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rolc-minutes-95dec.txt
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1996-06-03
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CURRENT MEETING REPORT
Reported by Howard Berkowitz, PSC International and Andrew Malis,
Ascom Nexion, Inc.
Minutes of the Routing Over Large Clouds Working Group (ROLC)
The ROLC Working Group met in two sessions at this IETF. There were
approximately 145 attendees.
Agenda:
o First Session
o Agenda bashing
o ATM Forum MPOA update
o Joint statement by the IPATM and ROLC chairs
o NHRP specification and open issues--draft-ietf-rolc-nhrp-06.txt
o Second Session
o ATM Forum Liaison
o Local/Remote Forwarding Decision--draft-ietf-rolc-apr-03.txt
o Mobile NHRP Devices--draft-horikawa-mobile-nhrp-00.txt
o ATMARP/NHRP Translation
o Router-Router NHRP
o Status and Workplan
SESSION ONE
ATM Forum MPOA Update
George Swallow, the ATM Forum Multi-Protocol Over ATM (MPOA)
Sub-Working Group Chair, reported that the MPOA current approach
is based upon NHRP and MARS. No protocol design is being done;
NHRP "out-of-the-box" is desired. The MPOA SWG appreciates the
work being done in the IETF to harmonize NHRP and MARS. There is
very little interest in the ATM Forum in RFC 1577 (Classical IP over
ATM). ATM Forum LAN Emulation (LANE) is used at layer 2. Both
"edge devices" and routers are supported by MPOA. Server redundancy
is a major concern. MPOA has additional concerns, such as edge device-
to-edge-device connectivity. The external ATM Forum MPOA and
PNNI mailing lists, as reported at the Stockholm ATM Forum BOF,
still have not been set up by the ATM Forum. It is premature for the
IETF to be citing ATM Forum UNI 4.0; its public release date is unclear,
with a current February goal for straw vote. Forum/ITU politics may
also delay its completion. Joint statement by the IPATM and ROLC
chairs
Mark Laubach (the IPATM chair) and Andy Malis presented a chair's
statement regarding ROLC and IPATM coordination of the transition
from ATMARP to ATMARP + NHRP to NHRP. A mention was made
that the IESG has stated that a well-defined step-wise transition plan
that emphasizes interoperability with the installed base is required
for any evolution of a widely deployed proposed standard. All clients
must be able to resolve the address of any other client by required
default behavior (for the given client type) regardless of
implementation or deployment. In the following discussion, the ROLC
Working Group asked that references to NHRP be removed from Mark's
IP/ATM Classic2 draft, to allow a separate transition plan to be
developed.
NHRP Specification and Open Issues
The working group next discussed some NHRP open issues from version-
06 and the mailing list.
1. MARS harmonization-Hardware Type field vs. Address Family
field: The motivation for each choice was continued from the mailing
list discussion. Good points were made on either side, after which the
clear working group consensus was to use Address Family to identify the
NBMA address type. Grenville Armitage made the corresponding
change to the MARS specification to allow continued NHRP and
MARS harmonization--see draft-ietf-ipatm-ipmc-10.txt.
2. MARS harmonization-address field coding and parsing: NHRP was
zero-filling addresses to 32-bit boundaries, while MARS was not. The
chair noted that it would be nice for them to be same, if only for code
reuse in your implementations. After discussing the relative merits, the
working group agreed to "align" with MARS and not zero-fill addresses
to 32-bit boundaries.
3. Destination prefix vs. mask: The consensus was to go back to the
prefix rather than the mask.
4. Using prefixes with purge messages: The consensus was to allow
prefixes with purges.
5. Purge acks: The working group discussed whether or not purges
should be acknowledged. The consensus was yes. It is up to each purge
sender to decide whether to wait for the ack and whether or not to
resend the purge if the ack doesn't come back, but purge receivers must
always send acks. There was little consensus one way or the other for
adding a bit to the purge specifying whether or not the receiver should
send an ack; this should be further discussed on the list.
6. MTU: The suggestion was made to use currently unused header space
for MTU discovery. There was clear consensus to add this feature, as it
is consistent with RFC 1626 requirements.
7. Server redundancy: This is not addressed in the current spec. A strict
reading suggests that if there is more than one NHS in a LIS, then
NHRP clients must register with all of them. The working group
agreed that addressing server redundancy is required before NHRP is
"ready for prime time". The working group agreed that it would be a
reasonable goal to leverage the IPATM Working Group's
synchronization method, if possible. This discussion will be continued
on the mailing list.
8. Autoconfiguration: The issue of how to configure clients and servers
came up during the redundancy discussion. There was strong consensus
for autoconfiguration capabilities, supported either from network
management via the NHRP MIB, or via a configuration server. The
view was expressed that while ATM anycasts are useful to find
configuration servers, they should not be used to find NHRP servers, but
the working group did not reach consensus on this point. There was
discussion of whether to use NBMA-level configuration services when
available; this led to a liaison to the ATM Forum regarding ROLC's
interest in using the ATM Forum's LAN Emulation Configuration Server
(see below). The point was also made that ATM Forum anycasts cannot
be used in an IETF document until UNI 4.0 is publicly available. The
autoconfiguration discussion will be continued on the list.
