical networks that are currently under
consideration: SDH/SONET network as defined in ITU G.707 and T1.105,
and OTN network as defined in ITU G.872.
We assume an optical transport network (OTN) is composed of a set of
optical cross-connects (OXC) and optical add-drop multiplexer (OADM)
which are interconnected in a general mesh topology using DWDM optical
line systems (OLS).
It is often convenient for easy discussion and description to treat an
optical network as an opaque subnetwork, in which the details of the
network become less important, instead focus is on the function and the
interfaces the optical network provides. In general, an opaque
subnetwork can be defined as a set of access points on the network
boundary and a set of point-to-point optical connections between those
access points.
5.2 Network Interfaces
draft-ietf-ipo-carrier-requirements-00.txt [page 11]
A generic carrier network reference model describes a multi-carrier
network environment. Each individual carrier network can be further
partitioned into domains or sub-networks based on administrative,
technological or architectural reasons. The demarcation between
(sub)networks can be either logical or physical and consists of a set
of reference points identifiable in the optical network. From the
control plane perspective, these reference points define a set of
control interfaces in terms of optical control and management
functionality. The following is an illustrative diagram for this.
draft-ietf-ipo-carrier-requirements-00.txt [page 12]
+---------------------------------------+
| |
+--------------+ | |
| | | +------------+ +------------+ |
| IP | | | | | | |
| Network +-E-UNI-+ Optical +-I-UNI--+ Carrier IP | |
| | | | Subnetwork | | network | |
+--------------+ | | +--+ | | |
| +------+-----+ | +------+-----+ |
| | | | |
| I-NNI I-NNI E-UNI |
+--------------+ | | | | |
| | | +------+-----+ | +------+-----+ |
| IP +-E-UNI-| | +-----+ | |
| Network | | | Optical | | Optical | |
| | | | Subnetwork +-I-NNI--+ Subnetwork | |
+--------------+ | | | | | |
| +------+-----+ +------+-----+ |
| | | |
+---------------------------------------+
I-UNI E-NNI
| |
+------+-------+ +----------------+
| | | |
| Other Client | | Other Carrier |
| Network | | Network |
| (ATM/SONET) | | |
+--------------+ +----------------+
Figure 5.1 Generic Carrier Network Reference Model
The network interfaces encompass two aspects of the networking
functions: user data plane interface and control plane interface. The
former concerns about user data transmission across the network
interface and the latter concerns about the control message exchange
across the network interface such as signaling, routing, etc. We call
the former physical interface (PI) and the latter control plane
interface. Unless otherwise stated, the control interface is assumed in
the remaining of this document.
Control Plane Interfaces
Control interface defines a relationship between two connected network
entities on both side of the interface. For each control interface, we
need to define an architectural function each side plays and a
controlled set of information, which can be exchanged across the
interface. The information flowing over this logical interface may
include:
- Endpoint name and address
draft-ietf-ipo-carrier-requirements-00.txt [page 13]
- Reachability/summarized network address information
- Topology/routing information
- Authentication and connection admission control information
- Connection service messages
- Network resource control information (I-NNI only)
Different types of the interfaces can be defined for the network
control and architectural purposes and can be used as the network
reference points in the control plane.
The User-Network Interface (UNI) is a bi-directional signaling
interface between service requester and service provider control plane
entities.
We differentiate between interior (I-UNI) and exterior (E-UNI) UNI as
follows:
E-UNI: A bi-directional signaling interface between service requester
and control plane entities belonging to different domains. Information
flows include support of connection flows and address resolution.
I-UNI: A bi-directional signaling interface between service requester
and control plane entities belonging to one or more domains having a
trusted relationship.
Editor's Note: Details of I-UNI have to be worked out.
The Network-Network Interface (NNI) is the interface between two
optical networks or sub-networks, specifically between the two directly
linked edge ONEs of the two interconnected networks.
We differentiate between interior (I-NNI) and exterior (E-NNI) NNI as
follows:
E-NNI: A bi-directional signaling interface between control plane
entities belonging to different domains. Information flows include
support of connection flows and also reachability information
exchanges.
I-NNI: A bi-directional signaling interface between control plane
entities belonging to one or more domains having a trusted
relationship. Information flows over I-NNI also include topology
information.
It should be noted that it is quite possible to use E-NNI even between
subnetworks with a trust relationship to keep topology information
exchanges only within the subnetworks.
Generally, two networks have a trust relationship if they belong to the
same administrative domain.
draft-ietf-ipo-carrier-requirements-00.txt [page 14]
Generally, two networks do not have a trust relationship if they belong
to the different administrative domains.
Generally speaking, the following levels of trust interfaces shall be
supported:
Interior interface: an interface is interior when there is a trusted
relationship between the two connected networks.
Exterior interface: an interface is exterior when there is no trusted
relationship between the two connected networks.
Interior interface examples include an I-NNI between two optical sub-
networks belonging to a single carrier or an I-UNI interface between
the optical transport network and an IP network owned by the same
carrier. Exterior interface examples include an E-NNI between two
different carriers or an E-UNI interface between a carrier optical
network and its customers.
The two types of interfaces may define different architectural
functions and distinctive level of access, security and trust
relationship.
Editor's Note: More work is needed in defining specific functions on
interior and exterior interfaces.
Requirement 5. The control plane interfaces shall be configurable and
their behavior shall be consistent with the configuration (i.e.,
exterior versus interior interfaces).
5.3 Intra-Carrier Network Model
The carrier's optical network is treated as a trusted domain, which is
defined as network under a single technical administration with full
trust relationship within the network. Within a trusted domain, all the
optical network elements and sub-networks are considered to be secure
and trusted by each other. A highly simplified optical networking
environment consists of an optical transport network and a set of
interconnected client networks of various types such as IP, ATM and
SONET.
In the intra-carrier model, within a carrier-owned network, generally
interior interfaces (I-NNI and I-UNI) are assumed.
The interfaces between the carrier-owned network equipment and the
optical network are a interior UNI and the interfaces between optical
sub-networks within a carrier's administrative domain are interior NNI;
while the interfaces between the carrier's optical network and its
users are exterior UNI, and the interfaces between optical networks of
different operators are the exterior NNI.
One business application for the interior UNI is the case wherea
carrier service operator offers data services such as IP, ATM and Frame
Relay over its optical core network. Data services network elements
draft-ietf-ipo-carrier-requirements-00.txt [page 15]
such as routers and ATM switches are considered to be internal optical
service client devices. The interconnection topology among the carrier
NEs should be completely transparent to the users of the data services.
5.3.1 Multiple Sub-networks
Without loss of generality, the optical network owned by a carrier
service operator can be depicted as consisting of one or more optical
sub-networks interconnected by direct optical links. There may be many
different reasons for more than one optical sub-networks It may be the
result of using hierarchical layering, different technologies across
access, metro and long haul (as discussed below), or a result of
business mergers and acquisitions or incremental optical network
technology deployment by the carrier using different vendors or
technologies.
A sub-network may be a single vendor and single technology network. But
in general, the carrier's optical network is heterogeneous in terms of
equipment vendor and the technology utilized in each sub-network. There
are four possible scenarios:
--- Single vendor and single technology
--- Single vendor and multiple technologies
--- Multiple vendor single technology
--- Multiple vendors and multiple technologies.
5.3.2 Access, Metro and Long-haul networks
Few carriers have end-to-end ownership of the optical networks. Even
ifthey do, access, metro and long-haul networks often belong to
different administrative divisions and they each for optical sub-
network. Therefore Inter-(sub)-networks interconnection is essential in
terms of supporting the end-to-end optical service provisioning and
management. The access, metro and long-haul networks may use different
technologies and architectures, and as such may have different network
properties.
In general, an end-to-end optical connection may easily cross multiple
sub-networks with the following possible scenarios
Access -- Metro -- Access
Access - Metro -- Long Haul -- Metro - Access
Editor's Note: More details will be added in a later revision of this
draft.
5.4 Inter-Carrier Network Model
The inter-carrier model focuses on the service and control aspects
between different carrier networks and describes the internetworking
relationship between the different carrier's optical networks. In the
inter-carrier network model, each carrier's optical network is a
draft-ietf-ipo-carrier-requirements-00.txt [page 16]
separate administrative domain. Both the UNI interface between the user
and the carrier network and the NNI interface between two carrier's
network are crossing the carrier's administrative boundaries and
therefore are by definition exterior interfaces.
Carrier Network Interconnection
Inter-carrier interconnection provides for connectivity among different
optical network operators. Just as the success and scalability of the
Internet has in large part been attributed by the inter-domain routing
protocol like BGP, so is the future success of the optical network. The
normal connectivity between the carriers may include:
Private Peering: Two carriers set up dedicated connection between them
via a private arrangement.
Public Peering: Two carriers set up a point-to-point connection between
them at a public optical network access points (ONAP)
Due to the nature of the automatic optical switched network, it is
possible to have the distributed peering where the connection between
two distant ONE's is connected via an optical connection.
6. Optical Service User Requirements
An optical connection will traverse two UNI interfaces and zero or more
NNI interfaces depending on If it is between two client network users
crossing a single carrier's network, or if it is between two client
network users crossing multiple carriers' networks.
6.1 Connection Management
6.1.1 Basic Connection Management
In a connection oriented transport network a connection must be
established before data can be transferred. This requires, as a
minimum, that the following connection management actions shall be
supported:
Set-up Connection is initiated by the management plane on behalf of an
end-user or by the end-user signaling device. The results are as
follows: If set-up of connection is successful, then optical circuit,
resources, or required bandwidth is dedicated to associated end-points.
Dedicated resources may include active resources as well as protection
or restoration resources in accordance with the class of service
indicated by the user. If set-up of connection is not successful, a
negative response is returned to initiating entity and any partial
allocation of resources is de-allocated.
Editor's Note - may need to mention the ACK from the user on connection
create confirmation.
Teardown Connection is initiated by the management plane on behalf of
an end-user or by the end-user signaling device. The results are as
follows: optical circuit, resources or the required bandwidth are freed
draft-ietf-ipo-carrier-requirements-00.txt [page 17]
up for ulterior usage. Dedicated resources are also freed. Shared
resources are only freed if there are no active connections sharing the
same protection or restoration resources. If tear down is not
successful, a negative response shall be returned to the end-user.
Query Connection is initiated by the management plane on behalf of an
end-user or by the end-user signaling device. Status report returned to
querying entity.
Accept/Reject Connection is initiated by the end-user signaling device.
This command is relevant in the context of switched connections only.
The destination end-user shall have the opportunity to accept or reject
new connection requests or connection modifications.
Furthermore, the following requirements need to be considered:
Requirement 6. The control plane shall support action results code
responses to any requests over the control interfaces.
Requirement 7. The control plane shall support requests for connection
set-up, subject to policies in effect between the user and the
network.
Requirement 8. The control plane shall support the destination user
edge device's decision to accept or reject connection creation
requests from the initiating user edge device.
Requirement 9. The control plane shall support the user request for
connection tear down.
Requirement 10. The control plane shall support management plane
and user edge device request for connection attributes or status
query.
