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Versions: (draft-beeram-teas-rsvp-te-scaling-rec) 00 01 02 03 04 05 06 07 08 09 RFC 8370

 TEAS Working Group                                  Vishnu Pavan Beeram
 Internet Draft                                         Juniper Networks
 Intended status: Proposed Standard                            Ina Minei
                                                             Google, Inc
                                                              Rob Shakir
                                                     Jive Communications
                                                           Dante Pacella
                                                                 Verizon
                                                              Tarek Saad
                                                           Cisco Systems
 
 Expires: September 21, 2016                              March 21, 2016
 
 
    Implementation Recommendations to Improve the Scalability of RSVP-TE
                                 Deployments
                       draft-ietf-teas-rsvp-te-scaling-rec-01
 
 
 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
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    This Internet-Draft will expire on September 21, 2016.
 
 Copyright Notice
 
    Copyright (c) 2016 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
 
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    (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.
 
 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 makes a set of implementation recommendations to help
    RSVP-TE deployments push the envelope on scaling and advocates the
    use of a couple of techniques - "Refresh Interval Independent RSVP
    (RI-RSVP)" and "Per-Peer flow-control" - for improving scaling.
 
 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].
 
 
 Table of Contents
 
    1. Introduction...................................................3
    2. Recommendations................................................3
       2.1. "RFC2961 specific" Recommendations........................3
          2.1.1. Basic Pre-Requisites.................................4
          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.............................6
          2.2.2. Compatibility........................................6
       2.3. Per-Peer RSVP Flow Control................................7
          2.3.1. Capability Advertisement.............................7
          2.3.2. Compatibility........................................8
       2.4. Other Recommendations.....................................8
          2.4.1. Summary FRR..........................................8
    3. Security Considerations........................................8
    4. IANA Considerations............................................9
       4.1. Capability Object Values..................................9
    5. References.....................................................9
 
 
 
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       5.1. Normative References......................................9
       5.2. Informative References...................................10
    6. Acknowledgments...............................................10
    Appendix A. Recommended Defaults.................................10
    Contributors.....................................................11
    Authors' Addresses...............................................11
 
 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
    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, but it is possible for an implementation to support just
    one but not the other.
 
 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 pre-requisites
 
 
 
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    for implementing either or both of the techniques discussed in
    Sections 2.2 and 2.3.
 
 2.1.1. Basic Pre-Requisites
 
    An implementation that supports either or both of the techniques
    discussed in Sections 2.2 and 2.3:
 
    - SHOULD indicate support for RSVP Refresh Overhead Reduction
      extensions (as specified in Section 2 of [RFC2961]) by default,
      with the ability to override the default via configuration.
 
    - MUST support reliable delivery of Path/Resv and the corresponding
      Tear/Err messages using the procedures specified in [RFC2961].
 
    - MUST support retransmit of all 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 either or both of 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
    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 it is the retransmission of Tear/Err messages and Rl has been
    reached, the router need not take any further actions. If it is the
    retransmission of Path/Resv messages and Rl has been reached, then
    the router starts periodic retransmission of these messages. The
 
 
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    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 SHOULD be less than
    the regular refresh interval. A default periodic retransmission
    interval of 30 seconds is RECOMMENDED by this document.
 
 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:
 
    - MUST support all the recommendations made in Section 2.1
 
    - 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.
 
    - 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.
 
    - 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]).
 
 
 
 
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    - (If Bypass FRR [RFC4090] is supported,) MUST implement procedures
      specified in [RI-RSVP-FRR] which describes methods to facilitate
      FRR that works independently of the refresh-interval.
 
    - 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.
 
    The new flag that will be introduced to CAPABILITY object is
    specified below.
 
        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            Length             | Class-Num(134)|  C-Type  (1)  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Reserved                      |I|T|R|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
 
    I bit
 
    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.
 
 2.2.2. Compatibility
 
    The RI-RSVP functionality MUST be activated only between peers that
    indicate their support for this functionality. The RI-RSVP specific
    Bypass FRR procedures discussed in [RI-RSVP-FRR] introduce a few new
    protocol extensions and those MUST get activated only if the
    participating nodes support RI-RSVP functionality.
 
