GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc7727

Internet Engineering Task Force (IETF) M. Zhang Request for Comments: 7727 H. Wen Category: Standards Track Huawei ISSN: 2070-1721 J. Hu

                                                         China Telecom
                                                          January 2016
              Spanning Tree Protocol (STP) Application
         of the Inter-Chassis Communication Protocol (ICCP)

Abstract

 The Inter-Chassis Communication Protocol (ICCP) supports an inter-
 chassis redundancy mechanism that is used to support high network
 availability.
 In this document, Provider Edge (PE) devices in a Redundancy Group
 (RG) running ICCP are used to offer multihomed connectivity to
 Spanning Tree Protocol (STP) networks to improve availability of the
 STP networks.  The ICCP TLVs and usage for the ICCP STP application
 are defined.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7727.

Zhang, et al. Standards Track [Page 1] RFC 7727 STP Application of ICCP January 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
 (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.

Zhang, et al. Standards Track [Page 2] RFC 7727 STP Application of ICCP January 2016

Table of Contents

 1. Introduction ....................................................4
    1.1. Conventions Used in This Document ..........................4
    1.2. Terminology ................................................4
 2. Use Case ........................................................5
 3. Spanning Tree Protocol Application TLVs .........................6
    3.1. STP Connect TLV ............................................6
    3.2. STP Disconnect TLV .........................................7
         3.2.1. STP Disconnect Cause Sub-TLV ........................8
    3.3. STP Configuration TLVs .....................................8
         3.3.1. STP System Config ...................................9
         3.3.2. STP Region Name ....................................10
         3.3.3. STP Revision Level .................................10
         3.3.4. STP Instance Priority ..............................11
         3.3.5. STP Configuration Digest ...........................12
    3.4. STP State TLVs ............................................12
         3.4.1. STP Topology Changed Instances .....................12
         3.4.2. STP CIST Root Time Parameters ......................14
         3.4.3. STP MSTI Root Time Parameter .......................15
    3.5. STP Synchronization Request TLV ...........................16
    3.6. STP Synchronization Data TLV ..............................17
 4. Operations .....................................................18
    4.1. Common AC Procedures ......................................18
         4.1.1. Remote PE Node Failure or Isolation ................19
         4.1.2. Local PE Isolation .................................19
    4.2. ICCP STP Application Procedures ...........................19
         4.2.1. Initial Setup ......................................19
         4.2.2. Configuration Synchronization ......................20
         4.2.3. State Synchronization ..............................21
         4.2.4. Failure and Recovery ...............................22
 5. Security Considerations ........................................22
 6. IANA Considerations ............................................23
 7. References .....................................................23
    7.1. Normative References ......................................23
    7.2. Informative References ....................................24
 Acknowledgements ................................................. 24
 Authors' Addresses ............................................... 25

Zhang, et al. Standards Track [Page 3] RFC 7727 STP Application of ICCP January 2016

1. Introduction

 Inter-Chassis Communication Protocol (ICCP [RFC7275]) specifies a
 multi-chassis redundancy mechanism that enables Provider Edge (PE)
 devices located in a multi-chassis arrangement to act as a single
 Redundancy Group (RG).
 With the Spanning Tree Protocol (STP), a spanning tree will be formed
 over connected bridges by blocking some links between these bridges
 so that forwarding loops are avoided.  This document introduces
 support of STP as a new application of ICCP.  When a bridged STP
 network is connected to an RG, this STP application of ICCP enables
 the RG members to act as a single root bridge participating in the
 operations of STP.
 STP-relevant information needs to be exchanged and synchronized among
 the RG members.  New ICCP TLVs for the ICCP STP application are
 specified for this purpose.
 From the point of view of the customer, the Service Provider is
 providing a Virtual Private LAN Service (VPLS) [RFC4762].

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 RFC 2119 [RFC2119].

1.2. Terminology

 ICCP: Inter-Chassis Communication Protocol
 VPLS: Virtual Private LAN Service
 STP:  Spanning Tree Protocol
 MSTP: Multiple Spanning Tree Protocol
 MST:  Multiple Spanning Trees
 CIST: Common and Internal Spanning Tree ([802.1q], Section 3.27)
 MSTI: Multiple Spanning Tree Instance ([802.1q], Section 3.138)
 BPDU: Bridge Protocol Data Unit
 In this document, unless otherwise explicitly noted, the term "STP"
 also covers MSTP.

