Internet DRAFT - draft-ietf-teas-rsvp-te-scaling-rec
draft-ietf-teas-rsvp-te-scaling-rec
TEAS Working Group V. Beeram, Ed.
Internet-Draft Juniper Networks
Intended status: Standards Track I. Minei
Expires: August 18, 2018 R. Shakir
Google, Inc
D. Pacella
Verizon
T. Saad
Cisco Systems
February 14, 2018
Techniques to Improve the Scalability of RSVP Traffic Engineering
Deployments
draft-ietf-teas-rsvp-te-scaling-rec-09
Abstract
At the time of writing, networks which utilize RSVP Traffic
Engineering (RSVP-TE) Label Switched Paths (LSPs) are encountering
limitations in the ability of implementations to support the growth
in the number of LSPs deployed.
This document defines two techniques, "Refresh-Interval Independent
RSVP (RI-RSVP)" and "Per-Peer Flow-Control", that reduce the number
of processing cycles required to maintain RSVP-TE LSP state in Label
Switching Routers (LSRs) and hence allow implementations to support
larger scale deployments.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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/.
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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, 2018.
Copyright Notice
Copyright (c) 2018 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirement for RFC2961 Support . . . . . . . . . . . . . . . 3
2.1. Required Functionality from RFC2961 to be Implemented . . 4
2.2. Making Acknowledgements Mandatory . . . . . . . . . . . . 4
3. Refresh-Interval Independent RSVP (RI-RSVP) . . . . . . . . . 4
3.1. Capability Advertisement . . . . . . . . . . . . . . . . 5
3.2. Compatibility . . . . . . . . . . . . . . . . . . . . . . 6
4. Per-Peer RSVP Flow-Control . . . . . . . . . . . . . . . . . 6
4.1. Capability Advertisement . . . . . . . . . . . . . . . . 7
4.2. Compatibility . . . . . . . . . . . . . . . . . . . . . . 7
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7.1. Capability Object Values . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Recommended Defaults . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
At the time of writing, networks which utilize RSVP Traffic
Engineering (RSVP-TE) [RFC3209] Label Switched Paths (LSPs) are
encountering limitations in the ability of implementations to support
the growth in the number of LSPs deployed.
The set of RSVP Refresh Overhead Reduction procedures [RFC2961]
serves as a powerful toolkit for RSVP-TE implementations to help
cover a majority of the concerns about soft-state scaling. However,
even with these tools in the toolkit, analysis of existing
implementations [RFC5439] indicates that the processing required
beyond a certain scale may still cause significant disruption to a
Label Switching Router (LSR).
This document builds on the scaling work and analysis that has been
done so far and defines protocol extensions to help RSVP-TE
deployments push the envelope further on scaling by increasing the
threshold above which an LSR struggles to achieve sufficient
processing to maintain LSP state.
This document defines two techniques, "Refresh-Interval Independent
RSVP (RI-RSVP)" and "Per-Peer Flow-Control", that cut down the number
of processing cycles required to maintain LSP state. "RI-RSVP" helps
completely eliminate RSVP's reliance on refreshes and refresh-
timeouts while "Per-Peer Flow-Control" enables a busy RSVP speaker to
apply back pressure to its peer(s). This document defines a unique
RSVP Capability [RFC5063] for each technique (Support for CAPABILITY
object is a prerequisite for implementing these techniques). Note
that the "Per-Peer Flow-Control" technique requires the "RI-RSVP"
technique as a prerequisite. In order to reap maximum scaling
benefits, it is strongly recommended that implementations support
both the techniques and have them enabled by default. Both the
techniques are fully backward compatible and can be deployed
incrementally.
2. Requirement for RFC2961 Support
The techniques defined in Section 3 and Section 4 are based on
proposals made in [RFC2961]. Implementations of these techniques
will need to support the RSVP messages and procedures defined in
[RFC2961] with some minor modifications and alterations to
recommended time intervals and iteration counts (see Appendix A for
the set of recommended defaults).
