One document matched: draft-ietf-ccamp-mpls-graceful-shutdown-03.txt
Differences from draft-ietf-ccamp-mpls-graceful-shutdown-02.txt
Networking Working Group
Internet Draft
Zafar Ali
Jean-Philippe Vasseur
Anca Zamfir
Cisco Systems, Inc.
Jonathan Newton
Cable and Wireless
Category: Informational
Expires: December 2007 June 2007
draft-ietf-ccamp-mpls-graceful-shutdown-03.txt
Graceful Shutdown in GMPLS Traffic Engineering Networks
Status of this Memo
By submitting this Internet-Draft, each author represents that
any applicable patent or other IPR claims of which he or she is
aware have been or will be disclosed, and any of which he or she
becomes aware will be disclosed, in accordance with Section 6 of
BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on December 07, 2007.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Expires December 2007 [Page 1]
draft-ietf-ccamp-mpls-graceful-shutdown-03.txt June 07
Abstract
GMPLS-TE Graceful shutdown is a method for explicitly notifying
the nodes in a Traffic Engineering (TE) enabled network that the
TE capability on a link or on an entire Label Switching Router
(LSR) is going to be disabled. GMPLS-TE graceful shutdown
mechanisms are tailored towards addressing the planned outage in
the network.
This document provides requirements and protocol mechanisms so as
to reduce/eliminate traffic disruption in the event of a planned
shutdown of a network resource. These operations are equally
applicable for both MPLS and its GMPLS extensions.
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 [i].
Table of Contents
1. Terminology.....................................................2
2. Introduction....................................................3
3. Requirements for Graceful Shutdown..............................4
4. Mechanisms for Graceful Shutdown................................4
4.1 RSVP-TE Signaling Mechanism for graceful shutdown............5
4.1.1 Graceful Shutdown of TE link(s)............................5
4.1.2 Graceful Shutdown of Component Link(s) in a Bundled TE Link 5
4.1.3 Graceful Shutdown of TE Node...............................6
4.2 OSPF/ ISIS Mechanisms for graceful shutdown..................6
4.2.1 Graceful Shutdown of TE link(s)............................6
4.2.2 Graceful Shutdown of Component Link(s) in a Bundled TE Link 7
4.2.3 Graceful Shutdown of TE Node...............................7
5. Security Considerations.........................................7
6. IANA Considerations.............................................7
7. Acknowledgments.................................................7
8. Reference.......................................................7
8.1 Normative Reference..........................................7
8.2 Informative Reference........................................8
9. Authors' Address:...............................................8
10. Intellectual Property Considerations...........................8
11. Disclaimer of Validity.........................................9
12. Copyright Statement............................................9
1. Terminology
LSR - Label Switching Device.
Expires December 2007 [Page 2]
draft-ietf-ccamp-mpls-graceful-shutdown-03.txt June 07
LSP - An MPLS Label Switched Path
Head-end or Ingress node: In this document the terms "head-end
node equally applies to the Ingress node that initiated signaling
for the Path or an intermediate node (in the case of loose hops
path computation) or a Path Computation Element (PCE) that
computes the routes on behalf of its clients (PCC).
GMPLS - The term GMPLS is used in this document to refer to both
classic MPLS, as well as the GMPLS extensions to MPLS.
TE Link - The term TE link refers to a physical link or an FA-
LSP, on which traffic engineering is enabled. A TE link can be
bundled or unbundled.
The terms node and LSR will be used interchangeably in this
document.
2. Introduction
When outages in a network are planned (e.g. for maintenance
purpose), some mechanisms can be used to avoid traffic
disruption. This is in contrast with unplanned network element
failure, where traffic disruption can be minimized thanks to
recovery mechanisms but may not be avoided. Hence, a Service
Provider may desire to gracefully (temporarily or definitely)
disable Traffic Engineering on a TE Link, a group of TE Links or
an entire node for administrative reasons such as link
maintenance, software/hardware upgrade at a node or significant
TE configuration changes. In all these cases, the goal is to
minimize the impact on the GMPLS traffic engineered flows carried
over TE LSPs in the network by triggering notifications so as to
graceful reroute such flows before the administrative procedures
are started.
Graceful shutdown of a resource may require several steps. These
steps can be broadly divided into two sets: disabling the
resource in the control plane and removing the resource for
forwarding. The node initiating the graceful shutdown condition
SHOULD delay the removal of the resources for forwarding, for
some period determined by local policy. This is to allow control
plane to gracefully divert the traffic away from the resource
being gracefully shutdown. Similarly, trigger for the graceful
shutdown event is a local matter at the node initiating the
graceful shutdown. Typically, graceful shutdown is triggered for
administrative reasons, such as link maintenance or
software/hardware upgrade at a node.
