Network Working Group G. Bernstein
Internet Draft Grotto-Networking
Expiration Date: August 2003 B. Rajagopalan
Document: draft-ietf-ipo-optical-inter-domain-02.txt D. Pendarakis
Tellium
Angela Chiu
John Strand
AT&T
V. Sharma
Metanoia
Dean Cheng
Polaris
Rauf Izmailov
NEC
Lyndon Ong
Ciena
Sudheer Dharanikota
Frank Hujber
February 2003
Optical Inter Domain Routing Considerations
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 [1].
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Abstract
This draft investigates the requirements for general inter-domain
and inter-area routing in optical networks and reviews the
applicability of existing route protocols in various optical routing
applications.
Table of Contents:
1 Introduction 2
1.1 Specification of Requirements 3
1.2 Abbreviations 3
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2 Background 3
2.1 Basic Concept of Domains and Network Partitioning 3
2.2 Major Differences between Optical and IP datagram Routing
6
2.3 Differences between MPLS and Optical Circuit routing 7
2.4 Diversity in Optical Routing 7
2.4.1 Generalizing Link Diversity 9
2.4.2 Generalizing Node Diversity 9
2.5 Routing Information Categorization 10
2.5.1 Link and Topology Related Information 10
2.5.2 Domain and Node Related Information 11
3 Applications of Inter Domain Optical Routing 12
3.1 Intra Carrier Applications of Optical Inter Domain Routing
12
3.1.1 Intra-Carrier Scalability 12
3.1.2 Intra-Carrier Inter-vendor 13
3.1.3 Inter-Layer Partitioning 16
3.1.4 Interaction with IP Layer Routing 17
3.1.5 Inter-Business Unit 18
3.2 Inter-Carrier Inter-Domain Optical Routing 19
3.3 Multi-Domain Connection Control 21
4 Multiple Layers of Optical Routing 22
5 Conclusion 24
6 Security Considerations 24
6.1.1 24
7 References 25
8 Acknowledgments 26
9 Author's Addresses 26
NOTE: This draft has been updated with more current author contact
information and references, but is otherwise unchanged from the
previous version.
1 Introduction
Multi Protocol Label Switching (MPLS) has received much attention
recently for use as a control plane for non-packet switched
technologies. In particular, optical technologies have a need to
upgrade their control plane as reviewed in reference [2]. Many
different optical switching and multiplexing technologies exist and
more are sure to come. For the purposes of this draft we only
consider non-packet (i.e. circuit switching) forms of optical
switching.
As the requirements for and extensions to interior gateway protocols
such as OSPF and IS-IS have begun to be investigated in the single
area case, e.g., reference [3], we consider the requirements that
optical networking and switching impose in the inter-domain case.
First we explore the definition of a control domain and its use in
optical and transport networking. This is explored again later in
the document when we consider a number of important applications,
networking scenarios, where the notions of inter-control domain
routing are important. We review the various differences between
routing in the datagram case, the virtual circuit case and the
(real) optical circuit case. Then we look at the optical path
selection/computation needs to provide for path diversity, switching
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capabilities, transport capabilities and impairments, and
bandwidth/resource status reporting.
To add to the concreteness of these considerations we try to
illustrate them with one or more specific examples from a particular
optical networking layer or technology. This is not to reduce the
generality of the requirement but to facilitate the understanding of
the requirement or concept.
1.1 Specification of Requirements
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.
1.2 Abbreviations
LSP Label Switched Path (MPLS terminology)
LSR Label Switched Router (MPLS terminology)
MPLS Multiprotocol Label Switching
SDH Synchronous Digital Hierarchy (ITU standard)
SONET Synchronous Optical NETwork (ANSI standard)
STM(-N) Synchronous Transport Module (-N)
STS(-N) Synchronous Transport Signal-Level N (SONET)
TU-n Tributary Unit-n (SDH)
TUG(-n) Tributary Unit Group (-n) (SDH)
VC-n Virtual Container-n (SDH)
VTn Virtual Tributary-n (SONET)
2 Background
2.1 Basic Concept of Domains and Network Partitioning
In this draft we use the term domain in a general sense, i.e.,
beyond the BGP interpretation of an Autonomous System. In this
draft we will consider domains as the result of partitioning of a
network into subnetworks, as shown in the network of Figure 1. A
network may be partitioned for a variety of reasons, such as:
* Administrative boundaries
* Scalability of routing or signaling
* Isolation of partitions for security or reliability reasons
* Technology differences in the systems in different domains
/------------------------------------\
/ \
/ /-\ \
| Domain |NE2|<--Internal Node |
| B /\-/\ |
| / \ |
| /-\/ \/-\ |
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| |NE1|-------|NE3| /
\+------\-/ \-/ /
/\ | | /
/ \------+-----------+-----------------/
/ | |<--- Inter-Domain Links
/ /------+-----------+-----------------\
| / | | \
| / | /-\ | /-\ \
| | Domain | |NE2|---+---------|NE3| |
| | A | /\-/\ | ------/\-/ |
| | | / \ | / | |
| | /-\/ \/-\/ | |
| | |NE1|-------|NE5|---- | /
| \ -- \-/ \-/ \ /-\ /
| \ / | | --|NE4| /
| \/ | | \-/ /
| /\-----+-----------+----------------/
Border Nodes | |<--- Inter-Domain Links
\ |<----------+---- (External Links)
/\------+-----------+-----------------\
/ \ | | \
/ \ /-\ /-\ |
| --|NE1|-----|NE2| |
| \-/ \-/ |
| Domain | |<--- Intra-Domain |
| C | | Links (Internal|
| /-\ /-\ Links) |
| |NE3|-----|NE3| |
| \-/ \-/ |
\ /
\------------------------------------/
Figure 1. Partitioning a network into domains.
The Inter-Domain interface is likely to have different
characteristics than the Intra-Domain interface as the domain
boundary exists for the purpose of hiding some aspect within the
domain from the outside world.
For the remainder of this draft we will be concerned with "control
domains" that is a control domain will be hiding the internal
details of its control plane from other control domains. This
definition has a number of important ramifications when we consider
inter-domain protocols for routing or signaling.
1. Inter-control domain routing or signaling is required to be
independent of a control domainËs internal signaling or route
protocol or lack of either a signaling or routing protocol. This
is sometimes referred to as the "domain independence" property.
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2. Inter-control domain routing or signaling can not count on
specific protocols being implemented within the domain.
3. Inter-control domain routing or signaling can not require that a
network element participate in the internal protocols of two
different control domains. This is sometimes refered to as
"boundary on the wire" property.