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2.1. Required Functionality from RFC2961 to be Implemented
An implementation that supports the techniques discussed in Section 3
and Section 4 must support the functionality described in [RFC2961]
as follows:
o It MUST indicate support for RSVP Refresh Overhead Reduction
extensions (as specified in Section 2 of [RFC2961]).
o It MUST support receipt of any RSVP Refresh Overhead Reduction
message as defined in [RFC2961].
o It MUST initiate all RSVP Refresh Overhead Reduction mechanisms as
defined in [RFC2961] (including the SRefresh message) with the
default behavior being to initiate the mechanisms but offering a
configuration override.
o It MUST support reliable delivery of Path/Resv and the
corresponding Tear/Err messages (as specified in Section 4 of
[RFC2961]).
o It MUST support retransmission of all unacknowledged RSVP-TE
messages using exponential-backoff (as specified in Section 6 of
[RFC2961]).
2.2. Making Acknowledgements Mandatory
The reliable message delivery mechanism specified in [RFC2961] states
that "Nodes receiving a non-out of order message containing a
MESSAGE_ID object with the ACK_Desired flag set, SHOULD respond with
a MESSAGE_ID_ACK object."
In an implementation that supports the techniques discussed in
Section 3 and Section 4, nodes receiving a non-out of order message
containing a MESSAGE_ID object with the ACK-Desired flag set, MUST
respond with a MESSAGE_ID_ACK object. This MESSAGE_ID_ACK object can
be packed along with other MESSAGE_ID_ACK or MESSAGE_ID_NACK objects
and sent in an Ack message (or piggy-backed in any other RSVP
message). This improvement to the predictability of the system in
terms of reliable message delivery is key for being able to take any
action based on a non-receipt of an ACK.
3. Refresh-Interval Independent RSVP (RI-RSVP)
The RSVP protocol relies on periodic refreshes for state
synchronization between RSVP neighbors and for recovery from lost
RSVP messages. It relies on refresh timeout for stale state cleanup.
The primary motivation behind introducing the notion of "Refresh
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Interval Independent RSVP" (RI-RSVP) is to completely eliminate
RSVP's reliance on refreshes and refresh timeouts. This is done by
simply increasing the refresh interval to a fairly large value.
[RFC2961] and [RFC5439] do talk about increasing the value of the
refresh interval to provide linear improvement of transmission
overhead, but also point out the degree of functionality that is lost
by doing so. This section revisits this notion, but also sets out
additional requirements to make sure that there is no loss of
functionality incurred by increasing the value of the refresh
interval.
An implementation that supports RI-RSVP:
o MUST support all the requirements specified in Section 2.
o MUST make the default value of the configurable refresh interval
(R) be a large value (10s of minutes). A default value of 20
minutes is RECOMMENDED by this document.
o MUST use a separate shorter refresh interval for refreshing state
associated with unacknowledged Path/Resv messages (uR). A default
value of 30 seconds is RECOMMENDED by this document.
o MUST implement coupling the state of individual LSPs with the
state of the corresponding RSVP-TE signaling adjacency. When an
RSVP-TE speaker detects RSVP-TE signaling adjacency failure, the
speaker MUST act as if all the Path and Resv states learnt via the
failed signaling adjacency have timed out.
o MUST make use of Node-ID based Hello Session ([RFC3209],
[RFC4558]) for detection of RSVP-TE signaling adjacency failures;
A default value of 9 seconds is RECOMMENDED by this document for
the configurable node hello interval (as opposed to the 5ms
default value proposed in Section 5.3 of [RFC3209]).
o MUST indicate support for RI-RSVP via the CAPABILITY object
[RFC5063] in Hello messages.
3.1. Capability Advertisement
An implementation supporting the RI-RSVP technique MUST set a new
flag "RI-RSVP Capable" in the CAPABILITY object signaled in Hello
messages.