9. [This was actually discussed in the second session, but logically fits
in here.] The question was asked why clients are configured with their
server's IP address. The consensus was that this was just a holdover
from server mode, and that it should be removed from the spec.
SESSION TWO
Joint ROLC/IPATM Liaison to the ATM Forum
The ATM Forum liaison was discussed and amended. The liaison
included two sections, one suggesting leveraging the LANE
configuration server for IETF uses, the second asking for LAN Emulation
Configuration Server redundancy. The liaison was later presented at
the IPATM Working Group meeting, where it was accepted and
forwarded to the ATM Forum liaison, Joel Halpern.
Local/Remote Forwarding Decision
Yakov Rehkter presented draft-ietf-rolc-apr-03.txt. His talk discussed
issues such as: Why do we care how the local/remote decision made?
When can SVCs be used effectively? When is the overhead of SVC
setup justified? Other issues discussed included connection
setup/teardown, Quality of Service, and SVC sharing. He pointed out
that we should rethink the subnet model, and replace it with a local
vs. remote model. Numerous options then result, significantly larger
than with the classic LIS model. If the model is relaxed, can link layer
connectivity always be reached? Try to establish connectivity--if not
reachable, then fall back to the routed path. How should we do
address assignment in the absence of the subnet model? Instead, use the
notion of "groups." A group implies assignment of end host and router
addresses from a single prefix. Routers in the group advertise routes to
the prefix. In discussion, the working group agreed to the term "Local
Address Group" (LAG) for this group. The working group also agreed
that Yakov will update the draft based upon the discussion, and there
will be a subsequent working group last call, followed by submitting the
draft to be published as an Informational RFC.
Mobile NHRP Devices
Hiroshi Suzuki presented draft-horikawa-mobile-nhrp-00.txt. He
began his talk by noting that it is more of a "NHRP Client
Autoconfiguration" than a "Mobile NHRP" talk, although mobility
issues were also included. He stated that autoconfiguration is required
to make supporting a large number of clients practical. He presented
the client's use of anycast to a "well-known" address to find any NHRP
server on the NBMA, not necessarily one in your LIS. If a server
receives a registration for a client in a LIS other than its own, then the
server forwards the registration to the client's home server along the
usual routed path (just like forwarding a NHRP Request). This
procedure only works when the client is in the same NBMA cloud as its
home LIS. The working group really liked this registration
optimization, and agreed to include it in the spec. To allow secure
registration, NHRP also needs end-to-end authentication in addition to
the current hop-by-hop authentication. The working group agreed that
in registration packets, encryption would be end-to-end, otherwise hop-
by-hop as before.
ATMARP/NHRP Translation
Rob Coltun presented one viewgraph on his approach to
ATMARP/NHRP translation. His ATMARP and NHRP servers are co-
resident. If an ATMARP pertaining to the local LIS arrives at the
server, the ARP code handles it. If it is beyond the local LIS, the
ATMARP code translates it into a NHRP request, and forwards it to the
NHRP code. The same model is also used for incoming NHRP requests.
Router-Router NHRP
Yakov Rehkter presented his approach to router-router NHRP, based
upon two messages he sent to the mailing list. Yakov discussed
tradeoffs required for cut-through paths, including increased state and
control traffic, how to determine whether a cut-through path is still
valid, how to avoid black holes and routing loops, how to determine
when to bring down SVCs, and interactions with BGP and inter-domain
routing. Yakov will be documenting this information in a forthcoming
draft, which the working group agreed will be the basis for further
work.
Status and Work Plan
The working group agreed that the charter and work plan need to be
revised; this will be done on the list. The tentative work plan
discussed in the meeting is:
December 1995 Produce version 07 of the NHRPv1 spec, new
LAG (was APR) draft.
January 1996 Final calls on these documents, submit
to IESG
March 1996 Discuss companion documents-NHRPv1
Applicability Statement, MIB, Protocol Analysis, router-to-router
(NHRP v2), server-to-server synchronization,transition plan, using
shortcuts for IP multicasting
June 1996 Discuss
implementation/interoperability issues, finalize NHRPv1 companion
documents, further discuss NHRPv2.
December 1996 Complete NHRPv2.
The meeting adjourned following this discussion.
Later in the week, the ROLC and IPATM chairs met with the Routing
Area Director (Joel Halpern) and the Internet Area Directors (Susan
Thomson and Frank Kastenholz) to discuss the transition plan and
direction of the working groups. The recommendations to the working
groups from this meeting are that:
The IPATM Classic2 draft should proceed with ATMARP and without
reference to NHRP, and include ATMARP server synchronization.
The IPATM and ROLC working groups should coordinate MIB
development, explore leveraging the same server synchronization
methods, and keep in mind that future IAB/IETF directions may require
authenticated address registration (i.e., this is a heads up, and don't
preclude a straightforward evolution to this as part of the
synchronization
work).
A future ROLC RFC will be used to specify how to substitute NHRP for
ATMARP; i.e., IPATM will continue to develop ATMARP in its work at
this time.