In addition, there are several actions that need to be supported, which
are not directly related to an individual connection, but are necessary
for establishing healthy interfaces. The requirements below show some
of these actions:
Requirement 11. UNI shall support initial registration of the UNI-C
with the network.
Requirement 12. UNI shall support registration and updates by the
UNI-C entity of the edge devices and user interfaces that it
controls.
Requirement 13. UNI shall support network queries of the user edge
devices.
Requirement 14. UNI shall support detection of user edge device or
of edge ONE failure.
In addition, connection admission control (CAC) is necessary for
authentication of the user and controlling access to network resources.
Requirement 15. CAC shall be provided as part of the control plane
functionality. It is the role of the CAC function to determine if
draft-ietf-ipo-carrier-requirements-00.txt [page 18]
there is sufficient free resource available to allow a new
connection.
Requirement 16. If there is sufficient resource available, the CAC
may permit the connection request to proceed.
Requirement 17. If there is not sufficient resource available, the
CAC shall notify the originator of the connection request that the
request has been denied.
6.2 Enhanced Connection Management
6.2.1 Compound Connections
Multiple point-to-point connections may be managed by the network so as
to appear as a single compound connection to the end-points. Examples
of such compound connections are connections based on virtual
concatenation, diverse routing, or restorable connections.
Compound connections are distinguished from basic connections in that a
UNI request will generate multiple parallel NNI signaling sessions.
Connection Restoration
The control plane should provide the signaling and routing capabilities
to permit connection restoration based on the user's request for its
assigned service class.
Diverse Routing
The control plane should provide the signaling and routing capabilities
to permit a user to request diversely routed connections from a carrier
who supports this functionality.
Multicast Connections
The control plane should provide the signaling and routing capabilities
to permit a user to request multicast connections from a carrier who
supports this functionality.
6.2.2 Supplemental Services
Requirement 18. The control plane shall provide support for the
development of supplementary services that are independent of the
bearer service.
Where these are carried across networks using a range of protocols, it
is necessary to ensure that the protocol interworking provides a
consistent service as viewed by the user regardless of the network
implementation.
draft-ietf-ipo-carrier-requirements-00.txt [page 19]
Requirement 19. The control plane shall support closed user groups.
This allows a user group to create, for example, a virtual private
network.
Supplementary services may be not required or possible for soft
permanent connections.
6.2.3 Optical VPNs
In optical virtual private networks, the customer contracts for
specific network resources (capacity between OXCs, OXC ports, OXC
switching resources) and is able to control these resources to
establish, disconnect, and reconfigure optical connection connections.
Requirement 20. The control plane should provide the signaling and
routing capabilities to permit a user to request optical virtual
private networks from a carrier who supports this functionality.
6.3 Optical Services
Optical services embody a large range of transport services. Currently,
most transport systems are SONET/SDH based, however, innovations in
optical technology such as photonic switching bring about the distinct
possibility of support for pure optical transport services, while the
proliferation of Ethernet coupled with advancements in the technology
to support 1Gb/s and 10 Gb/s interfaces are drivers to make this
service class widely available.
Transparent Service assumes that the user requires optical transport
without the network being aware of the framing. However, since
transmission systems and the engineering rules that apply have
dependencies on the signal bandwidth, even for transparent optical
services, knowledge of the bandwidth requirements is essential.
Opaque Service refers to transport services where signal framing is
negotiated between the user and the network operator, and only the
payload is carried transparently. SONET/SDH transport is most widely
used for network-wide transport, and such is discussed in most detail
in the following sections.
As stated above, Ethernet Services, specifically 1Gb/s and 1Gbs
Ethernet services are gaining more and more popularity due to the lower
costs of the customers' premises equipment and its simplified
management requirements (compared to SONET or SDH). Therefore, more and
more network customers have expressed a high level of interest in
support of these transport services.
draft-ietf-ipo-carrier-requirements-00.txt [page 20]
Ethernet services may be carried over either SONET/SDH or photonic
networks. As discussed in subsequent sections Ethernet service requests
require some service specific parameters: priority class, VLAN Id/Tag,
traffic aggregation parameters.
Also gaining ground in the industry are the Storage Area Network (SAN)
Services. ESCON and FICON are proprietary versions of the service,
while Fiber Channel is the standard alternative. As discussed in
subsequent sections Fiber Channel service may require a latency
parameter, since the protocol between the service clients and the
server may be dependent on the transmission delays (the service is
sensitive to delays in the range of hundreds of .s). As is the case with
Ethernet services, SAN services may be carried over either SONET/SDH
(using GFP mapping) or photonic networks. Currently SAN services
require only point-to-point connections, but it is envisioned that in
the future they may also require multicast connections.
6.4 Levels of Transparency
Bitstream connections are framing aware - the exact signal framing is
known or needs to be negotiated between network operator and user.
However, there may be multiple levels of transparency for individual
framing types. Current transport networks are mostly based on SONET/SDH
technology. Therefore, multiple levels have to be considered when
defining specific optical services.
The example below shows multiple levels of transparency applicable to
SONET/SDH transport.
- SONET Line and section OH (SDH multiplex and regenerator section OH)
are normally terminated and a large set of parameters can be
monitored by the network.
- Line and section OH are carried transparently
- Non-SONET/SDH transparent bit stream
6.5 Optical Connection granularity
The service granularity is determined by the specific technology,
framing and bit rate of the physical interface between the ONE and the
user edge device and by the capabilities of the ONE. The control plane
needs to support signaling and routing for all the services supported
by the ONE. Connection granularity is defined by a combination of
framing (e.g., SONET or SDH) and bandwidth of the signal carried over
the network for the user. The connection and associated properties may
define the physical characteristics of the optical connection. However,
the consumable attribute is bandwidth. In general, there should not be
a one-to-one correspondence imposed between the granularity of the
service provided and the maximum capacity of the interface to the user.
draft-ietf-ipo-carrier-requirements-00.txt [page 21]
Requirement 21. The SDH and SONET connection granularity, shown in
the table below, shall be supported by the control plane.
Any specific NE's control plane implementation needs to support only
the subset consistent with its hardware.
Editor's Note: An OTN table for service granularity will be added.
SDH SONET Transported signal
name name
RS64 STS-192 STM-64 (STS-192) signal without
Section termination of any OH.
RS16 STS-48 STM-16 (STS-48) signal without
Section termination of any OH.
MS64 STS-192 STM-64 (STS-192); termination of
Line RSOH (section OH) possible.
MS16 STS-48 STM-16 (STS-48); termination of
Line RSOH (section OH) possible.
VC-4- STS-192c- VC-4-64c (STS-192c-SPE);
64c SPE termination of RSOH (section OH),
MSOH (line OH) and VC-4-64c TCM OH
possible.
VC-4- STS-48c- VC-4-16c (STS-48c-SPE);
16c SPE termination of RSOH (section OH),
MSOH (line OH) and VC-4-16c TCM
OH possible.
VC-4-4c STS-12c- VC-4-4c (STS-12c-SPE); termination
SPE of RSOH (section OH), MSOH (line
OH) and VC-4-4c TCM OH possible.
VC-4 STS-3c- VC-4 (STS-3c-SPE); termination of
SPE RSOH (section OH), MSOH (line OH)
and VC-4 TCM OH possible.
VC-3 STS-1-SPE VC-3 (STS-1-SPE); termination of
RSOH (section OH), MSOH (line OH)
and VC-3 TCM OH possible.
Note: In SDH it could be a higher
order or lower order VC-3, this is
identified by the sub-addressing
scheme. In case of a lower order
VC-3 the higher order VC-4 OH can
be terminated.
VC-2 VT6-SPE VC-2 (VT6-SPE); termination of
RSOH (section OH), MSOH (line OH),
higher order VC-3/4 (STS-1-SPE) OH
and VC-2 TCM OH possible.
- VT3-SPE VT3-SPE; termination of section
OH, line OH, higher order STS-1-
SPE OH and VC3-SPE TCM OH
possible.
VC-12 VT2-SPE VC-12 (VT2-SPE); termination of
RSOH (section OH), MSOH (line OH),
draft-ietf-ipo-carrier-requirements-00.txt [page 22]
higher order VC-3/4 (STS-1-SPE) OH
and VC-12 TCM OH possible.
VC-11 VT1.5-SPE VC-11 (VT1.5-SPE); termination of
RSOH (section OH), MSOH (line OH),
higher order VC-3/4 (STS-1-SPE) OH
and VC-11 TCM OH possible.
Requirement 22. In addition, 1 Gb and 10 Gb granularity shall be
supported for 1 Gb/s and 10 Gb/s (WAN mode) Ethernet framing types,
if implemented in the hardware.
Requirement 23. For SAN services the following interfaces have been
defined and shall be supported by the control plane if the given
interfaces are available on the equipment:
- FC-12
- FC-50
- FC-100
- FC-200
In addition, extensions of the intelligent optical network
functionality towards the edges of the network in support of sub-rate
interfaces (as low as 1.5 Mb/s) will support of VT /TU granularity.
Requirement 24. Therefore, sub-rate extensions in ONEs supporting
sub-rate fabric granularity shall support VT-x/TU-1n granularity down
to VT1.5/TU-l1, consistent with the hardware.
Requirement 25. The connection types supported by control plane
shall be consistent with the service granularity and interface types
supported by the ONE.
The control plane and its associated protocols should be extensible to
support new services as needed.
Requirement 26. Encoding of service types in the protocols used
shall be such that new service types can be added by adding new
codepoint values or objects.
Note: Additional attributes may be required to ensure proper
connectivity between endpoints.
6.6 Other Service Parameters and Requirements
6.6.1 Classes of Service
We use "service level" to describe priority related characteristics of
connections, such as holding priority, set-up priority, or restoration
priority. The intent currently is to allow each carrier to define the
actual service level in terms of priority, protection, and restoration
draft-ietf-ipo-carrier-requirements-00.txt [page 23]
options. Therefore, mapping of individual service levels to a specific
set of priorities will be determined by individual carriers.
Requirement 27. Multiple service level options shall be supported
and the user shall have the option of selecting over the UNI a
service level for an individual connection.
However, in order for the network to support multiple grades of
restoration, the control plane must identify, assign, and track
multiple protection and restoration options.
Requirement 28. Therefore, the control plane shall map individual
service classes into specific protection and/or restoration options.
Specific protection and restoration options are discussed in Section
10. However, it should be noted that while high grade services may
require allocation of protection or restoration facilities, there may
be an application for a low grade of services for which pre-emptable
facilities may be used.
Individual carriers will select appropriate options for protection
and/or restoration in support of their specific network plans.
6.6.2 Connection Latency
Connection latency is a parameter required for support of Fibber
Channel services. Connection latency is dependent on the circuit
length, and as such for these services, it is essential that shortest
path algorithms are used and end-to-end latency is verified before
acknowledging circuit availability.
Editor's Note: more detail may be required here.
6.6.3 Diverse Routing Attributes
The ability to route service paths diversely is a highly desirable
feature. Diverse routing is one of the connection parameters and is
specified at the time of the connection creation. The following
provides a basic set of requirements for the diverse routing support.
