wdiff draft-przygienda-bier-isis-ranges-01.txt draft-przygienda-bier-isis-ranges-02.txt

Internet Engineering Task Force A. Przygienda
Internet-Draft Ericsson
Intended status: Standards Track L. Ginsberg
Expires: April 26, August 3, 2015 Cisco Systems
S. Aldrin
Huawei
J. Zhang
Juniper Networks, Inc.
October 23, 2014
January 30, 2015

BIER support via ISIS
draft-przygienda-bier-isis-ranges-01
draft-przygienda-bier-isis-ranges-02

Abstract

Specification of an ISIS extension to support BIER domains and sub-
domains.

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
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This Internet-Draft will expire on April 26, August 3, 2015.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. BIER Domains in Extended Reachability TLVs and Sub-Domains . . . . . . . . . . . . . . 4
4.2. BIER Domains
5. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Procedures
5.1. Enabling a BIER Sub-Domain . . . . . . . . . . . . . . . 5
5.2. Multi Topology and Sub-Domain . . . . . . . . . . 4
5.1. Enabling a BIER Domain . . . . 5
5.3. Encapsulation . . . . . . . . . . . . . 4
5.2. Encapsulation . . . . . . . . . 5
5.4. Tree Type . . . . . . . . . . . . . . . . . . . . . . . . 5
5.3.
5.5. Label Advertisements for MPLS encapsulated BIER sub-
domains . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.3.1.
5.5.1. Special Consideration . . . . . . . . . . . . . . . . 5
5.4. 6
5.6. BFR-id Advertisements . . . . . . . . . . . . . . . . . . 5
5.5. 6
5.7. Flooding . . . . . . . . . . . . . . . . . . . . . . . . 6
5.8. Version . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . 6 7
6.1. BIER Info sub-TLV . . . . . . . . . . . . . . . . . . . . 6 7
6.2. BIER MPLS Encapsulation sub-sub-TLV . . . . . . . . . . . 7 8
6.3. Optional BIER sub-domain Tree Type sub-sub-TLV . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 11
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 11
9. Normative References . . . . . . . . . . . . . . . . . . . . 8 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 12

1. Introduction

Bit Index Explicit Replication (BIER)
[I-D.draft-wijnands-bier-architecture-00]
[I-D.draft-wijnands-bier-architecture-02] defines an architecture
where all intended multicast receivers are encoded as bitmask in the
Multicast packet header within different encapsulations such as
[I-D.draft-wijnands-mpls-bier-encapsulation-01].
[I-D.draft-wijnands-mpls-bier-encapsulation-02]. A router that
receives such a packet will forward the packet based on the Bit
Position in the packet header towards the receiver(s), following a
precomputed tree for each of the bits in the packet. Each receiver
is represented by a unique bit in the bitmask.

This document presents first attempt at necessary extensions to the currently deployed
ISIS for IP [RFC1195] protocol to support distribution of information
necessary for operation of BIER domains. domains and sub-domains. This
document defines a new TLV to be advertised by every router
participating in such BIER domains. signaling.

2. Terminology

Some of the terminology specified in
[I-D.draft-wijnands-bier-architecture-00]
[I-D.draft-wijnands-bier-architecture-02] is replicated here and
extended by necessary definitions:

BIER: Bit Index Explicit Replication (The overall architecture of
forwarding multicast using a Bit Position).

BIER-OL: BIER Overlay Signaling. (The method for the BFIR to learn
about BFER's).

BM: Bit Mask (A bit stream of a certain fixed length. Each Bit
represents a receiver).

P-BM: Packet Bit Mask (A Bit Mask included in the Multicast Packet).

BP: Bit Position (A single Bit from the Bit Mask that represents a
receiver).

BFR: Bit Forwarding Router (A router that participates in Bit Index
Multipoint Forwarding). A BFR is identified by a unique BFR-
prefix in a BIER domain.

BFIR: Bit Forwarding Ingress Router (The ingress border router that
inserts the BM into the packet).

BFER: Bit Forwarding Egress Router. A router that participates in
Bit Index Forwarding as leaf. Each BFER must be a BFR. Each BFER
must have a valid BFR-id assigned.