4. The Inter-control domain routing or signaling protocol does not
require that the control domains be interconnected in any
particular fashion (except for general graph connectivity).
Example #1 (inter-control domain routing)
Consider a collection of BGP Autonomous Systems (AS). Each of these
may run their own internal IGP. Of these internal IGPs, OSPFv2 and
IS-IS are very popular but also incompatible with each other.
BGP does not rely on the Autonomous Systems running a particular
IGP, i.e., OSPF or IS-IS. Hence it meets the definition of an
inter-control domain routing protocol. Note that nothing prevents
BGP from being used within an ISP to glue together islands of
incompatible IGPs. In fact, the availability of private AS numbers
can help in this situation.
Example #2 (OSPF Areas)
An OSPF Area, on the other hand, is a mechanism within OSPF for
providing scalability. It assumes that within each OSPF area that
OSPF is being run in addition it requires that all border routers
participate in both the backbone area and one or more other their
own areas. Hence OSPF with its area concept equated with a control
domain doesn't meet the definition of an inter-control domain
routing protocol in two ways. It would require OSPF to run within
the domains and it requires that a network element (router)
participate in the internal routing protocol of two separate
domains.
Example #3 (PNNI routing Peer Groups)
With ATM's PNNI routing hierarchy the concept of a peer group is
introduced. PNNI with peer groups does not meet the definition of an
a inter-control domain routing protocol since it, like OSPF,
requires that within a peer group ATM PNNI routing is running.
However, it doesnËt require that border members of a peer group at a
given level in the hierarchy participate in the internal protocols
of both peer groups. In other words PNNI's hierarchical routing
allows for a "boundary on the wire" model.
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The domain concept as used here is orthogonal to the transport
network concept of layering. When the term layer is used with
respect to the transport network we are not referring to the 7-
layer OSI model which includes application, presentation, etc.,
layers. With regard to this model all the optical transport layers
would lie at the "physical layer". In the transport network, layers
are used for multiplexing, performance monitoring and fault
management purposes. Layers tend to be very technology specific. At
some point an optical routing protocol must include information
particular to the technology layer for which it is being used to
acquire/disseminate topology and resource status information. For
more information on layering and domain concepts see ITU-T
recommendation G.805 [14].
2.2 Major Differences between Optical and IP datagram Routing
Let us first review the major difference between routing for optical
(circuit switched networks) and IP datagram networks. In IP
datagram networks packet forwarding is done on a hop-by-hop basis
for each packet(no connection established ahead of time), while in
circuit switched optical networks end-to-end connections must be
explicitly established based on network topology and resource status
information. This topology and resource status information can be
obtained via routing protocols. Note that the routing protocols in
the circuit switch case are not involved with data (or bit)
forwarding, i.e., they are not "service impacting", while in the IP
datagram case the routing protocols are explicitly involved with
data plane forwarding decisions and hence are very much service
impacting. Note that signaling or label distribution protocols that
set up or tear down the virtual or real circuits are service
impacting.
This does not imply routing is unimportant in the optical case, only
that its service impacting effect is secondary. For example,
topology and resource status inaccuracies will affect whether a new
connection can be established (or a restoration connection can be
established) but will not (and should not) cause an existing
connection to be torn down.
This tends to lead to a slightly different view towards
incorporating new information fields (objects, LSA, etc.) into
optical routing protocols versus IP routing protocols. In the
optical circuit case, any information that can potentially aid in
route computations or be used in service differentiation may be
incorporated into the route protocol, as either a standard element
or a vendor specific extension. Whether a route computation
algorithm uses this information and whether two route computation
algorithms use this information in the same way doesnËt matter since
the optical connections are explicitly routed (although perhaps
loosely).
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Path selection or route computation in transport case may be based
on a different criteria or combination of criteria on a per path
basis. For example one connection may requests the lowest economic
cost available path while another may request the highest
reliability path. One important evaluation criteria for any proposed
inter-domain optical routing protocol is the variety of path
selection criteria with which it may work.
2.3 Differences between MPLS and Optical Circuit routing
The bandwidth accounting needed in optical circuit-switched networks
is also different than in packet networks. In packet networks using
either ATM QoS or MPLS-TE, complex statistical measures are used to
characterize the load on a link, often with varying degrees of
accuracy. The inexactness of such measures and the
compressibilityËË of statistically multiplexed traffic imply that a
small percentage change in link utilization can usually be absorbed
by the network.
By contrast, if an OC-192 link has just one STS-1 path occupied
(less than 1% of the link bandwidth), it cannot accommodate an STS-
192c path. Due to the relatively simple finite multiplex structures
currently use in optical networks tracking bandwidth resources is
much easier than packet switched networks, however much stricter
bandwidth accounting is required on circuit switched links. In
particular, it is expected that an individual optical circuit
switched link can be fully utilized, while due to queuing effects a
packet switched link on average can never be run at full capacity
and is typically run at less then 80% of capacity. This also
affects how protection (or restoration) bandwidth can be committed.
In a packet-based network, while the protection path can be
preconfigured, resources along it are not used until a failure
occurs. In circuit-based networks, a protection path generally
implies a committed resource. Such basic differences restrict the
direct applicability of some of the traffic engineering mechanisms
used in packet-switched networks to circuit-switched networks.
2.4 Diversity in Optical Routing
There are two basic demands that drive the need to discover diverse
routes for establishing optical paths:
1. Reliability/Robustness
2. Bandwidth capacity.
Many times multiple optical connections are set up between the same
end points. An important constraint on these connections is that
they must be diversely routed in some way [4]. In particular they
could be routed over paths that are link diverse, i.e., two
connections do not share any common link. Or the more stringent
constraint that the two paths should be node diverse, i.e., the two
paths do not traverse any common node.
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Additionally, insufficient bandwidth may exist to set up all the
desired connection across the same path (set of links) and hence we
need to know about alternative (diverse) ways of reaching the
destination that may still have unused capacity.
"Diversity" is a relationship between lightpaths. Two lightpaths are
said to be diverse if they have no single point of failure. In
traditional telephony the dominant transport failure mode is a
failure in the interoffice plant, such as a fiber cut inflicted by a
backhoe.
Data network operators have relied on their private line providers
to ensure diversity and so IP routing protocols have not had to deal
directly with the problem. GMPLS makes the complexities handled by
the private line provisioning process, including diversity, part of
the common control plane and so visible to all.
Diversity is discussed in the IPO WG document [5]. A key associated
concept, "Shared Risk Link Groups", is discussed in a number of
other IETF (refs) and OIF (refs) documents. Some implications for
routing that are drawn in [5] are:
. Dealing with diversity is an unavoidable requirement for
routing in the optical layer. It requires dealing with
constraints in the routing process but most importantly
requires additional state information -- the SRLG relationships
and also the routings of any existing circuits from which the
new circuit is to be diverse -- to be available to the routing process.
