Network Working Group C. Franke
Internet-Draft D. Lamparter
Intended status: Standards Track NetDEF
Expires: October 19, 2016 C. Hopps
Deutsche Telekom
April 17, 2016
IS-IS Point-to-Multipoint operation
draft-lamparter-isis-p2mp-02
Abstract
This document describes a new mode operation for IS-IS. In addition
to the existing LAN and point-to-point modes of operation, a point-
to-multipoint mode is defined. This mode is useful for operation
both on networks with more than two routers where multicast is
expensive in comparison to unicast, as well on networks where
creating a LAN pseudonode cannot adequately reflect metrics.
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 19, 2016.
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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
Franke, et al. Expires October 19, 2016 [Page 1]
Internet-Draft IS-IS Point-to-Multipoint operation April 2016
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Point-To-Multipoint Pseudocircuits . . . . . . . . . . . . . 3
2.1. Pseudocircuit behaviour . . . . . . . . . . . . . . . . . 3
2.1.1. Representation in LSPs . . . . . . . . . . . . . . . 3
2.1.2. Forwarding . . . . . . . . . . . . . . . . . . . . . 3
2.2. Neighbor IS discovery . . . . . . . . . . . . . . . . . . 3
2.2.1. Manual configuration . . . . . . . . . . . . . . . . 4
2.2.2. Lower layer autodiscovery . . . . . . . . . . . . . . 4
2.2.3. Multicast autodiscovery . . . . . . . . . . . . . . . 4
2.3. Adjacency formation . . . . . . . . . . . . . . . . . . . 5
2.4. Pseudocircuit teardown . . . . . . . . . . . . . . . . . 5
3. Configuration model . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Misconfiguration With P2P over LAN . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The core functionality of the protocol outlined in this document
consists of an additional Subnetwork dependent function per Section 8
of ISO/IEC 10589:2002 [IS-IS]. In that regard, the next section can
be understood as new section "8.5 Point-to-multipoint networks".
The outlined protocol is remotely similar to the derelict section
"8.3 ISO 8208 subnetworks" [X.25] in that multiple point-to-point
adjacencies are established on an interface.
Point-to-multipoint operation of IS-IS is thus not a new idea; in
fact section 6.2 already mentions "multipoint links." This document
re-enables the concept.
Franke, et al. Expires October 19, 2016 [Page 2]
Internet-Draft IS-IS Point-to-Multipoint operation April 2016
2. Point-To-Multipoint Pseudocircuits
In place of ISO 8473 call management [CLNS] establishing sessions,
this document establishes pairwise "pseudocircuits" between two IS on
a common medium. Multiple such pseudocircuits can normally exist on
one P2MP (Point-To-Multipoint) interface.
Each pseudocircuit operates, aside from subnetwork attachment
procedures, exactly as a P2P (Point-to-Point) link.
It should be noted that while the Multicast autodiscovery mechanism
requires broadcast capability, no other part of the protocol does.
The P2MP interface type can be used on non-transitive and/or non-
broadcast interfaces.
2.1. Pseudocircuit behaviour
An implementation maintains a set of pseudocircuits per P2MP
interface. Each pseudocircuit is uniquely identified by the local
interface and peer's SNPA address.
Each participating system MUST use a consistent SNPA address per
local interface. A change in SNPA address results in all neighbors
treating the interface as distinct from the previous one. A system
MAY support multiple SNPA addresses per interface by treating them as
distinct interfaces.
Unnumbered media are not supported by this protocol. Each
participant on a link MUST have an unique SNPA address on that link.
2.1.1. Representation in LSPs
Pseudocircuits are represented in LSPs as a regular P2P circuit would
be. As a result, their treatment in SPF calculations is also
identical to P2P circuits.
2.1.2. Forwarding
In scenarios where pseudocircuits do not form a full mesh of all
participants on a medium, the best path for a packet may be through
the same interface as the one it was received on.
Systems implementing this specification MUST therefore support
forwarding packets on the same interface that they were received on.
This applies only to interfaces configured for P2MP operation.
2.2. Neighbor IS discovery
Franke, et al. Expires October 19, 2016 [Page 3]
Internet-Draft IS-IS Point-to-Multipoint operation April 2016
The discovery machinery produces as output a "candidate neighbor
list," which is a list of possible neighbor's SNPAs and is maintained
per P2MP interface. Adding and removing entries to the candidate
neighbor list results in pseudocircuit creation and deletion.