BFT: Bit Forwarding Tree used to reach all BFERs in a domain.

BIFT: Bit Index Forwarding Table (A Bit index forwarding table). Table.

BMS: Bit Mask Set. Set containing bit positions of all BFER
participating in a set.

BMP: Bit Mask Position, a given bit in a BMS.

Invalid BMP: Unassigned Bit Mask Position, consisting of all 0s.

Invalid BFR-id: Unassigned BFR-id, consisting of all 0s.

IGP signalled BIER domain: A BIER domain underlay where the BIER
synchronization information is carried in IGP
and IGP. Observe that a
multi-topology is NOT a separate BIER domain in IGP.

BIER sub-domain: A further distinction within a BIER domain
identified by its multi-topology and bitmask length. unique sub-domain identifier. A BIER sub-domain
can support multiple BitString Lengths.

BFR-id: An optional, unique identifier for a BFR within a BIER sub-
domain.

Invalid BFR-id: Unassigned BFR-id, consisting of all 0s.

3. IANA Considerations

This document adds the following new sub-TLVs to the registry of sub-
TLVs for TLVs 235, 237 [RFC5120] and TLVs 135,236
[RFC5305],[RFC5308].

Value: 32 (suggested - to be assigned by IANA)

Name: BIER Info

4. Concepts

4.1. BIER Domains in Extended Reachability TLVs

This draft introduces a sub-TLV in the extended reachability TLVs to
distribute information about BIER domains and services they carry.
To satisfy the requirements for Sub-Domains

An ISIS signalled BIER prefixes per
[I-D.draft-wijnands-bier-architecture-00] additional information may
be carried domain is aligned with the scope of
distribution of BFR-prefixes that identify the BFRs within ISIS.
ISIS acts in [I-D.draft-ginsberg-isis-prefix-attributes].

4.2. such a case as the according BIER Domains underlay.

Within such a domain, ISIS extensions are capable of carrying BIER
information not only for
a single BIER domains but for multiple ones. A BIER domain in ISIS sub-domains. Each sub-domain is currently always
uniquely identified by its subdomain-id and each subdomain can reside
in any of the tuple ISIS topologies [RFC5120]. The mapping of multi-
topology MT and bitmask length ML it belongs sub-domains
to denoted as <MT,ML>.

Each such topologies is a local decision of each BFR currently but is
advertised throughout the domain itself to ensure routing consistency.

Each BIER sub-domain has as its unique attributes the encapsulation
used and the type of tree it is using to forward BIER frames
(currently always SPF). Additionally, per supported bitstring length
in the sub-domain, each router will advertise the necessary label
ranges to support it.

This RFC introduces a sub-TLV in the extended reachability TLVs to
distribute such information about BIER sub-domains. To satisfy the
requirements for BIER prefixes per
[I-D.draft-wijnands-bier-architecture-02] additional information will
be carried in [I-D.draft-ginsberg-isis-prefix-attributes].

5. Procedures
5.1. Enabling a BIER Domain Sub-Domain

A given domain sub-domain with masklength ML identifier BS with supported bitstring
lengths MLs in a multi-topology MT [RFC5120]
(denoted is denoted further as <MT,ML>)
<MT,SD,MLs> and is normally not advertised to preserve the scaling of
the protocol (i.e. ISIS carries no TLVs containing any of the
elements related to <MT,ML>) <MT,SD>) and is enabled by a first BIER sub-
TLV sub-TLV
(Section 6.1) containing <MT,ML> <MT,SD> being advertised into the area. The
trigger itself is outside the scope of this draft RFC but can be for
example a VPN desiring to initiate a BIER layer sub-domain as MI-PMSI
[RFC6513] tree. It is outside the scope of this document to describe
what trigger for a router capable of participating <MT,ML> in <MT,SD> is used
to start the origination of the necessary information to join into
it.

5.2. Multi Topology and Sub-Domain

All routers in the flooding scope of the BIER TLVs MUST advertise a
sub-domain within the same multi-topology. A router discovering a
sub-domain advertised within a topology that is different from its
own MUST report a misconfiguration of a specific sub-domain. Each
router MUST compute BFTs for a sub-domain using only routers
advertising it in the same topology.

