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Versions: (draft-zhang-trill-mtu-negotiation) 00 01 02 03 04 05 06 07 08

INTERNET-DRAFT                                                  M. Zhang
Intended Status: Standards Track                                X. Zhang
Updates: 6325, 7177, 7780                                    D. Eastlake
                                                                  Huawei
                                                              R. Perlman
                                                                     EMC
                                                           S. Chatterjee
                                                                   Cisco
Expires: February 3, 2018                                 August 2, 2017

         Transparent Interconnection of Lots of Links (TRILL):
                            MTU Negotiation
                draft-ietf-trill-mtu-negotiation-08.txt

Abstract

   The base IETF TRILL protocol has a TRILL campus-wide MTU feature,
   specified in RFC 6325 and RFC 7177, that assures that link state
   changes can be successfully flooded throughout the campus while being
   able to take advantage of a campus-wide capability to support jumbo
   packets. This document specifies recommended updates to that MTU
   feature to take advantage, for appropriate link-local packets, of
   link-local MTUs that exceed the TRILL campus MTU. In addition, it
   specifies an efficient algorithm for local MTU testing. This document
   updates RFC 6325, updates RFC 7177, and updates RFC 7780.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html





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Copyright and License Notice

   Copyright (c) 2017 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.


Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1. Conventions used in this document . . . . . . . . . . . . .  3
   2. Link-Wide TRILL MTU Size  . . . . . . . . . . . . . . . . . . .  3
     2.1. Operations  . . . . . . . . . . . . . . . . . . . . . . . .  5
   3. Link MTU Size Testing . . . . . . . . . . . . . . . . . . . . .  6
   4. Refreshing Sz . . . . . . . . . . . . . . . . . . . . . . . . .  8
   5. Relationship between Port MTU, Lz and Sz  . . . . . . . . . . .  9
   6. LSP Synchronization . . . . . . . . . . . . . . . . . . . . . .  9
   7. Recommendations for Traffic Link MTU Size Testing . . . . . . .  9
   8. Backwards Compatibility . . . . . . . . . . . . . . . . . . . . 10
   9. Security Considerations . . . . . . . . . . . . . . . . . . . . 10
   10. Additions to Configuration . . . . . . . . . . . . . . . . . . 11
     10.1. Per RBridge Configuration  . . . . . . . . . . . . . . . . 11
     10.2. Per RBridge Port Configuration . . . . . . . . . . . . . . 11
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 12
     13.2. Informative References . . . . . . . . . . . . . . . . . . 12
   Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14













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1. Introduction

   [RFC6325] describes the way RBridges agree on the campus-wide minimum
   acceptable inter-RBridge MTU (Maximum Transmission Unit) size (called
   "Sz") to ensure that link state flooding operates properly and all
   RBridges converge to the same link state. For the proper operation of
   TRILL IS-IS, all RBridges format their LSPs to fit in Sz.

   [RFC7177] diagrams the state transitions of an adjacency. If MTU
   testing is enabled, "Link MTU size is successfully tested" is part of
   an event (event A6) causing the transition from "2-way" state to
   "Report" state for an adjacency. This means the link MTU testing of
   size X succeeds, and X is greater than or equal to Sz [RFC6325]. If
   this link cannot support an MTU of Sz, it will not be reported as
   part of the campus topology.

   In this document, a new RECOMMENDED link-wide minimum inter-RBridge
   MTU size, Lz, is specified. As further discussed in Section 2, by
   calculating and using Lz as specified herein, link-scoped PDUs can be
   formatted greater than Sz, up to the link-wide minimum acceptable
   inter-RBridge MTU size potentially improving the efficiency of link
   utilization and speeding link state convergence.

   An optional TRILL MTU size-testing algorithm is specified in Section
   3 as an efficient method to update the old MTU testing method
   described in Section 4.3.2 of [RFC6325] and in [RFC7177]. The new MTU
   size testing method specified in this document is backward compatible
   with the old one. Multicasting the MTU-probes is recommended when
   there are multiple RBridges on a link responding to the probing with
   MTU-ack [RFC7177]. The testing method and rules of this document are
   devised in a way to minimize the number of MTU probes for testing,
   which therefore reduces the number of multicast packets for MTU
   testing.

   This document updates [RFC7780] as specified in Section 4.

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].

