wdiff rfc7356.original rfc7356.txt

Networking Working Group
Internet Engineering Task Force (IETF) L. Ginsberg
Internet-Draft
Request for Comments: 7356 S. Previdi
Intended status:
Category: Standards Track Y. Yang
Expires: December 6, 2014
ISSN: 2070-1721 Cisco Systems
June 4,
August 2014

IS-IS Flooding Scope LSPs
draft-ietf-isis-fs-lsp-02.txt Link State PDUs (LSPs)

Abstract

Intermediate System To Intermediate System (IS-IS) provides efficient
and reliable flooding of information to its peers. However peers; however, the
current flooding scopes are limited to either area wide scope or domain wide
scope. There are existing use cases where support of other flooding
scopes are is desirable. This document defines new Protocol Data Units
(PDUs) which that provide support for new flooding scopes as well as
additional space for advertising information targeted for the
currently supported flooding scopes. This document also defines
extended TLVs Type-Length-Values (TLVs) and sub-TLVs which that are encoded
using 16
bit 16-bit fields for type Type and length. Length.

The protocol extensions defined in this document are not backwards
compatible with existing implementations and so must be deployed with
care.

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 an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of six months RFC 5741.

Information about the current status of this document, any errata,
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This Internet-Draft will expire on December 6, 2014.
http://www.rfc-editor.org/info/rfc7356.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Extended TLVs . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Use of Extended TLVs and Extended sub-TLVs Sub-TLVs . . . . . . . 5
2.2. Use of Standard Code Points in Extended TLVs and Extended
sub-TLVs
Sub-TLVs . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Definition of New PDUs . . . . . . . . . . . . . . . . . . . 6 5
3.1. Flooding Scoped LSP Format . . . . . . . . . . . . . . . 6
3.2. Flooding Scoped CSNP Format . . . . . . . . . . . . . . . 9
3.3. Flooding Scope PSNP Format . . . . . . . . . . . . . . . 10 11
4. Flooding Scope Update Process Operation . . . . . . . . . . . 12 13
4.1. Scope Types . . . . . . . . . . . . . . . . . . . . . . . 12 13
4.2. Operation on Point-to-Point Circuits . . . . . . . . . . 12 14
4.3. Operation on Broadcast Circuits . . . . . . . . . . . . . 13 14
4.4. Use of Authentication . . . . . . . . . . . . . . . . . . 13 14
4.5. Priority Flooding . . . . . . . . . . . . . . . . . . . . 13 15
5. Deployment Considerations . . . . . . . . . . . . . . . . . . 14 15
6. Graceful Restart Interactions . . . . . . . . . . . . . . . . 14 15
7. Multi-instance Interactions . . . . . . . . . . . . . . . . . 14 16
8. Circuit Scoped Scope Flooding . . . . . . . . . . . . . . . . . . . 14 16
9. Extending LSP Set Capacity . . . . . . . . . . . . . . . . . 15 16
10. Domain Scoped Scope Flooding . . . . . . . . . . . . . . . . . . . 16 . 17
11. Announcing Support for Flooding Scopes . . . . . . . . . . . 17 18
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 19
13. Security Considerations . . . . . . . . . . . . . . . . . . . 19 21
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 21
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 21
15.1. Normative References . . . . . . . . . . . . . . . . . . 20 21
15.2. Informational Informative References . . . . . . . . . . . . . . . . 21
Appendix A. Change History . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 22

1. Introduction

The Update Process Process, as defined by [IS-IS] [IS-IS], provides reliable and
efficient flooding of information to all routers in a given flooding
scope. Currently Currently, the protocol supports two flooding scopes and
associated Protocol Data Units (PDUs). PDUs. Level 1 (L1) Link State PDUs (LSPs) are flooded to
all routers in an area. Level 2 (L2) LSPs are flooded to all routers
in the Level 2 sub-domain. subdomain. The basic operation of the Update Process
can be applied to any subset of the routers in a given topology so
long as that topology is not partitioned. It is therefore is, therefore, possible
to introduce new PDUs in support of other flooding scopes and utilize
the same Update Process machinery to provide the same reliability and
efficiency which that the Update Process currently provides for L1 and L2
scopes. This document defines these new PDUs and the modified Update
Process rules
which that are to be used in supporting new flooding scopes.

