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CURRENT_MEETING_REPORT_
Reported by George Clapp/Ameritech
IPLPDN Minutes
Opening Remarks
This was the second meeting of the IP over Large Public Data Networks
Working Group and the following was the Agenda of the meeting:
o Wednesday, March 13, 1991
- Tutorial on Frame Relay (FR) by Andy Malis
- Discussion of encapsulation and protocol multiplexing over FR
- Tutorial on ISDN (Wayne Heinmiller and Jim Loehndorf)
- Discussion of encapsulation and protocol multiplexing over ISDN
o Thursday, March 14, 1991
- Joint meeting with the BGP Working Group to discuss the use of
BGP for routing and address resolution (Paul Tsuchiya)
- Continued discussion of encapsulation and protocol multiplexing
Frame Relay Tutorial
Due to airplane troubles, Andy Malis had been unable to present his
tutorial on Frame Relay during the plenary the previous evening, so he
kindly presented his talk during the first half of Wednesday morning's
Working Group session. (Andy also presented this tutorial during the
Friday morning plenary, and a copy of his presentation is included in
the Proceedings for that session. A postscript version is online for
anonymous ftp at ``pub/ietf-frame-relay-intro.ps'' on ccv1.bbn.com) The
presentation was an excellent preparation for the discussion of
encapsulation and protocol multiplexing.
Encapsulation and Protocol Multiplexing for Frame Relay
After the tutorial Caralyn Brown presented the following encapsulation
and protocol multiplexing scheme for Frame Relay. The proposal is
documented in the draft ``Multiprotocol Interconnect over Frame Relay
Networks'', which is available online on ccv1.bbn.com for anonymous ftp
as ``pub/multiprotocol.txt''. (A copy of the viewgraphs of Caralyn's
presentation accompanies these minutes.)
1
+--------------------+
| LAPD flag (0x7E) |
+--------------------+
| DLCI |
+--------------------+
| DLCI... |
+--------------------+
| Format Identifier |
+--------------------+
|FCSP| Origin_Media |
+--------------------+
| ... |
+--------------------+
| Info |
+--------------------+
| ... |
+--------------------+
| Frame Ck Sequence |
+--------------------+
| Frame Ck Sequence |
+--------------------+
| LAPD flag (0x7E) |
+--------------------+
FCSP: Frame Check Sequence Preservation
The Format Identifier indicates whether 802.2 and SNAP or a bridged MAC
frame follows, and the Origin_Media indicates the type of the bridged
MAC frame. If a routed packet is being carried, then the Origin_Media
value is set to zero and the 802.2 LLC Type 1 and SNAP headers follow.
The Ethertype of the SNAP header is used to indicate the type of the
routed packet. This proposal was modified by Charles Carvalho, who
proposed that the 802.2/SNAP headers be eliminated by carrying both the
bridged MAC frame type and the Ethertype values within a combined Format
Identifier/Origin_Media field. There was qualified acceptance of this
approach before the group broke for lunch.
ISDN Tutorial and Proposal
Wayne Heinmiller with Jim Loehndorf presented an overview tutorial on
ISDN (a copy of the presentation accompanies these minutes). The
presentation led into a talk by Dory Leifer of proposed encapsulation,
protocol multiplexing, and fragmentation schemes for circuit and LAPD
ISDN. The proposal is documented in the draft ``A Subnetwork Control
Protocol for ISDN Circuit-Switching'', which is available online on
terminator.cc.umich.edu as `` ftp/isdn'' for anonymous ftp. Further
discussion was deferred until the next morning.
2
Joint Meeting with BGP Working Group
Paul Tsuchiya led a joint meeting of the IPLPDN and BGP Working Groups.
(A copy of his slides accompany the minutes.) Paul proposed alternative
mechanisms to support a simple and effective way for routers to obtain
routing and address resolution information from BGP servers. He also
proposed an extension to BGP in which both the next hop IP address and
the hardware, or SubNetwork Point of Attachment (SNPA), address would be
given to the requesting router.
Members of the BGP group were concerned with potential conflicts between
policies of the Autonomous Systems that might be traversed by a packet.
This discussion remained unresolved and Paul volunteered to work towards
a solution in time for the next meeting.
Encapsulation and Protocol Multiplexing
After the break, IPLPDN met separately from the BGP Working Group and
Caralyn Brown presented the modified proposal for encapsulation and
protocol multiplexing over Frame Relay. (A copy of the viewgraph of the
proposal accompanies the minutes.)
+--------------------+
| LAPD flag (0x7E) |
+--------------------+
| DLCI |
+--------------------+
| DLCI... |
+--------------------+
| Format ID 1 |
+--------------------+
| Format ID 2 |
+--------------------+
| ... |
+--------------------+
| Info |
+--------------------+
| ... |
+--------------------+
| Frame Ck Sequence |
+--------------------+
| Frame Ck Sequence |
+--------------------+
| LAPD flag (0x7E) |
+--------------------+
3
If the value of the Format Identifier is less than 1024 decimal (0x0400)
then the field is used to encode the MAC type and the code points are
identical to those in internet-draft ``Point to Point Protocol
Extensions for Bridging''. This is shown below.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 0 | 0 | 0 | 0 | 0 | 0 | F | Z | MAC TYPE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
The F bit is used to indicate the presence of the MAC Frame Check
Sequence, and the Z bit is used to indicate zero compression.
