wdiff rfc8249.original rfc8249.txt

INTERNET-DRAFT
Internet Engineering Task Force (IETF) M. Zhang
Intended Status: Standards Track
Request for Comments: 8249 X. Zhang
Updates: 6325, 7177, 7780 D. Eastlake 3rd
Category: Standards Track Huawei
ISSN: 2070-1721 R. Perlman
Dell EMC
S. Chatterjee
Cisco
Expires: February 3, 2018 August 2,
September 2017

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

Abstract

The base IETF TRILL (Transparent Interconnection of Lots of Links)
protocol has a TRILL campus-wide MTU feature, specified in RFC RFCs 6325
and RFC 7177, that assures that link state 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 RFCs 6325, updates RFC
7177, and updates RFC 7780.

Status of this This Memo

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Table of Contents

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

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 link-state flooding operates properly and all
RBridges converge to the same link state. For the proper operation
of TRILL (Transparent Interconnection of Lots of Links) IS-IS, all
RBridges format their LSPs Link State Protocol Data Units (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" the "2-Way" state
[RFC7177] to the "Report" state for an adjacency. This means that
the link MTU testing of size X x succeeds, and X 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, "Lz", is specified. As further discussed in Section 2, by
calculating and using Lz as specified herein, link-scoped PDUs Protocol
Data Units (PDUs) can be formatted greater than Sz, up to the
link-wide minimum acceptable inter-RBridge MTU size size, potentially
improving the efficiency of link utilization and speeding link state 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 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 an MTU-ack [RFC7177]. The testing method and rules
of this document are devised in a way to minimize that minimizes the number of MTU probes
MTU-probes for testing,
which therefore reduces reducing the number of multicast
packets for MTU testing.

This document updates RFCs 6325, 7177, and 7780. The update to
[RFC6325] and [RFC7177] is specified in Section 3. The update to
[RFC7780] as is specified in Section 4.

1.1. Conventions used Used in this document This Document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

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 upon amongst all RBridges on a
specific link. If the link is usable, Lz will be greater than or
equal to Sz.

Some TRILL IS-IS PDUs are exchanged only between neighbors instead of
throughout the whole campus. They are confined by the link-wide Lz
instead of Sz. CSNPs Complete Sequence Number PDUs (CSNPs) and PSNPs Partial
Sequence Number PDUs (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 that support flooding scopes in addition
to area-wide scope scopes and domain-wide scope. scopes. As specified in
[RFC8139], RBridges support the Extended L1 Circuit Scoped Scope (E-L1CS) flooding
scope
Flooding Scope LSP (FS-LSP) [RFC7780]. The originatingSNPBufferSize
for a port is the minimum of the following two quantities, 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
Scope Flooding Support TLV [RFC7356] in their TRILL Hellos.

The maximum sized level 1 size for a level-1 link-local PDU, such PDU (such as a PSNP or CSNP, which
CSNP) that 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 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 an E-L1CS FS-LSP fragment zero
or there is no fragment zero E-L1CS FS-LSP, FS-LSP fragment zero, it is assumed that its
originating IS is implicitly advertising its originatingSNPBufferSize
value as Sz octets.

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

Figure 2.1: 1: The originatingSNPBufferSize TLV. APPsub-TLV

Type: set Set to the originatingSNPBufferSize APPsubTLV APPsub-TLV (TRILL
APPsub-TLV type tbd). 21). Two bytes bytes, because this APPsub-TLV appears
in an Extended extended TLV [RFC7356].

Length: set Set to 2.

originatingSNPBufferSize: the The local value of
originatingL1SNPBufferSize as an unsigned integer, limited in to 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 APPsub-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 for
originatingSNPBufferSize, but not less than 1470 bytes, is used.

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 2 shows such a corner case. RB1, RB2 RB2, and RB3
are three RBridges on the same link and their Lz is 1800, so the link-
wide
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 those PDUs will be
discarded by B1.