Zhang, et al. Standards Track [Page 4] RFC 7727 STP Application of ICCP January 2016

2. Use Case

 Customers widely use Ethernet as an access technology [RFC4762].
 It's common that one customer's Local Area Network (LAN) has multiple
 bridges connected to a carrier's network at different locations for
 reliability purposes.  Requirements for this use case are listed as
 follows.
 o  Customers desire to balance the load among their available
    connections to the carrier's network; therefore, all the
    connections need to be active.
 o  When one connection to the carrier network fails, customers
    require a connection in another location to continue to work after
    the reconvergence of the STP rather than compromising the whole
    STP network.  The failure of the connection may be due to the
    failure of the PE, the attachment circuit (AC), or even the
    Customer Edge (CE) device itself.
 In order to meet these requirements, the 'ICCP-STP' model is
 proposed.  It introduces STP as a new application of ICCP.
           +--------------+       +=============+
           |              |       |             |
           |              |       |             |
           |       +---+  |       |  +-----+|<--|--Pseudowire-->|
           |   +---+CE1+<6>-------<5>+ PE1 ||   |               |
           |  <1>  +---+  |       |  +-----+|<--|--Pseudowire-->|
           | +-+-+        |       |     ||      |
           | |CE3|        |       |     ||ICCP  |--> Towards the Core
           | +-+-+        |       |     ||      |
           |  <2>  +---+  |       |  +-----+|<--|--Pseudowire-->|
           |   +---+CE2+<3>-------<4>+ PE2 ||   |               |
           |       +---+  |       |  +-----+|<--|--Pseudowire-->|
           |              |       |             |
           | Multihomed   |       |  Redundancy |
           | STP Network  |       |    Group    |
           +--------------+       +=============+
      Figure 1: A STP network is multihomed to an RG running ICCP
 Figure 1 shows an example topology of this model.  With ICCP, the
 whole RG will be virtualized to be a single bridge.  Each RG member
 has its BridgeIdentifier (the MAC address).  The numerically lowest
 one is used as the BridgeIdentifier of the 'virtualized root bridge'.
 The RG acts as if the ports connected to the STP network (ports <4>
 and <5>) are for the same root bridge.  All these ports send the
 configuration BPDU with the highest root priority to trigger the

Zhang, et al. Standards Track [Page 5] RFC 7727 STP Application of ICCP January 2016

 construction of the spanning tree.  The link between the peering PEs
 is not visible to the bridge domains of the STP network.  In this
 way, the STP will always break a possible loop within the multihomed
 STP network by breaking the whole network into separate islands so
 that each is attached to one PE.  That forces all PEs in the RG to be
 active.  This is different from a generic VPLS [RFC4762] where the
 root bridge resides in the customer network and the multihomed PEs
 act in the active-standby mode.  Note that the specification of VPLS
 remains unchanged other than for this operation.  For instance, a
 full-mesh of pseudowires (PWs) is established between PEs, and the
 "split horizon" rule is still used to perform the loop-breaking
 through the core.

3. Spanning Tree Protocol Application TLVs

 This section specifies the ICCP TLVs for the ICCP STP application.
 The Unknown TLV bit (U-bit) and the Forward unknown TLV bit (F-bit)
 of the following TLVs MUST be sent as cleared and processed on
 receipt as specified in [RFC7275].

3.1. STP Connect TLV

 This TLV is included in the RG Connect Message to signal the
 initiation of an ICCP STP application connection.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x2000               |    Length                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      Protocol Version         |A|         Reserved            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                      Optional Sub-TLVs                        |
 ~                                                               ~
 |                                                               |
 +                                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |             ...                 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x2000 for "STP Connect TLV"

Zhang, et al. Standards Track [Page 6] RFC 7727 STP Application of ICCP January 2016

  1. Length
      Length of the TLV in octets excluding the U-bit, F-bit, Type,
      and Length fields.
  1. Protocol Version
      The version of ICCP STP application protocol.  This document
      defines version 0x0001.
  1. A bit
      Acknowledgement Bit.  Set to 1 if the sender has received a STP
      Connect TLV from the recipient.  Otherwise, set to 0.
  1. Reserved
      Reserved for future use.  These bits MUST be sent as 0 and
      ignored on receipt.
  1. Optional Sub-TLVs
      There are no optional Sub-TLVs defined for this version of the
      protocol.