- Diversity compromises between two links being used for routing should
be defined in terms of Shared Risk Link Groups (SRLG - see [draft-
chaudhuri-ip-olxc-control-00.txt]]), a group of links which share
some resource, such as a specific sequence of conduits or a specific
office. A SRLG is a relationship between the links that should be
characterized by two parameters:
- Type of Compromise: Examples would be shared fiber cable, shared
conduit, shared right-of-way (ROW), shared link on an optical ring,
shared office - no power sharing, etc.)
- Extent of Compromise: For compromised outside plant, this would be
the length of the sharing.
draft-ietf-ipo-carrier-requirements-00.txt [page 24]
Requirement 29. The control plane routing algorithms shall be able
to route a single demand diversely from N previously routed demands,
where diversity would be defined to mean that no more than K demands
(previously routed plus the new demand) should fail in the event of a
single covered failure.
7. Optical Service Provider Requirements
7.1 Access Methods to Optical Networks
Multiple access methods shall be supported:
- Cross-office access (User NE co-located with ONE)
In this scenario the user edge device resides in the same office
as the ONE and has one or more physical connections to the ONE.
Some of these access connections may be in use, while others may
be idle pending a new connection request.
- Direct remote access
In this scenario the user edge device is remotely located from the
ONE and has inter-location connections to the ONE over multiple
fiber pairs or via a DWDM system. Some of these connections may be
in use, while others may be idle pending a new connection request.
- Remote access via access sub-network
In this scenario remote user edge devices are connected to the ONE
via a multiplexing/distribution sub-network. Several levels of
multiplexing may be assumed in this case. This scenario is
applicable to metro/access subnetworks of signals from multiple
users, out, of which only a subset have connectivity to the ONE.
Requirement 30. All access methods must be supported.
7.1.1 Dual Homing
Dual homing is a special case of the access network. Dual homing may
take different flavors, and as such affect interface designs in more
than one way:
- A client device may be dual homed on the same subnetwork
- A client device may be dual homed on different subnetworks within the
same administrative domain (and the same domain as the core
subnetwork)
- A client device may be dual homed on different subnetworks within the
same administrative domain (but a different domain from the core
subnetwork)
- A client device may be dual homed on different subnetworks off
different administrative domains.
- A metro subnetwork may be dual homed on the same core subnetwork,
within the same administrative domain
draft-ietf-ipo-carrier-requirements-00.txt [page 25]
- A metro subnetwork may be dual homed on the same core subnetwork, of
a different administrative domain
- A metro network may be dual homed to separate core subnetworks, of
different administrative domains.
The different flavors of dual homing will have great impact on
admission control, reachability information exchanges, authentication,
neighbor and service discovery across the interface.
Requirement 31. Dual homing must be supported.
7.2 Bearer Interface Types
Requirement 32. All the bearer interfaces implemented in the ONE
shall be supported by the control plane and associated signaling
protocols.
The following interface types shall be supported by the signaling
protocol:
- SDH
- SONET
- 1 Gb Ethernet, 10 Gb Ethernet (WAN mode)
- 10 Gb Ethernet (LAN mode)
- FC-N (N= 12, 50, 100, or 200) for Fiber Channel services
- OTN (G.709)
- PDH
- Transparent optical
7.3 Names and Address Management
In this section addressing refers to optical layer addressing and it is
an identifier required for routing and signaling protocol within the
optical network. Identification used by other logical entities outside
the optical network control plane (such as higher layer services
addressing schemes or a management plane addressing scheme) may be used
as naming schemes by the optical network. Recognizing that multiple
types of higher layer services need to be supported by the optical
network, multiple user edge device naming schemes must be supported,
including at the minimum IP and NSAP naming schemes.
The control plane shall use the higher layer service address as a name
rather than as a routable address. The control plane must know what
internal addressing scheme is used within the control plane domain.
Optical layer addresses shall be provisionable for each connection
point managed by the control plane. Dynamic address assignment schemes
are desirable in the control plane, however in the event the assignment
is not dynamic then connection point addresses need to be configurable
from the management plane. In either case, the management system must
be able to query the currently assigned value.
draft-ietf-ipo-carrier-requirements-00.txt [page 26]
While, IP-centric services are considered by many as one of the drivers
for optical network services, it is also widely recognized that the
optical network will be used in support of a large array of both data
and voice services. In order to achieve real-time provisioning for all
services supported by the optical network while minimizing OSS
development by carriers, it is essential for the network to support a
UNI definition that does not exclude non-IP services.
Requirement 33. For this reason, multiple naming schemes shall be
supported to allow network intelligence to grow towards the edges.
One example of naming is the use of physical entity naming.
Carrier Network Elements identify individual ports by their location
using a scheme based on "CO/NE/bay/shelf/slot/port" addressing schema.
Similarly, facilities are identified by route
"id/fiber/wavelength/timeslot".
Mapping of Physical Entity addressing to Optical Network addressing
shall be supported. Name to address translation should be supported
similar to DNS.
To realize fast provisioning and bandwidth on demand services in
response to router requests, it is essential to support IP naming.
Requirement 34. Mapping of higher layer user IP naming to Optical
Network Addressing shall be supported.
European carriers use NSAP naming for private lines and many US data
centric applications, including ATM-based services also use NSAP
addresses. As such it is important that NSAP naming should be
supported.
Requirement 35. Mapping of higher layer NSAP naming to Optical
Network shall be supported.
Requirement 36. Listed below are additional Optical Network
Addresses (ONA) requirements:
1) There shall be at least one globally unique address associated with
each user device. A user device may have one or more ports connected
to the network.
2) The address space shall support connection management across multiple
networks, both within one administrative domain and across multiple
administrative domains.
3) Address hierarchies shall be supported.
4) Address aggregation and summarization shall be supported. (This is
actually an NNI requirement).
5) Dual homing shall allow, but not require the use of multiple
addresses whether within the same administrative domain, or across
multiple administrative domains.
draft-ietf-ipo-carrier-requirements-00.txt [page 27]
6) Need an international body to administer the address space. Note that
this need is independent of what addressing scheme is used, and this
concerns the user and the network operator communities.
7) The size of the Optical Network Address shall be sufficient to avoid
address exhaustion within the next 50 years. The address space shall
scale up to a large base of customers and to a large number of
operators.
8) Internal switch addresses shall not be derivable from ONAs and shall
not be advertised to the customer.
9) The ONA shall not imply network characteristics (port numbers, port
granularity, etc).
10) ONA reachability deals with connectivity and not with the user
device being powered up (reachability updates triggered by
registration and deregistration, not by client device reboots) (Name
registration persists for as long as the user retains the same ONA -
until de-registration).
11) ONAs shall be independent of user names, higher layer services
(i.e., should support IP, ATM, PL, etc) and optical network internal
routing addresses. User names are opaque to optical network. User
equipment and other optical carriers have no knowledge of optical
network internal routing addresses, including ports information.
12) The client (user) name should not make assumptions on what
capabilities are offered by the server (service provider) name, and
thus the semantics of the two name spaces should be separate and
distinct. This does not place any constraints on the syntax of client
and server layer name spaces, or of the user and service provider
name spaces (G.astn draft)
13) The addressing scheme shall not impede use of either client-server
or peer model within an operator's network.
14) There should be a single standard, fixed space of addresses to
which names will be mapped from a wide range of higher layer
services.
7.3.1 Address Space Separation
Requirement 37. The control plane must support all types of client
addressing.
Requirement 38. The control plane must use the client address as a
name rather as a routable address.
Requirement 39. The control plane must know what internal
addressing scheme is used within the control plane domain.
7.3.2 Directory Services
draft-ietf-ipo-carrier-requirements-00.txt [page 28]
Requirement 40. Directory Services shall be supported to enable
operator to query the optical network for the optical network address
of a specified user.
Requirement 41. Address resolution and translation between various
user edge device name and corresponding optical network address shall
be supported.
Requirement 42. UNI shall use the user naming schemes for
connection request.
7.4 Link Identification
Optical devices might have thousands of incoming and outgoing
connections. This will be of concern when trying to provide globally
unique addresses to all optical nodes in an optical network.
Requirement 43. The control plane should be able to address NE
connection points with addresses that are locally defined.
Requirement 44. The control plane should be able to advertise and
signal for locally defined and non-unique addresses that have only
local significance. This would allow for re-use of the addressing
space.
There is the issue of providing addresses for the optical nodes or
devices that form the ASON/ASTN. The other issue is providing addresses
for the incoming and outgoing connections/ports within each optical
node/device. The first issue is not a problem, since the optical
devices/nodes can use the standard IP or NSAP address space. Providing
locally defined address space that can be re-used in other optical
nodes within the domain can solve providing address space for the
ports/connections within each node. So, the optical nodes within a
domain or multiple domains in the network can communicate with each
other using the standard address space like IP or NSAP. The switching &
forwarding within each optical node can be based on locally defined
addresses.
7.5 Policy-Based Service Management Framework
The IPO service must be supported by a robust policy-based management
system to be able to make important decisions.
Examples of policy decisions include:
- What types of connections can be set up for a given UNI?
- What information can be shared and what information must be
restricted in automatic discovery functions?
- What are the security policies over signaling interfaces?
Requirement 45. Service and network policies related to
configuration and provisioning, admission control, and support of
draft-ietf-ipo-carrier-requirements-00.txt [page 29]
Service Level Agreements (SLAs) must be flexible, and at the same
time simple and scalable.
Requirement 46. The policy-based management framework must be based
on standards-based policy systems (e.g. IETF COPS).
Requirement 47. In addition, the IPO service management system must
support and be backwards compatible with legacy service management
systems.
7.5.1 Admission control
Connection admission functionality required must include authentication
of client, verification of services, and control of access to network
resources.
Requirement 48. The policy management system must determine what
kind of connections can be set up for a given UNI.
Connection Admission Control (CAC) is required for authentication of
users (security), verification of connection service level parameters
and for controlling access to network resources. The CAC policy should
determine if there are adequate network resources available within the
carrier to support each new connection. CAC policies are outside the
scope of standardization.
Requirement 49. When a connection request is received by the
control plane, it is necessary to ensure that the resources exist
within the optical transport network to establish the connection.
Requirement 50. In addition to the above, the control plane
elements need the ability to rate limit (or pace) call setup attempts
into the network.
This is an attempt to prevent overload of the control plane processors.
In application to SPC type connections this might mean that the setup
message would be slowed or buffered in order to handle the current
load.
Another aspect of admission control is security.
Requirement 51. The policy-based management system must be able to
authenticate and authorize a client requesting the given service. The
management system must also be able to administer and maintain
various security policies over signaling interfaces.
7.5.2 SLA Support
Requirement 52. The service management system should employ
features to ensure client SLAs.
draft-ietf-ipo-carrier-requirements-00.txt [page 30]
In addition to setting up connections based on resource availability to
meet SLAs, the management system must periodically monitor connections
for the maintenance of SLAs. Complex SLAs, such as time-of-day or
multiple-service-class based SLAs, should also be satisfied. In order
to do this, the policy-based service management system should support
automated SLA monitoring systems that may be embedded in the management
system or may be separate entities. Mechanisms to report events of not
meeting SLAs, or a customer repeatedly using more than the SLA, should
be supported by the SLA monitoring system. Other off-line mechanisms
to forecast network traffic growth and congestion via simulation and
modeling systems, may be provided to aid in efficient SLA management.
