Network Working Group O. Gonzalez de Dios, Ed.
Internet-Draft Telefonica GCTO
Intended status: Informational J. Meuric, Ed.
Expires: August 18, 2014 Orange
D. Ceccarelli
Ericsson
February 14, 2014
Terminology and Models for Control of Traffic Engineered Networks with
Provider-Customer Relationship
draft-dios-ccamp-control-models-customer-provider-00
Abstract
Different kinds of relationships can be established among
interconnected Traffic Engineered Networks. In particular, this
document focuses on the case where there is a customer-provider
relation between the network domains. The domain interconnection is
a policy and administrative boundary. This informational document
collects current terminology and provides a taxonomy for the posible
control plane based operation models.
Each control model defines, on the one hand, the level of information
that the domain acting as customer receives by control plane means
from the domain acting as provider and, on the other hand, the
control model will determine what can be requested from the customer
domain to the provider domain.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 18, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Examples of Customer-Provider TE Network Domain Scenarios 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Customer Domain - Provider Domain Interface . . . . . . . 4
2.1.1. UNI in IP over Optical Networks . . . . . . . . . . . 4
2.1.2. ITU-T Definition of UNI . . . . . . . . . . . . . . . 4
2.1.3. OIF Definition of UNI . . . . . . . . . . . . . . . . 5
2.1.4. Proposed Vocabulary . . . . . . . . . . . . . . . . . 5
2.2. Reachability . . . . . . . . . . . . . . . . . . . . . . 6
2.2.1. Unqualified Reachability . . . . . . . . . . . . . . 6
2.2.2. Qualified Reachability . . . . . . . . . . . . . . . 6
2.2.3. Qualified Reachability with associated potential TE
path . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Control Models . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Signaling Only . . . . . . . . . . . . . . . . . . . . . 7
3.1.1. Signaling with Requirements . . . . . . . . . . . . . 8
3.1.2. Signaling with Collection . . . . . . . . . . . . . . 8
3.2. Signaling and Reachability Model . . . . . . . . . . . . 8
3.2.1. Signalling + Basic Reachability . . . . . . . . . . . 9
3.2.2. Signalling + Qualified Reachability . . . . . . . . . 9
3.2.3. Signalling + Qualified Reachability + Potential
Services . . . . . . . . . . . . . . . . . . . . . . 9
3.3. Other Models . . . . . . . . . . . . . . . . . . . . . . 9
3.3.1. Multi-Layer Networks / Multi-Region Networks . . . . 9
3.3.2. Management Model . . . . . . . . . . . . . . . . . . 10
4. Security Considerations . . . . . . . . . . . . . . . . . . . 10
5. Contributing Authors . . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . 10
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Traffic Engineered Networks can be interconnected, establishing
different types of relationships among them. For example, both
network can have a peering relation, where connections starting in
one domain and end in the other domain. This document is focused on
the case where the interconnected network domains have a customer-
provider relationship among them. Such customer-provider relation
comes from the two main points. On the one hand, end-to-end services
in the customer network can be set up using services of a network
acting as provider. On the other hand, the customer-provider
relation comes from the fact that their interconnection is a policy
and administrative boundary, limiting the amount of information
allowed to be exchanged between networks. In the case of
interconnected TE domains where there is no administrative nor strict
policy boundary between customer and provider (typically, just a
technolgy change), the MLN/MRN model can be applied.
The interface between the customer and the provider domain is
typically called "User-to-Network Interface" (UNI), and regarded as
signaling-only [RFC4208]. Due to the strict asociation of
functionality to the UNI term, its exact scope has become highly
controversial. This document compiles different definitions of the
term used so far and propose some terminology to serve as a
foundation to move the work forward.
What is more, the document compiles the possible operation models of
customer-provider network from the control plane perspective. Each
control model defines, on the one hand, the level of information of
the domain acting as customer provides through the control plane to
the domain acting as provider. On the other hand, the control model
will determine what can be requested from the customer domain to the
provider domain.
