IETF Internet Draft T. Otani
Proposed status: Informational KDDI R&D Labs
Expires:April 2006 S. Okamoto
NTT
October 2005
GMPLS Inter-domain routing problem statement and requirements
Document: draft-otani-ccamp-inter-domain-routing-req-00.txt
Status of this Memo
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Abstract
This draft provides problem statement and requirements of inter-
domain routing in a generalized multi-protocol label switching
(GMPLS) network. The reachability information exchange must be
supported for appropriate signaling operation in a GMPLS network, as
the same with the IP/MPLS inter-domain case.
Table of Contents
Status of this Memo................................................1
Abstract...........................................................1
1. Introduction....................................................3
2. Conventions used in this document...............................3
3. Problems statement of GMPLS inter-domain networks...............3
4. Requirement of GMPLS inter-domain routing.......................4
6. Security consideration..........................................6
7. Acknowledgement.................................................6
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8. Intellectual property considerations............................6
9. Informative references..........................................6
Author's Addresses.................................................7
Document expiration................................................7
Copyright statement................................................7
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1. Introduction
Initial efforts of GMPLS functions were focused on solving the
problem within an Autonomous System (AS) or area (hereinafter domain).
Service Providers (SPs) are getting to come up with difficulties to
design future GMPLS networks considering multi-domain extensions due
to no definition of inter-domain routing. Although documents of
inter-domain framework [Inter-domain] as well as inter-domain TE
requirements [Interas-te] touch upon the GMPLS inter-domain routing
architecture, there is no clear definition of GMPLS inter-domain
routing. Moreover, GMPLS inter-domain signaling is specifically
defined [Inter-signaling] assuming that the reachability information
is ensured between domains. On the other hand, standard organization
(SDOs) such as ITU-T and OIF have already define the same
functionality of iter-domain routing as E-NNI functional
specifications [ASON routing, OIF-ENNI].
At this moment, SPs who want to utilize IETF GMPLS network can not
imagine inter-domain GMPLS networks for inter-SPs as well as intra-SP
but only intra-domain GMPLS networks, while other SDOs support such
specifications.
If the MPLS world is looked at, the inter-domain requirements
[RFC4105] are assumed under the condition of routing information
exchange by BGP-4 between inter-domains.
[Interas-te] describes the requirements for extending TE mechanisms
across the GMPLS network domains. However, before considering such
requirements, the basic inter-domain routing requirement must be
discussed and assessed among the working group members in order to
assist appropriate GMPLS inter-domain signaling functionalities.
This document provides the problem statement in order to achieve
GMPLS inter-domain networks especially in inter-SP operational
environment. It also proposes to specify the functional requirements
to support of GMPLS inter-domain routing functions.
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 [RFC2119].
3. Problems statement of GMPLS inter-domain networks
Figure 1 depicts a typical network, consisting of several GMPLS
domains, assumed in this document. D1, D2, D3 and D4 have multiple
GMPLS inter-domain connections, and D5 has only one GMPLS inter-
domain connection. These domains follow the definition in [inter-
domain].
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+---------+
+---------|GMPLS D2|----------+
| +----+----+ |
+----+----+ | +----+----+ +---------+
|GMPLS D1| | |GMPLS D4|---|GMPLS D5|
+----+----+ | +----+----+ +---------+
| +----+----+ |
+---------|GMPLS D3|----------+
+---------+
Figure 1: GMPLS Inter-domain network model
Each domain is configured using various switching and link
technologies defined in [Arch] and an end-to-end route needs to
respect TE link attributes like multiplexing type, encoding type,
etc., making the problem a bit different from the case of classical
(packet) MPLS. In order to route from one GMPLS domain to another
GMPLS domain appropriately, each domain should advertise at least
reachability information, while concealing its internal topology
information through GMPLS exterior routing protocol, which has not
yet been defined. Additional TE information may be required in the
future, in order to improve the network control and management.
A signaling mechanism is required to specify a route consisting of
multiple domains. [ID-sig] defines the signaling mechanisms over
multiple domains, for example, to use loose hop expansion at the
domain border routers. It is quite difficult and less efficient from
the point of operation to set up the route without knowing
reachability information. In such a case, the operator must specify
the static route to the border node as well as appropriate border
node, although the crank back mechanism may solve this issue (if we
accept the possibility of multiple signaling tries).
In the IP/MPLS network, network nodes are only a packet switched
device. On the other hand, since the GMPLS network consists of
various devices such as optical cross-connect equipment, IP/MPLS
router, SDH-XC, and so forth, LSP end-point information may be useful
in order to use a forwarding adjacency as inter-domain routing
information.
Therefore, without sacrificing the operational efficiency as the same
with MPLS inter-domain network, the clear definition of GMPLS inter-
domain routing must be defined for SPs who think about adopting the
GMPLS technology to control their optical networks.