. At present SRLG information cannot be self-discovered. Indeed,
in a large network it is very difficult to maintain accurate
SRLG information. The problem becomes particularly daunting
whenever multiple administrative domains are involved, for
instance after the acquisition of one network by another,
because there normally is a likelihood that there are diversity
violations between the domains. It is very unlikely that
diversity relationships between carriers will be known any time
in the near future.
- Considerable variation in what different customers will mean by
acceptable diversity should be anticipated. Consequently we suggest
that an SRLG should be defined as follows: (i) It is a relationship
between two or more links, and (ii) it is characterized by two
parameters, the type of compromise (shared conduit, shared ROW,
shared optical ring, etc.) and the extent of the compromise (e.g.,
the number of miles over which the compromise persisted). This will
allow the SRLGËs appropriate to a particular routing request to be
easily identified.
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2.4.1 Generalizing Link Diversity
Optical networks may posses a number of hierarchical signaling
layers. For example two routers interconnected across an optical
network may communicate with IP packets encapsulated within an STS-
48c SONET path layer signal. Within the optical network this STS-
48c signal may be multiplexed at the SONET line layer into an OC-192
line layer signal. In addition this OC-192 may be wavelength
division multiplexed onto a fiber with other OC-192 signals at
different wavelengths (lambdas). These WDM signals can then be
either lambda switched, wave band switched or fiber switched. Hence
when we talk about diversity we need to specify the layer to which
we are referring. In the previous example we can talk about
diversity with respect to the SONET line layer, wave bands, and/or
optical fibers. A similar situation arises when we consider the
definition of node diversity. For example are we talking with
respect to a SONET path layer switch or an optical switch or
multiplexer?
The Shared Risk Link Group concept in reference [6] generalizes
the notion of link diversity (general list of numbers). First it's
useful with respect to major outages (cable cuts, natural disasters)
to have a few more types of diversity defined:
1. Cable (conduit) diversity (allows us to know which fibers
are in the same cable (conduit). This helps avoid sending
signals over routes that are most vulnerable to "ordinary"
cable cuts (technically known as backhoe fades).
2. Right of Way (ROW) diversity. This helps avoid sending
signals over routes that are subject to larger scale
disasters such as ship anchor drags, train derailments, etc.
3. Geographic Route diversity. This type of diversity can help
one avoid sending signals over routes that are subject to
various larger scale disasters such as earthquakes, floods,
tornadoes, hurricanes, etc. A route could be approximately
described by a piecewise set of latitude/longitude or UTM
coordinate pairs.
We also have a form of link abstraction/summarization via the link
bundling concept [7].
2.4.2 Generalizing Node Diversity
The concept of a node abstraction associated with GMPLS appears in
reference [11] where it is used to generalize the concept of an
explicitly routed path. In this case an abstract node can be a set
of IP addresses or an AS number. From the point of view of node
diverse routing specific concepts of interest include:
1. Nodes, i.e., individual switching elements.
2. Switching centers, i.e., a central office or exchange site.
3. Cities, or towns that contain more that one switching center.
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4. Metro areas, or counties
5. States,
6. Countries, or
7. Geographic Regions
2.5 Routing Information Categorization
Different applications of inter-domain optical routing call for
different types of information to be shared or hidden between
domains. In the following we decompose the information that can be
transferred via a routing protocol broadly into link/topology
information and node/domain information. We further subdivide these
categories and will use this taxonomy of routing information when
discussing the routing applications.
2.5.1 Link and Topology Related Information
-Internal topology- information is information concerning the nodes
and links and their connectivity within a domain. This type of
information is traditionally shared within a domain via an intra-
domain (interior gateway) routing protocol such as OSPF or IS-IS
within a single area. For example the existence of nodes that only
have links to other nodes within the domain, i.e., do not have links
to other domains, would be strictly internal topology information.
These nodes are known as internal nodes, while nodes with links to
other domains are known as border nodes. Also included in this
information is link/port property information such as whether the
link is protected and what type of protection is being used, e.g.,
linear 1+1, linear 1:N, or some type of ring such as a 4F-BLSR [cite
T1 document].
-Internal Resource- Information is concerned with the bandwidth
available on links within a domain and possibly other resource
related information. This information plays an important role in
path selection within a domain.
-Inter-Domain Topology- Information is concerned with how the
domains are interconnected. This information can be key in inter-
domain path selection, for example, in determining diverse routes.
For the network in Figure 1 this information would let us know that
domain A has two distinct links to domain B, domain A has two
distinct links to domain C, but that domains B and C are not
directly connected via any links.
-Inter-Domain Resource- Information is concerned with the available
bandwidth on inter-domain links. This information is important for
inter-domain path selection and inter-domain traffic engineering
purposes. For example in Figure 1 this information would give us
some kind of bandwidth or capacity measure on the links between
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domain A and domain B, and the links between domains A and C. The
exact nature of this information may be application/context
dependent.
2.5.2 Domain and Node Related Information
-Reachability- information tells us what addresses are directly
reachable via a particular domain. These systems can be end systems
(clients) to the network or nodes within the network depending upon
the application/context. Suppose in domain B of Figure 1 each of
the network elements, NE1-NE3, have subtending end systems, and that
NE1-NE3 do not represent a valid final destination for a path. Under
this assumption the collection of the addresses of all these
subtending end systems would form the reachability information for
domain B.
-Subnetwork Capability- information is concerned with the
capabilities or features offered by the domain as a whole. This
information is used in some applications where sharing the internal
topology and resource information is inappropriate. This information
can include: (a) Switching capabilities, (b) Protection
capabilities, (c) Some kind of overall available capacity measure,
(d) Reliability measures.
Examples:
1. For example, in the SONET realm, one subnetwork may switch down
to an STS-3c granularity while another switches down to an STS-
1 granularity. Understanding what types of signals within a
SDH/SONET multiplex structure can be switched by a subnetwork
is important. Similar examples of granularity in switching
apply to the waveband case.
2. Some networking technologies, particularly SONET/SDH, provide a
wide range of standardized protection technologies. But not all
domains will offer all protection options. For example, a 2/4-
F BLSR based subnetwork could offer extra data traffic, ring
protected traffic and non-preemptible unprotected traffic,
(NUT)[8], while a mesh network might offer shared SONET line
layer linear protection and some form of mesh protection.