5.3. Encapsulation

All routers in the flooding scope of the BIER TLVs SHOULD MUST advertise the
same encapsulation for a given <MT,ML>. <MT,SD>. A router discovering
encapsulation advertised that is different from its own MUST report a
misconfiguration of a specific <MT,ML>. <MT,SD>. Each router MUST compute
BFTs for <MT,ML> <MT,SD> using only routers having the same encapsulation as
its own advertised encapsulation in BIER sub-TLV for <MT,ML>. <MT,SD>.

5.4. Tree Type

All routers in the flooding scope of the BIER TLVs MUST advertise the
same tree type for a given <MT,SD>. In case of mismatch the behavior
is analogous to Section 5.3.

5.5. Label Advertisements for MPLS encapsulated BIER domains sub-domains

Each router MAY advertise within the BIER MPLS Encapsulation sub-sub-
TLV (Section 6.2) of a BIER Info sub-TLV (Section 6.1) for <MT,ML>
(denoted further 6.1, denoted as TLV<MT,ML>)
TLV<MT,SD>) for <MT,SD> for every supported bitstring length a valid
starting label value and a non-zero range length. It MUST advertise a
at least one valid label value and a non-zero range length for the
required bitstring lengths per
[I-D.draft-wijnands-bier-architecture-02] in case it has computed
itself as being on the BFT rooted at any of the BFRs with valid BFR-ids BFR-
ids (except itself if it does NOT have a valid BFR-id) participating
in <MT,ML>. <MT,SD>.

A router CAN MAY decide to not advertise its TLV<MT,ML> the BIER Info sub-TLV
(Section 6.1) for <MT,SD> if it does not want to participate in the domain
sub-domain due to resource constraints, label space optimization,
administrative configuration or any other reasons.

5.3.1.

5.5.1. Special Consideration

A router MUST advertise for <MT,ML> each bitstring length it supports in
<MT,SD> a label range size that guarantees to cover the maximum BFR-id BFR-
id injected into <MT,ML> <MT,SD> (which implies a certain maximum set id per
bitstring length as described in
[I-D.draft-wijnands-bier-architecture-00]).
[I-D.draft-wijnands-bier-architecture-02]). Any router that violates
this condition MUST be excluded from BIER BFTs for <MT,ML>.

5.4. <MT,SD>.

5.6. BFR-id Advertisements

Each BFER MAY advertise with its TLV<MT,ML> TLV<MT,SD> the BFR-id that it has
administratively chosen.

If a router discovers that two BFRs it can reach advertise the same
value for BFR-id for <MT,ML>, <MT,SD>, it MUST report a misconfiguration and
disregard those routers for all BIER calculations and procedures for
<MT,ML>
<MT,SD> to align with [I-D.draft-wijnands-bier-architecture-00]. [I-D.draft-wijnands-bier-architecture-02]. It
is worth observing that based on this procedure routers with
colliding BFR-id assignments in <MT,ML> <MT,SD> MAY still act as BFIRs in
<MT,ML>
<MT,SD> but will be never able to receive traffic from other BFRs in
<MT,ML>.

5.5.
<MT,SD>.

5.7. Flooding

BIER domain information SHOULD change and force flooding
infrequently. Further discussion TBD. Especially, the router SHOULD make every possible
attempt to bundle all the changes necessary to sub-domains and ranges
advertised with those into least possible updates.

5.8. Version

This RFC specifies Version 0 of the BIER extension encodings. Packet
encoding supports introduction of future, higher versions with e.g.
new sub-sub-TLVs or redefining reserved bits that can maintain the
compatiblity to Version 0 or choose to indicate that the
compatibility cannot be maintained anymore (changes that cannot work
with the provided encoding would necessitate obviously introduction
of completely new sub-TLV for BIER).

This kind of 'versioning' allows to introduce e.g. backwards-
compatible automatic assignment of unique BFR-ids within sub-domains
or addition of optional sub-sub-TLVs that can be ignored by version 0
BIER routers without the danger of incompatiblity.