3.2. STP Disconnect TLV

 This TLV is used in the RG Disconnect Message to indicate that the
 connection for the ICCP STP application is to be terminated.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x2001               |    Length                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                       Optional Sub-TLVs                       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x2001 for "STP Disconnect TLV"
  1. Length
      Length of the TLV in octets excluding the U-bit, F-bit, Type,
      and Length fields.

Zhang, et al. Standards Track [Page 7] RFC 7727 STP Application of ICCP January 2016

  1. Optional Sub-TLVs
      The only optional Sub-TLV defined for this version of the
      protocol is the "STP Disconnect Cause" sub-TLV, defined below:

3.2.1. STP Disconnect Cause Sub-TLV

  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x200C              |    Length                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                      Disconnect Cause String                  |
 ~                                                               ~
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x200C for "STP Disconnect Cause TLV"
  1. Length
      Length of the TLV in octets excluding the U-bit, F-bit, Type,
      and Length fields.
  1. Disconnect Cause String
      Variable-length string specifying the reason for the disconnect,
      encoded in UTF-8 [RFC3629] format.  Used for operational
      purposes.

3.3. STP Configuration TLVs

 The STP Configuration TLVs are sent in the RG Application Data
 Message.  When an STP Config TLV is received by a peer RG member, the
 member MUST synchronize with the configuration information contained
 in the TLV.  TLVs specified in Sections 3.3.1 to 3.3.5 define
 specific configuration information.

Zhang, et al. Standards Track [Page 8] RFC 7727 STP Application of ICCP January 2016

3.3.1. STP System Config

 This TLV announces the local node's STP System Parameters to the RG
 peers.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x2002               |    Length                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                              ROID                             |
 +                                                               +
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                         MAC Address                           |
 +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x2002 for "STP System Config TLV"
  1. Length
      Length of the ROID plus the MAC address in octets.  Always set
      to 14.
  1. ROID
      Redundant Object Identifier; format defined in Section 6.1.3 of
      [RFC7275].
  1. MAC Address
      The MAC address of the sender.  This MAC address is set to the
      BridgeIdentifier of the sender, as defined in [802.1q], Section
      13.26.2.  The numerically lowest 48-bit unsigned value of
      BridgeIdentifier is used as the MAC address of the Virtual Root
      Bridge mentioned in Section 2.

Zhang, et al. Standards Track [Page 9] RFC 7727 STP Application of ICCP January 2016

3.3.2. STP Region Name

 This TLV carries the value of Region Name.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x2003               |    Length                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                          Region Name                          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x2003 for "STP Region Name TLV"
  1. Length
      Length of the TLV in octets excluding the U-bit, F-bit, Type,
      and Length fields.
  1. Region Name
      The Name of the MST Region as specified in [802.1q], Section
      3.142.

3.3.3. STP Revision Level

 This TLV carries the value of Revision Level.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x2004               |    Length                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |       Revision Level          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x2004 for "STP Revision Level TLV".

Zhang, et al. Standards Track [Page 10] RFC 7727 STP Application of ICCP January 2016

  1. Length
      Length of the TLV in octets excluding the U-bit, F-bit, Type,
      and Length fields.  Always set to 2.
  1. Revision Level
      The Revision Level as specified in [802.1q], Section 13.8, item
      c.

3.3.4. STP Instance Priority

 This TLV carries the value of Instance Priority to other members in
 the RG.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x2005               |    Length                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  Pri  |      InstanceID       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x2005 for "STP Instance Priority TLV"
  1. Length
      Length of the TLV in octets excluding the U-bit, F-bit, Type,
      and Length fields.
  1. Pri
      The Instance Priority.  It is interpreted as unsigned integer
      with higher value indicating a higher priority.
  1. InstanceID
      The 12-bit Instance Identifier of the CIST or MSTI.  This
      parameter takes a value in the range 1 through 4094 for MSTI (as
      defined in [802.1q], Section 12.8.1.2.2) and takes value of 0
      for CIST.