3. Some domains may be in locations that have lower incidences of
link failure. Such information could be helpful in computing
routes to statistically "share the pain".
-End System Capabilities- information: While properties of the
subnetwork are very important when trying to decide which domain to
use to access a system (in the case of multi-homing), end systems
also posses a wide variety of capabilities. Throwing end system
capabilities such as a system's ability to support SONET/SDH virtual
concatenation for distribution into a routing protocol may not be
that advantageous since it somewhat counters the ability to
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summarize reachability information. Detailed end-system information
may alternatively be obtained via a directory service or some type
of direct query between the end systems.
3 Applications of Inter Domain Optical Routing
In this section we review some of the main applications of optical
inter-control domain routing. We also review which aspects of the
definition of control domain is most relevant to the application.
3.1 Intra Carrier Applications of Optical Inter Domain Routing
Intra Carrier inter domain routing refers to a situation where the
network that is to be partitioned into areas is under the control of
one administrative entity. The main reasons for this partitioning in
optical networks stem from scalability, inter-vendor
interoperability, legacy equipment interoperability, and inter-layer
partitioning.
3.1.1 Intra-Carrier Scalability
As networks grow it is useful to partition a carriers network into
separate optical routing domains which share limited or summarized
information amongst each other. This reduces the overhead of
information exchange across the network as a whole, and reduces the
convergence time of routing protocols within a particular area.
Hence we see in the inter-carrier scalability application that we
will hide or summarize internal topology and resource information,
while completely sharing inter-domain topology and resources
information so that diverse paths can still be calculated. Note that
general domain capabilities/capacity as well as reachability
information would tend to be shared as completely as possible. For
example the network shown in Figure 1 can be approximately
represented as shown in Figure 2. This summarized network topology
only has 4 links whose state need to be advertised in a routing
protocol versus 17 links in the original network. Note that we may
also advertise the capabilities of the three domains in Figure 2 as
opposed to the 12 nodes of Figure 1. In Note that this partitioning
into domains can recurse, i.e., we can have multiple levels of
routing hierarchy to permit larger and larger networks. Such was
the motivation behind the extensive hierarchical routing capability
within ATM's PNNI routing protocol. The trade off to partitioning
into domains for scalability is that less information is available
for use in the route selection process, which can lead to
inefficient utilization of network resources. On the other hand
frequently this partitioning occurs on somewhat "natural" boundaries
and as such the potential inefficiencies can be minimized.
-------- ------
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/- -\ /- -\ -----
// NE 3 \mmmmmm // \\ / \
/ Port 2 \ mmmmm NE 3 NE 5 \ /NE 3 \
/ \ / Port 4 Port 6 \ mmmmmPort 17 \
| | | mmmmm | |
| | | | | |
| | | Domain A | | Domain C |
| Domain B | | | | |
| | | NE 2 NE 1 | | |
| | |Port 5 Port 2 mmmmmmmmmNE 1 |
| mmm / \Port 21 /
\ NE 1 /mmmm \ / \ /
\ Port 7 mm \\ // \ /
\\ // \- -/ -----
\- -/ ------
--------
Figure 2. Summarized topology for the network of Figure 1.
Also in Figure 2 we show the end points of the links between being
identified by the triple of (domain, NE address, NE port number).
This information is available via the discovery process. Though not
strictly necessary including the identification of border nodes in a
domain, allowing other nodes to understand whether these links
terminate on the same or different nodes is valuable in setting up
diverse inter-domain paths.
In current intra-domain IP routing protocols, such as OSPF's, a
multiple area capability provides for intra-carrier scalability.
However, this is currently done by sharing reachability information
and using a distance-vector method to obtain routes. This does not
discover and propagate inter-domain topology information and hence
insufficient information is available for diverse route
calculations. In addition OSPF areas are required to be assembled in
a particular fashion with all areas bordering on a single backbone
area.
When the topology within the domain is approximated or hidden then
signaling and call processing at the domain border will receive an
approximated (loose) route and the border node or signaling entity
must then translate this to a precise route through the domain.
Hence there is some linkage between multi-domain connection control
and inter-area/inter-domain routing.
3.1.2 Intra-Carrier Inter-vendor
An important application of intra-carrier optical routing is the
intra-carrier inter-vendor scenario. From a carrierËs perspective,
the use of domains provides a clean way to isolate clouds of
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equipment belonging to different vendors, while at the same time
allowing for interoperability between the vendors.
An advantage of this method is that it allows the vendors complete
freedom to use any combination of routing protocols or traditional
management-based methods to propagate topology and resources
internal to their domains. In other words, the routing entity in
each domain could obtain this information either by participating in
a routing protocol like OSPF, or by querying each NE via an EMS, or
by simply having the required information manually configured into
it. Here the "domain independence" and "boundary on the wire"
properties of an inter-control domain routing protocol are being
stressed.
Note that the routing entity shown in each vendorËs cloud in Figure
3 is in reality an abstract representation of the routing
intelligence within the vendor cloud. This intelligence may either
be implemented in a distributed way, by having a routing protocol
running at each NE, or in a centralized way, through the use of an
intelligent, centralized routing entity that communicates with the
individual NEËs (either via a protocol or by querying individual
elements) to retrieve connectivity and resource information that it
uses to build a complete topology and resource map of the domain.
Therefore, vendors may use different protocols as the primary option
between their own devices, adding specialized features or optimizing
their performance based on their choice of protocol.
/------------------------------------\
/ /-\ \
/ Domain B |NE3| +-------+ \
| (Vendor 2) /\-/\ |Routing| |
| / \ |Entity | |
| /-\/ \/-\ +-------+ |
\ |NE1|-------|NE2| @ /
\ \-/: \-/ @ /
\------+-:---------+---------@-------/
Neighbor discovery | : | @ Exchange of routing
Between NEs in the | : | @ information between
same domain. ----> | : | @ the domains routing
| : | @ entities.
/------+-:---------+---------@-------\
/ | : | @ \
/ /-\ /-\ +-------+ \
| |NE1|-----|NE2| |Routing| |
| \-/\ /\-/ |Entity | |
| \/-\/ +-------+ |
| Domain A |NE3| |
| (Vendor 1) \-/ /
\ /
\------------------------------------/
Bernstein, G. [Page 14]
draft-ipo-optical-inter-domain-02.txt February 2003
Figure 3. Intra-Carrier Inter-vendor routing domains
Even if it is a centralized entity, the routing entity could still
be run on a given NE in the vendor cloud. In other words, these
entities could be distributed, or centralized onto a single node, or
independent of any of the nodes. In ATM's PNNI protocol, for
example, this was centralized on a node elected as the "peer group
leader". In the inter-vendor case, it can be particularly
advantageous to centralize this so that the flow of information can
be monitored. A centralized routing entity could apply flooding and
summarization mechanisms as if it is a switching system. Since this
is optical rather than IP routing, signaling would be carried by a
control channel between the routing entity and the neighboring
system, rather than being carried over the data links. The functions
of the routing entity include: (a) direct reachability exchange
(that is, which NEËs can be directly reached from this domain, (b)
verification of area connectedness (that is, understanding how the
two domains are interconnected), (c) area/domain topology (possibly
summarized) exchange and updates, and (d) topology updates
concerning other domains/areas.