Therefore

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

Figure 2: Link-Wide Lz = 1800 vs. Tested Link MTU Size = 1700

Therefore, the link MTU size SHOULD be tested. After the link MTU
size of an adjacency is successfully tested, those link-local PDUs PDUs,
such as CSNPs, PSNPs PSNPs, and E-L1CS FS-LSPs 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"
PDUs,
PDUs -- for example LSPs, not example, LSPs -- no greater than what they determine
as Sz.

3. Testing Link MTU Size Testing

[RFC7177] defines the event A6 as including "MTU indicating that the MTU test is successful" was
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.
condition:

o Event: The link MTU size has been tested.

o Condition: The link can support Sz.

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

x, lowerBound, and upperBound are local integer variables. The MTU-
probe
MTU-probe and MTU-ack PDUs are specified in Section 3 of [RFC7176].
It is RECOMMENDED that one Round-Trip Time (RTT) between the two
adjacent RBridges be used as the minimum interval between two
successive probes. Note that RTT estimation is out of scope for this
document. If operators cannot estimate the RTT, the default value of
5 milliseconds should be assumed.

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 3), 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. Lz. Stop.

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

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

b) Link The link MTU size is set to 1470, 1470; lowerBound is set to 1470, 1470;
upperBound is set to the link-wide Lz, Lz; x is set to
[(lowerBound + upperBound)/2], 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 - 1; x is set to
[(lowerBound +
upperBound)/2], upperBound) / 2], rounded down to the nearest
integer.

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

The link MTU size is set to x, x; lowerBound is set to x and x; x is set
to [(lowerBound + upperBound)/2], upperBound) / 2], rounded down to the nearest
integer. If lowerBound equals upperBound-1 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]) RBridge
(DRB) [RFC7177] take the responsibility to do the testing. Multicast MTU-
probes
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 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 of 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. MTU-probing.

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

(b) Else if "upperBound" upperBound <= Sz. This 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" lowerBound < Sz < "upperBound". 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 the link MTU size can be updated accordingly.

4. Refreshing Sz

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

1) Joining

a) When a new RBridge joins the campus and its
originatingL1LSPBufferSize is smaller than the current Sz,
reporting its originatingL1LSPBufferSize in its LSPs will cause
other RBridges to decrease their Sz. Then Then, any LSP greater
than the reduced Sz MUST be split 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 greater
than or equal to
or bigger than the 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 if
an RBridge leaves the campus while its RBridge's originatingL1LSPBufferSize is smaller than Sz. Sz,
this RBridge will not join this campus.

b) When an RBridge leaves the campus and its
originatingL1LSPBufferSize equals to Sz, its LSPs are purged from
the remaining remainder of the campus after reaching MaxAge [IS-IS]. Sz
MAY be recalculated and MAY increase. In other words, while in
most cases RB1 ignores link state 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 RBridge leaves the campus and its
originatingL1LSPBufferSize is greater than Sz, this Sz will not
update Sz be
updated, since Sz is determined by another RBridge with a
smaller originatingL1LSPBufferSize.

Frequent LSP "re-sizing" "resizing" 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 RBridge via a configurable
parameter, LSPresizeTime, 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 if some RBridges re-size resize upward more
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 issue of resource consuming
consumption from testing the link MTU size testing can be avoided according
to rule (a) or (b) as specified in Section 3. Otherwise, RBridges
test the link MTU size according to rule (c).

5. Relationship between Port MTU, Lz 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 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 CSNPs and PSNP PDUs PSNPs are
used for synchronization. On a point-to-point link, only PSNP PSNPs are
used.

The CSNPs and PSNPs can be formatted in chunks of size at most the (at most)
link-wide Lz but are processed normally if received having a 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
with a size no greater than that MTU, therefore 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 Testing of 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
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 testing the link MTU size testing can also be used
in TRILL traffic MTU size testing; in that case case, the link-wide Lz
used in that algorithm is replaced by the port MTU of the RBridge
sending MTU
probes. MTU-probes. The successfully tested size X x MAY be advertised
as an attribute of this link link, using the 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; path, and end stations should not generate frames that,
that -- when encapsulated as TRILL Data packets, packets -- exceed this
path MTU.

