Implementation Recommendations to Improve the Scalability of RSVP-TE Deployments
draft-ietf-teas-rsvp-te-scaling-rec-05
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (teas WG) | |
|---|---|---|---|
| Authors | Vishnu Pavan Beeram , Ina Minei , Rob Shakir , Dante Pacella , Tarek Saad | ||
| Last updated | 2017-07-09 (Latest revision 2017-07-02) | ||
| Replaces | draft-beeram-teas-rsvp-te-scaling-rec | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text htmlized pdfized bibtex | ||
| Reviews |
GENART Last Call review
(of
-06)
Not Ready
OPSDIR Last Call review
(of
-06)
Has Issues
RTGDIR Last Call review
Has Nits
|
||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Lou Berger | ||
| Shepherd write-up | Show Last changed 2017-07-09 | ||
| IESG | IESG state | Publication Requested | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Deborah Brungard | ||
| Send notices to | Lou Berger <lberger@labn.net> |
draft-ietf-teas-rsvp-te-scaling-rec-05
TEAS Working Group V. Beeram, Ed.
Internet-Draft Juniper Networks
Intended status: Standards Track I. Minei
Expires: January 3, 2018 R. Shakir
Google, Inc
D. Pacella
Verizon
T. Saad
Cisco Systems
July 2, 2017
Implementation Recommendations to Improve the Scalability of RSVP-TE
Deployments
draft-ietf-teas-rsvp-te-scaling-rec-05
Abstract
The scale at which RSVP-TE Label Switched Paths (LSPs) get deployed
is growing continually and the onus is on RSVP-TE implementations
across the board to keep up with this increasing demand.
This document introduces a couple of techniques - "Refresh-Interval
Independent RSVP (RI-RSVP)" and "Per-Peer Flow-Control" - to help
RSVP-TE deployments push the envelope on scaling.
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 January 3, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
Beeram, et al. Expires January 3, 2018 [Page 1]
Internet-Draft RSVP-TE Scaling - Impl. Rec July 2017
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 . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3
2. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. "RFC2961 Specific" Recommendations . . . . . . . . . . . 3
2.1.1. Basic Prerequisites . . . . . . . . . . . . . . . . . 3
2.1.2. Making Acknowledgements Mandatory . . . . . . . . . . 4
2.1.3. Clarifications On Reaching Rapid Retry Limit (Rl) . . 4
2.2. Refresh-Interval Independent RSVP . . . . . . . . . . . . 5
2.2.1. Capability Advertisement . . . . . . . . . . . . . . 5
2.2.2. Compatibility . . . . . . . . . . . . . . . . . . . . 6
2.3. Per-Peer RSVP Flow-Control . . . . . . . . . . . . . . . 6
2.3.1. Capability Advertisement . . . . . . . . . . . . . . 7
2.3.2. Compatibility . . . . . . . . . . . . . . . . . . . . 7
3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
4. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5.1. Capability Object Values . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Recommended Defaults . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
The scale at which RSVP-TE [RFC3209] Label Switched Paths (LSPs) get
deployed is growing continually and there is considerable onus on
RSVP-TE implementations across the board to keep up with this
increasing demand in scale.
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
Beeram, et al. Expires January 3, 2018 [Page 2]
Internet-Draft RSVP-TE Scaling - Impl. Rec July 2017
implementations [RFC5439] indicates that the processing required
under certain scale may still cause significant disruption to an LSR.
This document builds on the scaling work and analysis that has been
done so far and makes a set of concrete implementation
recommendations to help RSVP-TE deployments push the envelope further
on scaling - push higher the threshold above which an LSR struggles
to achieve sufficient processing to maintain LSP state.
This document advocates the use of a couple of techniques - "Refresh-
Interval Independent RSVP (RI-RSVP)" and "Per-Peer Flow-Control" -
for significantly cutting down the amount 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). In order to reap maximum scaling benefits, it is
strongly RECOMMENDED that implementations support both the
techniques.
1.1. 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 [RFC2119]
2. Recommendations
2.1. "RFC2961 Specific" Recommendations
The implementation recommendations discussed in this section are
based on the proposals made in [RFC2961] and act as prerequisites for
implementing the techniques discussed in Sections 2.2 and 2.3.
2.1.1. Basic Prerequisites
An implementation that supports the techniques discussed in Sections
2.2 and 2.3 must meet certain basic prerequisites.
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 SHOULD 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.
Beeram, et al. Expires January 3, 2018 [Page 3]
Internet-Draft RSVP-TE Scaling - Impl. Rec July 2017
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]).
2.1.2. 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
Sections 2.2 and 2.3, 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.
2.1.3. Clarifications On Reaching Rapid Retry Limit (Rl)
According to section 6 of [RFC2961] "The staged retransmission will
continue until either an appropriate MESSAGE_ID_ACK object is
received, or the rapid retry limit, Rl, has been reached." The
following clarifies what actions, if any, a router should take once
Rl has been reached.