2. Link-Wide TRILL MTU Size

   This document specifies a new value "Lz" for the minimum acceptable
   inter-RBridge link MTU size on a local link. Link-wide Lz is the
   minimum Lz supported and agreed amongst all RBridges on a specific
   link. If the link is usable, Lz will be greater than or equal to Sz.



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   Some TRILL IS-IS PDUs are exchanged only between neighbors instead of
   the whole campus. They are confined by the link-wide Lz instead of
   Sz. CSNPs and PSNPs are examples of such PDUs. These PDUs are
   exchanged only on the local link. (While TRILL IS-IS Hellos are also
   link local, they are always limited to 1470 bytes for robustness.)

   [RFC7356] defines the PDUs which support flooding scopes in addition
   to area-wide scope and domain-wide scope. As specified in [RFC8139],
   RBridges support the Extended L1 Circuit Scoped (E-L1CS) flooding
   scope LSP (FS-LSP) [RFC7780]. The originatingSNPBufferSize for a port
   is the minimum of the following two quantities, but not less than
   1470 bytes: (1) the maximum MTU of the port and (2) the maximum LSP
   size that the TRILL IS-IS implementation can handle. They use that
   flooding to exchange their maximum supported value of "Lz". The
   smallest value of the Lz advertised by the RBridges on a link, but
   not less than Sz, is the link-wide Lz. An RBridge on a local link
   will be able to tell which other RBridges on that link support E-L1CS
   FS-LSPs because, as required by [RFC7780], all RBridges include the
   Scoped Flooding Support TLV [RFC7356] in their TRILL Hellos.

   The maximum sized level 1 link-local PDU, such as PSNP or CSNP, which
   may be generated by a system is controlled by the value of the
   management parameter originatingL1SNPBufferSize. This value
   determines Lz. The TRILL APPsub-TLV shown in Figure 2.1 SHOULD be
   included in a TRILL GENINFO TLV [RFC7357] in an E-L1CS FS-LSP
   fragment zero. If it is missing from a fragment zero E-L1CS FS-LSP or
   there is no fragment zero E-L1CS FS-LSP, it is assumed that its
   originating IS is implicitly advertising its originatingSNPBufferSize
   value as Sz octets.

   E-L1CS FS-LSPs are link-local and can also be sent up to Lz in size
   but, for robustness, E-L1CS FS-LSP fragment zero MUST NOT exceed 1470
   bytes.

                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   | Type = tbd                    |   (2 byte)
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   | Length = 2                    |   (2 byte)
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   | originatingSNPBufferSize      |   (2 byte)
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 2.1: The originatingSNPBufferSize TLV.

   Type: set to originatingSNPBufferSize APPsubTLV (TRILL APPsub-TLV
   type tbd). Two bytes because this APPsub-TLV appears in an Extended
   TLV [RFC7356].




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   Length: set to 2.

   originatingSNPBufferSize: the local value of
   originatingL1SNPBufferSize as an unsigned integer, limited in the
   range from 1470 to 65,535 bytes. (A value less than 1470 will be
   ignored.)

2.1. Operations

   Lz MAY be reported using an originatingSNPBufferSize TLV that occurs
   in fragment zero of the RBridge's E-L1CS FS-LSP. An
   originatingSNPBufferSize APPsub-TLV occurring in any other fragment
   is ignored. If more than one originatingSNPBufferSize APPsub-TLV
   occurs in fragment zero, the one advertising the smallest value for
   originatingSNPBufferSize, but not less than 1470 bytes, is used.

                         Lz:1800               Lz:1800
                          +---+         |         +---+
                          |RB1|(2000)---|---(2000)|RB2|
                          +---+         |         +---+
                                        |
                  Lz:1800               |
                   +---+               +--+
                   |RB3|(2000)---(1700)|B1|
                   +---+               +--+
                                        |

   Figure 2.2: Link-wide Lz = 1800 v.s. tested link MTU size = 1700

   Even if all RBridges on a specific link have reached consensus on the
   value of link-wide Lz based on advertised originatingSNPBufferSize,
   it does not mean that these RBridges can safely exchange PDUs between
   each other. Figure 2.2 shows such a corner case. RB1, RB2 and RB3 are
   three RBridges on the same link and their Lz is 1800, so the link-
   wide Lz of this link is 1800. There is an intermediate bridge (say
   B1) between RB2 and RB3 whose port MTU size is 1700. If RB2 sends
   PDUs formatted in chunks of size 1800, it will be discarded by B1.