When a carrier partitions its network for inter-vendor
interoperability as described above, it may still share information
about the internal topology of the domains in some standardized form
that has been agreed upon between the vendors. Although one option
is to force both vendors to adopt a new common protocol, another is
to require that only a minimum subset of reachability/topology
information be shared between the vendor clouds. The latter option
helps during fault situations, by providing fault isolation at the
domain boundaries. It prevents an outage in a domain composed of one
vendorËs equipment from causing a reaction in an adjacent domain
composed of another vendorËs equipment, thus preventing a situation
that would typically degenerate into a process known as finger
pointingËË between the two vendors.
The setup described above takes into account the three most
important sub-cases of inter-carrier inter-vendor partitioning:
a. The first is where both vendor domains run distributed
routing protocols. This is the most flexible case, and is the
situation when new equipment capable of running such protocols
is deployed.
b. The second is where the optical subnetworks or domains
(which includes a large number of existing installations) do
not run any internal routing protocol (because the NEËs are not
capable of doing so), relying instead on EMS-based topology
discovery/resource management. In this case, interoperability
Bernstein, G. [Page 15]
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with other vendor clouds can be realized by having the routing
entity run as a separate software entity with access to the
appropriate information. These entities may exchange routing
proxy addresses through the neighbor discovery protocol, and
then exchange routing information (proxying for the entire
domain) with each other. The basic advantage here is that even
though the vendor specific element management system (EMS)
knows the topology of its subnetwork, it is far easier to get
an inter-domain routing protocol to share information than
trying to get the separate vendors management systems to
communicate.
c. The third is where one domain has a centralized routing
entity, while the other runs a distributed routing protocol.
Once again, the neighbor discovery process between the area
border NEËs could be used to advertise the address of the
routing entity.
3.1.3 Inter-Layer Partitioning
In transport networks layering is a part of the multiplex and OA&M
structure of the signals, playing a role in multiplexing, monitoring
and general link management. Layering in the transport network is
defined in fairly abstract terms in [G.805] and the concepts are
applied to SDH in [G.803]. As explained in a recent ITU SG15
document (WD45 Q.14/15) not all the layers in the transport network
are of interest to the control plane, or to routing in particular.
Some layers may not contain active switching elements, however this
does not mean that information flow concerning a non-switching layer
is not valuable in routing. For example in [GB-WDM-SRLG] static WDM
layer information was used to set the SRLGs for SONET lines (i.e.,
information passed around by a link state protocol operating at the
SONET line layer). It should be noted that much of the information
available from non-switching layers relates to performance
monitoring and fault management.
In this situation the network is partitioned into sub-networks that
operate at different switching layers. One reason for doing this is
that not all the information from one layer is necessary or relevant
to another layer. For example, between transparent optical switches
and SDH/SONET path (VC) layer switches, the optical switches have no
direct use for the SONET layer information. In addition optical
networks may keep a lot more physical layer information (such as the
properties of every optical amplifier on a WDM span) that is of no
use to the SONET layer. One again this promotes scalability, but
also simplifies the implementation by reducing inter-layer
information transfer to that which is actually useful.
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Now in network planning it is very useful to have a view of the
current higher layer traffic matrix [9] being satisfied and higher
layer traffic trend measurements over time. Although we can
somewhat see this in higher layer resource status changes over time,
this represents a link level view when we really desire the trend
(change in time) of the traffic matrices between sites. How this
information gets distributed is an open issue. Currently individual
nodes in a GMPLS network know only about connections that they
source or sink. Network planning is generally a longer time horizon
process than even traffic engineering hence it is an open question
as to whether this would ever be a useful function to incorporate
into a network element.
Now looking the other way is initially simpler, i.e., it is easier
to ask: what can a higher layer use for path selection/computation
from a lower layer. The first item that springs to mind is diversity
information. For example in setting up a SONET STS-1 path we can use
information from a WDM system concerning which SONET lines share
the same WDM fiber. This is information, however, is already
abstracted into routing protocols via SRLG concept. Other
information from a lower layer is of questionable value since it
tends to be technology specific and puts more and more burden on the
upper layer to be able to effectively understand and use this
information.
3.1.4 Interaction with IP Layer Routing
The applicability of IP-based routing protocols has, over the years,
been constantly expanded to increasingly more circuit-oriented
layers. The community began with pure datagram routing, gradually
expanded to cover virtual-circuit switched packet routing (for e.g.,
MPLS), and is finally looking at the application of routing
protocols to real circuit switching, e.g. the optical layer.
However, as pointed out earlier in this document, it is not clear
that the different layers should necessarily share the same instance
of the routing protocols. Indeed, there may be significant reasons
for not doing so and many carrier tend to partition their networks
along switching layer boundaries. For example, IP-layer reachability
information is not particularly useful for the optical layer, so it
seems an overkill to burden the optical equipment with storing and
distributing that information. (It is an extra expense on memory and
processing for information that the optical layer does not really
care about, so there is little incentive for a vendor to want to do
so.) Likewise, information on physical plant (fibers, conduits,
ducts) diversity, which is crucial at the optical transport layer,
is very unlikely to be used directly by the IP layer. So, it would
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be quite wasteful of resources to burden the IP layer routing with
distributing and manipulating this information. Thus, the extent of
interaction or integration with IP layer routing (if any) requires
careful consideration.
3.1.5 Inter-Business Unit
A slightly different but interesting application of intra-carrier
optical routing occurs in the intra-carrier inter-business unit
scenario. This arises because a carrier often has multiple
administrative domains, with groups of administrative domains being
under the purview of independent BUËs within the carrier.
Note that different BUËs represent independent cost centers with
their own profit objectives and sales targets. As a result, while
the BUËs can profitably share topology information and would like to
do so, they may not be so inclined to advertise the details of their
resource usage into domains belonging to other BUs. Since each BU
has its own revenue targets, advertising detailed resource
availability information to other, potentially competing, BUs can
have a negative impact on a BUs revenue generation. This is because
the knowledge of available resources in one BU may enable other BUs
within the carrier to requisition capacity from this BU. This would
force the BU in question to yield to their request, possibly at the
expense of selling capacity to more profitable, external, revenue
generating customers.
