Internet DRAFT - draft-ginsberg-isis-mi-bis
draft-ginsberg-isis-mi-bis
Networking Working Group L. Ginsberg
Internet-Draft S. Previdi
Intended status: Standards Track Cisco Systems
Expires: October 22, 2016 W. Henderickx
Nokia
April 20, 2016
IS-IS Multi-Instance
draft-ginsberg-isis-mi-bis-01.txt
Abstract
This draft describes a mechanism that allows a single router to share
one or more circuits among multiple Intermediate System To
Intermediate System (IS-IS) routing protocol instances.
Multiple instances allow the isolation of resources associated with
each instance. Routers will form instance specific adjacencies.
Each instance can support multiple topologies. Each topology has a
unique Link State Database (LSDB). Each Protocol Data Unit (PDU)
will contain a new Type Length Value (TLV) identifying the instance
and the topology(ies) to which the PDU belongs.
Requirements Language
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 22, 2016.
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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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Elements Of Procedure . . . . . . . . . . . . . . . . . . . . 4
2.1. Instance Identifier TLV . . . . . . . . . . . . . . . . . 4
2.2. Instance Membership . . . . . . . . . . . . . . . . . . . 6
2.3. Use of Authentication . . . . . . . . . . . . . . . . . . 6
2.4. Adjacency Establishment . . . . . . . . . . . . . . . . . 6
2.4.1. Point-to-Point Adjacencies . . . . . . . . . . . . . 6
2.4.2. Multi-Access Adjacencies . . . . . . . . . . . . . . 6
2.5. Update Process Operation . . . . . . . . . . . . . . . . 7
2.5.1. Update Process Operation on Point-to-Point Circuits . 7
2.5.2. Update Process Operation on Broadcast Circuits . . . 7
2.6. Interoperability Considerations . . . . . . . . . . . . . 7
2.6.1. Interoperability Issues on Broadcast Circuits . . . . 7
2.6.2. Interoperability Using Point-to-Point Circuits . . . 8
3. Usage Guidelines . . . . . . . . . . . . . . . . . . . . . . 9
3.1. One-to-One Mapping Between Topologies and Instances . . . 9
3.2. Many-to-One Mapping between Topologies and Instances . . 10
3.3. Considerations for the Number of Instances . . . . . . . 10
4. Relationship to M-ISIS . . . . . . . . . . . . . . . . . . . 10
5. Graceful Restart Interactions . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
9.1. Normative References . . . . . . . . . . . . . . . . . . 12
9.2. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. Changes to RFC 6822 . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
An existing limitation of the protocol defined by [ISO10589] is that
only one instance of the protocol can operate on a given circuit.
This document defines an extension to IS-IS to remove this
restriction. The extension is referred to as "Multi-instance IS-IS"
(MI-IS-IS).
Routers that support this extension are referred to as "Multi-
Instance capable routers" (MI-RTR).
The use of multiple instances enhances the ability to isolate the
resources associated with a given instance both within a router and
across the network. Instance-specific prioritization for processing
PDUs and performing routing calculations within a router may be
specified. Instance-specific flooding parameters may also be defined
so as to allow different instances to consume network-wide resources
at different rates.
Another existing protocol limitation is that a given instance
supports a single Update Process operating on a single Link State
Database (LSDB). This document defines an extension to IS-IS to
allow non-zero instances of the protocol to support multiple Update
Processes. Each Update Process is associated with a topology and a
unique topology specific LSDB. Non-zero instances of the protocol
are only supported by MI-RTRs. Legacy routers support the standard
or zero instance of the protocol. The behavior of the standard
instance is not changed in any way by the extensions defined in this
document.
MI-IS-IS might be used to support topology-specific routing. Two
methods of supporting such a use are defined in this document. One
supports the use of [RFC5120] within a reserved instance specific
topology. The second is an alternative to [RFC5120] which supports
topology-specific flooding of link state information.
MI-IS-IS might also be used to support advertisement of information
on behalf of applications [RFC6823]. The advertisement of
information not directly related to the operation of the IS-IS
protocol can therefore be done in a manner that minimizes its impact
on the operation of routing.
The above are examples of how MI-IS-IS might be used. The
specification of uses of MI-IS-IS is outside the scope of this
document.