   Therefore the link MTU size SHOULD be tested. After the link MTU size
   of an adjacency is successfully tested, those link-local PDUs such as
   CSNPs, PSNPs and E-L1CS FS-LSPs will be formatted no greater than the
   tested link MTU size and will be safely transmitted on this link.

   As for Sz, RBridges continue to propagate their
   originatingL1LSPBufferSize across the campus through the
   advertisement of LSPs as defined in Section 4.3.2 of [RFC6325]. The
   smallest value of Sz advertised by any RBridge, but not less than
   1470, will be deemed as Sz. Each RBridge formats their "campus-wide"



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   PDUs, for example LSPs, not greater than what they determine as Sz.

3. Link MTU Size Testing

   [RFC7177] defines the event A6 as including "MTU test is successful"
   if the MTU testing is enabled. As described in Section 4.3.2 of
   [RFC6325], this is a combination of the following event and
   condition.

   Event: The link MTU size has been tested.

   Condition: The link can support Sz.

   This condition can be efficiently tested by the following "Binary
   Search Algorithm" and rules. This updates [RFC7177] and [RFC6325].

   x, lowerBound, and upperBound are local integer variables. The MTU-
   probe and MTU-ack PDUs are specified in Section 3 of [RFC7176].

   Step 0: RB1 sends an MTU-probe padded to the size of link-wide Lz.

   1) If RB1 successfully receives the MTU-ack from RB2 to the probe of
      the value of link-wide Lz within k tries (where k is a
      configurable parameter whose default is 3. One Round Trip Time
      (RTT) between the two adjacent RBridges is RECOMMENDED to be used
      as the minimum interval between two successive probes. Note that
      RTT estimation is out of the scope for this document. If operators
      cannot not estimate the RTT, the default value 5-millisecond
      should be assumed.), link MTU size is set to the size of link-wide
      Lz and stop.

   2) RB1 tries to send an MTU-probe padded to the size 1470.

      a) If RB1 fails to receive an MTU-ack from RB2 after k tries (An
         MTU-ack should be considered to have failed two RTT after the
         probe is sent out.), RB1 sets the "failed minimum MTU test"
         flag for RB2 in RB1's Hello and stop.

      b) Link MTU size is set to 1470, lowerBound is set to 1470,
         upperBound is set to the link-wide Lz, x is set to [(lowerBound
         + upperBound)/2], rounded down to the nearest integer.

   Step 1: RB1 tries to send an MTU-probe padded to the size x.

   1) If RB1 fails to receive an MTU-ack from RB2 after k tries:

         upperBound is set to x-1 and x is set to [(lowerBound +
         upperBound)/2], rounded down to the nearest integer.



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   2) If RB1 receives an MTU-ack to a probe of size x from RB2:

         link MTU size is set to x, lowerBound is set to x and x is set
         to [(lowerBound + upperBound)/2], rounded down to the nearest
         integer. If lowerBound equals upperBound-1 then x is set to
         upperBound.

   3) If lowerBound >= upperBound or Step 1 has been repeated n times
      (where n is a configurable parameter whose default value is 5),
      stop.

   4) Repeat Step 1.

   After the testing, the two connected RBridges agree on the value of
   the link MTU size. MTU testing is only done in the Designated VLAN
   [RFC7177]. Since the execution of the above algorithm can be resource
   consuming, it is RECOMMENDED that the Designated RBRidge (DRB
   [RFC7177]) take the responsibility to do the testing. Multicast MTU-
   probes are used instead of unicast when multiple RBridges are desired
   to respond with an MTU-ack on the link. The Binary Search Algorithm
   given here is a way to minimize the probing attempts; it reduces the
   number of multicast packets for MTU-probing.

   The following rules are designed to determine whether the
   aforementioned "Condition" holds.

   RBridges have figured out the upper bound and lower bound for the
   link MTU size from the execution of the above algorithm. If Sz is
   smaller than the lower bound or greater than the upper bound,
   RBridges can directly judge whether the link supports Sz without MTU-
   probing.

   (a) If "lowerBound" >= Sz. This link can support Sz.

   (b) Else if "upperBound" <= Sz. This link cannot support Sz.