This is a quite common technique in software development today to
maintain and extend backwards compatible APIs.

6. Packet Formats

All ISIS BIER information is carried within the TLVs 235, 237
[RFC5120] and TLVs 135,236 [RFC5305],[RFC5308]. [RFC5305], [RFC5308].

6.1. BIER Info sub-TLV

This sub-TLV carries the information for the BIER domains sub-domains that
the router participates in as BFR. It can repeat multiple times for
different domain <MT,ML> sub-domain <MT,SD> combinations. If the same <MT,ML> domain is
advertised multiple times with different encapsulations, the result
is unspecified.

The sub-TLV carries a single <MT,ML> <MT,SD> combination followed by optional
sub-sub-TLVs specified within its context such as e.g. BIER MPLS
Encapsulation per Section 6.2.

On violation of any of the following conditions, the receiving router
SHOULD signal a misconfiguration condition. Further results are
unspecified unless described in the according section of this RFC:

o The subdomain-id MUST be included only within a single topology.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver|C| Reserved| subdomain-id | BM Len|Reservd| BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type: as indicated in IANA section.

Length: 1 octet.

Local BitMask Length (BM Len): Bitmask length for this

Version: Version of the BIER domain TLV advertised, must be 0 on
transmission by router implementing this RFC. Behavior on
reception depends on the 'C' bit. 2 bits

C-BIT: Compatibility bit indicating that the TLV can be interpreted
by routers implementing lower than the advertised version. Router
implementing this router version of the RFC MUST set it to 1. On
reception, IF the version of the protocol is advertising per
[I-D.draft-wijnands-mpls-bier-encapsulation-01]. 4 bits.

Reserved higher than 0 AND the
bit is set (i.e. its value is 1), the TLV MUST be processed
normally, IF the bit is clear (i.e. its value is 0), the TLV MUST
be ignored for further processing completely independent of the
advertised version. When processing this sub-TLV with
compatibility bit set, all sub-sub-TLV of unknown type MUST and
CAN be safely ignored. 1 bit

Reserved: reserved, must be 0 on transmission, ignored on reception.
4
May be used in future versions. 5 bits

BFR-id

subdomain-id: Unique value identifying the BIER sub-domain. 1 octet

BFR-id: A 2 octet field encoding the BFR-id, as documented in
[I-D.draft-wijnands-bier-architecture-00].
[I-D.draft-wijnands-bier-architecture-02]. If set to the invalid
BFR-id advertising router is not owning any BFR-id. a BFR-id in the sub-
domain.

6.2. BIER MPLS Encapsulation sub-sub-TLV

This sub-sub-TLV carries the information for the BIER MPLS
encapsulations
encapsulation and the necessary label ranges per bitstring length for
a certain <MT,ML> <MT,SD> and is carried within the BIER Info sub-TLV
(Section 6.1) that the router participates in as BFR.
It can repeat only

On violation of any of the following conditions, the receiving router
SHOULD signal a misconfiguration condition. Further results are
unspecified:

o The sub-sub-TLV MUST be included once AND ONLY once within it. If this the
sub-TLV.

o Label ranges within the sub-sub-TLV is included
more than once, MUST NOT overlap. A receiving
BFR MAY additionally check whether any of the result is unspecified. ranges in all the
sub-sub-TLVs advertised by another BFR overlap and apply the same
treatement on violations.

o Bitstring lengths within the sub-sub-TLV MUST NOT repeat.

o The sub-sub-TLV MUST include the required bitstring lengths per
[I-D.draft-wijnands-bier-architecture-02].

o All label range sizes MUST be greater than 0.

o All labels MUST represent valid label values.

Type: value of 0 indicating MPLS encapsulation.

Length: 1 octet.

Local BitString Length (BS Len): Bitstring length for the label
range that this router is advertising per
[I-D.draft-wijnands-mpls-bier-encapsulation-02]. 4 bits.

Label Range Size: Number of labels in the range used on
encapsulation for this BIER domain, sub-domain for this bitstring length,
1 octet. This MUST never be
advertise advertised as 0 (zero) and otherwise,
this sub-sub-TLV must be treated as if not present for BFT
calculations and a misconfiguration SHOULD be reported by the
receiving router.