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2. Elements Of Procedure
An Instance Identifier (IID) is introduced to uniquely identify an
IS-IS instance. The protocol extension includes a new TLV (IID-TLV)
in each IS-IS PDU originated by an MI-RTR except as noted in this
document. The IID-TLV identifies the unique instance as well as the
instance-specific topology/topologies to which the PDU applies. Each
IS-IS PDU is associated with only one IS-IS instance.
MI-RTRs form instance-specific adjacencies. The IID-TLV included in
Intermediate System-Intermediate System Hellos (IIH) includes the IID
and the set of Instance-Specific Topology Identifiers (ITIDs) that
the sending IS supports. When multiple instances share the same
circuit, each instance will have a separate set of adjacencies.
MI-RTRs support the exchange of topology specific Link State PDUs for
the IID/ITID pairs that each neighbor supports. A unique IS-IS
Update Process (see [ISO10589] operates for each IID/ITID pair. This
MAY also imply IID/ITID-specific routing calculations and IID/ITID-
specific routing and forwarding tables. However, this aspect is
outside the scope of this specification.
The mechanisms used to implement support of the separation of IS-IS
instances and topology-specific Update processes within a router are
outside the scope of this specification.
2.1. Instance Identifier TLV
A new TLV is defined in order to convey the IID and ITIDs supported.
The IID-TLV associates a PDU with an IS-IS instance using a unique
16-bit number. The IID-TLV is carried in all IS-IS PDUs that are
associated with a non-zero instance; this includes IIHs, Sequence
Number PDUs (SNPs) and Link State PDUs (LSPs)) .
Multiple instances of IS-IS may coexist on the same circuit and on
the same physical router. IIDs MUST be unique within the same
routing domain.
IID #0 is reserved for the standard instance supported by legacy
systems. IS-IS PDUs associated with the standard instance MUST NOT
include an IID-TLV except where noted in this document.
The IID-TLV MAY include one or more ITIDs. An ITID is a 16-bit
identifier where all values (0 - 65535) are valid.
The following format is used for the IID-TLV:
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Type: 7
Length: 2 - 254
Value:
No. of octets
+-------------------------+
| IID (0 - 65535) | 2
+-------------------------+
| Supported ITID | 2
+-------------------------+
: :
+-------------------------+
| Supported ITID | 2
+-------------------------+
When the IID = 0, the list of supported ITIDs MUST NOT be present.
An IID-TLV with IID = 0 MUST NOT appear in an SNP or LSP. When
the TLV appears (with a non-zero IID) in an SNP or LSP, exactly
one ITID MUST be present indicating the instance-specific topology
with which the PDU is associated. If no ITIDs or multiple ITIDs are
present or the IID is zero, then the PDU MUST be ignored.
When the IID is non-zero and the TLV appears in an IIH, the set
of ITIDs supported on the circuit over which the IIH is sent is
included. There MUST be at least one ITID present.
ITID #0 is reserved for a specific use case as described later
in this document. ITID #0 MUST NOT be supported in combination
with any non-zero ITID. If multiple ITIDs are advertised in
an IIH and one of the ITIDs is #0 then the PDU MUST be ignored.
Multiple IID-TLVs MAY appear in IIHs. If multiple IID-TLVs are
present and the IID value in all IID-TLVs is not the same, then
the PDU MUST be ignored.
A single IID-TLV will support advertisement of up to 126 ITIDs. If
multiple IID-TLVs are present in an IIH PDU the supported set of
ITIDs is the union of all ITIDs present in all IID-TLVs.
When an LSP purge is initiated, the IID-TLV MUST be retained, but the
remainder of the body of the LSP SHOULD be removed. The purge
procedure is described in [RFC6233] and [RFC6232].
It is recommended that (when present) the IID-TLV(s) be the first
TLVs in the PDU. This allows determination of the association of a
PDU with a particularf instance more quickly.
A PDU without an IID-TLV belongs to the standard instance.
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2.2. Instance Membership
Each MI-RTR is configured to be participating in one or more
instances of IS-IS. For each non-zero instance in which it
participates, an MI-RTR marks IS-IS PDUs (IIHs, LSPs, or SNPs)
generated that pertain to that instance by including the IID-TLV with
the appropriate instance identifier.