   Otherwise, RBridges SHOULD test whether the link can support Sz as in
   item (c) below. If they do not, the only safe assumption will be that
   the link cannot support Sz. This assumption, without testing, might
   rule out the use of a link that can, in fact, handle packets up to
   Sz. In the worst case, this might result in unnecessary network
   partition.

   (c) "lowerBound" < Sz < "upperBound". RBridges probe the link with
       MTU-probe messages padded to Sz. If an MTU-ack is received within
       k tries, this link can support Sz. Otherwise, this link cannot
       support Sz. Through this test, the lower bound and upper bound of
       link MTU size can be updated accordingly.



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4. Refreshing Sz

   RBridges may join or leave the campus, which may change Sz.

   1) Joining

      a) When a new RBridge joins the campus and its
         originatingL1LSPBufferSize is smaller than current Sz,
         reporting its originatingL1LSPBufferSize in its LSPs will cause
         other RBridges decrease their Sz. Then any LSP greater than the
         reduced Sz MUST be split and/or the LSP contents in the campus
         MUST be otherwise redistributed so that no LSP is greater than
         the new Sz.

      b) If the joining RBridge's originatingL1LSPBufferSize is equal to
         or bigger than current Sz, reporting its
         originatingL1LSPBufferSize will not change Sz.

   2) Leaving

      a) From the specification of the Joining process, we know it's
         non-applicable that an RBridge leaves the campus while its
         originatingL1LSPBufferSize is smaller than Sz.

      b) When an RBridge leaves the campus and its
         originatingL1LSPBufferSize equals to Sz, its LSPs are purged
         from the remaining campus after reaching MaxAge [IS-IS]. Sz MAY
         be recalculated and MAY increase. In other words, while in most
         cases RB1 ignores link state information for IS-IS unreachable
         RBridge RB2 [RFC7780], originatingL1LSPBufferSize is
         meaningful. Its value, even from IS-IS unreachable RBridges, is
         used in determining Sz. This updates [RFC7780].

      c) When an RBrige leaves the campus and its
         originatingL1LSPBufferSize is greater than Sz, this will not
         update Sz since Sz is determined by another RBridge with
         smaller originatingL1LSPBufferSize.

   Frequent LSP "re-sizing" is harmful to the stability of the TRILL
   campus, so, to avoid this, upward resizing SHOULD be dampened. When
   an upward resizing event is noticed by an RBridge, it is RECOMMENDED
   that a timer be set at that RBridge. This is a configurable
   parameter, LSPresizeTime, whose default value is 300 seconds. Before
   this timer expires, all subsequent upward resizing will be dampened
   (ignored). Of course, in a well-configured campus with all RBridges
   configured to have the same originatingL1LSPBufferSize, no resizing
   will be necessary. It does not matter if different RBridges have
   different dampening timers or some RBridges re-size upward more



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   quickly than others.

   If the refreshed Sz is smaller than the lower bound or greater than
   the upper bound of the tested link MTU size, the resource consuming
   link MTU size testing can be avoided according to rule (a) or (b)
   specified in Section 3. Otherwise, RBridges test the link MTU size
   according to rule (c).

5. Relationship between Port MTU, Lz and Sz

   When the port MTU of an RBridge is smaller than the local
   originatingL1SNPBufferSize of an RBridge (an inconsistent
   configuration), that port SHOULD be disabled since, in any case, an
   adjacency cannot be formed through such a port. On the other hand,
   when an RBridge receives an LSP or E-L1CS FS-LSP with size greater
   than the link-wide Lz or Sz but not greater than its port MTU size,
   this LSP is processed normally. If the size of an LSP is greater than
   the MTU size of a port over which it is to be propagated, this LSP
   MUST NOT be sent over the port and an LSPTooLargeToPropagate alarm
   shall be generated [IS-IS].

6. LSP Synchronization

   An RBridge participates in LSP synchronization on a link as soon as
   it has at least one adjacency on that link that has advanced to at
   least the 2-Way state [RFC7177]. On a LAN link, CSNP and PSNP PDUs
   are used for synchronization. On a point-to-point link, only PSNP are
   used.

   The CSNPs and PSNPs can be formatted in chunks of size at most the
   link-wide Lz but are processed normally if received larger than that
   size. Since the link MTU size may not have been tested in the 2-Way
   state, link-wide Lz may be greater than the supported link MTU size.
   In that case, a CSNP or PSNP may be discarded. After the link MTU
   size is successfully tested, RBridges will begin to format these PDUs
   in the size no greater than that MTU, therefore these PDUs will
   eventually get through.