New deployment cases have introduced the need for reliable and
efficient circuit scoped scope flooding. For example, Appointed Forwarder
information
information, as defined in [RFC7176] [RFC7176], needs to be flooded reliably
and efficiently to all RBridges Routing Bridges (RBridges) on a broadcast
circuit. Currently, only
Intermediate System to Intermediate System IS-IS Hellos (IIHs) have the matching scope -
-- but IIHs are unreliable i.e. unreliable, i.e., individual IIHs may be lost without
affecting correct operation of the protocol. To provide reliability
in cases where the set of information to be flooded exceeds the
carrying capacity of a single PDU requires sending the information
periodically even when no changes in the content have occurred. When
the information content is large large, this is inefficient and still does
not provide a guarantee of reliability. This document defines
circuit scoped scope flooding in order to provide a solution for such cases.

Another existing limitation of [IS-IS] is the carrying capacity of an
LSP set. It has been noted in [RFC5311] that the set of LSPs that
may be originated by a system at each level is limited to 256 LSPs LSPs,
and the maximum size of each LSP is limited by the minimum Maximum
Transmission Unit (MTU) of any link used to flood LSPs. [RFC5311]
has defined a backwards compatible backwards-compatible protocol extension which that can be
used to overcome this limitation if needed. While the [RFC5311]
solution is viable, in order to be interoperable with routers which that do
not support the extension extension, it imposes some restrictions on what
can/cannot can/
cannot be advertised in the Extended LSPs and requires allocation of
multiple unique system IDs to a given router. A more flexible and
less constraining solution is possible if interoperability with
legacy routers is not a requirement. As By definition, the introduction
of new PDUs required to support new flooding scopes is by definition not
interoperable with legacy routers, it is routers. It is, therefore, possible to
simultaneously introduce an alternative solution to the limited LSP
set carrying capacity of Level 1 and Level 2 LSPs as part of the
extensions defined in this document. This capability is also defined
in this document.

Standard IS-IS TLVs (Type/Length/Value) are encoded using an eight
bit 8-bit type and an 8 bit 8-bit
length. In cases where the set of information about a single object
exceeds 255 octets octets, multiple TLVs are required to encode all of the
relevant information. This document introduces extended TLVs and
extended sub-TLVs which that use a 16 bit type 16-bit Type field and a 16 bit length 16-bit Length
field.

The PDU type Type field in the common header for all IS-IS PDUs is a 5 bit 5-bit
field. The Therefore, possible PDU types supported by the protocol are
therefore
limited to a maximum of 32. In order to minimize the need to
introduce additional PDU types in the future, the new PDUs introduced
in this document are defined so as to allow multiple flooding scopes
to be associated with the same PDU type. This means if new flooding
scopes are required in the future future, the same PDU type can be used.

1.1. 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 [RFC2119].

2. Extended TLVs

Standard TLVs as defined in [IS-IS] as well as standard sub-TLVs
(first introduced in [RFC5305]) have an eight bit type 8-bit Type field and an
eight bit length
eight-bit Length field. This constrains the information included in
a single TLV or sub-TLV to 255 octets. With the increasing use of
sub-TLVs
sub-TLVs, it becomes more likely that the amount of information about
a single object which that needs to be advertised may exceed 255 octets.
In such cases cases, the information is encoded in multiple TLVs. This
leads to less efficient encoding since the information which that uniquely
identifies the object must be repeated in each TLV and requires
additional implementation complexity when receiving the information
to ensure that all information about the object is correctly
collected from the multiple TLVs.

This document introduces extended TLVs and extended sub-TLVs. These
are encoded using a 16 bit type 16-bit Type field and a 16 bit length 16-bit Length field.

2.1. Use of Extended TLVs and Extended sub-TLVs Sub-TLVs

The following restrictions apply to the use of extended TLVs and
extended sub-TLVs:

o Extended TLVs and extended sub-TLVs are permitted only in Flooding
Scoped
Scope PDUs which that have a flooding scope designated for their use
(defined later in this document)

o A given flooding scope supports either the use of either standard TLVs
and standard sub-TLVs or the use of extended TLVs and extended
sub-TLVs
sub-TLVs, but not both

o Extended TLVs and extended sub-TLVs MUST be used together together, i.e.,
using Standard sub-TLVs within an Extended TLV or using Extended
sub-TLVs within a Standard TLV is invalid

o If additional levels of TLVs (e.g., sub-sub-TLVs) are introduced
in the future future, then the size of the type/length Type and Length fields in
these new sub-types MUST match the size used in the parent

o The 16 bit type 16-bit Type and length Length fields are encoded in network byte
order

o Use of extended TLVs and extended sub-TLVs does not alter in any
way the maximum size of PDUs which that may sent or received