2.3. Use of Authentication
When authentication is in use, the IID, if present, is first used to
select the authentication configuration that is applicable. The
authentication check is then performed as normal. When multiple
ITIDs are supported, ITID-specific authentication MAY be used in SNPs
and LSPs.
2.4. Adjacency Establishment
In order to establish adjacencies, IS-IS routers exchange IIH PDUs.
Two types of adjacencies exist in IS-IS: point-to-point and
broadcast. The following subsections describe the additional rules
an MI-RTR MUST follow when establishing adjacencies for non-zero
instances.
2.4.1. Point-to-Point Adjacencies
MI-RTRs include the IID-TLV in the point-to-point Hello PDUs
associated with non-zero instances that they originate. Upon
reception of an IIH, an MI-RTR inspects the received IID-TLV and if
the IID matches any of the IIDs that the router supports on that
circuit, normal adjacency establishment procedures are used to
establish an instance-specific adjacency. Note that the absence of
the IID TLV implies IID #0. For instances other than IID #0, an
adjacency SHOULD NOT be established unless there is at least one ITID
in common.
This extension allows an MI-RTR to establish multiple adjacencies to
the same physical neighbor over a point-to-point circuit. However,
as the instances are logically independent, the normal expectation of
at most one neighbor on a given point-to-point circuit still applies.
2.4.2. Multi-Access Adjacencies
Multi-Access (broadcast) circuits behave differently than point-to-
point in that PDUs sent by one router are visible to all routers and
all routers must agree on the election of a Designated Intermediate
System (DIS) independent of the set of ITIDs supported.
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MI-RTRs will establish adjacencies and elect a DIS per IS-IS
instance. Each MI-RTR will form adjacencies only with routers that
advertise support for the instances that the local router has been
configured to support on that circuit. Since an MI-RTR is not
required to support all possible instances on a LAN, it's possible to
elect a different DIS for different instances.
2.5. Update Process Operation
For non-zero instances, a unique Update Process exists for each
supported ITID.
2.5.1. Update Process Operation on Point-to-Point Circuits
On Point-to-Point circuits - including Point-to-Point Operation over
LAN [RFC5309] - the ITID-specific Update Process only operates on
that circuit for those ITIDs that are supported by both ISs operating
on the circuit.
2.5.2. Update Process Operation on Broadcast Circuits
On broadcast circuits, a single DIS is elected for each supported IID
independent of the set of ITIDs advertised in LAN IIHs. This
requires that the DIS generate pseudo-node LSPs for all supported
ITIDs and that the Update Process for all supported ITIDs operate on
the broadcast circuit. Among MI-RTRs operating on a broadcast
circuit, if the set of supported ITIDs for a given non-zero IID is
inconsistent, connectivity for the topology (or topologies)
associated with the ITIDs not supported by some MI-RTRs can be
compromised.
2.6. Interoperability Considerations
[ISO10589] requires that any TLV that is not understood is silently
ignored without compromising the processing of the whole IS-IS PDU
(IIH, LSP, SNP).
To a router not implementing this extension, all IS-IS PDUs received
will appear to be associated with the standard instance regardless of
whether an IID TLV is present in those PDUs. This can cause
interoperability issues unless the mechanisms and procedures
discussed below are followed.
2.6.1. Interoperability Issues on Broadcast Circuits
In order for routers to correctly interoperate with routers not
implementing this extension and in order not to cause disruption, a
specific and dedicated Media Access Control (MAC) address is used for
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multicasting IS-IS PDUs with any non-zero IID. Each level will use a
specific layer 2 multicast address. Such an address allows MI-RTRs
to exchange IS-IS PDUs with non-zero IIDs without these PDUs being
processed by legacy routers, and therefore no disruption is caused.
When sending SNPs, LSPs, and LAN IIHs for the standard instance (IID
#0) an MI-RTR will use the AllL1IS and AllL2IS ISIS MAC layer
addresses (as defined in [ISO10589]) as the destination address.
When sending SNPs, LSPs, and LAN IIHs for any non-zero IID an MI-RTR
will use one of two new dedicated layer 2 multicast addresses
(AllL1MI-ISs or AllL2MI- IS) as the destination address. These
addresses are specified in Section 6.