 
 
 
 
 
 
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 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":
 
    - MUST support all the recommendations made in Section 2.1
 
    - MUST use 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.)
 
    - SHOULD use a Retry Limit (Rl) value of 7 (Section 6.2 of
      [RFC2961], suggests using 3).
 
    - 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.
 
    - MUST indicate support for all recommendations in this section via
      the CAPABILITY object in Hello messages.
 
 
 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.
 
    The new flag that will be introduced to CAPABILITY object is
    specified below.
 
        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            Length             | Class-Num(134)|  C-Type  (1)  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Reserved                    |F|I|T|R|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
 
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    F bit
 
    Indicates that the sender supports Per-Peer RSVP Flow Control
 
    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.
 
 2.3.2. Compatibility
 
    The "Per-Peer Flow Control" functionality MUST be activated only if
    both peers support it. 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.
 
 2.4. Other Recommendations
 
    The following scaling recommendations have no interdependency with
    any of the techniques/recommendations specified in Sections 2.2 and
    2.3. These are stand-alone functionalities that help improve RSVP-TE
    scalability.
 
 2.4.1. Summary FRR
 
    If Bypass FRR [RFC4090] is supported by an implementation, it SHOULD
    support the procedures discussed in [SUMMARY-FRR]. These procedures
    reduce the amount of RSVP signaling required for Fast Reroute
    procedures and subsequently improve the scalability of RSVP-TE
    signaling when undergoing FRR convergence post a link or node
    failure.
 
 3. 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.
 
 
 
 
 
 
 
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 4. IANA Considerations
 
 4.1. 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
    --------------------------------------------------------------------
    TBA       TBA      RI-RSVP Capable (I)                 Section 2.2.1
    TBA       TBA      Per-Peer Flow Control Capable (F)   Section 2.3.1
 
 5. References
 
 5.1. Normative References
 
    [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.
 
    [RFC2205]   Braden, R., "Resource Reservation Protocol (RSVP)",
                RFC 2205, September 1997.
 
    [RFC2961]   Berger, L., "RSVP Refresh Overhead Reduction
                Extensions", RFC 2961, April 2001.
 
    [RFC3209]   Awduche, D., "RSVP-TE: Extensions to RSVP for LSP
                Tunnels", RFC 3209, December 2001.
 
    [RFC4090]   Pan, P., "Fast Reroute Extensions to RSVP-TE for LSP
                Tunnels", RFC 4090, May 2005.
 
    [RFC4558]   Ali, Z., "Node-ID Based Resource Reservation (RSVP)
                Hello: A Clarification Statement", RFC 4558, June 2006.
 
    [RFC5063]   Satyanarayana, A., "Extensions to GMPLS Resource
                Reservation Protocol Graceful Restart", RFC5063, October
                2007.
 
    [RI-RSVP-FRR] Ramachandran, C., "Refresh Interval Independent FRR
 
 
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                Facility Protection", draft-chandra-mpls-ri-rsvp-frr,
                (work in progress)
 
    [SUMMARY-FRR] Taillon, M., "RSVP-TE Summary Fast Reroute Extensions
                for LSP Tunnels", draft-mtaillon-mpls-summary-frr-
                rsvpte, (work in progress)
 
 5.2. Informative References
 
    [RFC5439]   Yasukawa, S., "An Analysis of Scaling Issues in MPLS-TE
                Core Networks", RFC 5439, February 2009.
 
    [RFC5920]   Fang, L., "Security Framework for MPLS and GMPLS
                Networks", RFC5920, July 2010.
 
 
 6. Acknowledgments
 
    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 for providing
    detailed review comments.
 
 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.
 
 
 
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    (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.
 
 Contributors
 
    Markus Jork
    Juniper Networks
    Email: mjork@juniper.net
 
    Ebben Aries
    Juniper Networks
    Email: exa@juniper.net
 
 
 Authors' Addresses
 
    Vishnu Pavan Beeram (Ed)
    Juniper Networks
    Email: vbeeram@juniper.net
 
    Ina Minei
    Google, Inc
    Email: inaminei@google.com
 
    Rob Shakir
    Jive Communications, 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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