Label: First label of the range used on encapsulation for this BIER
domain and service,
sub-domain for this bitstring length, 20 bits. The label is used
for example by
[I-D.draft-wijnands-mpls-bier-encapsulation-01] [I-D.draft-wijnands-mpls-bier-encapsulation-02] to
forward traffic to sets of BFERs.

Reserved reserved, must

6.3. Optional BIER sub-domain Tree Type sub-sub-TLV

This sub-sub-TLV carries the information of the BIER tree type for a
certain <MT,SD>. It is carried within the BIER Info sub-TLV
(Section 6.1) that the router participates in as BFR. This sub-sub-
TLV is optional and its absence indicates the same as its presence
with Tree Type value 0 (SPF). BIER implementation following this
version of the RFC SHOULD NOT advertise this TLV.

On violation of any of the following conditions, the receiving router
implementing this RFC SHOULD signal a misconfiguration condition.
Further results are unspecified unless described further:

o The sub-sub-TLV MUST be included once AND ONLY once.

o The advertised BIER TLV version is 0 on transmission, ignored on reception. and the value of Tree Type
MUST be 0 (SPF).

Type: value of 1 indicating BIER Tree Type.

Length: 1 octet.

Tree Type: The only supported value today is 0 and indicates that
BIER uses normal SPF computed reachability to construct BIFT.
BIER implementation following this RFC MUST ignore the node for
purposes of the sub-domain <MT,SD> if this field has any value
except 0.

Tree type specific opaque data: Opaque data up to the length of the
TLV carrying tree type specific parameters. For Tree Type 0 (SPF)
no such data is included and therefore TLV Length is 1.

7. Security Considerations

Implementations must assure that malformed TLV and Sub-TLV
permutations do not result in errors which cause hard protocol
failures.

8. Acknowledgements

The draft RFC is aligned with the [I-D.draft-psenak-ospf-bier-extension-01]
draft as far as the protocol mechanisms overlap.

Many thanks for comments from (in no particular order) Hannes
Gredler, Ijsbrand Wijnands and Peter Psenak.

9. Normative References

[I-D.draft-ginsberg-isis-prefix-attributes]
Ginsberg et al., U., "IS-IS Prefix Attributes for Extended
IP and IPv6 Reachability", internet-draft draft-ginsberg-
isis-prefix-attributes-00.txt, October 2014.

[I-D.draft-psenak-ospf-bier-extension-01]
Psenak, P. and IJ. Wijnands, "OSPF Extension for Bit Index
Explicit Replication", internet-draft draft-ietf-ospf-
prefix-link-attr-01.txt, October 2014.

[I-D.draft-wijnands-bier-architecture-00]

[I-D.draft-wijnands-bier-architecture-02]
Wijnands, IJ., "Stateless Multicast using Bit Index
Explicit Replication Architecture", internet-draft draft-
wijnands-bier-architecture-00.txt,
wijnands-bier-architecture-02.txt, February 2014.

[I-D.draft-wijnands-mpls-bier-encapsulation-01]

[I-D.draft-wijnands-mpls-bier-encapsulation-02]
Wijnands et al., IJ., "Bit Index Explicit Replication
using MPLS encapsulation", internet-draft draft-wijnands-
mpls-bier-encapsulation-01.txt,
mpls-bier-encapsulation-02.txt, February 2014.

[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, December 1990.

[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.

[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120, February 2008.

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

[RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, October
2008.

[RFC6513] Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
VPNs", RFC 6513, February 2012.

Authors' Addresses

Tony Przygienda
Ericsson
300 Holger Way
San Jose, CA 95134
USA

Email: antoni.przygienda@ericsson.com

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

Email: ginsberg@cisco.com

Sam Aldrin
Huawei
2330 Central Expressway
Santa Clara, CA 95051
USA

Email: aldrin.ietf@gmail.com
Jeffrey (Zhaohui) Zhang
Juniper Networks, Inc.
10 Technology Park Drive
Westford, MA 01886
USA

Email: zzhang@juniper.net