When operating in point-to-point mode on a broadcast circuit
[RFC5309], an MI-RTR will use AllL1IS, AllL2IS, or AllIS MAC-layer
address when sending point-to-point IIHs associated with the standard
instance. When sending point-to-point IIHs for a non-zero IID an MI-
RTR MUST use one of the two new multicast addresses (AllL1MI-ISs or
AllL2MI- IS) as the destination address (either address will do).
MI-RTRs MUST discard IS-IS PDUs received if either of the following
is true:
o The destination multicast address is AllL1IS, AllL2IS, or AllIS
and the PDU contains an IID-TLV
o The destination multicast address is one of the two new addresses
and the PDU contains an IID-TLV with a zero value for the IID or
has no IID-TLV.
NOTE: If the multicast addresses AllL1IS, AllL2IS, or AllIS are
improperly used to send IS-IS PDUs for non-zero IIDs, legacy systems
will interpret these PDUs as being associated with IID #0. This will
cause inconsistencies in the LSDB in those routers, may incorrectly
maintain adjacencies, and may lead to inconsistent DIS election.
2.6.2. Interoperability Using Point-to-Point Circuits
In order for an MI-RTR to interoperate over a point-to-point circuit
with a router that does NOT support this extension, the MI-RTR MUST
NOT send IS-IS PDUs for instances other than IID #0 over the point-
to-point circuit as these PDUs may affect the state of IID #0 in the
neighbor.
The presence or absence of the IID-TLV in an IIH indicates that the
neighbor does or does not support this extension, respectively.
Therefore, all IIHs sent on a point-to-point circuit by an MI-RTR
MUST include an IID-TLV. This includes IIHs associated with IID #0.
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Once it is determined that the neighbor does not support this
extension, an MI-RTR MUST NOT send PDUs (including IIHs) for
instances other than IID #0.
Until an IIH is received from a neighbor, an MI-RTR MAY send IIHs for
a non-zero instance. However, once an IIH with no IID TLV has been
received - indicating that the neighbor is not an MI-RTR - the MI-RTR
MUST NOT send IIHs for a non-zero instance. The temporary relaxation
of the restriction on sending IIHs for non-zero instances allows a
non-zero instance adjacency to be established on an interface on
which an MI-RTR does NOT support the standard instance.
Point-to-point adjacency setup MUST be done through the use of the
three-way handshaking procedure as defined in [RFC5303] in order to
prevent a non-MI capable neighbor from bringing up an adjacency
prematurely based on reception of an IIH with an IID-TLV for a non-
zero instance.
3. Usage Guidelines
As discussed above, MI-IS-IS extends IS-IS to support multiple
instances on a given circuit. Each instance is uniquely identified
by the IID and forms instance-specific adjacencies. Each instance
supports one or more topologies as represented by the ITIDs. All
topologies associated with a given instance share the instance-
specific adjacencies. The set of topologies supported by a given IID
MAY differ from circuit to circuit. Each topology has its own set of
LSPs and runs a topology-specific Update Process. Flooding of
topology-specific LSPs is only performed on circuits on which both
the local router and the neighbor(s) support a given topology (i.e.,
advertise the same ITID in the set of supported ITIDs sent in the
IID-TLV included in IIHs).
The following subsections provide some guidelines for usage of
instances and topologies within each instance. While this represents
examples based on the intent of the authors, implementors are not
constrained by the examples.
3.1. One-to-One Mapping Between Topologies and Instances
When the set of information to be flooded in LSPs is intended to be
flooded to all MI-RTRs supporting a given IID, a single topology MAY
be used. The information contained in the single LSDB MAY still
contain information associated with multiple applications as the
GENINFO TLV for each application has an application-specific ID that
identifies the application to which the TLV applies [RFC6823].
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3.2. Many-to-One Mapping between Topologies and Instances
When the set of information to be flooded in LSPs includes subsets
that are of interest to a subset of the MI-RTRs supporting a given
IID, support of multiple ITIDs allows each subset to be flooded only
to those MI-RTRs that are interested in that subset. In the simplest
case, a one-to-one mapping between a given application and an ITID
allows the information associated with that application to be flooded
only to MI-RTRs that support that application - but a many-to-one
mapping between applications and a given ITID is also possible. When
the set of application-specific information is large, the use of
multiple ITIDs provides significantly greater efficiencies, as MI-
RTRs only need to maintain the LSDB for applications of interest and
that information only needs to be flooded over a topology defined by
the MI-RTRs who support a given ITID.