Zhang, et al. Standards Track [Page 11] RFC 7727 STP Application of ICCP January 2016

3.3.5. STP Configuration Digest

 This TLV carries the value of STP VLAN Instance Mapping.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x2006             |    Length                     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                    Configuration Digest                       |
 ~                                                               ~
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x2006 for "STP Configuration Digest TLV"
  1. Length
      Length of the STP Configuration Digest in octets.  Always set to
      16.
  1. Configuration Digest
      As specified in [802.1q], Section 13.8, item d.

3.4. STP State TLVs

 The STP State TLVs are sent in the RG Application Data Message.  They
 are used by a PE device to report its STP status to other members in
 the RG.  Such TLVs are specified in the following subsections.

3.4.1. STP Topology Changed Instances

 This TLV is used to report the Topology Changed Instances to other
 members of the RG.  The sender monitors Topology Change Notification
 (TCN) messages and generates this list.  The receiving RG member MUST
 initiate the Topology Change event, including sending BPDU with the
 Topology Change flag set to 1 out of the designated port(s) of the
 Topology Changed bridge domains of the STP network, and flushing out
 MAC addresses relevant to the instances listed in this TLV.
 If the PE device supports MAC Address Withdrawal (see Section 6.2 of
 [RFC4762]), it SHOULD send a Label Distribution Protocol (LDP)
 Address Withdraw Message with the list of MAC addresses towards the
 core over the corresponding LDP sessions.  It is not necessary to

Zhang, et al. Standards Track [Page 12] RFC 7727 STP Application of ICCP January 2016

 send such a message to PEs of the same RG since the flushing of their
 MAC address tables should have been performed upon receipt of the STP
 Topology Changed Instances TLV.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x2007               |    Length                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                       InstanceID List                         |
 ~                                                               ~
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x2007 for "STP Topology Changed Instances TLV"
  1. Length
      Length of the TLV in octets excluding the U-bit, F-bit, Type,
      and Length fields.
  1. InstanceID List
      The list of the InstanceIDs of the CIST or MSTIs whose
      topologies have changed as indicated by the TCN messages as
      specified in [802.1q], Section 13.14.  The list is formatted by
      padding each InstanceID value to the 16-bit boundary as follows,
      where the bits in the "R" fields MUST be sent as 0 and ignored
      on receipt.
     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |R|R|R|R| InstanceID#1          |R|R|R|R| InstanceID#2          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~                             ... ...                           ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Zhang, et al. Standards Track [Page 13] RFC 7727 STP Application of ICCP January 2016

3.4.2. STP CIST Root Time Parameters

 This TLV is used to report the Value of CIST Root Time Parameters
 ([802.1q], Section 13.26.7) to other members of the RG.  All time
 parameter values are in seconds with a granularity of 1.  For ranges
 and default values of these parameter values, refer to [802.1d1998],
 Section 8.10.2, Table 8-3; [802.1d2004] Section 17.14, Table 17-1;
 and [802.1q], Section 13.26.7.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x2008               |    Length                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    MaxAge                     |   MessageAge                  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    FwdDelay                   |   HelloTime                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | RemainingHops |
 +-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x2008 for "STP CIST Root Time TLV"
  1. Length
      Length of the TLV in octets excluding the U-bit, F-bit, Type,
      and Length fields.  Always set to 9.
  1. MaxAge
      The Max Age of the CIST.  It is the maximum age of the
      information transmitted by the bridge when it is the Root Bridge
      ([802.1d2004], Section 17.13.8).
  1. MessageAge
      The Message Age of the CIST (see [802.1q], Section 13.26.7).
  1. FwdDelay
      The Forward Delay of the CIST.  It is the delay used by STP
      Bridges to transition Root and Designated Ports to Forwarding
      ([802.1d2004], Section 17.13.5).

Zhang, et al. Standards Track [Page 14] RFC 7727 STP Application of ICCP January 2016

  1. HelloTime
      The Hello Time of the CIST.  It is the interval between periodic
      transmissions of Configuration Messages by Designated Ports
      ([802.1d2004], Section 17.13.6).
  1. RemainingHops
      The remainingHops of the CIST ([802.1q], Section 13.26.7).