4. Requirement of GMPLS inter-domain routing
In this section, we describe the requirements of GMPLS inter-domain
routing for the computation of GMPLS paths over multiple domains.
In IP/MPLS networks, inter-AS routing is assumed to reuse the
existing EGP of BGP-4 and such architecture is widely established.
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However, such inter-domain routing has not been clearly defined so
far for GMPLS inter-domain networks, even if it may be a straight
forward to reuse the same protocol as IP/MPLS networks.
Therefore, inter-domain routing is required to support multiple GMPLS
domains.
5.2.1 Reachability information exchange
GMPLS inter-domain routing mechanism must support the exchange of
reachability information over each domain. Reachability information
includes:
(1) Reachable IP address (Node ID or Interface IP address)
(2) Interface ID (unnumbered link)
The reachability information must be advertised in accordance with
their belonging domain information in order to calculate the GMPLS
LSP over multiple domains [id-sig]. The reachability information may
be aggregated depending on the domains policy.
The scalability of inter-domain routing should be considered in
designing future GMPLS extensions to allow exchange of TE information
in addition to the above reachability information. Furthermore, the
GMPLS inter-domain routing should be designed to achieve such
operation that defects in one domain do not affect the scalability of
an intra-domain routing of IGPs in other domains, although the GMPLS
inter-domain routing should promptly advertise the failure within the
domain, ensuring the GMPLS inter-domain connection establishment.
The GMPLS network, in general, consists of various devices such as
optical cross-connect equipment, IP/MPLS router, SDH-XC, and so forth,
and LSP end-point information should be useful in order to use a
forwarding adjacency as inter-domain routing information.
GMPLS inter-domain routing must basically follow the GMPLS
architecture [Arch], including the support of its exchange over out
of band control channel.
5.2.2 Reachability information redistribution requirement
GMPLS inter-domain routing must provide redistribution mechanisms
within the domain in a scalable manner. These information
redistribution mechanisms must be designed to achieve such operation
that a defect in a domain does not affect the scalability of intra-
domain routing in a different domain, although the GMPLS inter-domain
routing must promptly advertise the failure within the domain,
ensuring the GMPLS inter-domain connection establishment.
Mechanisms for redistributing GMPLS reachability information within
the GMPLS domain can be I-BGP session, or re-injection to IGP.
Especially, it is useful to adopt GMPLS end-to-end basis path
calculation.
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GMPLS inter-domain routing must have the functionality to consider
any policies for controlling reachability information to be flooded,
which will be defined between domains on a business or operational
strategy basis. GMPLS inter-domain routing policy should be able to
be changed and configured on a per domain basis. This policy control
especially in terms of switching capability may be applicable to the
extensions of hierarchical routing. Each domain should control the
advertisement of the switching capability or re-advertisement of
received switching capability.
6. Security consideration
GMPLS inter-domain routing should be implemented under a certain
security consideration of the control plane as well as the data plane
itself. Indeed, this will not change the underlying security issues.
7. Acknowledgement
The authors would like to express the thanks to Naoaki Yamanaka for
his support.
8. Intellectual property considerations
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
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The IETF invites any interested party to bring to its attention any
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this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
9. Informative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[Inter-domain] A. Farrel, et al, "A framework for inter-domain MPLS
traffic engineering", draft-ietf-ccamp-inter-fomain-
framework-01.txt, February 2005.
[Interas-te] T. Otani, et al, GMPLS Inter-domain Traffic
Engineering Requirements, draft-otani-ccamp-interas-
gmpls-te-03.txt, July 2005.
[ASON routing] G.8080
[OIF-ENNI] DDPR
[RFC 4105] R. Zhan, et al, "Requirements for Inter-Area MPLS
Traffic Engineering, RFC4105, June 2005.
[Arch] E. Mannie, et al, "Generalized Multi-Protocol Label
Switching Architecture", RFC3945, October, 2004.
[ID-sig] A. Ayyangar, Inter domain GMPLS Traffic Engineering
- RSVP-TE extensions, draft-ietf-ccamp-inter-domain-
rsvp-te-02.txt, Oct. 2005.
Author's Addresses
Tomohiro Otani
KDDI R&D Laboratories, Inc.
2-1-15 Ohara Fujimino-shi Phone: +81-49-278-7357
Saitama, 356-8502. Japan Email: otani@kddilabs.jp
Satoru Okamoto
NTT Network Service System Laboratories
3-9-11 Midori-cho, Musashino-shi, Phone: +81-422-59-4353
Tokyo, 180-8585. Japan Email: okamoto.satoru@lab.ntt.co.jp
Document expiration
This document will be expired in April 30, 2006, unless it is updated.
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