The use of multiple ITIDs also allows the dedication of a full LSP
set (256 LSPs at each level) for the use of a given (set of)
applications, thereby minimizing the possibility of exceeding the
carrying capacity of an LSP set. Such a possibility might arise if
information for all applications were to be included in a single LSP
set.
Note that the topology associated with each ITID MUST be fully
connected in order for ITID-specific LSPs to be successfully flooded
to all MI-RTRs that support that ITID.
When multiple ITIDs are supported by an instance ITID #0 MUST NOT be
supported.
3.3. Considerations for the Number of Instances
The support of multiple topologies within the context of a single
instance provides better scalability in support of multiple
applications both in terms of the number of adjacencies that are
required and in the flooding of topology-specific LSDB. In many
cases, the use of a single non-zero instance would be sufficient and
optimal. However, in cases where the set of topologies desired in
support of a set of applications is largely disjoint from the set of
topologies desired in support of a second set of applications, it
could make sense to use multiple instances.
4. Relationship to M-ISIS
[RFC5120] defines support for multi-topology routing. In that
document 12-bit Multi-Topology Identifiers (MTIDs) are defined to
identify the topologies that an IS-IS instance (a "standard instance"
as defined by this document) supports. There is no relationship
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between the Multi-topology IDs defined in [RFC5120] and the ITIDs
defined in this document.
An MI-RTR MAY use the extensions defined in this document to support
multiple topologies in the context of an instance with a non-zero
IID. Each MI topology is associated with a unique LSDB identified by
an ITID. An ITID-specific IS-IS Update Process operates on each
topology. This differs from [RFC5120] where a single LSDB and single
IS-IS Update Process is used in support of all topologies. In such
cases if an MI-RTR uses the extensions in support of the BFD Enabled
TLV [RFC6213] , the ITID MUST be used in place of the MTID in which
case all 16 bits of the identifier field are useable.
An MI-RTR MAY support [RFC5120] multi-topology within a non-zero
instance when ITID #0 is supported. When ITID #0 is supported it
MUST be the only ITID supported by that instance. In such cases if
an MI-RTR uses the extensions in support of the BFD Enabled TLV
[RFC6213] , the [RFC5120] MTID MUST be used as specified in
[RFC6213].
An MI-RTR MUST NOT support [RFC5120] multi-topology within a non-zero
instance when any non-zero ITID is supported. The following TLVs
MUST NOT be sent in an LSP associated with a non-zero instance which
supports a non-zero ITID and such an LSP MUST be ignored when
received:
TLV 222 - MT IS Neighbors
TLV 235 - MT IP Reachability
TLV 237 - MT IPv6 Reachability
5. Graceful Restart Interactions
[RFC5306] defines protocol extensions in support of graceful restart
of a routing instance. The extensions defined there apply to MI-RTRs
with the notable addition that as there are topology-specific LSP
databases all of the topology-specific LSP databases must be
synchronized following restart in order for database synchronization
to be complete. This involves the use of additional T2 timers. See
[RFC5306] for further details.
6. IANA Considerations
Per [RFC6822], IANA has registered a new IS-IS TLV, which is
reflected in the "IS-IS TLV Codepoints" registry:
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Type Description IIH LSP SNP Purge
---- --------------------- --- --- --- -----
7 Instance Identifier y y y y
Per [RFC6822], IANA has registered two EUI-48 multicast addresses
from the IANA-managed EUI address space as specified in [RFC7042].
The addresses are as follows:
01-00-5E-90-00-02 AllL1MI-ISs
01-00-5E-90-00-03 AllL2MI-ISs
7. Security Considerations
Security concerns for IS-IS are addressed in [ISO10589, [RFC5304],
and [RFC5310].
8. Acknowledgements
For the first version of this specification the authors acknowledged
contributions made by Dino Farinacci and Tony Li.
For the new version of this specification the authors would like to
acknowledge Paul Wells.