1.1. Examples of Customer-Provider TE Network Domain Scenarios
The most typical example of interconnected TE domains that follow a
customer-provider relation is an IP/MPLS domain using the services of
an optical OTN/WDM network. Note that the interconnected domain can
be part of the same organization, but with different administration.
A particular network scenario that has attracted lot of attention
from the industry is the IP/MPLS/OTN/WDM over WDM. The customer
network is based on multi-layer routers able to set up packet-based
TE connections over wavelengths. The provider network is a WDM
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optical network that provides the switching for the wavelenghts as
well as restoration capabilities of the optical channels.
Another example is MPLS over MPLS, where both customer and provider
networks are able to set up packet based TE connections. This is the
case, for example, of carrier-over-carrier scenarios.
Summing up, there number of applicable scenarios is wide.
2. Terminology
2.1. Customer Domain - Provider Domain Interface
The interface between the customer and the provider domain is
typically called "User-to-Network Interface" (UNI). However, the
term "UNI" has been used in different contexts and SDOs. As a
consequence, the exact definition of UNI and the functionalities
included depend on the application. Bellow, as a reference, it is
shown a set of the different definitions of UNI.
2.1.1. UNI in IP over Optical Networks
[RFC3717] says: "The client-optical internetwork interface (UNI)
represents a service boundary between the client (e.g., IP router)
and the optical network. The client and server (optical network) are
essentially two different roles: the client role requests a service
connection from a server; the server role establishes the connection
to fulfill the service request -- provided all relevant admission
control conditions are satisfied."
In other words, this definition refers to a signaling protocol
between two administrative domains with a customer-provider
relationship. It is agnostic to the existence of a data plane
client-server relationship and to the side(s) of the boundary where
it may happen, if any.
2.1.2. ITU-T Definition of UNI
ITU-T has defined the term UNI in the context of control plane.
[G.807] [G.8081] (ITU-T): "User-Network Interface for the control
plane (UNI): A bidirectional signaling interface between service
requester and service provider control plane entities."
The terms "requester/provider" are used to refer to the relationship.
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2.1.3. OIF Definition of UNI
UNI: "The service control interface between a client device and the
transport network."
UNI-C: "The logical entity that terminates UNI signalling on the
client device side."
UNI-N: "The logical entity that terminates UNI signalling on the
transport network side."
The terms "client/transport" and "client/network" are used to refer
to the relationship.
2.1.4. Proposed Vocabulary
As listed above, the existing terminology is far from unique. To
avoid overloaded concepts, this document proposes to use the
"customer/provider" terms.
Unless stated, this document focuses on control protocol exchanges
and their uses across administrative boundaries for customer-provider
interconnection. Data plane transition and/or client-server
relationship may not be aligned with the boundary.
2.1.4.1. Customer network
A Customer network is defined as a network domain able to request a
connectivity service to a provider network domain across an
administrative boundary.
2.1.4.2. Provider network
A Provider network is defined as a network domain able to deliver
connectivity services to a customer network domain across an
administrative boundary.
2.1.4.3. Customer-Provider Control Plane Interface
The control plane interface between the customer network domain and
the provider network domain convey a set of control functionalities
that help to operate such kind of networks. The exact
functionalities of this Interface (and then the level of information
exchanged) depend on the chosen control model. This document
presents a taxonomy with the possible control models.
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2.2. Reachability
In graph theory, reachability refers to the ability to get from one
vertex to another within a graph. Thus, a vertex can reach another
vertex if there exists a sequence of adjacent vertices which starts
with the source vertex and ends with the destination vertex.
The document [draft-farrel-interconnected-te-info-exchange-02]
provides the definition of what is reachability for client-server
networks. [EDITOR's note: Text from draft-farrel-interconnected-te-
info-exchange has been borrowed for this first version. Duplicated
text will be deleted at later stages]
In an IP network, reachability is the ability to deliver a packet to
a specific address or prefix. That is, the existence of an IP path
to that address or prefix. TE reachability is the ability to reach a
specific address along a TE path.