2.2. Use of Standard Code Points in Extended TLVs and Extended sub-TLVs Sub-TLVs

Standard TLV and standard sub-TLV code points as defined in the IANA
IS-IS
"IS-IS TLV Codepoints Registry Codepoints" registry MAY be used in extended TLVs and
extended sub-TLVs. Encoding is as specified for each of the standard
TLVs and standard sub-TLVs with the following differences:

o The eight bit type 8-bit Type field is encoded as an unsigned 16 bit 16-bit integer
where the 8 MSBs most significant bits (MSBs) are all 0

o The eight bit length 8-bit Length field is replaced by the 16 bit length 16-bit Length field

o The length MAY take on values greater than 255

3. Definition of New PDUs

In support of new flooding scopes scopes, the following new PDUs are
required:

o Flooding Scoped Scope LSPs (FS-LSPs)
o Flooding Scoped Scope Complete Sequence Number PDUs (FS-CSNPs)

o Flooding Scoped Scope Partial Sequence Number PDUs (FS-PSNPs)

Each of these PDUs is intentionally defined with a header as similar
in format as possible to the corresponding PDU types currently
defined in [IS-IS]. Although it might have been possible to
eliminate or redefine PDU header fields in a new way way, the existing
formats are retained in order to allow maximum reuse of existing PDU
processing logic in an implementation.

Note that in the case of all FS PDUs, the Maximum Area Addresses
field in the header of the corresponding standard PDU has been
replaced with a Scope field. The Therefore, maximum area addresses
checks specified in [IS-IS] are therefore not performed on FS PDUs.

3.1. Flooding Scoped LSP Format

An FS-LSP has the following format:

No. of octets
+-------------------------+
| Intradomain Routeing | 1
| Protocol Discriminator |
+-------------------------+
| Length Indicator | 1
+-------------------------+
| Version/Protocol ID | 1
| Extension |
+-------------------------+
| ID Length | 1
+-------------------------+
|R|R|R| PDU Type | 1
+-------------------------+
| Version | 1
+-------------------------+
| Reserved | 1
+-------------------------+
|P| Scope | 1
+-------------------------+
| PDU Length | 2
+-------------------------+
| Remaining Lifetime | 2
+-------------------------+
| FS LSP ID | ID Length + 2
+-------------------------+
| Sequence Number | 4
+-------------------------+
| Checksum | 2
+-------------------------+
|Reserved|LSPDBOL|IS Type | 1
+-------------------------+
: Variable Length Fields : Variable
+-------------------------+

Intradomain Routeing Protocol Discriminator - Discriminator: 0x83 (as defined in [IS-IS])
[IS-IS]).

Length Indicator - Indicator: Length of the Fixed Header fixed header in octets octets.

Version/Protocol ID Extension - Extension: 1

ID Length - Length: As defined in [IS-IS] [IS-IS].

PDU Type - Type: 10 (Subject to assignment by IANA) - Format as defined in [IS-IS]

Version - [IS-IS].

Version: 1

Reserved - transmitted
Reserved: Transmitted as zero, ignored on receipt

Scope - receipt.

Scope: Bits 1-7 define the flooding scope.

The value 0 is reserved and MUST NOT be used. Received FS-LSPs
with a scope of 0 MUST be ignored and MUST NOT be flooded.
P -

P: Bit 8 - Priority Bit. If set to 1 1, this LSP SHOULD be
flooded at high priority.

Scopes (1 - 63) are reserved for use with standard TLVs and
standard sub-TLVs.

Scopes (64 - 127) are reserved for use with extended TLV TLVs and
extended sub-TLVs.

PDU Length - Length: Entire Length length of this PDU, in octets, including the
header.

Remaining Lifetime - Lifetime: Number of seconds before this FS-LSP is
considered expired.

FS LSP ID - the ID: The system ID of the source of the FS-LSP. One of the
following two formats is used:

FS LSP ID Standard Format

+-------------------------+
| Source ID | ID Length
+-------------------------+
| Pseudonode ID | 1
+-------------------------+
| FS LSP Number | 1
+-------------------------+

FS LSP ID Extended Format

+-------------------------+
| Source ID | ID Length
+-------------------------+
| Extended FS LSP Number | 2
+-------------------------+

Which format is used is specific to the Scope scope and MUST be defined
when the specific flooding scope is defined.

Sequence Number - sequence Number: Sequence number of this FS-LSP

Checksum - FS-LSP.

Checksum: Checksum of contents of FS-LSP from the Source ID to the
end. Checksum is computed as defined in [IS-IS].

Reserved/LSPDBOL/IS Type

Bits 4-8 are reserved, which means they are transmitted as 0
and ignored on receipt.

LSPDBOL -

LSPDBOL: Bit 3 - A value of 0 indicates no FS-LSP Database
Overload and a value of 1 indicates that the FS-LSP Database is
overloaded. The overload condition is specific to FS-LSPs with
the scope specified in the scope Scope field.

IS Type - Type: Bits 1 and 2. The type of Intermediate System as
defined in [IS-IS].