If the value of the Format Identifier is 1024 decimal (0x0400) then the
802.2 LLC header follows the Format Identifier field, as shown below.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| DSAP | SSAP |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Control |
+---+---+---+---+---+---+---+---+
If the value of the Format Identifier is greater than 1024 decimal
(0x0400) then the encoded Format Identifier is equivalent to the
Digital-Intel-Xerox (DIX) Ethertype, as shown below.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Digital-Intel-Xerox (DIX) Ethertype |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Caralyn continued with a discusion of mechanisms for address resolution
and proposed that ARP be used to discover the DLCI associated with an IP
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address. She also proposed an extension to ARP named Inverse ARP to
discover the IP address associated with a DLCI. This latter proposal is
documented in the draft ``Inverse Address Resolution Protocol'', which
is available online by anonymous ftp on ccv1.bbn.com as
``pub/inarp.txt''.
After some discussion and modifications, all of these proposals appeared
to be acceptable to the group.
IP over ISDN
Dory Leifer continued with a discussion of the following issues:
o Fragmentation - do we need it considering the access network may
impose small max frames?
Resolution: further study
o End-to-end link state for switched access, i.e., XID frames?
Resolution: no
o ACK mode support or at least include CONTROL field for Q.921
compatibility?
Resolution: the group accepted the CONTROL field with a pad in the
encapsulation scheme. The revised scheme is shown below.
+-----------+
| flag |
+-----------+-----------+
| DLCI | DLCI.. |
+-----------+-----------+
| Control | PAD |
+-----------+-----------+
| Format ID | Format ID |
+-----------+-----------+
| info.. | ... |
+-----------+-----------+
| ... | ... |
+-----------+-----------+
| CRC | CRC |
+-----------+-----------+
| flag |
+-----------+
o Discovery protocol of Max frame size?
No resolution
5
o Code point for in-connection management protocol?
No resolution
At this point, time ran out and the group adjourned until the next
meeting in Atlanta, GA, in July 1991.
Attendees
Karl Auerbach karl@eng.sun.com
William Babson bill%penril@uunet.UU.NET
Fred Baker fbaker@emerald.acc.com
Atul Bansal bansal@netrix.nac.dec.com
Ron Bhanukitsiri rbhank@wsl.dec.com
Caralyn Brown cbrown@wellfleet.com
Howard Brown brown@ctron.com
Theodore Brunner tob@thumper.bellcore.com
Lida Carrier lida@apple.com
Eric Carroll eric@utcs.utoronto.ca
Charles Carvalho charles@sage.acc.com
Martina Chan mchan@mot.com
Cho Chang chang_c@apollo.hp.com
George Clapp clapp@uunet.uu.net
Graham Cobb cobb@marvin.enet.dec.com
Richard Colella colella@osi3.ncsl.nist.gov
Nabil Damouny
Tom Easterday tom@cic.net
Gus Elmer arch1!ae@att.com
Dennis Ferguson dennis@canet.ca
Peter Ford peter@lanl.gov
Daniel Friedman danfriedman@bbn.com
Charles Gallucci
Dave Geurs dgeurs@mot.com
Bret Gorsline jinx@engin.umich.edu
Martin Gray mg@spider.co.uk
Olafur Gudmundsson ogud@cs.umd.edu
Frank Heath
Kathleen Huber khuber@bbn.com
B.V. Jagadeesh bvj@esd.3com.com
Dan Jordt danj@nwnet.net
Ajay Kachrani kachrani@regent.enet.dec.com
Manu Kaycee kaycee@trlian.enet.dec.com
Nam Keung
Peter Kirstein kirstein@cs.ucl.ac.uk
Mary Louise Laier laierl@applelink.apple.com
Michelle Landriault crm57a@bnr.ca
Joseph Lawrence jcl@sabre.bellcore.com
Dory Leifer Dory.Leifer@terminator.cc.umich.edu
Richard Libby libby@c10sd6.stpaul.ncr.com
Mike Little little@ctt.bellcore.com
Then Liu
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John LoVerso loverso@westford.ccur.com
Andrew Malis malis@bbn.com
Glenn McGregor ghm@merit.edu
Robert Meierhofer bobm@cl0sd6.stpaul.ncr.com
Linda Melvin infopath@well.sf.ca.us
Agnes Moran
Robert Peglar robp@anubis.network.com
James Philippou japhilippou@eng.xyplex.com
Rehmi Post rehmi@ftp.com
Stephanie Price price@cmc.com
Ron Roberts roberts@jessica.stanford.edu
Manoel Rodrigues manoel.rodrigues@att.com
Allyn Romanow allyn@eng.sun.com
Allan Rubens acr@merit.edu
Ray Samora rvs@proteon.com
Paul Selkirk paul@ftp.com
Marc Sheldon ms@Germany.eu.net
Daisy Shen daisy@watson.ibm.com
Stephen Shew sdshew@bnr.ca
William Townsend townsend@xylogics.com
Paul Tsuchiya tsuchiya@bellcore.com
Robert Ullmann ariel@relay.prime.com
Kannan Varadhan kannan@oar.net
Francis Waldman
Wing Fai Wong wfwong@malta.sbi.com
Chin Yuan cxyuan@pacbell.com
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