One document matched: draft-hegde-ospf-node-admin-tag-01.txt
Differences from draft-hegde-ospf-node-admin-tag-00.txt
Open Shortest Path First IGP S. Hegde
Internet-Draft H. Raghuveer
Intended status: Standards Track H. Gredler
Expires: August 18, 2014 Juniper Networks, Inc.
R. Shakir
British Telecom
A. Smirnov
Cisco Systems, Inc.
February 14, 2014
Advertising per-node administrative tags in OSPF
draft-hegde-ospf-node-admin-tag-01
Abstract
This document describes an extension to OSPF protocol [RFC2328] to
add an optional operational capability, that allows tagging and
grouping of the nodes in an OSPF domain. This allows
simplification,ease of management and control over route and path
selection based on configured policies.
This document describes the protocol extensions to disseminate per-
node admin-tags to the OSPFv2 and OSPFv3 protocol.
Requirements Language
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].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 18, 2014.
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Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Administrative Tag TLV . . . . . . . . . . . . . . . . . . . . 3
4. OSPF per-node administrative tag TLV . . . . . . . . . . . . . 3
4.1. TLV format . . . . . . . . . . . . . . . . . . . . . . . . 3
4.2. Elements of procedure . . . . . . . . . . . . . . . . . . . 4
5. Applications . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
This document provides mechanisms to advertise per-node
administrative tags in the OSPF Router Information LSA [RFC4970]. In
certain path-selection applications like for example in traffic-
engineering or LFA backup selection there is a need to tag the nodes
based on their roles in the network and have policies to prefer or
prune a certain group of nodes.
2. Applicability
For the purpose of advertising per-node administrative tags within
OSPF a new TLV is proposed. Because path selection is a functional
set which applies both to TE and non-TE applications, this new TLV is
carried in the Router Information LSA (RI LSA) [RFC4970]
3. Administrative Tag TLV
An administrative Tag is a 32-bit integer value that can be used to
identify a group of nodes in the OSPF domain.
The new TLV defined will be carried within an RI LSA for OSPFV2 and
OSPFV3. Router information LSA [RFC4970] can have link,area or AS
level flooding scope. Choosing the flooding scope to flood the group
tags are defined by the policies and is a local matter.
The TLV specifies one or more administrative tag values. An OSPF
node advertises the set of groups it is part of in the OSPF domain.
(for example, all PE-nodes are configured with certain tag value, all
P-nodes are configured with a different tag value in a domain).
4. OSPF per-node administrative tag TLV
4.1. TLV format
The format of the TLVs within the body of an RI LSA is the same as
the format used by the Traffic Engineering Extensions to OSPF
[RFC3630].
The LSA payload consists of one or more nested Type/Length/Value
(TLV) triplets. The format of each TLV is:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Administrative Tag #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Administrative Tag #2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Administrative Tag #N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: OSPF per-node Administrative Tag TLV
Type : TBA
Length: A 16-bit field that indicates the length of the value portion
in octets and will be a multiple of 4 octets dependent on the number
of tags advertised.
Value: A sequence of multiple 4 octets defining the administrative
tags. The number of tags carried in this TLV is restricted to 64.
4.2. Elements of procedure
Meaning of the Node administrative tags is generally opaque to OSPF.
Router advertising the Node administrative tag (or tags) may be
configured to do so without knowing (or even explicitly supporting)
functionality implied by the tag.
Interpretation of the tag values is implementation-specific. The
meaning of a Node administrative tag is defined by the network local
policy and is controlled via the configuration. There are no tag
values defined by this specification.
The semantics of the tag order are implementation-dependent. That
is, there is no implied meaning to the ordering of the tags that
indicates a certain operation or set of operations that need to be
performed based on the ordering.
Each tag SHOULD be treated as an independent identifier that MAY be
used in policy to perform a policy action. Whether or not tag A
precedes or succeeds tag B SHOULD not change the meaning of the tag
set.
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To avoid incomplete or inconsistent interpretations of the Node
administrative tags the same tag value MUST NOT be advertised by a
router in RI LSAs of different scopes. The same tag MAY be
advertised in multiple RI LSAs of the same scope, for example, OSPF
Area Border Router (ABR) may advertise the same tag in area-scope RI
LSAs in multiple areas connected to the ABR.
The Node administrative tags are not meant to be extended by the
future OSPF standards. The new OSPF extensions MUST NOT require use
of Node administrative tags or define well-known tag values.
Instead, the future OSPF extensions must define their own data
signaling tailored to the needs of the feature.
Being part of the RI LSA, the Node administrative tag TLV must be
reasonably small and stable. In particular, but not limited to,
implementations supporting the Node administrative tags MUST NOT tie
advertised tags to changes in the network topology (both within and
outside the OSPF domain) or reachability of routes.
5. Applications
This section lists several examples of how implementations might use
the Node administrative tags. These examples are given only to
demonstrate generic usefulness of the router tagging mechanism.
Implementation supporting this specification is not required to
implement any of the use cases. It is also worth noting that in some
described use cases routers configured to advertise tags help other
routers in their calculations but do not themselves implement the
same functionality.