   Note that the link MTU size is frequently greater than Sz. Link-local
   PDUs are limited in the size by the link MTU size rather than Sz,
   which, when Lz is greater than Sz, promises a reduction in the number
   of PDUs and a faster LSP synchronization process.

7. Recommendations for Traffic Link MTU Size Testing

   Sz and link-wide Lz are used to limit the size of most TRILL IS-IS
   PDUs. They are different from the MTU size restricting the size of
   TRILL Data packets. The size of a TRILL Data packet is restricted by



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   the physical MTU of the ports and links the packet traverses. It is
   possible that a TRILL Data packet successfully gets through the
   campus but its size is greater than Sz or link-wide Lz values.

   The algorithm defined for link MTU size testing can also be used in
   TRILL traffic MTU size testing; in that case the link-wide Lz used in
   that algorithm is replaced by the port MTU of the RBridge sending MTU
   probes. The successfully tested size X MAY be advertised as an
   attribute of this link using MTU sub-TLV defined in [RFC7176].

   Unlike RBridges, end stations do not participate in the exchange of
   TRILL IS-IS PDUs; therefore, they cannot grasp the traffic link MTU
   size from a TRILL campus automatically. An operator may collect these
   values using network management tools such as TRILL ping or
   TraceRoute. Then, the path MTU can be set as the smallest tested link
   MTU on this path; and end stations should not generate frames that,
   when encapsulated as TRILL Data packets, exceed this path MTU.

8. Backwards Compatibility

   There can be a mixture of Lz-ignorant and Lz-aware RBridges on a
   link. This will act properly although, it may not be as efficient as
   it would be if all RBridges on the link are Lz-aware.

   For an Lz-ignorant RBridge, TRILL IS-IS PDUs are always formatted not
   greater than Sz. Lz-aware RBridges as receivers can handle these PDUs
   since they cannot be greater than the link-wide Lz.

   For an Lz-aware RBridge, in the case that link-wide Lz is greater
   than Sz, larger link-local TRILL IS-IS PDUs can be sent out to gain
   efficiencies. Lz-ignorant RBridges as receivers will have no problem
   handling them since the originatingL1LSPBufferSize value of these
   RBridges had been tested and the link-wide Lz is not greater than
   that value.

   An Lz-ignorant RBridge might not support the link MTU testing
   algorithm defined in Section 3 but could be using some algorithm just
   to test for Sz MTU on the link. In any case, if an RBridge per
   [RFC6325] receives an MTU-probe, it MUST respond with an MTU-ack
   padded to the same size as the MTU-probe.

9. Security Considerations

   This document raises no significant new security issues for TRILL. In
   TRILL, RBridges are generally considered to be trusted devices.
   Protection against forged TRILL IS-IS PDUs, including forged Hellos
   containing originatingSNPBufferSize APP-subTLVs, can be obtained
   through IS-IS PDU cryptographic authentication [RFC5310]. The worst



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   that an RBridge can do by reporting an erroneous
   originatingSNPBufferSize is reduce Lz to Sz and thus make unavailable
   the optimization of being able to use link MTUs that exceed the
   campus wide MTU for link local TRILL IS-IS PDUs.

   For general and adjacency related TRILL security considerations, see
   [RFC6325] and [RFC7177].

10. Additions to Configuration

   Implementation of the features specified in this document adds two
   RBridge configuration parameters as follows:

10.1. Per RBridge Configuration

   Each RBridge implementing the RECOMMENDED LSP re-sizing damping
   strategy specified in Section 4 has an LSPresizeTime parameter that
   is an integer in the range of 0-65,535 which defaults to 300. It is
   the number of seconds for which an RBridge determines that Sz has
   increased before it will create any LSP or E-L1FS FS-LSP fragments.

10.2. Per RBridge Port Configuration

   Each RBridge port on which the calculation and use of Lz is
   implemented has an originatingL1SNPBufferSize parameter that is an
   integer in the range of 1,470-65,535. This parameter defaults to the
   minimum of the size that the port can accommodate and the size link-
   local IS-IS PDU that the TRILL implementation can accommodate.