Variable Length Fields which length fields that are allowed in an FS-LSP are specific
to the defined scope.

3.2. Flooding Scoped CSNP Format

An FS-CSNP has the following format:

No. of octets
+-------------------------+
| Intradomain Routeing | 1
| Protocol Discriminator |
+-------------------------+
| Length Indicator | 1
+-------------------------+
| Version/Protocol ID | 1
| Extension |
+-------------------------+
| ID Length | 1
+-------------------------+
|R|R|R| PDU Type | 1
+-------------------------+
| Version | 1
+-------------------------+
| Reserved | 1
+-------------------------+
|R| Scope | 1
+-------------------------+
| PDU Length | 2
+-------------------------+
| Source ID | ID Length + 1
+-------------------------+
| Start FS-LSP ID | ID Length + 2
+-------------------------+
| End FS-LSP ID | ID Length + 2
+-------------------------+
: Variable Length Fields : Variable
+-------------------------+

Intradomain Routeing Protocol Discriminator - Discriminator: 0x83 (as defined in [IS-IS]
[IS-IS].

Length Indicator - Indicator: Length of the Fixed Header fixed header in octets octets.

Version/Protocol ID Extension - Extension: 1

ID Length - Length: As defined in [IS-IS] [IS-IS].

PDU Type - Type: 11 (Subject to assignment by IANA) - Format as defined in
[IS-IS]

Version - [IS-IS].

Version: 1

Reserved - transmitted

Reserved: Transmitted as zero, ignored on receipt

Scope - receipt.

Scope: Bits 1-7 define the flooding scope.

The value 0 is reserved and MUST NOT be used. Received
FS-CSNPs FS-
CSNPs with a scope of 0 MUST be ignored.

Bit 8 is Reserved Reserved, which means it is transmitted as 0 and
ignored on receipt.

Scopes (1 - 63) are reserved for use with standard TLVs and
standard sub-TLVs.

Scopes (64 - 127) are reserved for use with extended TLV and
extended sub-TLVs.

PDU Length - Length: Entire Length length of this PDU, in octets, including the
header.

Source ID - the ID: The system ID of the Intermediate System (with zero
Circuit ID) generating this Sequence Numbers PDU Number's PDU.

Start FS-LSP ID - ID: The FS-LSP ID of the first FS-LSP with the
specified scope in the range covered by this FS-CSNP.

End FS-LSP ID - ID: The FS-LSP ID of the last FS-LSP with the specified
scope in the range covered by this FS-CSNP.

Variable Length Fields which length fields that are allowed in an FS-CSNP are limited
to those TLVs which that are supported by standard CSNP.

3.3. Flooding Scope PSNP Format

An FS-PSNP has the following format:

No. of octets
+-------------------------+
| Intradomain Routeing | 1
| Protocol Discriminator |
+-------------------------+
| Length Indicator | 1
+-------------------------+
| Version/Protocol ID | 1
| Extension |
+-------------------------+
| ID Length | 1
+-------------------------+
|R|R|R| PDU Type | 1
+-------------------------+
| Version | 1
+-------------------------+
| Reserved | 1
+-------------------------+
|U| Scope | 1
+-------------------------+
| PDU Length | 2
+-------------------------+
| Source ID | ID Length + 1
+-------------------------+
: Variable Length Fields : Variable
+-------------------------+

Intradomain Routeing Protocol Discriminator - Discriminator: 0x83 (as defined in [IS-IS]
[IS-IS].

Length Indicator - Indicator: Length of the Fixed Header fixed header in octets octets.

Version/Protocol ID Extension - Extension: 1

ID Length - Length: As defined in [IS-IS] [IS-IS].

PDU Type - Type: 12 (Subject to assignment by IANA) - Format as defined in [IS-IS]

Version - [IS-IS].

Version: 1

Reserved - transmitted

Reserved: Transmitted as zero, ignored on receipt

Scope - receipt.

Scope: Bits 1-7 define the flooding scope.

The value 0 is reserved and MUST NOT be used. Received
FS-PSNPs FS-
PSNPs with a scope of 0 MUST be ignored.
U -

U: Bit 8 - A value of 0 indicates that the specified flooding
scope is supported. A value of 1 indicates that the specified
flooding scope is unsupported. When U = 1, variable length
fields other than authentication MUST NOT be included in the
PDU.

Scopes (1 - 63) are reserved for use with standard TLVs and
standard sub-TLVs.

Scopes (64 - 127) are reserved for use with extended TLV TLVs and
extended sub-TLVs.

PDU Length - Length: Entire Length length of this PDU, in octets, including the
header.