3.4.3. STP MSTI Root Time Parameter

 This TLV is used to report the parameter value of MSTI Root Time to
 other members of the RG.  As defined in [802.1q], Section 13.26.7, it
 is the value of remainingHops for the given MSTI.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x2009              |    Length                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  Pri  |  InstanceID           | RemainingHops |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x2009 for "STP MSTI Root Time TLV"
  1. Length
      Length of the TLV in octets excluding the U-bit, F-bit, Type,
      and Length fields.  Always set to 3.
  1. Pri
      The Instance Priority.  It is interpreted as an unsigned integer
      with higher value indicating a higher priority.
  1. InstanceID
      The 12-bit Instance Identifier of the Multiple Spanning Tree
      Instance (MSTID).  As defined in [802.1q], Section 12.8.1.2.2,
      this parameter takes a value in the range 1 through 4094.

Zhang, et al. Standards Track [Page 15] RFC 7727 STP Application of ICCP January 2016

  1. RemainingHops
      The remainingHops of the MSTI.  It is encoded in the same way as
      in [802.1q], Section 14.4.1, item f.

3.5. STP Synchronization Request TLV

 The STP Synchronization Request TLV is used in the RG Application
 Data Message.  This TLV is used by a device to request that its peer
 retransmit configuration or operational state.  The following
 information can be requested:
  1. configuration and/or state of the STP system,
  2. configuration and/or state for a given list of instances.
 The format of the TLV is as follows:
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x200A              |    Length                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      Request Number           |C|S|   Request Type            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                       InstanceID List                         |
 ~                                                               ~
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      Set to 0x200A for "STP Synchronization Request TLV"
  1. Length
      Length of the TLV in octets excluding the U-bit, F-bit, Type,
      and Length fields.  Always set to 4.
  1. Request Number
      2 octets.  Unsigned integer uniquely identifying the request.
      Used to match the request with a corresponding response.  The
      value of 0 is reserved for unsolicited synchronization, and it
      MUST NOT be used in the STP Synchronization Request TLV.  As
      indicated in [RFC7275], given the use of TCP, there are no
      issues associated with the wrap-around of the Request Number.

Zhang, et al. Standards Track [Page 16] RFC 7727 STP Application of ICCP January 2016

  1. C-bit
      Set to 1 if the request is for configuration data.  Otherwise,
      set to 0.
  1. S-bit
      Set to 1 if the request is for running state data.  Otherwise,
      set to 0.
  1. Request Type
      14 bits specifying the request type, encoded as follows:
          0x00   Request System Data
          0x01   Request data of the listed instances
          0x3FFF Request System Data and data of all instances
  1. InstanceID List
      The InstanceIDs of the CIST or MSTIs; format specified in
      Section 3.4.1.

3.6. STP Synchronization Data TLV

 The pair of STP Synchronization Data TLVs are used by the sender to
 delimit a set of TLVs that are being transmitted in response to an
 STP Synchronization Request TLV.  The delimiting TLVs signal the
 start and end of the synchronization data, and they associate the
 response with its corresponding request via the Request Number field.
 It's REQUIRED that each pair of STP Synchronization Data TLVs occur
 in the same fragment.  When the total size of the TLVs to be
 transmitted exceeds the maximal size of a fragment, these TLVs MUST
 be divided into multiple sets, delimited by multiple pairs of STP
 Synchronization Data TLVs, and filled into multiple fragments.  With
 the Request Number, lost fragments can be identified and
 re-requested.
 The STP Synchronization Data TLVs are also used for unsolicited
 advertisements of complete STP configuration and operational state
 data.  The Request Number field MUST be set to 0 in this case.

Zhang, et al. Standards Track [Page 17] RFC 7727 STP Application of ICCP January 2016

 STP Synchronization Data TLV has the following format:
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |U|F|   Type=0x200B              |    Length                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Request Number            |    Reserved                 |S|
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  1. U=F=0
  1. Type
      set to 0x200B for "STP Synchronization Data TLV"
  1. Length
      Length of the TLV in octets excluding the U-bit, F-bit, Type,
      and Length fields.  Always set to 4.
  1. Request Number
      2 octets.  Unsigned integer identifying the Request Number of
      the "STP Synchronization Request TLV" that initiated this
      synchronization data response.
  1. Reserved
      Reserved bits for future use.  These MUST be sent as 0 and
      ignored on receipt.
  1. S
      S = 0: Synchronization Data Start
      S = 1: Synchronization Data End

4. Operations

 Operational procedures for AC redundancy applications have been
 specified in Section 9.2 of [RFC7275].  The operational procedures of
 the ICCP STP application should follow those procedures, with the
 changes presented in this section.