In the context of Traffic Engineered networks with customer and
provider relationships, we can define several types of reachabiity:
[draft-farrel-interconnected-te-info-exchange-02]
2.2.1. Unqualified Reachability
Two customer domain nodes are said to be reachable if, either there
exists at least one path through the customer domain that connects
both nodes, or, in the case that there is no path exclusively through
the customer domain network, there exists al least one path
connecting nodes of customer and provider domain by which both
customer nodes can be connected.
In the case of basic reachability, it is only known that it is
possible to connect the nodes, but there is no notion of the details
of such possible connections, such as, for example, bandwidth
available or performance metrics. Also, the exact path to connect
both nodes is not known to the client network. Note that, even if
two nodes are reachable, there may not be enough resources for a
desired TE connection with specific TE constraints.
2.2.2. Qualified Reachability
In this case, on top of the basic reachability, it is known some TE
attributes of the possible connection (or connections). Examples of
such attributes are: TE metrics, hop count, available bandwidth,
delay, SRLG list. Note that this information is specific per
connection. Thus, if there are several posible TE paths, there are a
set of attributes.
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2.2.3. Qualified Reachability with associated potential TE path
In this particular case, on top of the qualified reachability, there
exists an associated potential TE path that satisfies the TE
connection between two client nodes. Thus, in this case, the
customer Network has the information that there exists a TE path that
can be set up at any time.
3. Control Models
The control of the networks formed by interconnected domains with a
customer-provider relations between them can be done following
different models. Each control model defines, on the one hand, the
level of information that the domain acting as customer recieves by
control plane means about the services given by the domain acting as
provider. This information, for example, can vary from a complete
lack of information, so the customer domain only knows that it could
be possible to reach another point of its domain via the provider
network, to a detailed view on the possibilities offered by the
provider network. The level of detail of this information will
determine which information is exchanged between both networks. On
the other hand, the control model will determine what can be
requested from the customer domain to the provider domain. As an
example, the most basic use is spcecifying just the end-points to
connect. Other cases may include the possibility to request a
service specifying a set of constraints, like bandwidth, diversity,
an optimization criteria, etc.
Which control model to choose depends on several factors. For the
network operators, the main concern will be related to the level of
trustness and relationship between customer and provider domains.
Also, one key factor to take into account is the protocol
interoperability. Note that, equipment in the interconnected domains
may be from different technologies (but not necessarily) and are
likely to use different implementations. The higher the level of
functionality included in the control plane, the higher the protocol
interoperability requirements, as it will force all implementations
to support many functionality. Finally, scalability, that is, the
ability of the control plane to provide the same functionality
regarding the number of equipment, needs to be taken into account:
the amount of information in each option will have different limits
in terms on number of interconnected nodes.
3.1. Signaling Only
This first model considers that the sole functionality allowed in the
control plane is signaling, that is the ability to request services
from customer to provider domain.
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In this model, the control plane does not provide a priori hints to
the customer domain about the state of the provider domain (e.g.,
resource availability). This model does not preclude that, by other
means like the management plane, the customer domain know what is
possible or not. Such management actions are out of the scope of the
control plane. Thus, it perfectly feasible that the reachability
information is provided either statically or by some management
platform.
The most basic case relies on sending a loose ERO from the customer,
specifying the edges of the connection.
In a trusted interconnection mode, the signalling allows the customer
domain to provide a full ERO, given to client network by external
tools.
3.1.1. Signaling with Requirements
The control plane may allow to express complex requests to the
provider domain. That is, through the signaling protocol, it is
allowed to not only request a connection between two points of the
customer domain, but also to include some constraints: e.g., minimum
bandwidth, maximum delay, optimization criteria, or request diversity
from another service. The policy at the edged of the provider
network will determine which constraints are accepted. Note the many
of the requirements that can be expressed in the request are similar
to what would be asked to a path computation function.