This document describes the mechanisms that can be used to
gracefully shutdown GMPLS Traffic Engineering on a resource. As
mentioned earlier, the graceful shutdown of the Traffic
Expires December 2007 [Page 3]
draft-ietf-ccamp-mpls-graceful-shutdown-03.txt June 07
Engineering capability on a resource could be incorporated in the
traditional shutdown operation of an interface, but it is a
separate step that is taken before the IGP on the link is brought
down and before the interface is brought down at different
layers. This document only addresses TE node and TE resources.
3. Requirements for Graceful Shutdown
This section lists the requirements for graceful shutdown in the
context of GMPLS Traffic Engineering.
- Graceful shutdown must address graceful removal of one TE link,
one component link within a bundled TE link, a set of TE links, a
set of component links or an entire node.
- It is required to prevent other network nodes to use the
network resources that are about to be shutdown, should new TE
LSP be set up. However, if the resource being shutdown is a last
resort, it can be used. Time or decision for removal of the
resource being shutdown is based on a local decision at the node
initiating the graceful shutdown procedure.
- It is required to reduce/eliminate traffic disruption on the
LSP(s) using the network resources which are about to be
shutdown.
- Graceful shutdown mechanisms are equally applicable to intra-
domain and TE LSPs spanning multiple domains. Here, a domain is
defined as either an IGP area or an Autonomous System [INTER-
AREA-AS].
- Graceful shutdown is equally applicable to GMPLS-TE, as well as
packet-based (MPLS) TE LSPs.
- In order to make rerouting effective, it is required to
communicate information about the TE resource under graceful
shutdown.
4. Mechanisms for Graceful Shutdown
An IGP only based solution is not applicable when dealing with
Inter-area and Inter-AS traffic engineering, as IGP LSA/LSP
flooding is restricted to IGP areas/levels. Consequently, RSVP
based mechanisms are required to cope with TE LSPs spanning
multiple domains. At the same time, RSVP mechanisms only convey
the information for the transiting LSPs to the router along the
upstream Path and not to all nodes in the network. Furthermore,
it must be noted that graceful shutdown notification via IGP
flooding is required to discourage a node from establishing new
LSPs through the resources being shutdown. In the following
Expires December 2007 [Page 4]
draft-ietf-ccamp-mpls-graceful-shutdown-03.txt June 07
sections the complementary mechanisms for RSVP-TE and IGP for
Graceful Shutdown are described.
4.1 RSVP-TE Signaling Mechanism for graceful shutdown
As discussed in Section 3, one of the requirements for the
signaling mechanism for graceful shutdown is to carry information
about the resource under graceful shutdown. The Graceful Shutdown
mechanism outlined in the following section, uses Path Error and
where available, Notify message, in order to achieve this
requirement. Such mechanisms relying on signaling are only
applicable to the existing LSPs.
Setup request for new LSPs over the TE resource being gracefully
shutdown SHOULD be rejected using the existing mechanisms that
are applied when the TE resource is not available.
4.1.1 Graceful Shutdown of TE link(s)
The node where graceful shutdown of a link or a set of links is
desired MUST trigger a Path Error message with "local link
maintenance required" sub-code for all affected LSPs. The "local
TE link maintenance required" error code is defined in [PATH-
REOPT]. If available, and where notify requests were included
when the LSPs were initially setup, Notify message (as defined in
RFC 3471, RFC 3473) MAY also be used for delivery of this
information to the head-end nodes.
When a GS operation is performed along the path of a protected
LSP, based on a local decision, the PLR or branch node MAY
redirect the traffic onto the local detour or protecting segment.
In any case, the PLR or branch node MUST forward the Path Error
to the head-end LSR.
When a head-end LSR receives a Path Error (or Notify) message
with sub-code "Local Maintenance on TE Link required Flag", it
SHOULD immediately trigger a make-before-break procedure. A head-
end node SHOULD avoid the IP address contained in the PathErr (or
Notify message) when performing path computation for the new LSP.
If the resource being gracefully shutdown is on the Path of the
protecting LSP/ local detour, the branch node/ PLR reroutes the
protecting LSP/ local detour just a head-end LSR would reroute
any other LSP.
4.1.2 Graceful Shutdown of Component Link(s) in a Bundled TE Link
MPLS TE Link Bundling [BUNDLE] requires that an LSP is pinned
down to component link(s). Hence, when a component link is
shutdown, the TE LSPs affected by such maintenance action needs
to be resignaled.
Expires December 2007 [Page 5]
draft-ietf-ccamp-mpls-graceful-shutdown-03.txt June 07
Graceful shutdown of a component link in a bundled TE link
differs from graceful shutdown of unbundled TE link or entire
bundled TE link. Specifically, in the former case, when only a
subset of component links and not the entire TE bundled link is
being shutdown, the remaining component links of the TE links may
still be able to admit new LSPs. Consequently a new error sub-
code for the RSVP error-code "Routing Problem" (24) [RSVP-TE] is
needed:
9 (TBA) Local component link maintenance required
Error Sub-code for "Local component link maintenance required" is
to be assigned by IANA.
If the last component link is being shutdown, the procedure
outlined in Section 5.1 is used.