Bit Number TBA1 (TBA2) - RI-RSVP Capable (I-bit):
Indicates that the sender supports RI-RSVP.
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Any node that sets the new I-bit in its CAPABILITY object MUST also
set the Refresh-Reduction-Capable bit in the common header of all
RSVP-TE messages. If a peer sets the I-bit in the CAPABILITY object
but does not set the Refresh-Reduction-Capable bit, then the RI-RSVP
functionality MUST NOT be activated for that peer.
3.2. Compatibility
The RI-RSVP functionality MUST NOT be activated with a peer that does
not indicate support for this functionality. Inactivation of the RI-
RSVP functionality MUST result in the use of the traditional smaller
refresh interval [RFC2205].
4. Per-Peer RSVP Flow-Control
The functionality discussed in this section provides an RSVP speaker
with the ability to apply back pressure to its peer(s) to reduce/
eliminate a significant portion of the RSVP-TE control message load.
An implementation that supports "Per-Peer RSVP Flow-Control":
o MUST support all the requirements specified in Section 2.
o MUST support "RI-RSVP" (Section 3).
o MUST treat lack of ACKs from a peer as an indication of peer's
RSVP-TE control plane congestion. If congestion is detected, the
local system MUST throttle RSVP-TE messages to the affected peer.
This MUST be done on a per-peer basis. (Per-peer throttling MAY
be implemented by a traffic shaping mechanism that proportionally
reduces the RSVP signaling packet rate as the number of
outstanding Acks increases. And when the number of outstanding
Acks decreases, the send rate would be adjusted up again.)
o SHOULD use a Retry Limit (Rl) value of 7 (Section 6.2 of
[RFC2961], suggests using 3).
o SHOULD prioritize Hello messages and messages carrying
Acknowledgements over other RSVP messages.
o SHOULD prioritize Tear/Error over trigger Path/Resv (messages that
bring up new LSP state) sent to a peer when the local system
detects RSVP-TE control plane congestion in the peer.
o MUST indicate support for this technique via the CAPABILITY object
[RFC5063] in Hello messages.
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4.1. Capability Advertisement
An implementation supporting the "Per-Peer Flow-Control" technique
MUST set a new flag "Per-Peer Flow-Control Capable" in the CAPABILITY
object signaled in Hello messages.
Bit Number TBA3 (TBA4) - Per-Peer Flow-Control Capable (F-bit):
Indicates that the sender supports Per-Peer RSVP Flow-Control.
Any node that sets the new F-bit in its CAPABILITY object MUST also
set Refresh-Reduction-Capable bit in common header of all RSVP-TE
messages. If a peer sets the F-bit in the CAPABILITY object but does
not set the Refresh-Reduction-Capable bit, then the Per-Peer Flow-
Control functionality MUST NOT be activated for that peer.
4.2. Compatibility
The Per-Peer Flow-Control functionality MUST NOT be activated with a
peer that does not indicate support for this functionality. If a
peer hasn't indicated that it is capable of participating in "Per-
Peer Flow-Control", then it SHOULD NOT be assumed that the peer would
always acknowledge a non-out of order message containing a MESSAGE_ID
object with the ACK-Desired flag set.
5. Acknowledgements
The authors would like to thank Yakov Rekhter for initiating this
work and providing valuable inputs. They would like to thank
Raveendra Torvi and Chandra Ramachandran for participating in the
many discussions that led to the techniques discussed in this
document. They would also like to thank Adrian Farrel, Lou Berger
and Elwyn Davies for providing detailed review comments and text
suggestions.
6. Contributors
Markus Jork
Juniper Networks
Email: mjork@juniper.net
Ebben Aries
Juniper Networks
Email: exa@juniper.net
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7. IANA Considerations
7.1. Capability Object Values
IANA maintains all the registries associated with "Resource
Reservation Protocol (RSVP) Paramaters" (see
http://www.iana.org/assignments/rsvp-parameters/rsvp-
parameters.xhtml). "Capability Object Values" Registry (introduced
by [RFC5063]) is one of them.