Source ID - the ID: The system ID of the Intermediate System (with zero
Circuit ID) generating this Sequence Numbers PDU Number's PDU.

Variable Length Fields which length fields that are allowed in an FS-PSNP are limited
to those TLVs which that are supported by standard PSNPs.

4. Flooding Scope Update Process Operation

The Update Process Process, as defined in [IS-IS] [IS-IS], maintains a Link State
Database (LSDB) for each level supported. Each level specific level-specific LSDB
contains the full set of LSPs generated by all routers operating in
that level specific level-specific scope. The introduction of FS-LSPs creates
additional LSDBs (FS-LSDBs) for each additional scope supported. The
set of FS-LSPs in each FS-LSDB consists of all FS-LSPs generated by
all routers operating in that scope. There Therefore, there is therefore an
additional instance of the Update Process for each supported flooding
scope.

Operation of the scope specific scope-specific Update Process follows the Update
Process specification in [IS-IS]. The circuit(s) on which FS-LSPs
are flooded are is limited to those circuits which that are participating in
the given scope. Similarly Similarly, the sending/receiving of FS-CSNPs and FS-
PSNPs
FS-PSNPs is limited to the circuits participating in the given scope.

Consistent support of a given flooding scope on a circuit by all
routers operating on that circuit is required.

4.1. Scope Types

A flooding scope may be limited to a single circuit (circuit scope).
Circuit scopes may be further limited by level (L1 circuit scope/L2
circuit scope). Circuit Scope / L2
Circuit Scope).

A flooding scope may be limited to all circuits enabled for L1
routing (area scope).

A flooding scope may be limited to all circuits enabled for L2
routing (L2 sub-domain subdomain scope).

Additional scopes may be defined which that include all circuits enabled
for either L1 or L2 routing (domain-wide (domain scope).

4.2. Operation on Point-to-Point Circuits

When a new adjacency is formed, synchronization of all FS-LSDBs
supported on that circuit is required. Therefore required; therefore, FS-CSNPs for all
supported scopes MUST be sent when a new adjacency reaches the UP
state. The Send Receive Message (SRM) bit MUST be set for all
FS-LSPs associated with the scopes supported on that circuit.
Receipt of an FS-PSNP with the U bit equal to 1 indicates that the
neighbor does not support that scope (although it does support FS
PDUs). This MUST cause the SRM bit to be cleared for all FS-LSPs
with the matching scope scope, which are currently marked for flooding on
that circuit.

4.3. Operation on Broadcast Circuits

FS PDUs are sent to the same destination address(es) as standard PDUs
for the given protocol instance. For specification of the defined
destination addresses addresses, consult [IS-IS], [IEEEaq], [RFC6822], and
[RFC6325].

The Designated Intermediate System (DIS) for a broadcast circuit has
the responsibility to generate periodic scope specific scope-specific FS-CSNPs for
all supported scopes. A scope specific scope-specific DIS is NOT elected as all
routers on a circuit MUST support a consistent set of flooding
scopes.

It is possible that a scope may be defined which that is not level
specific. In such a case case, the DIS for each level enabled on a
broadcast circuit MUST independently send FS PDUs for that scope to
the appropriate level specific level-specific destination address. This may result
in redundant flooding of FS-LSPs for that scope.

4.4. Use of Authentication

Authentication TLVs MAY be included in FS PDUs. When authentication
is in use, the scope is first used to select the authentication
configuration that is applicable. The authentication check is then
performed as normal. Although scope specific scope-specific authentication MAY be
used, sharing of authentication among multiple scopes and/or with the
standard LSP/CSNP/PSNP PDUs LSPs/CSNPs/PSNPs is considered sufficient.

4.5. Priority Flooding

When the FS LSP ID Extended Format format is used used, the set of LSPs generated
by an IS may be quite large. It may be useful to identify those LSPs
in the set which that contain information of higher priority. Such LSPs
will have the P bit set to 1 in the Scope field in the LSP header.
Such LSPs SHOULD be flooded at a higher priority than LSPs with the P
bit set to 0. This is a suggested behavior on the part of the
originator of the LSP. When an LSP is purged purged, the original state of
the P bit MUST be preserved.

5. Deployment Considerations

Introduction of new PDU types is incompatible with legacy
implementations. Legacy implementations do not support the FS
specific
FS-specific Update process(es) and therefore and, therefore, flooding of the
FS-LSPs throughout the defined scope is unreliable when not all
routers in the defined scope support FS PDUs. Further, legacy
implementations will likely treat the reception of an FS PDUs PDU as an
error. Even when all routers in a given scope support FS PDUs, if
not all routers in the flooding domain for a given scope support that
scope, then flooding of the FS-LSPs may be compromised. Therefore all routers in
the flooding domain for When
deploying a given scope SHOULD support new flooding scope, correct operation therefore requires
that both FS PDUs and the specified scope before use of that new scope can be enabled. supported by all routers in
the flooding domain of the new scope.