Another key aspect to SLA management is SLA translation.
Requirement 53. In particular, policy-based Class of Service
management schemes that accurately translate customer SLAs to
parameters that the underlying mechanisms and protocols in the
optical transport network can understand, must be supported.
Consistent interpretation and satisfaction of SLAs is especially
important when an IPO spans multiple domains or service providers.
7.6 Inter-Carrier Connectivity
Inter-carrier connectivity has specific implications on the admission
control and SLA support aspects of the policy-based service management
system.
Multiple peering interfaces may be used between two carriers, whilst
any given carrier is likely to peer with multiple other carriers. These
peering interfaces must support all of the functions defined in section
9, although each of these functions has a special flavor when applied
to this interface.
Carriers will not allow other carriers control over their network
resources, or visibility of their topology or resources. Therefore,
topology and resource discovery should not be supported between
carriers. There may of course be instances where there is high degree
of trust between carriers, allowing topology and resource discovery,
but this would be a rare exception.
Requirement 54. Inter-carrier connectivity shall be based on E-NNI.
To provide connectivity between clients connected to different carriers
requires that client reachability information be exchanged between
carriers. Additional information regarding network peering points and
summarized network topology and resource information will also have to
be conveyed beyond the bounds of a single carrier. This information is
required to make route selections for connections traversing multiple
carriers.
Given that detailed topology and resource information is not available
outside a carrier's trust boundary, routing of connections over
draft-ietf-ipo-carrier-requirements-00.txt [page 31]
multiple carriers will involve selection of the autonomous systems
(ASs) traversed. This can be defined using a series of peering points.
More detailed route selection is then performed on a per carrier basis,
as the signaling requests are received at each carrier's peering
points. The detailed connection routing information should not be
conveyed across the carrier trust boundary.
CAC, as described above, is necessary at each trust interface,
including those between carriers (see Section 11.2 for security
considerations).
Similar to dual homing it is possible to have inter-carrier
connectivity over multiple diverse routes. These connectivity models
support multi hosting.
Editor's Note: further discussion on this will be added in a later
revision.
7.7 Multiple Hierarchies
Transport networks are built in a tiered, hierarchal architecture.
Also, by applying control plane support to service and facilities
management, separate and distinct network layers may need to be
supported across the same inter-domain interface. Furthermore, for
large networks, it may be required to support multiple levels of
routing domains.
Requirement 55. Multi level hierarchy must be supported.
Editor's Note: more details will be added as required.
Network layer hierarchies
Services (IP, SAN, Ethernet)
Transport: SONET/SDH/Ethernet
DWDM, Optics
Address space hierarchies
Geographical hierarchies
Functional hierarchies
Network Topology hierarchies
Access, metro, inter-city, long haul - as routing areas. Any one
large routing area may need to be decomposed in sub-areas.
8. Control Plane Functional Requirements for Optical Services
8.1 Control Plane Capabilities and Functions
8.1.1 Network Control Capabilities
The following capabilities are required in the network control plane to
successfully deliver automated provisioning:
- Neighbor discovery
- Address assignment
- Connection topology discovery
- Address resolution
draft-ietf-ipo-carrier-requirements-00.txt [page 32]
- Reachability information dissemination
- Connection Management
These capabilities may be supported by a combination of functions
across the control and the management planes.
8.1.2 Control Plane Functions
The following are essential functions needed to support network control
capabilities:
- Signaling
- Routing
- Resource and Service discovery
Signaling is the process of control message exchange using a well-
defined signaling protocol to achieve communication between the
controlling functional entities connected through a specified
communication channel. It is often used for dynamic connection set-up
across a network. Signaling is used to disseminate information between
network entities in support of all network control capabilities.
Routing is a distributed networking process within the network for
dynamic dissemination and propagation of the network information among
all the routing entities based on a well-defined routing protocol. It
enables the routing entity to compute the best path from one point to
another.
Resource and service discovery is the automatic process between the
connected network devices using a resource/service discovery protocol
to determine the available services and identify connection state
information.
Requirement 56. The general requirements for the control plane
functions to support optical networking functions include:
1. The control plane must have the capability to establish,
teardown and maintain the end-to-end connection.
2. The control plane must have the capability to establish,
teardown and maintain the hop-by-hop connection segments
between two end-points.
3. The control plane must have the capability to support traffic-
engineering requirements including resource discovery and
dissemination, constraint-based routing and path computation.
4. The control plane must have the capability to support
reachability information dissemination.
5. The control plane shall support network status or action
result code responses to any requests over the control
interfaces.
6. The control plane shall support resource allocation on both UNI
and NNI.
draft-ietf-ipo-carrier-requirements-00.txt [page 33]
7. Upon successful connection teardown all resources associated
with the connection shall become available for access for new
requests.
8. The control plane shall ensure that there will not be unused,
frozen network resources.
9. The control plane shall ensure periodic or on demand clean-up
of network resources.
10. The control plane shall support management plane request for
connection attributes/status query.
11. The control plane must have the capability to support various
protection and restoration schemes for the optical channel
establishment.
12. Control plane failures shall not affect active connections.
13. The control plane shall be able to trigger restoration based
on alarms or other indications of failure.
8.2 Signaling Network
The signaling network consists of a set of signaling channels that
interconnect the nodes within the control plane. Therefore, the
signaling network must be accessible by each of the communicating nodes
(e.g., OXCs).
Requirement 57. The signaling network must terminate at each of the
communicating nodes.
Requirement 58. The signaling network shall not be assumed to have
the same physical connectivity as the data plane, nor shall the data
plane and control plane traffic be assumed to be congruently routed.
A signaling channel is the communication path for transporting
signaling messages between network nodes, and over the UNI (i.e.,
between the UNI entity on the user side (UNI-C) and the UNI entity on
the network side (UNI-N)). There are three different types of signaling
methods depending on the way the signaling channel is constructed:
. In-band signaling: The signaling messages are carried over a logical
communication channel embedded in the data-carrying optical link or
channel. For example, using the overhead bytes in SONET data framing
as a logical communication channel falls into the in-band signaling
methods.
. In fiber, Out-of-band signaling: The signaling messages are carried
over a dedicated communication channel separate from the optical
data-bearing channels, but within the same fiber. For example, a
dedicated wavelength or TDM channel may be used within the same fiber
as the data channels.
. Out-of-fiber signaling: The signaling messages are carried over a
dedicated communication channel or path within different fibers to
draft-ietf-ipo-carrier-requirements-00.txt [page 34]
those used by the optical data-bearing channels. For example,
dedicated optical fiber links or communication path via separate and
independent IP-based network infrastructure are both classified as
out-of-fiber signaling.
In-band signaling is particularly important over a UNI interface, where
there are relatively few data channels. Proxy signaling is also
important over the UNI interface, as it is useful to support users
unable to signal to the optical network via a direct communication
channel. In this situation a third party system containing the UNI-C
entity will initiate and process the information exchange on behalf of
the user device. The UNI-C entities in this case reside outside of the
user in separate signaling systems.
In-fiber, out-of-band and out-of-fiber signaling channel alternatives
are particularly important for NNI interfaces, which generally have
significant numbers of channels per link. Signaling messages relating
to all of the different channels can then be aggregated over a single
or small number of signaling channels.
The signaling network forms the basis of the transport network control
plane. To achieve reliable signaling, the control plane needs to
provide reliable transfer of signaling messages, its own OAM mechanisms
and flow control mechanisms for restricting the transmission of
signaling packets where appropriate.
Requirement 59. The signaling protocol shall support reliable
message transfer.
Requirement 60. The signaling network shall have its own OAM
mechanisms.
Requirement 61. The signaling protocol shall support congestion
control mechanisms.
In addition, the signaling network should support message priorities.
Message prioritization allows time critical messages, such as those
used for restoration, to have priority over other messages, such as
other connection signaling messages and topology and resource discovery
messages.
Requirement 62. The signaling network should support message
priorities.
The signaling network must be highly scalable, with minimal performance
degradations as the number of nodes and node sizes increase.
Requirement 63. The signaling network shall be highly scalable.
draft-ietf-ipo-carrier-requirements-00.txt [page 35]
The signaling network must also be highly reliable, implementing
mechanisms for failure recovery. Furthermore, failure of signaling
links or of the signaling software must not impact established
connections or cause partially established connections, nor should they
impact any elements of the management plane.
Requirement 64. The signaling network shall be highly reliable and
implement failure recovery.
Requirement 65. Control channel and signaling software failures
shall not cause disruptions in established connections within the
data plane, and signaling messages affected by control plane outages
should not result in partially established connections remaining
within the network.
Requirement 66. Control channel and signaling software failures
shall not cause management plane failures.
Security is also a crucial issue for the signaling network. Transport
networks are generally expected to carry large traffic loads and high
bandwidth connections. The consequence is significant economic impacts
should hackers disrupt network operation, using techniques such as the
recent denial of service attacks seen within the Internet.
Requirement 67. The signaling network shall be secure, blocking all
unauthorized access.
Requirement 68. The signaling network topology and signaling node
addresses shall not be advertised outside a carrier's domain of
trust.
8.3 Control Plane Interface to Data Plane
In the situation where the control plane and data plane are provided by
different suppliers, this interface needs to be standardized.
Requirements for a standard control -data plane interface are under
study. Control plane interface to the data plane is outside the scope
of this document.
8.4 Control Plane Interface to Management Plane
The control plane is considered a managed entity within a network.
Therefore, it is subject to management requirements just as other
managed entities in the network are subject to such requirements.
8.4.1 Allocation of resources
The management plane is responsible for identifying which network
resources that the control plane may use to carry out its control
draft-ietf-ipo-carrier-requirements-00.txt [page 36]
functions. Additional resources may be allocated or existing resources
deallocated over time.
Requirement 69. Resources shall be able to be allocated to the
control plane for control plane functions include resources involved
in setting up and tearing down calls and control plane specific
resources. Resources allocated to the control plane for the purpose
of setting up and tearing down calls include access groups (a set of
access points), connection point groups (a set of connection points).
Resources allocated to the control plane for the operation of the
control plane itself may include protected and protecting control
channels.
Requirement 70. Resources allocated to the control plane by the
management plane shall be able to be de-allocated from the control
plane on management plane request.
Requirement 71. If resources are supporting an active connection
and the resources are requested to be de-allocated from the control
plane, the control plane shall reject the request. The management
plane must either wait until the resources are no longer in use or
tear down the connection before the resources can be de-allocated
from the control plane. Management plane failures shall not affect
active connections.
Requirement 72. Management plane failures shall not affect the
normal operation of a configured and operational control plane or
data plane.
8.4.2 Soft Permanent Connections (Point-and click provisioning)
In the case of SPCs, the management plane requests the control plane to
set up/tear down a connection rather than a request coming over a UNI.