A neighbors presence on the candidate list may be supported by
multiple sources. These sources are described in the following
sections
The IS-IS implementation SHOULD provide user configuration to disable
or filter individual sources.
2.2.1. Manual configuration
A list of neighbor IS MAY be configured by the user, providing
possible neighbor's SNPAs on an interface.
2.2.2. Lower layer autodiscovery
Lower protocol layers (VPLS, IEEE 802.11) may be able to provide a
list of attached neighbors. This list MAY be fed into the candidate
neighbor list.
2.2.3. Multicast autodiscovery
For broadcast capable networks, this document defines an
autodiscovery mechanism based on multicasting Hello packets. This
mechanism MAY be disabled by the user, but MUST be implemented for
all lower layer link types with (limited or full) broadcast
capability.
A multicast autodiscovery packet is defined as a P2P IIH which is
multicast over the LAN media as defined in [RFC5309]. Additionally
it must include a Three-Way Adjacency TLV as defined in [RFC5303]
indicating the circuit is in the DOWN state (i.e., 1 octet of value
indicating the DOWN state). Receiving such a Hello places the
sending IS on the candidate list for as long as the PDU's holdtime
indicates.
A system MAY implement a receive-only passive multicast autodiscovery
mode where it adds candidates (forms pseudocircuits) on receiving
autodiscovery PDU, but does not send such PDUs itself.
If either passive or full multicast autodiscovery is enabled,
receiving a unicast autodiscovery PDU also adds the neighbor to the
candidate list.
Franke, et al. Expires October 19, 2016 [Page 4]
Internet-Draft IS-IS Point-to-Multipoint operation April 2016
2.3. Adjacency formation
Since there may be no underlying protocol layer partitioning the link
into actual P2P circuits in this case, additional handling is
required on bringing up the individual pseudocircuit adjacencies.
To prevent different pseudocircuits from "bleeding" into each other,
implementations of this protocol MUST enable [RFC5303] on all P2MP
pseudocircuits, with changes as follows:
o Received IIH PDUs on P2MP pseudocircuits without the Point-to-
Point Three-Way Adjacency option MUST be discarded.
2.4. Pseudocircuit teardown
Pseudocircuits are destroyed when their P2P state machine has
transitioned into "Down" state and they are no longer supported as a
candidate by any discovery mechanism.
As long as a pseudocircuit is present, its P2P state machine will, as
expected for P2P circuits, trigger transmission of further Hello
PDUs, even when it is in Down state.
3. Configuration model
TODO: YANG model
4. Security Considerations
TODO.
5. Privacy Considerations
TODO.
6. Acknowledgements
Acknowledge Les Ginsberg for pointing out that P2P Hellos rather than
LAN hellos could and should be used.
7. Change Log
April 2016 [-02]: (no changes/keepalive)
October 2015 [-01]: Moved from new P2MP Hello PDU to using existing
P2P PDU.
July 2015 [-00]: Initial Version
Franke, et al. Expires October 19, 2016 [Page 5]
Internet-Draft IS-IS Point-to-Multipoint operation April 2016
8. References
8.1. Normative References
[IS-IS] ISO/IEC, "Intermediate System to Intermediate System
Intra-Domain Routing Exchange Protocol for use in
Conjunction with the Protocol for Providing the
Connectionless-mode Network Service (ISO 8473)", ISO/IEC
10589:2002, Second Edition, 2002.
[RFC5303] Katz, D., Saluja, R., and D. Eastlake, "Three-Way
Handshake for IS-IS Point-to-Point Adjacencies", RFC 5303,
October 2008.
[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>.
8.2. Informative References
[CLNS] ISO/IEC, "Protocol for providing the connectionless-mode
network service: Protocol specification", ISO/IEC
8473-1:1998, 1998.
[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.
[RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding
Scope Link State PDUs (LSPs)", RFC 7356, September 2014.
[X.25] ISO/IEC, "X.25 Packet Layer Protocol for Data Terminal
Equipment", ISO/IEC 8208:2000, 2000.
Appendix A. Misconfiguration With P2P over LAN
TODO.
Authors' Addresses
Christian Franke
NetDEF
Leipzig
DE
Email: chris@opensourcerouting.org
Franke, et al. Expires October 19, 2016 [Page 6]
Internet-Draft IS-IS Point-to-Multipoint operation April 2016
David Lamparter
NetDEF
Leipzig 04229
Germany
Email: david@opensourcerouting.org
Christian E. Hopps
Deutsche Telekom
Email: chopps@chopps.org
Franke, et al. Expires October 19, 2016 [Page 7]