8. Backwards Backward Compatibility

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

For an Lz-ignorant RBridge, TRILL IS-IS PDUs are always formatted not
no greater than Sz. Lz-aware RBridges as receivers can handle these PDUs
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.
increase efficiency. Lz-ignorant RBridges as receivers will have
no problem handling them 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 size-testing
algorithm defined in Section 3 but could be using some algorithm just
to test for the 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, APPsub-TLVs, can be obtained
through IS-IS PDU cryptographic authentication [RFC5310]. The worst
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
campus-wide MTU for link local link-local TRILL IS-IS PDUs.

For general and adjacency related 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 parameters, as follows:

10.1. Per RBridge Per-RBridge Configuration

Each RBridge implementing the RECOMMENDED LSP re-sizing resizing damping
strategy specified in Section 4 has an LSPresizeTime parameter that
is an integer in the range of 0-65,535 which and that 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 Per-RBridge Port Configuration

Each RBridge port on which the calculation and use of Lz is are
implemented has an originatingL1SNPBufferSize parameter that is an
integer in the range of 1,470-65,535. 1470-65,535. This parameter defaults to the
minimum of the size that the port can accommodate and the size link-
local link-local
IS-IS PDU size that the TRILL implementation can accommodate.

11. IANA Considerations

IANA is requested to assign has assigned a new APPsub-TLV number type for the TRILL
originatingSNPBufferSize APPsub-TLV defined in Section 2 of this
document. This new type has been assigned 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. registry. The entry is as follows:

Type Name Reference
---- ------------------------ ---------------
tbd ---------
21 originatingSNPBufferSize [this document] RFC 8249

12. Acknowledgements

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

13. References

13.1.

12.1. 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>.
<https://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>. <https://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]
<https://www.rfc-editor.org/info/rfc6325>.

[RFC7176] Eastlake 3rd, D., Perlman, R., Senevirathne, T., Ghanwani, A., Yang, H., Dutt,
D., and
V. Manral, A. Banerjee, "Transparent Interconnection of Lots
of Links
(TRILL): Adjacency", (TRILL) Use of IS-IS", RFC 7177, 7176,
DOI 10.17487/RFC7177, 10.17487/RFC7176, May 2014, <http://www.rfc-editor.org/info/rfc7177>.

[RFC7176]
<https://www.rfc-editor.org/info/rfc7176>.

[RFC7177] Eastlake 3rd, D., Senevirathne, T., Perlman, R., Ghanwani, A., Dutt, D., Yang, H., and A. Banerjee,
V. Manral, "Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS",
(TRILL): Adjacency", RFC 7176, 7177, DOI
10.17487/RFC7176, 10.17487/RFC7177,
May 2014, <http://www.rfc-
editor.org/info/rfc7176>. <https://www.rfc-editor.org/info/rfc7177>.

[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>.
<https://www.rfc-editor.org/info/rfc7356>.

[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, <https://www.rfc-editor.org/info/rfc7357>.

[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>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in
RFC 7357, 2119 Key Words", BCP 14, RFC 8174,
DOI 10.17487/RFC7357,
September 2014, <http://www.rfc-editor.org/info/rfc7357>.

13.2. 10.17487/RFC8174, May 2017,
<https://www.rfc-editor.org/info/rfc8174>.

12.2. Informative References

[IS-IS] International Organization for Standardization,
"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>.

Author's <https://www.rfc-editor.org/info/rfc8139>.

Acknowledgements

The authors would like to thank Vishwas Manral for his comments and
suggestions.

Authors' 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, Eastlake 3rd
Huawei Technologies
155 Beaver Street
Milford, MA 01757
United States of America

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

Radia Perlman
Dell EMC
2010 256th Avenue NE, #200
Bellevue,
505 1st Ave South
Seattle, WA 98007 98104
United States of America

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