11. IANA Considerations

   IANA is requested to assign a new APPsub-TLV number from the range
   less than 256 in the "TRILL APPsub-TLV Types under IS-IS TLV 251
   Application Identifier 1" registry for the TRILL
   originatingSNPBufferSize sub-TLV defined in Section 2 of this
   document. The entry is as follows:

   Type  Name                      Reference
   ----  ------------------------  ---------------
   tbd   originatingSNPBufferSize  [this document]


12. Acknowledgements

   Authors would like to thank the comments and suggestions from Vishwas
   Manral.

13. References



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13.1. 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>.

   [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
             and M. Fanto, "IS-IS Generic Cryptographic Authentication",
             RFC 5310, DOI 10.17487/RFC5310, February 2009,
             <http://www.rfc-editor.org/info/rfc5310>.

   [RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
             Ghanwani, "Routing Bridges (RBridges): Base Protocol
             Specification", RFC 6325, DOI 10.17487/RFC6325, July 2011,
             <http://www.rfc-editor.org/info/rfc6325>.

   [RFC7177] Eastlake 3rd, D., Perlman, R., Ghanwani, A., Yang, H., and
             V. Manral, "Transparent Interconnection of Lots of Links
             (TRILL): Adjacency", RFC 7177, DOI 10.17487/RFC7177, May
             2014, <http://www.rfc-editor.org/info/rfc7177>.

   [RFC7176] Eastlake 3rd, D., Senevirathne, T., Ghanwani, A., Dutt, D.,
             and A. Banerjee, "Transparent Interconnection of Lots of
             Links (TRILL) Use of IS-IS", RFC 7176, DOI
             10.17487/RFC7176, May 2014, <http://www.rfc-
             editor.org/info/rfc7176>.

   [RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding
             Scope Link State PDUs (LSPs)", RFC 7356, DOI
             10.17487/RFC7356, September 2014, <http://www.rfc-
             editor.org/info/rfc7356>.

   [RFC7780] Eastlake 3rd, D., Zhang, M., Perlman, R., Banerjee, A.,
             Ghanwani, A., and S. Gupta, "Transparent Interconnection of
             Lots of Links (TRILL): Clarifications, Corrections, and
             Updates", RFC 7780, DOI 10.17487/RFC7780, February 2016,
             <http://www.rfc-editor.org/info/rfc7780>.

   [RFC7357] Zhai, H., Hu, F., Perlman, R., Eastlake 3rd, D., and O.
             Stokes, "Transparent Interconnection of Lots of Links
             (TRILL): End Station Address Distribution Information
             (ESADI) Protocol", RFC 7357, DOI 10.17487/RFC7357,
             September 2014, <http://www.rfc-editor.org/info/rfc7357>.

13.2. Informative References

   [IS-IS]   International Organization for Standardization,



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             "Information technology -- Telecommunications and
             information exchange between systems -- Intermediate System
             to Intermediate System intra-domain routeing information
             exchange protocol for use in conjunction with the protocol
             for providing the connectionless-mode network service (ISO
             8473)", ISO/IEC 10589:2002, Second Edition, November 2002.

   [RFC8139] Eastlake 3rd, D., Li, Y., Umair, M., Banerjee, A., and F.
             Hu, "Transparent Interconnection of Lots of Links (TRILL):
             Appointed Forwarders", RFC 8139, DOI 10.17487/RFC8139, June
             2017, <http://www.rfc-editor.org/info/rfc8139>.








































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Author's Addresses

   Mingui Zhang
   Huawei Technologies
   No. 156 Beiqing Rd. Haidian District
   Beijing 100095
   China

   Phone: +86-13810702575
   Email: zhangmingui@huawei.com


   Xudong Zhang
   Huawei Technologies
   No. 156 Beiqing Rd. Haidian District
   Beijing 100095
   China

   Email: zhangxudong@huawei.com


   Donald E. Eastlake, 3rd
   Huawei Technologies
   155 Beaver Street
   Milford, MA 01757
   United States

   Phone: +1-508-333-2270
   EMail: d3e3e3@gmail.com


   Radia Perlman
   EMC
   2010 256th Avenue NE, #200
   Bellevue, WA 98007
   United States

   Email: radia@alum.mit.edu


   Somnath Chatterjee
   Cisco Systems
   SEZ Unit, Cessna Business Park
   Outer Ring Road
   Bangalore - 560087
   India

   Email: somnath.chatterjee01@gmail.com



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