Thus, this scenario is likely to have an additional dimension of
information sharing, namely, policy-based information sharing, which
does not apply to the other cases that we have discussed so far.
Two examples where the inter-business unit scenario could become
important are in the case of metro-core-metro networks within a
given carrier, and in the case of regional networks within a
carrier.
In the metro-core-metro situation, such as the one depicted in
resource sharing between them.
/------------------------------------\
/ \
/ /-\ \
| Domain |NE2| |
Metro BU | B /\-/\<-- Metro Ring |
Network | / \ |
| /-\/ \/-\ |
| |NE1|-------|NE3| /
\ \-/ \-/ /
\ | | /
Bernstein, G. [Page 18]
draft-ipo-optical-inter-domain-02.txt February 2003
\------+-----------+-----------------/
| |
/------+-----------+-----------------\
/ | | \
/ | /-\ | /-\ \
| Domain | |NE2|---+---------|NE3| |
CORE BU | A | /\-/\ | ------/\-/ |
Network | | / \ | / | |
| /-\/ \/-\/ |<--Core |
| |NE1|-------|NE5|---- | Mesh /
\ \-/ \-/ \ /-\ /
\ | | --|NE4| /
\ | | \-/ /
\-----+-----------+----------------/
| |
/------+-----------+-----------------\
/ | | \
/ /-\ /-\ \
| |NE1|-----|NE2| |
Metro BU | Domain \-/ \-/ |
Network | C | |<--- Metro Ring |
| | | |
| /-\ /-\ |
| |NE3|-----|NE3| |
| \-/ \-/ |
\ /
\------------------------------------/
Figure 4, the metro network domains could be under the jurisdiction Deleted of one BU, while the core network domains belong to a different BU.
In this case, for example, it is possible that the metro BU, armed
with resource availability information about the core BUËs domains,
could requisition capacity from the core network when needed. This
may harm the core networkËs profit goals, because they may not be
able to charge an internal customer the same rates that they could
charge for the same capacity from an external customer, thus
motivating the need for selective, policy-based resource sharing
between them.
/------------------------------------\
/ \
/ /-\ \
| Domain |NE2| |
Metro BU | B /\-/\<-- Metro Ring |
Network | / \ |
| /-\/ \/-\ |
| |NE1|-------|NE3| /
\ \-/ \-/ /
\ | | /
\------+-----------+-----------------/
| |
/------+-----------+-----------------\
/ | | \
Bernstein, G. [Page 19]
draft-ipo-optical-inter-domain-02.txt February 2003
/ | /-\ | /-\ \
| Domain | |NE2|---+---------|NE3| |
CORE BU | A | /\-/\ | ------/\-/ |
Network | | / \ | / | |
| /-\/ \/-\/ |<--Core |
| |NE1|-------|NE5|---- | Mesh /
\ \-/ \-/ \ /-\ /
\ | | --|NE4| /
\ | | \-/ /
\-----+-----------+----------------/
| |
/------+-----------+-----------------\
/ | | \
/ /-\ /-\ \
| |NE1|-----|NE2| |
Metro BU | Domain \-/ \-/ |
Network | C | |<--- Metro Ring |
| | | |
| /-\ /-\ |
| |NE3|-----|NE3| |
| \-/ \-/ |
\ /
\------------------------------------/
Figure 4. Intra-carrier inter-business unit routing domains.
3.2 Inter-Carrier Inter-Domain Optical Routing
In this case we are talking about dealing with outside entities,
i.e., between service providers. There may be a range of levels of
trust here; for example there might be some level of trust between
two providers that have formed a marketing alliance or have some
other form of business relationship. In general, however, trust can
not be assumed. In this case, all the concerns of revealing too much
information about one's network come into play. However, not
revealing enough, say about diversity capabilities may also lead
customers elsewhere. Also there are some other security issues not
seen before. For example, in route distribution one carrier might
not be inclined to pass on routing information that could point the
way to competitive alternatives. This impacts the methods for route
updates, etc.
With the interest in bandwidth trading [10] we can also look at this
as an advertisement of network connectivity and capability with of
course any "warts" covered up. This would include reliance on other
carrier for fibers or lambdas. Also a fair amount of details such
as "unused capacity" would not be advertised since this maybe
financially sensitive information.
Private line pricing today is based primarily on the service itself
(bandwidth, end-points, etc.) and the holding time, and there is no
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reason to expect that this will change. When multiple service
providers are involved the algorithm for dividing up the revenue
stream (which can be quite large even for a single connection) must
be explicit by connect time. This could be done off-line or could be
done at connect time. In either case, the entity or entities doing
the routing will need to take provider pricing structures into
account whenever there is a choice between providers that needs to
be made. The routing logic could do this explicitly if the prices
are captured in the advertised metrics or some other advertised
data; alternatively it could be done by some sort of policy control,
as it is today by BGP.
The essence of bandwidth trading is the existence of competing price
structures that are known to the entity deciding which competitor to
use. It is possible to create plausible bandwidth trading scenarios
involving the UNI, the NNI, or both. If the NNI is involved, these
price structures will need to be established across it. The
situation is further complicated by the fact that bandwidth trading
could be realized using any one of a number of business models, each
with its own information requirements. To give two examples: If an
auction model were used the buyer might repeatedly broadcast the
lowest bid received to date and solicit lower bids from the
competing providers. On the other hand, if there were a more formal
market the providers might post their asking prices in some public
fashion and a buyer would be matched by some third party with the
lowest offer.
In the inter-carrier case notions of hierarchy seem rather
sensitive, i.e., he who controls the summarization and advertisement
may have an undue advantage over competitors. In addition, a
"bandwidth aggregator" may want to advertise capabilities that he
has put together via deals with multiple carriers...
Notes: We can attempt to extend the SRLG concept to links between
ASs but we will need the two ASs to agree on the meaning and number
of the list of 32 bit integers that comprise the SRLG, i.e.,
previously the SRLG concept was one of AS scope. And this is also
where things get tricky since it may not be possible to distinguish
diverse routes based upon differing path vectors (i.e., AS number
traversal list). The reason for this is due the fact that many
carriers "fill out" their networks by renting either dark fiber or
"lambdas" from a WDM system and hence although the path vectors may
be AS diverse they may not even be fiber diverse.
Hence there is a need for sharing of diversity information or
constraints between ASs when setting up diverse connections across
multiple ASs. This gets us somewhat into a quandary over which
information needs to be public and how to coordinate its
distribution. In this sense geographic link information may be the
simplest and least contentious to get various players to disclose
and standardize.