The U bit in FS-PSNPs provides a means to suppress retransmissions of
unsupported scopes. Routers which that support FS PDUs SHOULD support the
sending of PSNPs with the U bit equal to 1 when an FS-LSP is received
with a scope which that is unsupported. Routers which that support FS PDUs
SHOULD trigger management notifications when FS PDUs are received for
unsupported scopes and when PSNPs with the U bit equal to 1 are
received.

6. Graceful Restart Interactions

[RFC5306] defines protocol extensions in support of graceful restart
of a routing instance. Synchronization of all supported FS-LSDBs is
required in order for database synchronization to be complete. This
involves the use of additional T2 timers. Receipt of a PSNP with the
U bit equal to 1 will cause FS-LSDB synchronization with that
neighbor to be considered complete for that scope. See [RFC5306] for
further details.

7. Multi-instance Interactions

In cases where FS-PDUs are associated with a non-zero instance instance, the
use of IID-TLVs Instance Identifier TLVs (IID-TLVs) in FS-PDUs follows the
rules for use in LSPs, CSNPs, and PSNPs as defined in [RFC6822].

8. Circuit Scoped Scope Flooding

This document defines four circuit scoped scope flooding identifiers:

o Level 1 circuit scope Circuit Scope (L1CS) - -- this uses standard TLVs and
standard sub-TLVs

o Level 2 circuit scope Circuit Scope (L2CS) - -- this uses standard TLVs and
standard sub-TLVs

o Extended Level 1 circuit scope Circuit Scope (E-L1CS) - -- this uses extended TLVs
and extended sub-TLVs

o Extended Level 2 circuit scope (E-L1CS) - Circuit Scope (E-L2CS) -- this uses extended TLVs
and extended sub-TLVs

FS-LSPs with the scope Scope field set to one of these values contain
information specific to the circuit on which they are flooded. When
received, such FS-LSPs MUST NOT be flooded on any other circuit. The
FS LSP ID Extended format is used in these PDUs. The FS-LSDB
associated with circuit scoped scope FS-LSPs consists of the set of FS-LSPs
which
that both have matching circuit scope scopes and are transmitted (locally
generated) or received on a specific circuit.

The set of TLVs which that may be included in such FS-LSPs is specific to
the given use case and is outside the scope of this document.

9. Extending LSP Set Capacity

The need for additional space in the set of LSPs generated by a
single IS has been articulated in [RFC5311]. When legacy
interoperability is not a requirement, the use of FS-LSPs meets that
need without requiring the assignment of alias system-ids to a single
IS. Four flooding scopes are defined for this purpose:

o Level 1 Flooding Scope (L1FS) - -- this uses standard TLVs and
standard sub-
TLVs sub-TLVs

o Level 2 Flooding Scope (L2FS) - -- this uses standard TLVs and
standard sub-
TLVs sub-TLVs
o Extended Level 1 Flooding Scope (E-L1FS) - -- this uses extended
TLVs and extended sub-TLVs

o Extended Level 2 Flooding Scope (E-L2FS) - -- this uses extended
TLVs and extended sub-TLVs

L1FS and E-L1FS LSPs are flooded on all L1 circuits. L2FS and E-L2FS
LSPs are flooded on all L2 circuits.

The FS LSP ID Extended format is used in these PDUs. This provides
64K
64 K of additional LSPs which that may be generated by a single system at
each level.

LxFS and E-LxFS LSPs are used by the level specific level-specific Decision Process
(defined in [IS-IS]) in the same manner as standard LSPs (i.e. (i.e., as
additional information sourced by the same IS) subject to the
following restrictions:

o A valid version of standard LSP #0 from the same IS at the
corresponding Level level MUST be present in the LSDB in order for the
LxFS
LxFS/E-LxFS set to be usable usable.

o Information in an LxFS of E-LxFS LSP (e.g. (e.g., IS-Neighbor
information) which that supports using the originating IS as a transit
node MUST NOT be used when the Overload bit is set in the
corresponding standard LSP #0 #0.

o TLVs which that are restricted to standard LSP #0 MUST NOT appear in
LxFS LSPs.

There are no further restrictions as to what TLVs may be advertised
in FS-LSPs.