4.1. Common AC Procedures

 The following changes are introduced to the generic procedures of AC
 redundancy applications defined in Section 9.2.1 of [RFC7275].

Zhang, et al. Standards Track [Page 18] RFC 7727 STP Application of ICCP January 2016

4.1.1. Remote PE Node Failure or Isolation

 When a local PE device detects that a remote PE device that is a
 member of the same RG is no longer reachable (using the mechanisms
 described in Section 5 of [RFC7275]), the local PE device checks if
 it has redundancy ACs for the affected services.  If redundant ACs
 are present, and if the local PE device has the new highest bridge
 priority, the local PE device becomes the virtual root bridge for
 corresponding ACs.

4.1.2. Local PE Isolation

 When a PE device detects that it has been isolated from the core
 network, then it needs to ensure that its AC redundancy mechanism
 will change the status of all active ACs to standby.  The AC
 redundancy application SHOULD then send an RG Application Data
 Message in order to trigger failover to another active PE device in
 the RG.  Note that this works only in the case of dedicated
 interconnect (Sections 3.2.1 and 3.2.3), since ICCP will still have
 the path to the peer, even though the PE device is isolated from the
 MPLS core network.

4.2. ICCP STP Application Procedures

 This section defines the procedures of the ICCP STP application that
 are applicable for Ethernet ACs.

4.2.1. Initial Setup

 When an RG is configured on a system that supports the ICCP STP
 application, such systems MUST send an RG Connect Message with an STP
 Connect TLV to each PE device that is a member of the RG.  The
 sending PE device MUST set the A bit to 1 in that TLV if it has
 received a corresponding STP Connect TLV from its peer PE; otherwise,
 the sending PE device MUST set the A bit to 0.  If a PE device
 receives an STP Connect TLV from its peer after sending its own TLV
 with the A bit set to 0, it MUST resend the TLV with the A bit set to
 1.  A system considers the ICCP STP application connection to be
 operational when it has both sent and received STP Connect TLVs with
 the A bit set to 1.  When the ICCP STP application connection between
 a pair of PEs is operational, the two devices can start exchanging RG
 Application Data Messages for the ICCP STP application.  This
 involves having each PE device advertise its STP configuration and
 operational state in an unsolicited manner.  A PE device SHOULD
 follow the order below when advertising its STP state upon initial
 application connection setup:

Zhang, et al. Standards Track [Page 19] RFC 7727 STP Application of ICCP January 2016

  1. Advertise the STP System Config TLV
  2. Advertise remaining Configuration TLVs
  3. Advertise State TLVs
 The update of the information contained in the State TLVs depends on
 that in the Configuration TLVs.  By sending the TLVs in the above
 order, the two peers may begin to update STP state as early as
 possible in the middle of exchanging these TLVs.
 A PE device MUST use a pair of STP Synchronization Data TLVs to
 delimit the entire set of TLVs that are being sent as part of this
 unsolicited advertisement.
 If a system receives an RG Connect Message with an STP Connect TLV
 that has a differing Protocol Version, it MUST follow the procedures
 outlined in the Section 4.4.1 ("Application Versioning") of
 [RFC7275].
 After the ICCP STP application connection has been established, every
 PE device MUST communicate its system-level configuration to its
 peers via the use of STP System Config TLV.
 When the ICCP STP application is administratively disabled on the PE,
 or on the particular RG, the system MUST send an RG Disconnect
 Message containing STP Disconnect TLV.

4.2.2. Configuration Synchronization

 A system that supports ICCP STP application MUST synchronize the
 configuration with other RG members.  This is achieved via the use of
 STP Configuration TLVs.  The PEs in the RG MUST all agree on the
 common MAC address to be associated with the virtual root bridge.  It
 is possible to achieve this via consistent configuration on member
 PEs.  However, in order to protect against possible
 misconfigurations, a virtual root bridge identifier MUST be set to
 the MAC address advertised by the PE device with the numerically
 lowest BridgeIdentifier (i.e., the MAC address of the bridge) in the
 RG.
 Furthermore, for a given ICCP STP application, an implementation MUST
 advertise the configuration prior to advertising its corresponding
 state.  If a PE device receives any STP State TLV that it had not
 learned of before via an appropriate STP Configuration TLV, then the
 PE device MUST request synchronization of the configuration and state
 from its peer.  If during such synchronization a PE device receives a
 State TLV that it has not learned before, then the PE device MUST
 send a NAK TLV for that particular TLV.  The PE device MUST NOT
 request resynchronization in this case.