IANA is requested to assign two new Capability Object Value bit flags
as follows:
Bit Hex Name Reference
Number Value
------------------------------------------------------------------
TBA1 TBA2 RI-RSVP Capable (I) Section 3
TBA3 TBA4 Per-Peer Flow-Control Capable (F) Section 4
8. Security Considerations
This document does not introduce new security issues. The security
considerations pertaining to the original RSVP protocol [RFC2205] and
RSVP-TE [RFC3209] and those that are described in [RFC5920] remain
relevant.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
editor.org/info/rfc2119>.
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
September 1997, <https://www.rfc-editor.org/info/rfc2205>.
[RFC2961] Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F.,
and S. Molendini, "RSVP Refresh Overhead Reduction
Extensions", RFC 2961, DOI 10.17487/RFC2961, April 2001,
<https://www.rfc-editor.org/info/rfc2961>.
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[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
[RFC4558] Ali, Z., Rahman, R., Prairie, D., and D. Papadimitriou,
"Node-ID Based Resource Reservation Protocol (RSVP) Hello:
A Clarification Statement", RFC 4558,
DOI 10.17487/RFC4558, June 2006, <https://www.rfc-
editor.org/info/rfc4558>.
[RFC5063] Satyanarayana, A., Ed. and R. Rahman, Ed., "Extensions to
GMPLS Resource Reservation Protocol (RSVP) Graceful
Restart", RFC 5063, DOI 10.17487/RFC5063, October 2007,
<https://www.rfc-editor.org/info/rfc5063>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
9.2. Informative References
[RFC5439] Yasukawa, S., Farrel, A., and O. Komolafe, "An Analysis of
Scaling Issues in MPLS-TE Core Networks", RFC 5439,
DOI 10.17487/RFC5439, February 2009, <https://www.rfc-
editor.org/info/rfc5439>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<https://www.rfc-editor.org/info/rfc5920>.
Appendix A. Recommended Defaults
(a) Refresh-Interval (R)- 20 minutes (Section 3):
Given that an implementation supporting RI-RSVP doesn't rely on
refreshes for state sync between peers, the function of RSVP
refresh interval is analogous to that of IGP refresh interval (the
default of which is typically in the order of 10s of minutes).
Choosing a default of 20 minutes allows the refresh timer to be
randomly set to a value in the range [10 minutes (0.5R), 30
minutes (1.5R)].
(b) Node Hello-Interval - 9 Seconds (Section 3):
[RFC3209] defines the hello timeout as 3.5 times the hello
interval. Choosing 9 seconds for the node hello-interval gives a
hello timeout of 3.5*9 = 31.5 seconds. This puts the hello
timeout value in the vicinity of the IGP hello timeout value.
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(c) Retry-Limit (Rl) - 7 (Section 4):
Choosing 7 as the retry-limit results in an overall rapid
retransmit phase of 31.5 seconds. This matches up with the 31.5
seconds hello timeout.
(d) Refresh-Interval for refreshing state associated with
unacknowledged Path/Resv messages (uR) - 30 seconds (Section 3):
The recommended refresh interval (R) value of 20 minutes (for an
implementation supporting RI-RSVP) can not be used for refreshing
state associated with unacknowledged Path/Resv messages. This
document recommends the use of the traditional default refresh
interval value of 30 seconds for uR.
Authors' Addresses
Vishnu Pavan Beeram (editor)
Juniper Networks
Email: vbeeram@juniper.net
Ina Minei
Google, Inc
Email: inaminei@google.com
Rob Shakir
Google, Inc
Email: rjs@rob.sh
Dante Pacella
Verizon
Email: dante.j.pacella@verizon.com
Tarek Saad
Cisco Systems
Email: tsaad@cisco.com
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