Requirement 73. The management plane shall be able to query on
demand the status of the connection request
Requirement 74. The control plane shall report to the management
plane, the Success/Failures of a connection request
Requirement 75. Upon a connection request failure, the control
plane shall report to the management plane a cause code identifying
the reason for the failure.
Requirement 76. In a set up connection request, the management
plane shall be able to specify the service class that is required for
the connection.
8.4.3 Resource Contention resolution
Since resources are allocated to the control plane for use, there
should not be contention between the management plane and the control
draft-ietf-ipo-carrier-requirements-00.txt [page 37]
plane for connection set-up. Only the control plane can establish
connections for allocated resources. However, in general, the
management plane shall have authority over the control plane.
Requirement 77. The control plane shall not assume authority over
management plane provisioning functions.
In the case of fault management, both the management plane and the
control plane need fault information at the same priority.
Requirement 78. The control plane shall not interfere with the
speed or priority at which the management plane would receive alarm
information from the NE or the transport plane in the absence of a
control plane.
The control plane needs fault information in order to perform its
restoration function (in the event that the control plane is providing
this function). However, the control plane needs less granular
information than that required by the management plane. For example,
the control plane only needs to know whether the resource is good/bad.
The management plane would additionally need to know if a resource was
degraded or failed and the reason for the failure, the time the failure
occurred and so on.
Requirement 79. Accounting information shall be provided by the
control plane to the management plane. Again, there is no
contention. This is addressed in the billing section.[open issue -
what happens to accounting data histories when resource moved from
control plane to management plane?]
Performance management shall be a management plane function only.
Again, there is no contention between the management plane and the
control plane.
Requirement 80. The control plane shall not assume authority over
management plane performance management functions.
8.4.4 MIBs
Requirement 81. A standards based MIB shall be used for control
plane management.
Requirement 82. The standards based MIB definition shall support
all management functionality required to manage the control plane.
Requirement 83. The standards based MIB definition should support
all optional management functionality desired to manage the control
plane.
8.4.5 Alarms
The control plane is not responsible for monitoring and reporting
problems in the transport plane or in the NE that are independent of
draft-ietf-ipo-carrier-requirements-00.txt [page 38]
the control plane. It is responsible, however for monitoring and
reporting control plane alarms. The requirements in this section are
applicable to the monitoring and reporting of control plane alarms.
Requirement 84. The Control Plane shall not lose alarms. Alarms
lost due to transmission errors between the Control Plane and the
Management Plane shall be able to be recovered through Management
Plane queries to the alarm notification log.
Requirement 85. Alarms must take precedence over all other message
types for transmission to the Management Plane.
Requirement 86. Controls issued by the Management Plane must be
able to interrupt an alarm stream coming from the Control Plane.
Requirement 87. The alarm cause shall be based on the probableCause
list in M.3100.
Requirement 88. Detailed alarm information shall be included in the
alarm notification including: the location of the alarm, the time the
alarm occurred, and the perceived severity of the alarm.
Requirement 89. The Control Plane shall send clear notifications
for Critical, Major, and Minor alarms when the cleared condition is
detected.
Requirement 90. The Control Plane shall support Autonomous Alarm
Reporting.
Requirement 91. The Control Plane shall support Alarm Reporting
Control (See M.3100, Amendment 3).
Requirement 92. The Control Plane shall support the ability to
configure and query the management plane applications that Autonomous
Alarm Reporting will be sent.
Requirement 93. The Control Plane shall support the ability to
retrieve all or a subset of the Currently Active Alarms.
Requirement 94. The Control Plane shall support Alarm Report
Logging.
Requirement 95. The Control Plane should support the ability to
Buffer Alarm Reports separately for each management plane application
that an Alarm Report is destined (See X.754, Enhanced Event Control
Function).
draft-ietf-ipo-carrier-requirements-00.txt [page 39]
Requirement 96. The Control Plane shall support the ability to
cancel a request to retrieve all or a subset of the Currently Active
Alarms (See Q.821, Enhanced Current Alarm Summary Control).
Requirement 97. The Control Plane should support the ability to
Set/Get Alarm Severity Assignment per object instance and per Alarm
basis.
Requirement 98. The Control Plane shall log autonomous Alarm Event
Reports / Notifications.
Requirement 99. The Control Plane shall not report the symptoms of
control plane problems as alarms (For example, an LOF condition shall
not be reported when the problem is a supporting facility LOS).
8.4.6 Status/State
Requirement 100. The management plane shall be able to query the
operational state of all control plane resources.
Requirement 101. In addition, the control plane shall provide a log
of current period and historical counts for call attempts and call
blocks and capacity data for both UNI and NNI interfaces.
3. The management plane shall be able to query current period and
historical logs.
8.4.7 Billing/Traffic and Network Engineering Support
Requirement 102. The control plane shall record usage per UNI and
per link connection.
Requirement 103. Usage information shall be able to be queried by
the management plane.
8.4.8 Policy Information
Requirement 104. In support of CAC, the management plane shall be
able to configure multiple service classes and identify protection
and or restoration allocations required for each service class, and
then assign services classes on a per UNI basis.
8.4.9 Control Plane Provisioning
Requirement 105. Topological information learned in the discovery
process shall be able to be queried on demand from the management
plane.
Requirement 106. The management plane shall be able to configure UNI
and NNI protection groups.
draft-ietf-ipo-carrier-requirements-00.txt [page 40]
Requirement 107. The management plane shall be able to prohibit the
control plane from using certain transport resources not currently
being used for a connection for new connection set-up requests.
There are various reasons for the management plane needing to do this
including maintenance actions.
Requirement 108. The management plane shall be able to tear down
connections established by the control plane both gracefully and
forcibly on demand.
8.5 Control Plane Interconnection
The interconnection of the IP router (client) and optical control
planes can be realized in a number of ways depending on the required
level of coupling. The control planes can be loosely or tightly
coupled. Loose coupling is generally referred to as the overlay model
and tight coupling is referred to as the peer model. Additionally
there is the augmented model that is somewhat in between the other two
models but more akin to the peer model. The model selected determines
the following:
- The details of the topology, resource and reachability information
advertised between the client and optical networks
- The level of control IP routers can exercise in selecting paths
across the optical network
The next three sections discuss these models in more details and the
last section describes the coupling requirements from a carrier's
perspective.
8.5.1 Peer Model (I-NNI like model)
Under the peer model, the IP router clients act as peers of the optical
transport network, such that single routing protocol instance runs over
both the IP and optical domains. In this regard the optical network
elements are treated just like any other router as far as the control
plane is concerned. The peer model, although not strictly an internal
NNI, behaves like an I-NNI in the sense that there is sharing of
resource and topology information.
Presumably a common IGP such as OSPF or IS-IS, with appropriate
extensions, will be used to distribute topology information. One tacit
assumption here is that a common addressing scheme will also be used
for the optical and IP networks. A common address space can be
trivially realized by using IP addresses in both IP and optical
domains. Thus, the optical networks elements become IP addressable
entities.
The obvious advantage of the peer model is the seamless interconnection
between the client and optical transport networks. The tradeoff is
draft-ietf-ipo-carrier-requirements-00.txt [page 41]
that the tight integration and the optical specific routing information
that must be known to the IP clients.
The discussion above has focused on the client to optical control plane
inter-connection. The discussion applies equally well to inter-
connecting two optical control planes.
8.5.2 Overlay (UNI-like model)
Under the overlay model, the IP client routing, topology distribution,
and signaling protocols are independent of the routing, topology
distribution, and signaling protocols at the optical layer. This model
is conceptually similar to the classical IP over ATM model, but applied
to an optical sub-network directly.
Though the overlay model dictates that the client and optical network
are independent this still allows the optical network to re-use IP
layer protocols to perform the routing and signaling functions.
In addition to the protocols being independent the addressing scheme
used between the client and optical network must be independent in the
overlay model. That is, the use of IP layer addressing in the clients
must not place any specific requirement upon the addressing used within
the optical control plane.
The overlay model would provide a UNI to the client networks through
which the clients could request to add, delete or modify optical
connections. The optical network would additionally provide
reachability information to the clients but no topology information
would be provided across the UNI.
8.5.3 Augmented model (E-NNI like model)
Under the augmented model, there are actually separate routing
instances in the IP and optical domains, but information from one
routing instance is passed through the other routing instance. For
example, external IP addresses could be carried within the optical
routing protocols to allow reachability information to be passed to IP
clients. A typical implementation would use BGP between the IP client
and optical network.
The augmented model, although not strictly an external NNI, behaves
like an E-NNI in that there is limited sharing of information.
8.5.4 Carrier Control Plane Coupling Requirements
Choosing the level of coupling depends upon a number of different
factors, some of which are:
- Variety of clients using the optical network
- Relationship between the client and optical network
- Operating model of the carrier
draft-ietf-ipo-carrier-requirements-00.txt [page 42]
Generally in a carrier environment there will be more than just IP
routers connected to the optical network. Some other examples of
clients could be ATM switches or SONET ADM equipment. This may drive
the decision towards loose coupling to prevent undue burdens upon non-
IP router clients. Also, loose coupling would ensure that future
clients are not hampered by legacy technologies.
Additionally, a carrier may for business reasons want a separation
between the client and optical networks. For example, the ISP business
unit may not want to be tightly coupled with the optical network
business unit. Another reason for separation might be just pure
politics that play out in a large carrier. That is, it would seem
unlikely to force the optical transport network to run that same set of
protocols as the IP router networks. Also, by forcing the same set of
protocols in both networks the evolution of the networks is directly
tied together. That is, it would seem you could not upgrade the
optical transport network protocols without taking into consideration
the impact on the IP router network (and vice versa).
Operating models also play a role in deciding the level of coupling.
[Freeland] gives four main operating models envisioned for an optical
transport network:
- ISP owning all of its own infrastructure (i.e., including fiber and
duct to the customer premises)
- ISP leasing some or all of its capacity from a third party
- Carriers carrier providing layer 1 services
- Service provider offering multiple layer 1, 2, and 3 services over a
common infrastructure
Although relatively few, if any, ISPs fall into category 1 it would
seem the mostly likely of the four to use the peer model. The other
operating models would lend themselves more likely to choose an overlay
model. Most carriers would fall into category 4 and thus would most
likely choose an overlay model architecture.
In the context of the client and optical network control plane
interconnection the discussion here leads to the conclusion that the
overlay model is required and the other two models (peer and augmented)
are optional.
Requirement 109. Overlay model (UNI like model) shall be supported
for client to optical control plane interconnection
Requirement 110. Other models are optional for client to optical
control plane interconnection
Requirement 111. For optical to optical control plane
interconnection all three models shall be supported
9. Requirements for Signaling, Routing and Discovery
draft-ietf-ipo-carrier-requirements-00.txt [page 43]
9.1 Signaling Functions
Connection management signaling messages are used for connection
establishment and deletion. These signaling messages must be
transported across UNIs, between nodes within a single carrier's
domain, over I-NNIs and E-NNIs.