1. Service auto-discovery
Router tagging may be used to automatically discover group of
routers sharing a particular service.
For example, service provider might desire to establish full mesh
of MPLS TE tunnels between all PE routers in the area of MPLS VPN
network. Marking all PE routers with a tag and configuring
devices with a policy to create MPLS TE tunnels to all other
devices advertising this tag will automate maintenance of the
full mesh. When new PE router is added to the area, all other PE
devices will open TE tunnels to it without the need of
reconfiguring them.
2. Fast-Rerouting policy
Increased deployment of Loop Free Alternates (LFA) as defined in
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[RFC5286] poses operation and management challenges.
[I-D.litkowski-rtgwg-lfa-manageability] proposes policies which,
when implemented, will ease LFA operation concerns.
One of the proposed refinements is to be able to group the nodes
in IGP domain with administrative tags and engineer the LFA based
on configured policies.
(a) Administrative limitation of LFA scope
Service provider access infrastructure is frequently
designed in layered approach with each layer of devices
serving different purposes and thus having different
hardware capabilities and configured software features.
When LFA repair paths are being computed, it may be
desirable to exclude devices from being considered as LFA
candidates based on their layer.
For example, if the access infrastructure is divided into
the Access, Distribution and Core layers it may be desirable
for a Distribution device to compute LFA only via
Distribution or Core devices but not via Access devices.
This may be due to features enabled on Access routers; due
to capacity limitations or due to the security requirements.
Managing such a policy via configuration of the router
computing LFA is cumbersome and error prone.
With the Node administrative tags it is possible to assign a
tag to each layer and implement LFA policy of computing LFA
repair paths only via neighbors which advertise the Core or
Distribution tag. This requires minimal per-node
configuration and network automatically adapts when new
links or routers are added.
(b) LFA calculation optimization
Calculation of LFA paths may require significant resources
of the router. One execution of Dijkstra algorithm is
required for each neighbor eligible to become next hop of
repair paths. Thus a router with a few hundreds of
neighbors may need to execute the algorithm hundreds of
times before the best (or even valid) repair path is found.
Manually excluding from the calculation neighbors which are
known to provide no valid LFA (such as single-connected
routers) may significantly reduce number of Dijkstra
algorithm runs.
LFA calculation policy may be configured so that routers
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advertising certain tag value are excluded from LFA
calculation even if they are otherwise suitable.
3. Controlling Remote LFA tunnel termination
[I-D.ietf-rtgwg-remote-lfa] proposed method of tunneling traffic
after connected link failure to extend the basic LFA coverage and
algorithm to find tunnel tail-end routers fitting LFA
requirement. In most cases proposed algorithm finds more than
one candidate tail-end router. In real life network it may be
desirable to exclude some nodes from the list of candidates based
on the local policy. This may be either due to known limitations
of the node (the router does accept targeted LDP sessions
required to implement Remote LFA tunneling) or due to
administrative requirements (for example, it may be desirable to
choose tail-end router among co-located devices).
The Node administrative tag delivers simple and scalable
solution. Remote LFA can be configured with a policy to accept
during the tail-end router calculation as candidates only routers
advertising certain tag. Tagging routers allows to both exclude
nodes not capable of serving as Remote LFA tunnel tail-ends and
to define a region from which tail-end router must be selected.
6. Security Considerations
This document does not introduce any further security issues other
than those discussed in [RFC2328] and [RFC5340].
7. IANA Considerations
IANA maintains the registry for the TLVs. OSPF Administrative Tags
will require one new type code for the TLV defined in this document.
8. Acknowledgments
Thanks to Bharath R and Pushpasis Sarakar for useful inputs.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
September 2003.
[RFC4970] Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R., and S.
Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 4970, July 2007.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008.
9.2. Informative References
[I-D.ietf-rtgwg-remote-lfa]
Bryant, S., Filsfils, C., Previdi, S., Shand, M., and S.
Ning, "Remote LFA FRR", draft-ietf-rtgwg-remote-lfa-02
(work in progress), May 2013.
[I-D.litkowski-rtgwg-lfa-manageability]
Litkowski, S., Decraene, B., Filsfils, C., and K. Raza,
"Operational management of Loop Free Alternates",
draft-litkowski-rtgwg-lfa-manageability-01 (work in
progress), February 2013.
[RFC5286] Atlas, A. and A. Zinin, "Basic Specification for IP Fast
Reroute: Loop-Free Alternates", RFC 5286, September 2008.
Authors' Addresses
Shraddha Hegde
Juniper Networks, Inc.
Embassy Business Park
Bangalore, KA 560093
India
Email: shraddha@juniper.net
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Harish Raghuveer
Juniper Networks, Inc.
Embassy Business Park
Bangalore 560093
India
Email: hraghuveer@juniper.net
Hannes Gredler
Juniper Networks, Inc.
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US
Email: hannes@juniper.net
Rob Shakir
British Telecom
Email: rob.shakir@bt.com
Anton Smirnov
Cisco Systems, Inc.
De Kleetlaan 6a
Diegem, 1831
Belgium
Email: as@cisco.com
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