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Notes: (1) The real issue is consistency between the cloud/ASËs
since in many cases they are sharing conduit, ROW, etc. Getting
this to happen could be very problematic. It would be preferable to
see a diversity option that doesnËt require this. For example,
ensure that there is diversity within each cloud and then do
restoration separately within each cloud. (2) See the definition of
SRLG in the Carrier Requirements -- an equivalence class of links,
the extent of violation, and the level. (3) Flexibility in defining
the level of violation seems very desirable -- these historically
have drifted in time. There are many others -- eg, if the shared
resources are SPRING protected thatËs less of a problem than
otherwise.
Notes: Participation in the inter-domain network carries constraints
on the carriers. First, in order to participate, each provider
network MUST be willing to advertise the destinations that are
reachable through his network at each entry point and advertise the
formats available. Without providing such information, there is
little motivation to participate since it is unlikely that others
will be able to access services of which they are not aware. Second,
every participating carriers MUST agree to fairly include the
information made available by every other carrier so that each
carrier has an equal opportunity to provide services. There may be
specific exceptions, but the carrier claiming those exceptions MUST
advertise the exceptions themselves. In this manner, other carriers
that might otherwise be aware of distant services can be prompted to
seek those services manually. Note a combination of minimal
required information transferred with deferral to the originating
subnetwork along with some basic security mechanisms such as
integrity and non-repudiation may be useful in helping organizations
to "play nice".
3.3 Multi-Domain Connection Control
MPLSË loose routing capability allows one to specify a route for an
optical connection in terms of a sequence of optical AS numbers.
This, for example, is handled via RSVP-TEËs abstract node concept
[11]. Currently there is nothing in the GMPLS signaling
specification that differentiates between intra AS boundaries, i.e.,
between two neighbor optical LSRs in the same AS, and inter AS
boundaries, i.e. between two neighbor optical LSRs in different ASs.
Note that these same notions can apply to separate routing domains
within an AS. There may, however, be some useful reasons for
differentiating these two cases:
1. Separation of signaling domains,
2. Separation of protection domains.
While routing protocols (used for their topology information) in the
optical case are not "service impacting", signaling protocols most
certainly are. It is desirable to build some type of "wall" between
optical ASs so that faults in one that lead to "signaling storms" do
not get propagated to other ASs. Note that the same motivation
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applies for isolating other kinds of clouds, like vendors specific
ones.
The natural situation where "signaling storms" would be most likely
to arise is during network restoration signaling, i.e., signaling to
recover connections during major network outages, e.g., natural
disasters etc. In this case it may be very advantageous to break up
general source reroute forms of restoration into per domain segments
or to start reroute at domain boundaries rather than all the way
back at the originating node. Note that this has the advantage of
reducing the need for globally consistent SRLGËs. (See earlier SRLG
comment.) Such a capability requires some loose coordination between
the local, intermediate and global protection mechanisms [12]. This
is typically implemented via hold off timers, i.e., one layer of
protection will not attempt restoration until a more fundamental
(local) form has been given a chance to recover the connection [12].
In other words, prevention of restoration related signaling storms
may require the breaking up of a large network into multiple
signaling (and hence routing) domains. These domains could be within
the same AS.
4 Multiple Layers of Optical Routing
As previously discussed, there are multiple layers of signals
included in what in the IP model one would call the Physical Layer.
One could separate the layers by creating sublayers in the Physical
Layer. For example, sublayers in the Physical Layer might be, top
to bottom: SDH LOVCs, SDH HOVCs, and Lambdas. If a system supports
only one of the three, then isolation of the sublayers is a given;
it's geographical. But there are systems which will support more
than one physical sublayer, therefore, it is necessary to establish
whether or not there is a need to isolate the sublayers in the same
manner. Or put another way is there a reason to "integrate" the
sublayers for the purposes of routing (topology dissemination).
If they are isolated, then there will be separate topological models
for each sublayer: one mesh for the LOVC, one for the HOVC, one for
the Lambda, and possibly others. The appropriate way to access a
sublayer is via the use of sublayer SAPs (service access points).
For example, in this way, one may find that use of Lambdas is more
efficient because each sublayer can assess the availability of
services at its own layer before searching for coarser-granularity
services. On the other hand, the control plane must accommodate
three separate routing protocols, or at least three separate
instances of the same routing protocol, all operating at both intra
and inter-domain level.
Example (SDH multiplexing)
For transport across an SDH network, the lower order signals must be
multiplexed into a non-concatenated higher order signal. Hence LOVCs
are not routed independently, but only as tributaries of HOVCs. In
addition in the SDH hierarchy there is a signal, VC3, that can be
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draft-ipo-optical-inter-domain-02.txt February 2003
treated (multiplexed) as either a LOVC or a HOVC. With this tight
and somewhat confused coupling of these layers it may beneficial to
sometimes combine them into the same route protocol instance.
The alternative to separate routing protocols per sublayer is the
original notion behind GMPLS routing and the forwarding adjaciency
concept [13]. Rather than separating the route protocols into
separate layers (or sublayers) with distinct topologies, each ONE
would advertise the services it can provide, along with its topology
information. For example, a ONE (optical network element) might
advertise that it carries a route to node A with STS-N service and
clear-channel lambda service and carries multiple routes to node B
with STS-N service. It might, alternatively, advertise its entire
network with summarized link capacity information for every included
link. Neighboring carriers would, implicitly, be allowed to
summarize that information for internal advertisement via its IGP.
Further consideration could be given to a query service, where a
carrier advertises the geographical area it serves without detailed
reachability or capacity information. A second carrier desiring
service could query the first carrier as to reachability for a
specific destination, and the first carrier would respond with
availability and capacity information.
Integrating multiple layers into the same routing protocol instance
leaves us fewer routing protocols to manage. The downside of this is
that more information must be exchanged via this routing protocol
and more network elements participate in this single instance of the
routing protocol which can lead to scalability concerns. If the
equipment working on the different sublayers comes from different
vendors there would be little incentive to integrate multiple layers
into the routing protocol for a single layer product.
Regardless of whether multiple layers are integrated into the same
routing protocol instance it can be very useful to share information
between layers as illustrated by the following examples:
o Drop side links between layers: Capabilities of the links
that are between the (client and server) layers need to be
propagated into the routing protocol.
o Summarize link capabilities: Summarizing the server layer
capabilities in the client layer will reduce the amount of
information required for multi-layer constraint based path
computation.
o Send only that are required: Sending only the capabilities
that are useful in the constraint path computation in the
client layer.