A mixture of hop-by-hop routing, explicit/source routing and
hierarchical routing will likely be used within future transport
networks, so all three mechanisms must be supported by the control
plane. Using hop-by-hop message routing, each node within a network
makes routing decisions based on the message destination, and the local
routing tables. However, achieving efficient load balancing and
establishing diverse connections are impractical using hop-by-hop
routing. Instead, explicit (or source) routing may be used to send
signaling messages along a route calculated by the source. This route,
described using a set of nodes/links, is carried within the signaling
message, and used in forwarding the message.
Finally, network topology information must not be conveyed outside a
trust domain. Thus, hierarchical routing is required to support
signaling across multiple domains. Each signaling message should
contain a list of the domains traversed, and potentially details of the
route within the domain being traversed.
Signaling messages crossing trust boundaries must not contain
information regarding the details of an internal network topology. This
is particularly important in traversing E-UNIs and E-NNIs. Connection
routes and identifiers encoded using topology information (e.g., node
identifiers) must also not be conveyed over these boundaries.
9.1.1 Connection establishment
Connection establishment is achieved by sending signaling messages
between the source and destination. If inadequate resources are
encountered in establishing a connection, a negative acknowledgment
shall be returned and allocated resources shall be released. A positive
acknowledgment shall be used to acknowledge successful establishment of
a connection (including confirmation of successful cross-connection).
For connections requested over a UNI, a positive acknowledgment shall
be used to inform both source and destination clients of when they may
start transmitting data.
The transport network signaling shall be able to support both uni-
directional and bi-directional connections. Contention may occur
between two bi-directional connections, or between uni-directional and
bi-directional connections. There shall be at least one attempt and at
a most N attempts at contention resolution before returning a negative
acknowledgment where N is a configurable parameter with devalue value
of 3.
9.1.2 Connection deletion
draft-ietf-ipo-carrier-requirements-00.txt [page 44]
When a connection is no longer required, connectivity to the client
shall be removed and network resources shall be released.
Partially deleted connections are a serious concern. As a result,
signaling network failures shall not result in partially deleted
connections remaining in the network. An end-to-end deletion signaling
message acknowledgment is required to avoid such situations.
Many signaling protocols use a single message pass to delete a
connection. However, in all-optical networks, loss of light will
propagate faster than the deletion message. Thus, downstream cross-
connects will detect loss of light and potentially trigger protection
or restoration. Such behavior is not acceptable.
Instead, connection deletion in all-optical networks shall involve a
signaling message sent in the forward direction that shall take the
connection out of service, de-allocating the resources, but not
removing the cross-connection. Upon receipt of this message, the last
network node must respond by sending a message in the reverse direction
to remove the cross-connect at each node.
Requirement 112. The following requirements are imposed on
signaling:
- Hop-by-hop routing, explicit / source-based routing and hierarchical
routing shall all be supported.
- A negative acknowledgment shall be returned if inadequate resources
are encountered in establishing a connection, and allocated resources
shall be released.
- A positive acknowledgment shall be returned when a connection has
been successfully established.
- For connections requested over a UNI, a positive acknowledgment shall
be used to inform both source and destination clients of when they
may start transmitting data.
- Signaling shall be supported for both uni-directional and bi-
directional connections.
- When contention occurs in establishing bi-directional connections,
there shall be at least one attempt at a most N attempts at
contention resolution before returning a negative acknowledgment
where N is a configurable parameter with devalue value of 3.
- Partially deleted connections shall not remain within the network.
- End-to-end acknowledgments shall be used for connection deletion
requests.
- Connection deletion shall not result in either restoration or
protection being invoked.
- Connection deletion shall at a minimum use a two pass signaling
process, removing the cross-connection only after the first signaling
pass has completed.
draft-ietf-ipo-carrier-requirements-00.txt [page 45]
- Signaling shall not progress through the network with unresolved
label contention left behind.
- Acknowledgements of any requests shall not be sent until all
necessary steps to ensure request fulfillment have been successful.
- Label contention resolution attempts shall not result in infinite
loops.
Signaling for connection protection and restoration is addressed in a
later section.
9.2 Routing Functions
9.2.1 General Description
Routing is an important component of the control plane. It includes
neighbor discovery, reachability information propagation, network
topology information dissemination, service capability discovery. The
objective of neighbor discovery is to provide the information needed to
identify the neighbor relationship and neighbor connectivity over each
link. Neighbor discovery may be realized via manual configuration or
protocol automatic identification, such as link management protocol
(LMP). Neighbor discovery exists between user network to optical
network interface, network node to network node interface, network to
network interface. In optical network, each connection involves two
user endpoints. When user endpoint A requests a connection to user
endpoint B, the optical network needs the reachability information to
select a path for the connection. If a user endpoint is unreachable, a
connection request to that user endpoint shall be rejected. Network
topology information dissemination is to provide each node in the
network with stabilized and consistent information about the carrier
network such that a single node is able to support constrain-based path
selection. Service capability discovery is strongly related to routing
functions. Specific services of optical network require specific
network resource information. Routing functions support service
capabilities.
9.2.2 I-UNI, E-UNI, I-NNI and E-NNI
There are four types of interfaces where the routing information
dissemination may occur: I-UNI, E-UNI, I-NNI and E-NNI. Different types
of interfaces shall impose different requirements and functionality due
to their different trust relationships.
Due to business, geographical, technology, economic considerations, the
global optical network is usually partitioned into several carrier
autonomous systems (AS). Inside each carrier AS, the optical network
may be separate into several routing domains. In each routing domain,
the routing protocol may or may not be the same.
draft-ietf-ipo-carrier-requirements-00.txt [page 46]
While the I-UNI assumes a trust relationship, the user network and the
transport network form a client-server relationship. Therefore, the
benefits of dissemination of routing information from the transport
network to the user network should be studied carefully. Sufficient,
but only necessary information, should be disseminated across the I-
UNI. In E-UNI, neighbor discovery, reachability information and service
capability discovery are allowed to cross the interface, but any
information related to network resources, topology shall not be
exchanged.
Any network topology and network resources information is may be
exchanged across I-NNI. The routing protocol may exchange sufficient
network topology and resource information.
Requirement 113. However, to support scalability requirements, only
the information necessary for optimized path selection shall be
exchanged.
Requirement 114. Over E-NNI only reachability information, next
routing hop and service capability information should be exchanged.
Any other network related information shall not leak out to other
networks. Policy based routing should be applied to disseminate
carrier specific network information.
9.2.3 Requirements for routing information dissemination
Routing protocols must propagate the appropriate information
efficiently to network nodes. A major concern for routing protocol
performance is scalability and stability issues. Scalability requires
that the routing protocol performance shall not largely depend on the
scale of the network (e.g. the number of nodes, the number of links,
end user etc.).
Requirement 115. The routing protocol design shall keep the network
size effect as small as possible.
Different scalability techniques should be considered.
Requirement 116. Routing protocol shall support hierarchical routing
information dissemination, including topology information aggregation
and summarization.
This technique is widely used in conventional networks, such as OSPF
routing for IP networks and PNNI for ATM networks. But the tradeoff
between the number of hierarchies and the degree of network information
accuracy should be considered carefully. Too many aggregations may lose
network topology information.
- Optical transport switches may contain thousands of physical ports.
The detailed link state information for a network element could be
huge.
draft-ietf-ipo-carrier-requirements-00.txt [page 47]
Requirement 117. The routing protocol shall be able to minimize
global information and keep information locally significant as much
as possible.
There is another tradeoff between accuracy of the network
topology information and the routing protocol scalability.
Requirement 118. Routing protocol shall distinguish static routing
information and dynamic routing information.
Static routing information does not change due to connection
operations, such as neighbor relationship, link attributes,
total link bandwidth, etc. On the other hand, dynamic routing
information updates due to connection operations, such as link
bandwidth availability, link multiplexing fragmentation, etc.
The routing protocol operation shall consider the difference of
these two types of routing information.
Requirement 119. Only dynamic routing information needs to be
updated in real time.
Requirement 120. Routing protocol shall be able to control the
dynamic information updating frequency through different types of
thresholds. Two types of thresholds could be defined: absolute
threshold and relative threshold. The dynamic routing information
will not be disseminated if its difference is still inside the
threshold. When an update has not been sent for a specific time (this
time shall be configurable the carrier), an update is automatically
sent. Default time could be 30 minutes.
All these techniques will impact the network resource representation
accuracy. The tradeoff between accuracy of the routing information
and the routing protocol scalability should be well studied. A well-
designed routing protocol should provide the flexibility such that
the network operators are able to adjust the balance according to
their networks' specific characteristics.
9.2.4 Requirements for path selection
The optical network provides connection services to its clients. Path
selection requirements may be determined service parameters. However,
path selection abilities are determined by routing information
dissemination. In this section, we focus on path selection
requirements. Service capabilities, such as service type requirements,
bandwidth requirements, protection requirements, diversity
requirements, bit error rate requirements, latency requirements
including/excluding area requirements, can be satisfied via constraint
based path calculation. Since a specific path selection is done in a
single network element, the specific path selection algorithm and its
interaction with the routing protocol are not discussed in this
draft-ietf-ipo-carrier-requirements-00.txt [page 48]
document. Note that a path consists of a series of links. The
characteristics of a path are those of the weakest link. For example,
if one of the links does not have link protection capability, the whole
path should be declared as having no link-based protection.
Requirement 121. Path selection shall support shortest path as well
as constraint-based routing. Constraint-based path selection shall
consider the whole network performance and provide traffic
engineering capability.
- A carrier would want to operate its network most efficiently, such
as increasing network throughput and decreasing network blocking
probability. The possible solution could be shortest path calculation
or load balancing under congestion conditions.
Requirement 122. Path selection shall be able to include/exclude
some specific locations, based on policy.
Requirement 123. Path selection shall be able to support protection/
restoration capability. Section 10 discusses this subject in more
detail.
Requirement 124. Path selection shall be able to support different
levels of diversity, including diversity routing and protection/
restoration diversity. The simplest form of diversity is link
diversification. More complete notions of diversity can be addressed
by logical attributes such as shared risk link groups (SRLG).
Requirement 125. Path selection algorithms shall provide carriers'
the ability to support a wide range of services and multiple levels
of service classes. Parameters such as service type, transparency,
bandwidth, latency, bit error rate, etc. may be relevant.
The inputs for path selection include connection end addresses, a
set of requested routing constraints, and constraints of the
networks. Some of the network constraints are technology specific,
such as the constraints in all-optical networks addressed in
[John_Angela_IPO_draft]. The requested constraints may include
bandwidth requirement, diversity requirements, path specific
requirements, as well as restoration requirements.
9.3 Automatic Discovery Functions
This section describes the specifications for automatic discovery to
aid distributed connection management (DCM) in the context of
automatically switched transport networks (ASTN/ASON). This section
describes the requirements for the Automatically Switched Transport
Networks (ASTN) as specified in ITU-T Rec.G.807. Auto-discovery is
applicable to the User-to-Network Interface (UNI), Network-Node
Interfaces (NNI) and to the Transport Plane Interfaces (TPI) as shown
in ASTN reference model.
draft-ietf-ipo-carrier-requirements-00.txt [page 49]
Neighbor Discovery can be described as an instance of auto-discovery
that is used for associating two subnet points that form a trail or a
link connection in a particular layer network. The association created
through neighbor discovery is valid so long as the trail or link
connection that forms the association is capable of carrying traffic.
This is referred to as transport plane neighbor discovery. In addition
to transport plane neighbor discovery, auto-discovery can also be used
for distributed subnet controller functions to establish adjacencies.
This is referred to as control plane neighbor discovery.
It is worthwhile to mention that the Sub network points that are
associated as part of neighbor discovery do not have to be contained in
network elements with physically adjacent ports. Thus neighbor
discovery is specific to the layer in which connections are to be made
and consequently is principally useful only when the network has
switching capability at this layer.
Service Discovery can be described as an instance of auto-discovery
that is used for verifying and exchanging service capabilities that are
supported by a particular link connection or trail. It is assumed that
service discovery would take place after two Sub Network Points within
the layer network are associated through neighbor discovery. However,
since service capabilities of a link connection or trail can
dynamically change, service discovery can take place at any time after
neighbor discovery and any number of times as may be deemed necessary.
Resource discovery can be described as an instance of auto-discovery
that is used for verifying the physical connectivity between two ports
on adjacent network elements in the network. Resource discovery is
also concerned with the ability to improve inventory management of
network resources, detect configuration mismatches between adjacent
ports, associating port characteristics of adjacent network elements,
etc.
Automatic discovery runs over UNI, NNI and TPI interfaces[reference to
g.disc].
9.3.1 Neighbor discovery
This section provides the requirements for the automatic neighbor for
the UNI and NNI and Physical Interface (PI). This requirement does not
preclude specific manual configurations that may be required and in
particular does not specify any mechanism that may be used for
optimizing network management.
Neighbor discovery is primarily concerned with automated discovery of
port connectivity between network elements that form the transport
plane and also involves the operations of connectivity verification,
and bootstrapping of channels in the control plane for carrying
discovery information between elements in the transport plane. This
applies to discovery of port connectivity across a UNI between the
elements in the user network and the transport plane. The information
draft-ietf-ipo-carrier-requirements-00.txt [page 50]
that is learnt is subject to various policy restrictions between
administrative domains.
Given that Automatic Neighbor Discovery (AND) is applicable across the
whole network, it is important that AND supports protocol independence,
and should be specified to allow ease of mapping into multiple protocol
specifications. The actual implementation of AND depends on the
protocols that are used for the purpose of automatic neighbor
discovery.
As mentioned earlier, AND runs over both UNI and NNI type interfaces in
the control plane. Given that port connectivity discovery and
connectivity verification (e.g., fiber connectivity verification) are
to be performed at the transport plane, PI interfaces (IrDI and IaDI)
are also considered as AND interfaces. Further information is
available in Draft ITU-T G.ndisc.
Although the minimal set of parameters for discovery includes the SP
and User NE names, there are several policy restrictions that are
considered while exchanging these names across untrusted boundaries.
Several security requirements on the information exchanged needs to be
considered. In addition to these, there are other security/reliability
requirements on the actual control plane communications channels.
These requirements are out of scope of this document. Draft ITU-T Rec.
G.dcn discusses these requirements in much detail.
9.3.2 Resource Discovery
Resource discovery happens between neighbors. A mechanism designed for
a technology domain can be applied to any pair of NEs interconnected
through interfaces of the same technology. However, because resource
discovery means certain information disclosure between two business
domains, it is under the service providers' security and policy
control. In certain network scenario, a service provider who owns the
transport network may not be willing to disclose any internal
addressing scheme to its client. So a client NE may not have the
neighbor NE address and port ID in its NE level resource table.
Interface ports and their characteristics define the network element
resources. Each network can store its resources in a local table that
could include switching granularity supported by the network element,
ability to support concatenated services, range of bandwidths supported
by adaptation, physical attributes signal format, transmission bit
rate, optics type, multiplexing structure, wavelength, and the
direction of the flow of information. Resource discovery can be
achieved through either manual provisioning or automated procedures.
The procedures are generic while the specific mechanisms and control
information can be technology dependent.
Resource discovery can be achieved in several methods. One of the
methods is the self-resource discovery by which the NE populates its
draft-ietf-ipo-carrier-requirements-00.txt [page 51]
resource table with the physical attributes and resources. Neighbor
discovery is another method by which NE discovers the adjacencies in
the transport plane and their port association and populates the
neighbor NE. After neighbor discovery resource verification and
monitoring must be performed to verify physical attributes to ensure
compatibility. Resource monitoring must be performed periodically since
neighbor discovery and port association are repeated periodically.
Further information can be found in [GMPLS-ARCH].
10. Requirements for service and control plane resiliency
There is a range of failures that can occur within a network, including
node failures (e.g. office outages, natural disasters), link failures
(e.g. fiber cuts, failures arising from diverse circuits traversing
shared facilities (e.g. conduit cuts)) and channel failures (e.g. laser
failures).
Failures may be divided into those affecting the data plane and the
control plane .
Requirement 126. The ASON architecture and associated protocols
shall include redundancy/protection options such that any single
failure event shall not impact the data plane or the control plane.
10.1 Service resiliency
Rapid protection/restoration from data plane failures is a crucial
aspect of current and future transport networks. Rapid recovery is
required by transport network providers to protect service and also to
support stringent Service Level Agreements (SLAs) that dictate high
reliability and availability for customer connectivity.
The choice of a protection/restoration policy is a tradeoff between
network resource utilization (cost) and service interruption time.
Clearly, minimized service interruption time is desirable, but schemes
achieving this usually do so at the expense of network resource
utilization, resulting in increased cost to the provider. Different
protection/restoration schemes operate with different tradeoffs between
spare capacity requirements and service interruption time.
In light of these tradeoffs, transport providers are expected to
support a range of different service offerings, with a strong
differentiating factor between these service offerings being service
interruption time in the event of network failures. For example, a
provider's highest offered service level would generally ensure the
most rapid recovery from network failures. However, such schemes (e.g.,
1+1, 1:1 protection) generally use a large amount of spare restoration
capacity, and are thus not cost effective for most customer
applications. Significant reductions in spare capacity can be achieved
by instead sharing this capacity across multiple independent failures.
draft-ietf-ipo-carrier-requirements-00.txt [page 52]
Clients will have different requirements for connection availability.
These requirements can be expressed in terms of the "service level",
which describes restoration/protection options and priority related
connection characteristics, such as holding priority(e.g. pre-emptable
or not), set-up priority, or restoration priority. Therefore, mapping
of individual service levels to a specific set of
protection/restoration options and connection priorities will be
determined by individual carriers.
Requirement 127. In order for the network to support multiple grades
of service, the control plane must identify, assign, and track
multiple protection and restoration options.
For the purposes of this discussion, the following
protection/restoration definitions have been provided:
Reactive Protection: This is a function performed by either equipment
management functions and/or the transport plane (i.e. depending on if
it is equipment protection or facility protection and so on) in
response to failures or degraded conditions. Thus if the control plane
and/or management plane is disabled, the reactive protection function
can still be performed. Reactive protection requires that protecting
resources be configured and reserved (i.e. they cannot be used for
other services). The time to exercise the protection is technology
specific and designed to protect from service interruption.
Proactive Protection: In this form of protection, protection events are
initiated in response to planned engineering works (often from a
centralized operations center). Protection events may be triggered
manually via operator request or based on a schedule supported by a
soft scheduling function. This soft scheduling function may be
performed by either the management plane or the control plane but could
also be part of the equipment management functions. If the control
plane and/or management plane is disabled and this is where the soft
scheduling function is performed, the proactive protection function
cannot be performed. [Note that In the case of a hierarchical model of
subnetworks, some protection may remain available in the case of
partial failure (i.e. failure of a single subnetwork control plane or
management plane controller) relates to all those entities below the
failed subnetwork controller, but not its parents or peers.] Proactive
protection requires that protecting resources be configured and
reserved (i.e. they cannot be used for other services) prior to the
protection exercise. The time to exercise the protection is technology
specific and designed to protect from service interruption.
Reactive Restoration: This is a function performed by either the
management plane or the control plane. Thus if the control plane and/or
management plane is disabled, the restoration function cannot be
performed. [Note that in the case of a hierarchical model of
subnetworks, some restoration may remain available in the case of
partial failure (i.e. failure of a single subnetwork control plane or
draft-ietf-ipo-carrier-requirements-00.txt [page 53]
management plane controller) relates to all those entities below the
failed subnetwork controller, but not its parents or peers.]
Restoration capacity may be shared among multiple demands. A
restoration path is created after detecting the failure. Path
selection could be done either off-line or on-line. The path selection
algorithms may also be executed in real-time or non-real time depending
upon their computational complexity, implementation, and specific
network context.
. Off-line computation may be facilitated by simulation and/or network
planning tools. Off-line computation can help provide guidance to
subsequent real-time computations.
. On-line computation may be done whenever a connection request is
received.
Off-line and on-line path selection may be used together to make
network operation more efficient. Operators could use on-line
computation to handle a subset of path selection decisions and use off-
line computation for complicated traffic engineering and policy related
issues such as demand planning, service scheduling, cost modeling and
global optimization.
Proactive Restoration: This is a function performed by either the
management plane or the control plane. Thus if the control plane and/or
management plane is disabled, the restoration function cannot be
performed. [Note that in the case of a hierarchical model of
subnetworks, some restoration may remain available in the case of
partial failure (i.e. failure of a single subnetwork control plane or
management plane controller) relates to all those entities below the
failed subnetwork controller, but not its parents or peers.]
Restoration capacity may be shared among multiple demands. Part or all
of the restoration path is created before detecting the failure
depending on algorithms used, types of restoration options supported
(e.g. shared restoration/connection pool, dedicated restoration pool),
whether the end-end call is protected or just UNI part or NNI part,
available resources, and so on. In the event restoration path is fully
pre-allocated, a protection switch must occur upon failure similarly to
the reactive protection switch. The main difference between the
options in this case is that the switch occurs through actions of the
control plane rather than the transport plane Path selection could be
done either off-line or on-line. The path selection algorithms may also
be executed in real-time or non-real time depending upon their
computational complexity, implementation, and specific network context.
. Off-line computation may be facilitated by simulation and/or network
planning tools. Off-line computation can help provide guidance to
subsequent real-time computations.
. On-line computation may be done whenever a connection request is
received.
draft-ietf-ipo-carrier-requirements-00.txt [page 54]
Off-line and on-line path selection may be used together to make
network operation more efficient. Operators could use on-line
computation to handle a subset of path selection decisions and use off-
line computation for complicated traffic engineering and policy related
issues such as demand planning, service scheduling, cost modeling and
global optimization.
Multiple protection/restoration options are required in the network to
support the range of offered services. NNI protection/restoration
schemes operate between two adjacent nodes, with NNI
protection/restoration involving switching to a protection/restoration
connection when a failure occurs. UNI protection schemes operate
between the edge device and a switch node (i.e. at the access or drop),
End-End Path protection/restoration schemes operate between access
points (i.e. connections are protected/restored across all NNI and UNI
interfaces supporting the call).