10. Domain Scoped Scope Flooding

Existing support for flooding information throughout a domain wide (i.e. (i.e.,
to L1 routers in all areas as well as to routers in the Level 2 sub-domain)
subdomain) requires the use of leaking procedures between levels.
For further
details details, see [RFC4971]. This is sufficient when the data
being flooded domain-wide throughout the domain consists of individual TLVs. If
it is desired to retain the identity of the originating IS for the
complete contents of a PDU, then support for flooding the unchanged
PDU is desirable. This document therefore document, therefore, defines two flooding
scopes in support of
domain-wide domain flooding. FS-LSPs with this scope MUST
be flooded on all circuits regardless of what level(s) are is supported
on that circuit.

o Domain Flooding Scope (DSFS) - (DFS) -- this uses standard TLVs and
standard sub-
TLVs sub-TLVs

o Extended Domain Flooding Scope (E-DSFS) - (E-DFS) -- this uses extended TLVs
and extended sub-TLVs

The FS LSP ID Extended format is used in these PDUs.

Use of information in FS-LSPs for a given scope depends on
determining the reachability to the IS originating the FS-LSP. This
presents challenges for FS-LSPs with domain-scopes domain scopes because no single
IS has the full view of the topology across all areas. It is
therefore is,
therefore, necessary for the originator of domain scoped scope DSFS and
E-DSFS LSPs to advertise an identifier which that will allow an IS who
receives such an FS-LSP to determine whether the source of the FS-LSP
is currently reachable. The identifier required depends on what
"address-families" are being advertised.

When IS-IS is deployed in support of Layer 3 routing for IPv4 and/or
IPv6
IPv6, then FS-LSP #0 with domain-wide domain scope MUST include at least one of
the following TLVs:

o IPv4 Traffic Engineering Router ID (TLV 134)

o IPv6 Traffic Engineering Router ID (TLV 140)

When IS-IS is deployed in support of Layer 2 routing, current
standards (e.g. (e.g., [RFC6325]) only support a single area. Therefore
domain-wide Therefore,
domain scope is not yet applicable. When the Layer 2 standards are
updated to include multi-area support support, the identifiers which that can be
used to support inter-area reachability will be defined - -- at which
point the use of domain-wide domain scope for Layer 2 can be fully defined.

11. Announcing Support for Flooding Scopes

Announcements of support for flooding scope may be useful in
validating that full support has been deployed and/or in isolating
the reasons for incomplete flooding of FS-LSPs for a given scope.

ISs supporting FS-PDUs MAY announce supported scopes in IIH PDUs. To
do so so, a new TLV is defined.

Scoped

Scope Flooding Support
Type: 243 (suggested - to be assigned by IANA)
Length: 1 - 127
Value
No of octets
+----------------------+
|R| Supported Scope | 1
+----------------------+
: :
+----------------------+
|R| Supported Scope | 1
+----------------------+

A list of the circuit scopes supported on this circuit and
other non-circuit flooding non-circuit-flooding scopes supported.

R bit MUST be 0 and is ignored on receipt.

In a Point-Point IIH Point-to-Point IIH, L1, L2, domain-wide, domain, and all circuit scopes
MAY be advertised.

In Level 1 LAN IIHs IIHs, L1, domain-wide, domain, and L1 circuit scopes Circuit Scopes MAY
be advertised. L2 scopes Scopes and L2 circuit scopes Circuit Scopes MUST NOT be
advertised.

In Level 2 LAN IIHs IIHs, L2, domain-wide, domain, and L2 circuit scopes Circuit Scopes MAY
be advertised. L1 scopes Scopes and L1 circuit scopes Circuit Scopes MUST NOT be
advertised.

Information in this TLV MUST NOT be considered in adjacency
formation.

Whether information in this TLV is used to determine when FS-LSPs
associated with a locally supported scope are flooded is an
implementation choice.

12. IANA Considerations

This document requires includes the definition of three new PDU types that
need to be are
reflected in the ISIS "IS-IS PDU registry. Values below are
suggested values subject to assignment by IANA. Registry".

Value Description
---- ---------------------
10 FS-LSP
11 FS-CSNP
12 FS-PSNP

This document requires that a
A new IANA registry be has been created to control the assignment of
scope identifiers in FS-PDUs. The registration procedure is "Expert
Review" as defined in [RFC5226]. Suggested The registry name is "LSP Flooding Scoped
Scope Identifier Registry". A scope identifier is a number from 1-127
1-127, inclusive. Values 1 - 63 are reserved for PDUs which that use
standard TLVs and standard sub-TLVs. Values 64 - 127 are reserved
for PDUs which that use extended TLVs and extended sub-TLVs. The list of hello
Hello PDUs in which support for a given scope MAY be announced (using
Scope Flooding Support TLV) is specified for each defined scope.

The following scope identifiers are defined by this document. Values
are suggested values subject to assignment by IANA.