Zhang, et al. Standards Track [Page 20] RFC 7727 STP Application of ICCP January 2016

4.2.3. State Synchronization

 PEs within the RG need to synchronize their state for proper STP
 operation.  This is achieved by having each system advertise its
 running state in STP State TLVs.  Whenever any STP parameter either
 on the CE or PE side is changed, the system MUST transmit an updated
 TLV for the affected STP instances.  Moreover, when the
 administrative or operational state changes, the system MUST transmit
 an updated State TLV to its peers.
 A PE device MAY request its peer to retransmit previously advertised
 state.  This is useful in case the PE device is recovering from a
 soft failure and attempting to relearn state.  To request such
 retransmissions, a PE device MUST send a set of one or more STP
 Synchronization Request TLVs.
 A PE device MUST respond to a STP Synchronization Request TLV by
 sending the requested data in a set of one or more STP Configuration
 or State TLVs delimited by a pair of STP Synchronization Data TLVs.
 Note that the response may span across multiple RG Application Data
 Messages, for example, when MTU limits are exceeded; however, the
 above ordering MUST be retained across messages, and only a single
 pair of Synchronization Data TLVs MUST be used to delimit the
 response across all RG Application Data Messages.
 A PE device MAY readvertise its STP state in an unsolicited manner.
 This is done by sending the appropriate State TLVs delimited by a
 pair of STP Synchronization Data TLVs and using a Request Number of
 0.
 While a PE device has sent out a synchronization request for a
 particular PE device, it SHOULD silently ignore all TLVs that are
 from that node, are received prior to the synchronization response,
 and carry the same type of information being requested.  This saves
 the system from the burden of updating state that will ultimately be
 overwritten by the synchronization response.  Note that TLVs
 pertaining to other systems should continue to be processed normally.
 If a PE device receives a synchronization request for an instance
 that doesn't exist or is not known to the PE, then it MUST trigger
 the unsolicited synchronization of all information by restarting the
 initialization.
 If during the synchronization operation a PE device receives an
 advertisement of a Node ID value that is different from the value
 previously advertised, then the PE device MUST purge all state data
 previously received from that peer prior to the last synchronization.

Zhang, et al. Standards Track [Page 21] RFC 7727 STP Application of ICCP January 2016

4.2.4. Failure and Recovery

 When a PE device that is active for the ICCP STP application
 encounters a core isolation fault [RFC7275], it SHOULD attempt to
 fail over to a peer PE device that hosts the same RG.  The default
 failover procedure is to have the failed PE device bring down the
 link(s) towards the multihomed STP network.  This will cause the STP
 network to reconverge and to use the other links that are connected
 to the other PE devices in the RG.  Other procedures for triggering
 failover are possible and are outside the scope of this document.
 If the isolated PE device is the one that has the numerically lowest
 BridgeIdentifier, PEs in the RG MUST synchronize STP Configuration
 and State TLVs and determine a new virtual root bridge as specified
 in Section 4.2.2.
 Upon recovery from a previous fault, a PE device SHOULD NOT reclaim
 the role of the virtual root for the STP network even if it has the
 numerically lowest BridgeIdentifier among the RG.  This minimizes
 traffic disruption.
 Whenever the virtual root bridge changes, the STP Topology Changed
 Instances TLV lists the instances that are affected by the change.
 These instances MUST undergo a STP reconvergence procedure when this
 TLV is received as defined in Section 3.4.1.

5. Security Considerations

 This document specifies an application running on the channel
 provided by ICCP [RFC7275].  The security considerations on ICCP
 apply in this document as well.
 For the ICCP STP application, an attack on a channel (running in the
 provider's network) can break not only the ability to deliver traffic
 across the provider's network, but also the ability to route traffic
 within the customer's network.  That is, a careful attack on a
 channel (such as the DoS attacks as described in [RFC7275]) can break
 STP within the customer network.  Implementations need to provide
 mechanisms to mitigate these types of attacks.  For example, the port
 between the PE device and the malicious CE device may be blocked.