In general, the following protection schemes should be considered for
all protection cases within the network:
. Dedicated protection (e.g., 1+1, 1:1)
. Shared protection (e.g., 1:N, M:N). This allows the network to ensure
high quality service for customers, while still managing its physical
resources efficiently.
. Unprotected
In general, the following restoration schemes should be considered for
all restoration cases within the network:
Dedicated restoration capacity
Shared restoration capacity. This allows the network to ensure high
quality of service for customers, while still managing its physical
resources efficiently.
. Un-restorable
To support the protection/restoration options:
Requirement 128. The control plane shall support multiple options
for access (UNI), span (NNI), and end-to-end Path
protection/restoration.
Requirement 129. The control plane shall support configurable
protection/restoration options via software commands (as opposed to
needing hardware reconfigurations) to change the
protection/restoration mode.
Requirement 130. The control plane shall support mechanisms to
establish primary and protection paths.
Requirement 131. The control plane shall support mechanisms to
modify protection assignments, subject to service protection
constraints.
Requirement 132. The control plane shall support methods for fault
notification to the nodes responsible for triggering restoration /
draft-ietf-ipo-carrier-requirements-00.txt [page 55]
protection (note that the transport plane is designed to provide the
needed information between termination points. This information is
expected to be utilized as appropriate.)
Requirement 133. The control plane shall support mechanisms for
signaling rapid re-establishment of connection connectivity after
failure.
Requirement 134. The control plane shall support mechanisms for
reserving restoration bandwidth.
Requirement 135. The control plane shall support mechanisms for
normalizing connection routing after failure repair.
Requirement 136. The signaling control plane should implement
signaling message priorities to ensure that restoration messages
receive preferential treatment, resulting in faster restoration.
Requirement 137. Normal connection operations (e.g., connection
deletion) shall not result in protection/restoration being initiated.
Requirement 138. Restoration shall not result in miss-connections
(connections established to a destination other than that intended),
even for short periods of time (e.g., during contention resolution).
For example, signaling messages, used to restore connectivity after
failure, should not be forwarded by a node before contention has been
resolved.
Requirement 139. In the event of there being insufficient bandwidth
available to restore all connections, restoration priorities / pre-
emption should be used to determine which connections should be
allocated the available capacity.
The amount of restoration capacity reserved on the restoration paths
determines the robustness of the restoration scheme to failures. For
example, a network operator may choose to reserve sufficient capacity
to ensure that all shared restorable connections can be recovered in
the event of any single failure event (e.g., a conduit being cut). A
network operator may instead reserve more or less capacity than that
required to handle any single failure event, or may alternatively
choose to reserve only a fixed pool independent of the number of
connections requiring this capacity (i.e., not reserve capacity for
each individual connection).
10.2 Control plane resiliency
Requirement 140. The optical control plane network shall support
protection and restoration options to enable it to be robust to
failures.
Requirement 141. The control plane shall support the necessary
options to ensure that no service-affecting module of the control
plane (software modules or control plane communications) is a single
point of failure.
draft-ietf-ipo-carrier-requirements-00.txt [page 56]
Requirement 142. The control plane should support options to enable
it to be self-healing.
Requirement 143. The control plane shall provide reliable transfer
of signaling messages and flow control mechanisms for restricting the
transmission of signaling packets where appropriate.
The control plane may be affected by failures in signaling network
connectivity and by software failures (e.g., signaling, topology and
resource discovery modules).
Requirement 144. Control plane failures shall not cause failure of
established data plane connections.
Fast detection and recovery from failures in the control plane are
important to allow normal network operation to continue in the event of
signaling channel failures.
Requirement 145. Control network failure detection mechanisms shall
distinguish between control channel and software process failures.
Different recovery techniques are initiated for the different failures.
When there are multiple channels (optical fibers or multiple
wavelengths) between network elements and / or client devices, failure
of the control channel will have a much bigger impact on the service
availability than in the single case. It is therefore recommended to
support a certain level of protection of the control channel. Control
channel failures may be recovered by either using dedicated protection
of control channels, or by re-routing control traffic within the
control plane (e.g., using the self-healing properties of IP). To
achieve this requires rapid failure detection and recovery mechanisms.
For dedicated control channel protection, signaling traffic may be
switched onto a backup control channel between the same adjacent pairs
of nodes. Such mechanisms protect against control channel failure, but
not against node failure.
Requirement 146. If a dedicated backup control channel is not
available between adjacent nodes, or if a node failure has occurred,
then signaling messages should be re-routed around the failed link /
node.
Requirement 147. Fault localization techniques for the isolation of
failed control resources shall be supported.
Recovery from signaling process failures can be achieved by switching
to a standby module, or by re-launching the failed signaling module.
draft-ietf-ipo-carrier-requirements-00.txt [page 57]
Requirement 148. Recovery from software failures shall result in
complete recovery of network state.
Control channel failures may occur during connection establishment,
modification or deletion. If this occurs, then the control channel
failure must not result in partially established connections being left
dangling within the network. Connections affected by a control channel
failure during the establishment process must be removed from the
network, re-routed (cranked back) or continued once the failure has
been resolved. In the case of connection deletion requests affected by
control channel failures, the connection deletion process must be
completed once the signaling network connectivity is recovered.
Requirement 149. Connections shall not be left partially established
as a result of a control plane failure.
Requirement 150. Connections affected by a control channel failure
during the establishment process must be removed from the network,
re-routed (cranked back) or continued once the failure has been
resolved.
Requirement 151. Partial connection creations and deletions must be
completed once the control plane connectivity is recovered.
11. Security concerns and requirements
In this section, security concerns and requirements of optical
connections are described.
11.1 Data Plane Security and Control Plane Security
In terms of security, an optical connection consists of two aspects.
One is security of the data plane where an optical connection itself
belongs, and the other is security of the control plane by which an
optical connection is controlled.
11.1.1 Data Plane Security
Requirement 152. Misconnection shall be avoided in order to keep
user's data confidential.
Requirement 153. For enhancing integrity and confidentiality of
data, it may be helpful to support scrambling of data at layer 2 or
encryption of data at a higher layer.
11.1.2 Control Plane Security
It is desirable to decouple the control plane from the data plane
physically.
Additional security mechanisms should be provided to guard against
intrusions on the signaling network.
draft-ietf-ipo-carrier-requirements-00.txt [page 58]
Requirement 154. Network information shall not be advertised across
exterior interfaces (E-UNI or E-NNI). The advertisement of network
information across the E-NNI shall be controlled and limited in a
configurable policy based fashion. The advertisement of network
information shall be isolated and managed separately by each
administration.
Requirement 155. Identification, authentication and access control
shall be rigorously used for providing access to the control plane.
Requirement 156. UNI shall support ongoing identification and
authentication of the UNI-C entity (i.e., each user request shall be
authenticated.
Editor's Note: The control plane shall have an audit trail and log with
timestamp recording access.
11.2 Service Access Control
>From a security perspective, network resources should be protected from
unauthorized accesses and should not be used by unauthorized entities.
Service Access Control is the mechanism that limits and controls
entities trying to access network resources. Especially on the public
UNI, Connection Admission Control (CAC) should be implemented and
support the following features:
Requirement 157. CAC should be applied to any entity that tries to
access network resources through the public UNI. CAC should include
an authentication function of an entity in order to prevent
masquerade (spoofing). Masquerade is fraudulent use of network
resources by pretending to be a different entity. An authenticated
entity should be given a service access level in a configurable
policy basis.
Requirement 158. Each entity should be authorized to use network
resources according to the service level given.
Requirement 159. With help of CAC, usage based billing should be
realized. CAC and usage based billing should be enough stringent to
avoid any repudiation. Repudiation means that an entity involved in a
communication exchange subsequently denies the fact.
11.3 Optical Network Security Concerns
Since optical service is directly related to the layer 1 network that
is fundamental for telecom infrastructure, stringent security assurance
mechanism should be implemented in optical networks. When designing
equipment, protocols, NMS, and OSS that participate in optical service,
every security aspect should be considered carefully in order to avoid
any security holes that potentially cause dangers to an entire network,
such as DoS attack, unauthorized access and etc.
Acknowledgements
The authors of this document would like to acknowledge the valuable
inputs from Yangguang Xu, Deborah Brunhard, Daniel Awduche, Jim
Luciani, Mark Jones and Gerry Ash.
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[G.807] ITU-T Recommendation G.807 (2001), "Requirements for the
Automatic Switched Transport Network (ASTN)".
[G.dcm] ITU-T New Recommendation G.dcm, "Distributed Connection
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[G.ason] ITU-T New recommendation G.ason, "Architecture for the
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draft-wlai-tewg-measure-01.txt, IETF, May, 2001.
[ccamp-g.709] A. Bellato, "G. 709 Optical Transport Networks GMPLS
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[onni-frame] D. Papadimitriou, "Optical Network-to-Network Interface
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Author's Addresses
Yong Xue
UUNET/WorldCom
22001 Loudoun County Parkway
Ashburn, VA 20147
Phone: +1 (703) 886-5358
Email: yxue@uu.net
John Strand
AT&T Labs
100 Schulz Dr.,
Rm 4-212 Red Bank,
NJ 07701, USA
Phone: +1 (732) 345-3255
Email: jls@att.com
Monica Lazer
AT&T
900 ROUTE 202/206N PO BX 752
BEDMINSTER, NJ 07921-0000
mlazer@att.com
draft-ietf-ipo-carrier-requirements-00.txt [page 62]
Jennifer Yates,
AT&T Labs
180 PARK AVE, P.O. BOX 971
FLORHAM PARK, NJ 07932-0000
jyates@research.att.com
Dongmei Wang
AT&T Labs
Room B180, Building 103
180 Park Avenue
Florham Park, NJ 07932
mei@research.att.com
Ananth Nagarajan
Wesam Alanqar
Lynn Neir
Tammy Ferris
Sprint
9300 Metcalf Ave
Overland Park, KS 66212, USA
ananth.nagarajan@mail.sprint.com
wesam.alanqar@mail.sprint.com
lynn.neir@mail.sprint.com
tammy.ferris@mail.sprint.com
Hirokazu Ishimatsu
Japan Telecom Co., LTD
2-9-1 Hatchobori, Chuo-ku,
Tokyo 104-0032 Japan
Phone: +81 3 5540 8493
Fax: +81 3 5540 8485
EMail: hirokazu@japan-telecom.co.jp
Olga Aparicio
Cable & Wireless Global
11700 Plaza America Drive
Reston, VA 20191
Phone: 703-292-2022
Email: olga.aparicio@cwusa.com
Steven Wright
Science & Technology
BellSouth Telecommunications
41G70 BSC
675 West Peachtree St. NE.
Atlanta, GA 30375
Phone +1 (404) 332-2194
Email: steven.wright@snt.bellsouth.com
draft-ietf-ipo-carrier-requirements-00.txt [page 63]