FS LSP ID Format/ IIH Announce
Value Description TLV Format P2P L1LAN L2LAN
----- ------------------------------ ----------------- ---------------
1 Level 1 Circuit Flooding Scope Extended/Standard Y Y N
2 Level 2 Circuit Flooding Scope Extended/Standard Y N Y
3 Level 1 Flooding Scope Extended/Standard Y Y N
4 Level 2 Flooding Scope Extended/Standard Y N Y
5 Domain-wide Domain Flooding Scope Extended/Standard Y Y Y
(6-63)Unassigned

64 Level 1 Circuit Flooding Scope Extended/Extended Y Y N
65 Level 2 Circuit Flooding Scope Extended/Extended Y N Y
66 Level 1 Flooding Scope Extended/Extended Y Y N
67 Level 2 Flooding Scope Extended/Extended Y N Y
68 Domain-wide Domain Flooding Scope Extended/Extended Y Y Y
(69-127) Unassigned

This document requires the

The definition of a new IS-IS TLV to be is reflected in the "IS-IS TLV
Codepoints" registry:

Type Description

Value Name IIH LSP SNP Purge
---- ------------ --- --- --- -----
243 Circuit Scoped Scope Flooding Support Y N N N

The IANA "IS-IS TLV codepoints Codepoints" registry is has been extended to allow
definition of codepoints less than or equal to 65535. Codepoints
greater than 255 can only be used in PDUs designated to support
extended TLVs. This registry has also been updated to point to this
document as a reference (in addition to [RFC3563] and [RFC6233]).

13. Security Considerations

Security concerns for IS-IS are addressed in [IS-IS], [RFC5304], and
[RFC5310].

The new PDUs introduced are subject to the same security issues
associated with their standard LSP/CSNP/PSNP counterparts. To the
extent that additional PDUs represent additional load for routers in
the network network, this increases the opportunity for denial of service denial-of-service
attacks.

14. Acknowledgements

The authors wish to thank Ayan Banerjee, Donald Eastlake, Hannes
Gredler, and Mike Shand for their comments.

15. References

15.1. Normative References

[IEEEaq] IEEE, "Standard for Local and metropolitan area networks: networks
-- Media Access Control (MAC) Bridges and Virtual Bridged
Local Area Networks - -- Amendment 20: Shortest Path
Bridging", IEEE Std 802.1aq-2012, 29 June 2012.", 2012.

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

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC4971] Vasseur, JP., Shen, N., and R. Aggarwal, "Intermediate
System to Intermediate System (IS-IS) Extensions for
Advertising Router Information", RFC 4971, July 2007.

[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.

[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, October 2008.

[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.

[RFC5306] Shand, M. and L. Ginsberg, "Restart Signaling for IS-IS",
RFC 5306, October 2008.

[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, February 2009.

[RFC6822] Previdi, S., Ginsberg, L., Shand, M., Roy, A., and D.
Ward, "IS-IS Multi-Instance", RFC 6822, December 2012.

15.2. Informational Informative References

[RFC3563] Zinin, A., "Cooperative Agreement Between the ISOC/IETF
and ISO/IEC Joint Technical Committee 1/Sub Committee 6
(JTC1/SC6) on IS-IS Routing Protocol Development", RFC
3563, July 2003.

[RFC5311] McPherson, D., Ginsberg, L., Previdi, S., and M. Shand,
"Simplified Extension of Link State PDU (LSP) Space for
IS-IS", RFC 5311, February 2009.

[RFC6233] Li, T. and L. Ginsberg, "IS-IS Registry Extension for
Purges", RFC 6233, May 2011.

[RFC6325] Perlman, R., Eastlake, D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC 6325, July 2011.

[RFC7176] Eastlake, D., Senevirathne, T., Ghanwani, A., Dutt, D.,
and A. Banerjee, "Transparent Interconnection of Lots of
Links (TRILL) Use of IS-IS", RFC 7176, May 2014.

Appendix A. Change History

Changes from 01 to 02 version

o Updated Section 11 to state what scopes MUST NOT be announced in a
given IIH PDU

o Updated IANA section for new "LSP Flooding Scoped Identifier
Registry" to include the hello PDUs in which a given scope may be
announced.

Authors' Addresses

Les Ginsberg
Cisco Systems
510 McCarthy Blvd.
Milpitas, CA 95035
USA

Email:

EMail: ginsberg@cisco.com
Stefano Previdi
Cisco Systems
Via Del Serafico 200
Rome 0144
Italy

Email:

EMail: sprevidi@cisco.com

Yi Yang
Cisco Systems
7100-9 Kit Creek Road
Research Triangle Park, North Carolina 27709-4987
USA

Email:

EMail: yiya@cisco.com