3.1.2. Signaling with Collection
Even though the only protocol enabled is signaling, it may be
beneficial for the customer domain to be able to know some updated
information of the services that it has requested to the provider.
Thus, this case considers the possibility that, through the signaling
protocol, the customer domain can receive some information. What
information it is allowed to collect will be determined by the policy
of the provider domain.
3.2. Signaling and Reachability Model
This second model considers that, in addition to signaling, the
customer domain receives some reachability information through a
control plane mechanism.
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3.2.1. Signalling + Basic Reachability
In this particular case, through control plane mechanisms, the
customer domain knows whether it is possible to reach a remote end
point. The customer domain should also remain aware of this
information if there are failures in the provider domain or if the
associated capacity has been filled.
3.2.2. Signalling + Qualified Reachability
The control plane will provide information not only about the
possibility to reach a remote end point, but also some TE information
of possible connections. For example, the customer domain will know
that it is possible to reach another point with some bandwidth or
delay. Note that, in this case, such information is sent by control
plane mechanisms (not statically configured by managament plane).
3.2.3. Signalling + Qualified Reachability + Potential Services
In addition to the TE information of the possible connections between
two points, the control plane will also provide to the customer
domain information about potential provider's services which could
satisfy given requirements. By control plane procedures, the
customer domain can request, with respect to its needs, a service
using such potential service and make high level path selection
within the provider domain.
3.3. Other Models
3.3.1. Multi-Layer Networks / Multi-Region Networks
MLN/MRN extensions to control protocols have been defined. They are
well scoped for client and server data plane domains without
administrative boundary between them. This allows MLN nodes to
participate in common control protocol instances. There is a full
set of mechanisms to operate such networks [Editor's note: add refs
to MLN/MRN)]. Typical use cases are switches combining both low- and
high-order Sonet/SDH, or both ODUk and wavelengths.
However, MLN/MRN assumes no policy boundary between customer and
provider domains. Thus, the level of information exchanged is not
restricted, and full interoperability of both the signaling and
routing protocols is required.
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3.3.2. Management Model
In this particular case, the role of the control plane is limited to
operate independently in each of the domains. [Editor's note: Common
Control... WG => do we leave it?]
4. Security Considerations
TBD
5. Contributing Authors
6. Acknowledgments
The authors would like to thank Lou Berger for pointing out the
direction of the document and Dieter Beler for his review. The
authors would like to specially thank all the authors of draft-
farrel-interconnected-te-info-exchange-02
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in
BGP-4", RFC 3107, May 2001.
[RFC3717] Rajagopalan, B., Luciani, J., and D. Awduche, "IP over
Optical Networks: A Framework", RFC 3717, March 2004.
[RFC4208] Swallow, G., Drake, J., Ishimatsu, H., and Y. Rekhter,
"Generalized Multiprotocol Label Switching (GMPLS) User-
Network Interface (UNI): Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Support for the Overlay
Model", RFC 4208, October 2005.
7.2. Informative References
[draft-farrel-interconnected-te-info-exchange-02]
"Farrel, A., Drake, J., Bitar, N., Swallow, G.,
Ceccarelli, D. draft-farrel-interconnected-te-info-
exchange-02 Problem Statement and Architecture for
Information Exchange Between Interconnected Traffic
Engineered Networks", 2014.
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Authors' Addresses
Oscar Gonzalez de Dios (editor)
Telefonica GCTO
Don Ramon de la Cruz 82-84
Madrid 28045
Spain
Phone: +34913128832
Email: ogondio@tid.es
Julien Meuric (editor)
Orange
2 avenue Pierre Marzin
Lannion 22300
France
Email: julien.meuric@orange.com
Daniele Ceccarelli
Ericsson
Via Calda 5
Genova
Italy
Phone: +39 010 600 2512
Email: daniele.ceccarelli@ericsson.com
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