When a head-end LSR receives an RSVP Path Error or Notify message
with sub-code "local component link maintenance required" Flag
set, it SHOULD immediately perform a make-before-break to avoid
traffic loss. The head-end LSR MAY still use the IP address
contained in the Path Error or Notify message in performing path
computation for rerouting the LSP. This is because, this address
is an IP address of the component link and the flag is an
implicit indication that the TE link may still have capacity to
admit new LSPs. However, if the ERO is computed such that it also
provides details of the component link selection(s) along the
Path, the component link selection with IP address contained in
the Path Error or Notify message SHOULD be avoided.
Based on a local decision, PLR/ branch node MAY trigger FRR/
segment recovery to recover from failure of a component link.
4.1.3 Graceful Shutdown of TE Node
When graceful shutdown at node level is desired, the node in
question follows the procedure specified in the previous section
for all TE Links.
4.2 OSPF/ ISIS Mechanisms for graceful shutdown
The procedures provided in this section are equally applicable to
OSPF and ISIS.
4.2.1 Graceful Shutdown of TE link(s)
The node where graceful-shutdown of a link is desired MUST
originate the TE LSA/LSP containing Link TLV for the link under
graceful shutdown with Traffic Engineering metric set to
0xffffffff, 0 as unreserved bandwidth, and if the link has LSC or
FSC as its Switching Capability then also with 0 as Max LSP
Expires December 2007 [Page 6]
draft-ietf-ccamp-mpls-graceful-shutdown-03.txt June 07
Bandwidth. This would discourage new LSP establishment through
the link under graceful shutdown.
Neighbors of the node where graceful shutdown procedure is in
progress SHOULD continue to advertise the actual unreserved
bandwidth of the TE links from the neighbors to that node,
without any routing adjacency change.
4.2.2 Graceful Shutdown of Component Link(s) in a Bundled TE Link
If graceful shutdown procedure is performed for a component link
within a TE Link bundle and it is not the last component link
available within the TE link, the link attributes associated with
the TE link are recomputed. If the removal of the component link
results in a significant bandwidth change event, a new LSA is
originated with the new traffic parameters. If the last component
link is being shutdown, the routing procedure outlined in Section
4.2.1 is used.
4.2.3 Graceful Shutdown of TE Node
When graceful shutdown at node level is desired, the node in
question follows the procedure specified in the previous section
for all TE Links.
5. Security Considerations
This document does not introduce new security issues. The
security considerations pertaining to the original RSVP protocol
[RSVP] remain relevant.
6. IANA Considerations
A new error sub-code for Path Error and Notify message is needed
for "Local component link maintenance required" flag.
7. Acknowledgments
The authors would like to acknowledge useful comments from David
Ward, Sami Boutros, Adrian Farrel and Dimitri Papadimitriou.
8. Reference
8.1 Normative Reference
[RSVP-TE] D. Awduche, L. Berger, D. Gan, T. Li, V. Srinivasan,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels",
RFC 3209, December 2001.
[PATH-REOPT] Jean-Philippe Vasseur, et al "Reoptimization of MPLS
Traffic Engineering loosely routed LSP paths", RFC 4736.
Expires December 2007 [Page 7]
draft-ietf-ccamp-mpls-graceful-shutdown-03.txt June 07
8.2 Informative Reference
[RSVP] Braden, et al, "Resource ReSerVation Protocol (RSVP) -
Version 1, Functional Specification", RFC 2205, December 1997.
[INTER-AREA-AS] Adrian Farrel, Jean-Philippe Vasseur, Arthi
Ayyangar, "A Framework for Inter-Domain MPLS Traffic
Engineering", RFC 4726.
[BUNDLE] Kompella, K., Rekhter, Y., Berger, L., "Link Bundling in
MPLS Traffic Engineering", RFC 4201.
9. Authors' Address:
Zafar Ali
Cisco systems, Inc.,
2000 Innovation Drive
Kanata, Ontario, K2K 3E8
Canada.
Email: zali@cisco.com
Jean Philippe Vasseur
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough , MA - 01719
USA
Email: jpv@cisco.com
Anca Zamfir
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario, K2K 3E8
Canada
Email: ancaz@cisco.com
Jonathan Newton
Cable and Wireless
jonathan.newton@cw.com
10. 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 might or might not be available; nor does it
represent that it has made any independent effort to identify any
such rights. Information on the procedures with respect to
rights in RFC documents can be found in BCP 78 and BCP 79.
Expires December 2007 [Page 8]
draft-ietf-ccamp-mpls-graceful-shutdown-03.txt June 07
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the
use of such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR
repository at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention
any copyrights, patents or patent applications, or other
proprietary rights that may cover technology that may be required
to implement this standard. Please address the information to
the IETF at ietf-ipr@ietf.org.
11. Disclaimer of Validity
This document and the information contained herein are provided
on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE
IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE
ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE.
12. Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
Expires December 2007 [Page 9]
| PAFTECH AB 2003-2026 | 2026-04-23 06:09:58 |