If Rl has been reached for the retransmission of a message that is
neither a Path nor a Resv message, then the router need not take any
further action. If Rl has been reached for the retransmission of a
Path or a Resv message, then the router starts periodic
retransmission of these on a slower timer. The retransmitted
messages MUST carry MESSAGE_ID object with ACK_Desired flag set.
This periodic retransmission SHOULD continue until an appropriate
MESSAGE_ID_ACK object is received indicating acknowledgement of the
(retransmitted) Path/Resv message. The configurable periodic
retransmission interval for this slower timer SHOULD be less than the
regular refresh interval. A default periodic retransmission interval
interval (for this slower timer) of 30 seconds is RECOMMENDED by this
document.
Beeram, et al. Expires January 3, 2018 [Page 4]
Internet-Draft RSVP-TE Scaling - Impl. Rec July 2017
2.2. Refresh-Interval Independent 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
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 on transmission
overhead, but also point out the degree of functionality that is lost
by doing so. This section revisits this notion, but also proposes
sufficient recommendations 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 recommendations made in Section 2.1.
o MUST make the default value of the configurable refresh interval
be a large value (10s of minutes). A default value of 20 minutes
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 the all the Path and Resv state learnt via
the failed signaling adjacency has 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 in
Hello messages.
2.2.1. Capability Advertisement
An implementation supporting the RI-RSVP recommendations 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):
Beeram, et al. Expires January 3, 2018 [Page 5]
Internet-Draft RSVP-TE Scaling - Impl. Rec July 2017
Indicates that the sender supports RI-RSVP.
Any node that sets the new I-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 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.
2.2.2. Compatibility
The RI-RSVP functionality MUST NOT be activated with a peer that does
not indicate support for this functionality.
2.3. Per-Peer RSVP Flow-Control
The set of recommendations discussed in this section provide an RSVP
speaker with the ability to apply back pressure to its peer(s) to
reduce/eliminate RSVP-TE control plane congestion.
An implementation that supports "Per-Peer RSVP Flow-Control":
o MUST support all the recommendations made in Sections 2.1 and 2.2.
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 all recommendations in this section via
the CAPABILITY object in Hello messages.
Beeram, et al. Expires January 3, 2018 [Page 6]
Internet-Draft RSVP-TE Scaling - Impl. Rec July 2017
2.3.1. Capability Advertisement
An implementation supporting the "Per-Peer Flow-Control"
recommendations 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.
2.3.2. 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 is risky to assume that the peer would
always acknowledge a non-out of order message containing a MESSAGE ID
object with the ACK-Desired flag set.
3. 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 recommendations made in this
document. They would also like to thank Adrian Farrel and Lou Berger
for providing detailed review comments.
4. Contributors
Markus Jork
Juniper Networks
Email: mjork@juniper.net
Ebben Aries
Juniper Networks
Email: exa@juniper.net
Beeram, et al. Expires January 3, 2018 [Page 7]
Internet-Draft RSVP-TE Scaling - Impl. Rec July 2017
5. IANA Considerations
5.1. 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 2.2.1
TBA3 TBA4 Per-Peer Flow-Control Capable (F) Section 2.3.1
6. 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.
7. References
7.1. 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,
<http://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, <http://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,
<http://www.rfc-editor.org/info/rfc2961>.
Beeram, et al. Expires January 3, 2018 [Page 8]
Internet-Draft RSVP-TE Scaling - Impl. Rec July 2017
[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,
<http://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,
<http://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,
<http://www.rfc-editor.org/info/rfc5063>.
7.2. 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,
<http://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,
<http://www.rfc-editor.org/info/rfc5920>.
Appendix A. Recommended Defaults
(a) Refresh-Interval (R)- 20 minutes (Section 2.2) Given that an
implementation supporting RI-RSVP doesn't rely on refreshes for
state sync between peers, the RSVP refresh interval is sort of
analogous to 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 2.2) [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 to be in the same ballpark as the IGP hello timeout value.
(c) Retry-Limit (Rl) - 7 (Section 2.3) Choosing 7 as the retry-
limit results in an overall rapid retransmit phase of 31.5
seconds. This nicely matches up with the 31.5 seconds hello
timeout.
Beeram, et al. Expires January 3, 2018 [Page 9]
Internet-Draft RSVP-TE Scaling - Impl. Rec July 2017
(d) Periodic Retransmission Interval - 30 seconds (Section 2.1.3)
If the Retry-Limit (Rl) is 7, then it takes about 30 (31.5 to be
precise) seconds for the 7 rapid retransmit steps to max out.
(The last delay from message 6 to message 7 is 16 seconds). The
30 seconds interval also matches the traditional default refresh
time.
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
Beeram, et al. Expires January 3, 2018 [Page 10]