9. References
9.1. Normative References
[ISO10589]
"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.", Nov 2002.
[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>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<http://www.rfc-editor.org/info/rfc5120>.
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[RFC5303] Katz, D., Saluja, R., and D. Eastlake 3rd, "Three-Way
Handshake for IS-IS Point-to-Point Adjacencies", RFC 5303,
DOI 10.17487/RFC5303, October 2008,
<http://www.rfc-editor.org/info/rfc5303>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <http://www.rfc-editor.org/info/rfc5304>.
[RFC5306] Shand, M. and L. Ginsberg, "Restart Signaling for IS-IS",
RFC 5306, DOI 10.17487/RFC5306, October 2008,
<http://www.rfc-editor.org/info/rfc5306>.
[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>.
[RFC6213] Hopps, C. and L. Ginsberg, "IS-IS BFD-Enabled TLV",
RFC 6213, DOI 10.17487/RFC6213, April 2011,
<http://www.rfc-editor.org/info/rfc6213>.
[RFC6232] Wei, F., Qin, Y., Li, Z., Li, T., and J. Dong, "Purge
Originator Identification TLV for IS-IS", RFC 6232,
DOI 10.17487/RFC6232, May 2011,
<http://www.rfc-editor.org/info/rfc6232>.
[RFC6233] Li, T. and L. Ginsberg, "IS-IS Registry Extension for
Purges", RFC 6233, DOI 10.17487/RFC6233, May 2011,
<http://www.rfc-editor.org/info/rfc6233>.
[RFC6822] Previdi, S., Ed., Ginsberg, L., Shand, M., Roy, A., and D.
Ward, "IS-IS Multi-Instance", RFC 6822,
DOI 10.17487/RFC6822, December 2012,
<http://www.rfc-editor.org/info/rfc6822>.
[RFC6823] Ginsberg, L., Previdi, S., and M. Shand, "Advertising
Generic Information in IS-IS", RFC 6823,
DOI 10.17487/RFC6823, December 2012,
<http://www.rfc-editor.org/info/rfc6823>.
9.2. Informative References
[RFC5309] Shen, N., Ed. and A. Zinin, Ed., "Point-to-Point Operation
over LAN in Link State Routing Protocols", RFC 5309,
DOI 10.17487/RFC5309, October 2008,
<http://www.rfc-editor.org/info/rfc5309>.
Ginsberg, et al. Expires October 22, 2016 [Page 13]
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[RFC7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and
IETF Protocol and Documentation Usage for IEEE 802
Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042,
October 2013, <http://www.rfc-editor.org/info/rfc7042>.
Appendix A. Changes to RFC 6822
RFC 6822 prohibited the use of RFC 5120 Multi-Topology (MT) support
in a non-zero instance. However, deployment experience since the
writing of RFC 6822 has revealed a desire to be able to support RFC
5120 style MT using multiple non-zero instances as an alternative
means of controlling leaking of information between L1 areas while
also supporting incongruent topologies for different address
families. The rules have therefore been relaxed to allow use of RFC
5120 MT in a non-zero instance so long as ITID #0 is the only
instance topology (ITID) supported by the instance. Note that this
change is not backwards compatible with implementations strictly
following RFC 6822. As of this writing all known implementations are
compatible with this change.
A suggestion has been added to place the IID-TLV as the first TLV in
a PDU to speed recognition of the correct instance when parsing a
received PDU.
Clarification that the IID-TLV is only included in Pt-Pt IIHs
associated with non-zero instances has been added. This addresses
Errata ID #4519.
Clarification of the appropriate MAC multicast addresses to use when
sending PDUs on a broadcast interface for both standard instance and
non-zero instances has been provided. This addresses Errata ID
#4520.
Authors' Addresses
Les Ginsberg
Cisco Systems
510 McCarthy Blvd.
Milpitas, CA 95035
USA
Email: ginsberg@cisco.com
Ginsberg, et al. Expires October 22, 2016 [Page 14]
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Stefano Previdi
Cisco Systems
Via Del Serafico 200
Rome 0144
Italy
Email: sprevidi@cisco.com
Wim Henderickx
Nokia
BE
Email: wim.henderickx@nokia.com
Ginsberg, et al. Expires October 22, 2016 [Page 15]