5 Conclusion
Bernstein, G. [Page 24]
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Key properties of optical control domains and an optical inter
control domain routing protocol were reviewed. The stringent
properties of "independence of internal domain control plane
mechanisms" as well as support for "boundary on the wire" were shown
to be crucial to the definition of control domain by showing their
use in several mainstream optical inter-networking scenarios.
Via examples we saw that BGP is the only existing IP routing
protocol for which the "internal domain independence" and "boundary
on the wire" property hold. However, it was described how important
the ability to diversely route optical connections is to the
reliability and resilience of the optical network. In addition it
was pointed out that flexibility in choosing/computing paths can be
very important to an optical network operator so that they can offer
a range of differentiated services. In this light BGP does not
currently meet the needs of an optical inter control domain routing
protocol.
As of this writing we are therefore looking at two alternatives for
an optical inter control domain routing protocol. (1) Extensions to
a link state type protocol (such as OSPF, IS-IS or PNNI routing) to
work at the control domain level rather than node to node level. Or
(2) Extensions to a path vector type protocol (such as BGP) to
provide diverse routing support and enhance path selection/network
optimization.
6 Security Considerations
6.1.1
Protection of the routing information exchanged across an optical
inter-domain interface is of high importance; erroneous reachability
or topology information may result in connection provisioning
requests that either fail or are routed across sub-optimal paths. It
is also possible that failed requests may consume significant
control and transport resources for a transient amount of time. It
follows that erroneous routing information could result in degraded
carrier network operation, or even render a carrierËs network
inoperable. Security requirements are expected to be of higher
importance in interfaces between different administrative domains.
Therefore, an optical inter-domain routing protocol should provide
the following:
1. Authenticate entities with which routing information is exchanged.
For example, a carrier should authenticate the identity of other
carriers it is connected to. The specific mechanisms used for
authentication should provide protection against attacks; for
example they should not be based on simple clear-text password
authentication schemes.
2. Guarantee the integrity of routing information (topology,
reachability and resource status) exchanged across the interface.
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This requirement can be satisfied using security mechanisms at
different layers. For example, each routing message could be
individually authenticated using a keyed message digest, which is
embedded in the message. Both OSPF and BGP provide such options.
Alternatively, the two parties could establish a security
association at the network layer using IPSEC, which could be used
to provide security services to the optical inter-domain routing
protocol.
From the point of view of routing, information integrity is likely
to be the most important requirement. However, in some cases it
might be necessary to provide confidentiality of the routing
information as well. A possible scenario for this is when a carrier
would like to advertise information privately to another carrier,
but does not wish to publicly disseminate this information, due to
policy constraints.
It should be noted than none of the known mechanisms that provide
information integrity (such as keyed digests or IPSEC) can provide
adequate protection against a compromised node participating in the
inter-domain routing protocol. This is an item for further study.
7 References
[1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
[2] G. Bernstein, J. Yates, D. Saha, "IP-Centric Control and
Management of Optical Transport Networks", IEEE Communications
Magazine, October 2000.
[3] G. Bernstein, E. Mannie, V. Sharma, "Framework for MPLS-based
Control of Optical SDH/SONET Networks", <draft-ietf-ccamp-
sdhsonet-control-02.txt>, February 2003.
[4] Ramesh Bhandari, Survivable Networks: Algorithms for Diverse
Routing, Kluwer Academic Publishers,1999.
[5] Strand, J. (ed.) "Impairments And Other Constraints On Optical
Layer Routing", work in progress, draft-ietf-ipo-impairments-
00.txt, May 2001.
[6] Kompella, K., et. al. "IS-IS Extensions in Support of
Generalized MPLS", Work in Progress, draft-ietf-isis-gmpls-
extensions-16.txt, December 2002.
[7] K. Kompella, et. al. "Link Bundling in MPLS Traffic
Engineering", Work in Progress, draft-ietf-mpls-bundle-
04.txt, July 2002.
Bernstein, G. [Page 26]
draft-ipo-optical-inter-domain-02.txt February 2003
[8] ANSI T1.105.01-1995, Synchronous Optical Network (SONET)
Automatic Protection Switching, American National Standards
institute.
[9] Robert S. Cahn, Wide Area Network Design: Concepts and Tools
for Optimization, Morgan Kaufmann Publishers, Inc., 1998.
[10] Meghan Fuller, "Bandwidth trading no longer a case of 'if' but
'when' says report", Lightwave, June 2001. (www.light-wave.com)
[11] RFC 3209, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", December 2001.
[12] K. Owens, V. Sharma, M. Oommen, "Network Survivability
Considerations for Traffic Engineered IP Networks", Work in
Progress, draft-owens-te-network-survivability-03.txt, May 2002.
[13] K. Kompella and Y. Rekhter, "LSP Hierarchy with MPLS TE",
draft-ietf-mpls-lsp-hierarchy-08.txt, Internet Draft, Work in
Progress, September 2002.
[14] G.805, Generic Functional Architecture of Transport Networks,
ITU-T, March 2000.
8 Acknowledgments
The authors would like to thank Shezad Mirza of BT and Cheryl
Sanchez of Calix for their help.
9 Author's Addresses
Greg Bernstein
Grotto-Networking
Phone: (510) 573-2237
Email: gregb@grotto-networking.com
Lyndon Ong
Ciena Corporation
5965 Silver Creek Valley Road
San Jose, CA 95015
Phone: (408) 834-7894
Email: lyong@ciena.com
Bala Rajagopalan, Dimitrios Pendarakis
Tellium, Inc
2 Crescent Place
Ocean Port, NJ 07757
Email: braja@tellium.com, dpendarakis@Tellium.com
Angela Chiu
John Strand
AT&T Labs
Bernstein, G. [Page 27]
draft-ipo-optical-inter-domain-02.txt February 2003
200 Laurel Ave.
Middletown, NJ 07748
Phone:(732) 420-9061 Angela, (732) 420-9036 John
Email: chiu@research.att.com, jls@research.att.com
Vishal Sharma
Metanoia, Inc.
335 Elan Village Lane, Unit 203
San Jose, CA 95134
Phone: +1 408 943 1794
Email: v.sharma@ieee.org
Rauf Izmailov
NEC USA, Inc.
4 Independence Way
Princeton, NJ 08540
Email: rauf@nec-lab.com
Dean Cheng
Polaris Networks Inc.
6810 Santa Teresa Bl.
San Jose CA 95119
Email: dcheng@polarinetworks.com
Sudheer Dharanikota
Frank Hujber
Bernstein, G. [Page 28]