Zhang, et al. Standards Track [Page 22] RFC 7727 STP Application of ICCP January 2016

6. IANA Considerations

 The IANA maintains a top-level registry called "Pseudowire Name
 Spaces (PWE3)".  It has a subregistry called "ICC RG Parameter
 Types".
 IANA has made 13 allocations from this registry as shown below.  IANA
 has allocated the codepoints from the range marked for assignment by
 IETF Review (0x2000-0x2FFF) [RFC5226].  Each assignment references
 this document.
    Parameter Type Description
    -------------- ---------------------------------
    0x2000         STP Connect TLV
    0x2001         STP Disconnect TLV
    0x2002         STP System Config TLV
    0x2003         STP Region Name TLV
    0x2004         STP Revision Level TLV
    0x2005         STP Instance Priority TLV
    0x2006         STP Configuration Digest TLV
    0x2007         STP Topology Changed Instances TLV
    0x2008         STP CIST Root Time TLV
    0x2009         STP MSTI Root Time TLV
    0x200A         STP Synchronization Request TLV
    0x200B         STP Synchronization Data TLV
    0x200C         STP Disconnect Cause TLV

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>.
 [RFC3629]    Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
              2003, <http://www.rfc-editor.org/info/rfc3629>.
 [RFC4762]    Lasserre, M., Ed., and V. Kompella, Ed., "Virtual
              Private LAN Service (VPLS) Using Label Distribution
              Protocol (LDP) Signaling", RFC 4762,
              DOI 10.17487/RFC4762, January 2007,
              <http://www.rfc-editor.org/info/rfc4762>.

Zhang, et al. Standards Track [Page 23] RFC 7727 STP Application of ICCP January 2016

 [RFC7275]    Martini, L., Salam, S., Sajassi, A., Bocci, M.,
              Matsushima, S., and T. Nadeau, "Inter-Chassis
              Communication Protocol for Layer 2 Virtual Private
              Network (L2VPN) Provider Edge (PE) Redundancy",
              RFC 7275, DOI 10.17487/RFC7275, June 2014,
              <http://www.rfc-editor.org/info/rfc7275>.
 [802.1q]     IEEE, "IEEE Standard for Local and Metropolitan Area
              Networks -- Bridges and Bridged Networks", IEEE Std
              802.1Q-2014, DOI 10.1109/IEEESTD.2014.6991462, 2014.
 [802.1d1998] IEEE, "Information technology -- Telecommunications and
              information exchange between systems -- Local and
              metropolitan area networks -- Common specifications --
              Part 3: Media Access Control (MAC) Bridges", ANSI/IEEE
              Std 802.1D-1998, DOI 10.1109/IEEESTD.1998.95619, 1998.
 [802.1d2004] IEEE, "IEEE Standard for Local and metropolitan area
              networks -- Media Access Control (MAC) Bridges", IEEE
              Std 802.1D-2004, DOI 10.1109/ieeestd.2004.94569, 2004.

7.2. Informative References

 [RFC5226]    Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

Acknowledgements

 The authors would like to thank the comments and suggestions from
 Ignas Bagdonas, Adrian Farrel, Andrew G. Malis, Gregory Mirsky, and
 Alexander Vainshtein.

Zhang, et al. Standards Track [Page 24] RFC 7727 STP Application of ICCP January 2016

Authors' Addresses

 Mingui Zhang
 Huawei Technologies
 No. 156 Beiqing Rd. Haidian District,
 Beijing 100095
 China
 Email: zhangmingui@huawei.com
 Huafeng Wen
 Huawei Technologies
 101 Software Avenue,
 Nanjing 210012
 China
 Email: wenhuafeng@huawei.com
 Jie Hu
 China Telecom
 Beijing Information Science & Technology Innovation Park
 Beiqijia Town Changping District,
 Beijing 102209
 China
 Email: hujie@ctbri.com.cn

Zhang, et al. Standards Track [Page 25]

/data/webs/external/dokuwiki/data/pages/rfc/rfc7727.txt · Last modified: 2016/01/22 23:52 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki