Internet Info 1997 December/Internet_Info_CD-ROM_Walnut_Creek_December_1997.iso/ietf/mobileip/mobileip-minutes-93nov.txt

Text File | 1994-02-08 | 15KB | 380 lines

CURRENT_MEETING_REPORT_

Reported by Greg Minshall/Novell

Minutes of the IP Routing for Wireless/Mobile Hosts Working Group
(MOBILEIP)

Thanks to Pierre Dupont for taking notes for these minutes.

Greg Minshall provided opening remarks and a brief history of the
MOBILEIP Working Group.

Charlie Kunzinger gave a short presentation on the current Mobile IP
Draft.  A question and answer session followed the presentation.


   o Q: Why not two IP addresses for MH?
     A:(Charlie Kunsinger) No need for two addresses
     A:(Steve Deering) MH can acquire pop-up address to act as its own
     FA

   o Q:(Tony LI) Does FA decrement TTL in IP header before forwarding
     message to MH? Will this interfere with traceroute and MH location
     privacy?
     A: general discussion ensued on security requirements and the
     pors/cons of TTL being decremented by FA. Issue was left for
     further discussion on mailing list.

   o Q: How do two hosts with same subnet address communicate (one
     local, other mobile)?
     A: Proxy-ARP can be used to resolve addresses

   o Q: why not use source routing instead of tunneling?
     A: too many problems with source routing, so it was agreed in NJ to
     use encapsulation

   o Q:(Phil Karn) Can an MH be registered with more than one FA at the
     same time?  This would allow MH to use either FA, and prevent
     continuous registration flip/flop between FAs when MH is on a cell
     boundary.
     A: general discussion followed, with no clear consensus on whether
     this would be beneficial.  For further discussion on mailing list?

   o Q:(Yakov Rekhter) Draft document should be clear about how mobile
     IP breaks the IP subnet model.
     A: Deferred for later discussion.

   o Q: Why use IP for registration protocol?  why not use UDP?
     A: Discussion on 'architectural purity' vs ease of implementation
     followed.  Some IP implementations do not provide an IP interface,
     while all have a UDP interface.  Deferred for further discussion.

   o Q: Can Yakov expand on subnet model question?
     A:(Yakov Rekhter) The IP over Shared Media draft addresses similar
     problem.  The traditional model assumes that only hosts with same
     subnet address can talk directly to each other.  Mobile IP means
     that some hosts with same subnet ID cannot communicate directly.
     Also, how do mobile hosts with different subnet IDs but on same
     physical subnet communicate?

   o Q: Request that an authorization type be included before all
     authorization fields in mobile IP messages.
     A: Agreed.

   o Q:(Tony Li) Question on Incarnation number in Agent Advertisement
     message.  Some MH may not have non-volatile storage.  Also, how is
     it used?
     A:(Dave Johnson) It is so that visiting MH can tell if FA has
     crashed, an therefore if it must re-register with FA.

   o Q: Why not use Internet Security Protocol?
     A: No decision has been reached on this yet.  Adopt a wait and see
     attitude with respect to IP security.  It is not the mobile-ip wg's
     job to solve IP security problems.  A suggestion was made to not
     include any security fields in mobile IP messages.

   o Q: Are timer values defined?
     A: The units and field sizes are defined, but not the recommended
     values.  There may be dependancies between timers that need to be
     considered.

   o Q: How and when does HA advertise reachability by proxy-arp?
     A:(Andrew Myles) HA should never advertise unless its a router
     also.  A HA that is not a router uses proxy-ARP to intercept
     messages for MH. A discussion followed on whether the HA should
     always be a router.

   o Q: Would like to see characteristics and behavior of HA included in
     draft.
     A: Agreed.

   o Q:(Steve Deering) When tunneling to FA, what happens when the MH is
     not being served by the FA? Does packet go back to HA?
     A: IMHP deals with this.

   o Q: If address resolution mechanism is not ARP, there may be a
     problem using proxy-ARP.

   o Q: Why wait for a Home-Foreign confirm before sending notification
     to the prior foreign agent?
     A: The new FA is not authorized to serve the MH until it receives
     the confirm message from the HA. A message to the prior FA may not
     be required in this case, since the HA will direct messages to the
     new FA as soon as it has authorized it, therefore there is no need
     for the old FA to inform prior FA (the HA can inform the prior FA,
     after it has authorized the new FA).


IMHP Draft

Andew Myles gave a presentation on the IMHP draft.  Topics included:


   o A definition of the MH, FA and HA elements.

   o The HA configuration (i.e., HA is not necessarily a router).

   o A new element, the cache agent, which keeps track of [MH, FA]
     bindings.

   o Security (rationale for weak security).

   o Home subnet communication (performance requirements, routing
     options).

   o Notification to the prior FA.


On this final point it was mentioned that notification to the prior FA
must be fast so that it does not become a black hole for packets.  The
protocol should allow the new FA to accept packets from the prior FA
before the MH is authorized to use the new FA. The MH must inform the
prior FA as soon as it moves to a new FA. A period of questions and
answers followed.


   o Q:(Steve Deering) How are loops eliminated?
     A: A number of alternative mechanisms exist to break routing loops.

   o Q:(Steve Deering) How does routing work when a FA crashes?  (Black
     Hole)
     A: A timeout will occur on cache entries, causing polling to the
     destination FA (the Cache Agent polls the FA every timeout secs)

   o Q: How does Cache Agent get bindings?
     A: Snooping can be used for dumb hosts.  This can be turned off in
     the Cache agent is desired.

   o Q:What if MH moves from an authorized FA to an unauthorized FA? The
     MH will be temporarily using an unauthorized FA.
     A: During discussion it was pointed out that the FA may want to
     bill someone (HA) for the service to the MH. Therefore the new FA
     may not want to provide service to the MH until it is authorized to
     do so by the HA.

   o Q: The Cache Agent may send redirect packets to any host.  This
     could compromise security/privacy (e.g., location information).
     A: A flag could be used to prohibit route forwarding

   o Q: What about ad-hoc networking?
     A: for further study

   o Q: The cache timeout/polling mechanism may generate too much
     network traffic.
     A: Polling would only occur when the route is "active".



Outstanding Issues

Charlie Kunzinger presented a list of outstanding issues for discussion.


   o Encapsulation method.  Generic or Home-grown?

     We need at least one required method.  Steve Deering argued against
     negotiation.  Tony Li mentioned there already exists an
     Internet-Draft on encapsulation (Generic Routing Encapsulation).
     Dave Johnson stated that it had a large overhead and may not be
     compatible with ICMP (in terms of header size).  Yakov Rekhter
     stated that GRE was already implemented and being deployed.  Steve
     Deering stated that generic encapsulation can be used with a reason
     encoding (e.g., Mobile IP host).  Greg Minshall recommended that
     the group continue discussion on the mailing list and pick an
     encapsulation method later.

   o Foreign Agent receives forwarded message to MH for which it has no
     binding.  What does it do with the message?  This issue was
     discussed at the last session.

   o Should address fields be expanded to include address type and
     length?

     Steve said that it may depend on how often packets are sent.  Dave
     said the protocol is IP specific, address must fit into 64 ICMP
     bits and Tony recommends addresses be TLV fields to support multi
     protocols (e.g., Mobile appletalk).  No consensus was reached.

   o Do we need to control the number or frequency of registration
     requests?

     A discussion followed on whether to allow MH to register in
     multiple cells (i.e., with more than one FA) and have HA duplicate
     messages to both FAs.  Steve suggested that protocol should not
     disallow this, but recommended it be deferred to the advanced
     functionality issue list.  This issue was left unresolved.

   o Is there a need for a retransmission timer on a registration
     request by the MH?

     It was suggested that the MH be allowed to retransmit a request and
     that the FA could respond with an in-progress message if it is
     awaiting a response from the HA on a previous request for the MH.

   o State diagrams in draft document?

     This will be included in the next revision.

   o Should the protocol allow a hierarchy of HA?

     Should not preclude this option in draft.

   o Can TOS bit in IP header be used to identify mobile hosts?

     Dave stated that RFC 1122 suggests this is not possible.

   o Why can an FA terminate service to an MH? Also, HA can deregister
     MH.

     It was suggested that there is no need to include FA to MH
     deregistration since it will time out eventually.

   o Several comments were made on the style, packet format and byte
     alignment in the draft.

   o Should ICMP or UDP be used for registration protocol?

     After some discussion, a poll was taken on the preferred method and
     UDP was selected by a majority of those responding.

   o Weak security:  definition needs to be included in the draft.

   o To what degree do we break the subnet model?

     This is similar to the problem with large public data networks
     (e.g., ATM). Yakov volunteered to communicate to the IAB how Mobile
     IP will break the subnet model (and write an Internet-Draft?).



Cache Agent Model

A discussion on the pros and cons of the intermediate Cache Agent model
followed, with no consensus being reached on how to proceed.  Some
argued it should be left out of the initial draft while others argued
the group should continue with plans to merge IMHP into the draft.



Documentation and Implementation Milestones

The group needs a specification which can be used to implement test
systems (would like the specification before Christmas).  Charlie will
continue work as the document editor.



Interim Meeting

An Interim meeting of the Mobile IP Working Group was proposed for
January at Xerox PARC. It was suggested that implementors and
specification writers convene for two days.


Attendees

Kannan Alagappan         [e-mail]
Kenneth Albanese         [e-mail]
Nick Alfano              [e-mail]
Stephen Batsell          [e-mail]
Tom Benkart              [e-mail]
Mark Beyer               [e-mail]
Ram Bhide                [e-mail]
Steven Blair             [e-mail]
Jon Boone                [e-mail]
Monroe Bridges           [e-mail]
Glen Cairns              [e-mail]
Ken Carlberg             [e-mail]
Lida Carrier             [e-mail]
Bill Cash                [e-mail]
Bilal Chinoy             [e-mail]
Frank Ciotti             [e-mail]
David Clark              [e-mail]
Thomas Coradetti         [e-mail]
Stephen Deering          [e-mail]
Thomas Dimitri           [e-mail]
Waychi Doo               [e-mail]
Avri Doria               [e-mail]
Robert Downs             [e-mail]
Pierre Dupont            [e-mail]
Julio Escobar            [e-mail]
Craig Fox                [e-mail]
Richard Fox              [e-mail]
John Garrett             [e-mail]
Robert Gilligan          [e-mail]
Ramesh Govindan          [e-mail]
Darren Griffiths         [e-mail]
Robert Grow              [e-mail]
Regina Hain              [e-mail]
Jari Hamalainen          [e-mail]
Marc Hasson              [e-mail]
Cornelius Healy          [e-mail]
Juha Heinanen            [e-mail]
Kathryn Hill             [e-mail]
Robert Hinden            [e-mail]
Kevin Jackson            [e-mail]
David Jacobson           [e-mail]
B.V. Jagadeesh           [e-mail]
David Johnson            [e-mail]
Timo Jokiaho             [e-mail]
Rick Jones               [e-mail]
Elizabeth Kaufman        [e-mail]
Byonghak Kim             [e-mail]
Mark Knopper             [e-mail]
Tony Li                  [e-mail]
Tracy Mallory            [e-mail]
Wayne McDilda            [e-mail]
Marjo Mercado            [e-mail]
Greg Minshall            [e-mail]
William Miskovetz        [e-mail]
Randy Miyazaki           [e-mail]
Robert Moose             [e-mail]
Sandra Murphy            [e-mail]
Andrew Myles             [e-mail]
Erik Nordmark            [e-mail]
Masataka Ohta            [e-mail]
Todd Palgut              [e-mail]
Steve Parker             [e-mail]
Ismat Pasha              [e-mail]
John Penners             [e-mail]
Charles Perkins          [e-mail]
Wayne Peters             [e-mail]
Ram Ramanathan           [e-mail]
Jim Rees                 [e-mail]
Yakov Rekhter            [e-mail]
Mike Ritter              [e-mail]
Benny Rodrig             [e-mail]
Greg Ruth                [e-mail]
Richard Schmalgemeier    [e-mail]
Martin Schulman          [e-mail]
Dallas Scott             [e-mail]
Isil Sebuktekin          [e-mail]
Michael See              [e-mail]
Satya Sharma             [e-mail]
William Simpson          [e-mail]
Henry Sinnreich          [e-mail]
James Solomon            [e-mail]
Michael St.  Johns       [e-mail]
Martha Steenstrup        [e-mail]
Robert Stevens           [e-mail]
David Stine              [e-mail]
John Tavs                [e-mail]
Fumio Teraoka            [e-mail]
Susan Thomson            [e-mail]
Akihiro Tominaga         [e-mail]
Paul Traina              [e-mail]
Hoe Trinh                [e-mail]
Keisuke Uehara           [e-mail]
John Veizades            [e-mail]
Gerry White              [e-mail]
Steve Willens            [e-mail]
Bradley Wilson           [e-mail]
David Woodgate           [e-mail]
Richard Woundy           [e-mail]
Honda Wu                 [e-mail]
Jean Yao                 [e-mail]
Weiping Zhao             [e-mail]