Subject: Re: [mobile-ip] IPv6 Regional Registration - identifying requirements

From: James Kempf <[email-masked]>
Date: Mon, 9 Apr 2001 09:52:28 -0700 (PDT)

Ok, second time I'm sending this out. Hopefully the server won't crash
again.

>1) Regional registration shall be introduced to minimize the signaling
>traffic to the home agent or correspondent nodes for intra-domain mobility

This is the basic requirement. If the regional reg proposal doesn't
do this, then it isn't necessary. Maybe we would also like to tighten
this up and require that the protocol provide additional support
beyond simply introducing a local home agent and requiring the mobile
node to get it's global IP address from the local home agent every
time it started? The point of this is that if something as simple
as introducing a local home agent will work, then why go for any more
elaborate scheme.

>2) Regional registration shall not introduce new overhead on links between
>the mobile and the regional registration agents

This is crucial. The ROHC group has yet to prove that even a change
of CoA with context transfer will work, not to mention additional
overhead. Therefore, it is prudent that we design RegReg so that
we do not make assumptions about what ROHC will do. We have already
run into a case where we have made assumptions about what another
working group's work will do (namely IPSEC) and it has gotten us
into trouble. In that case, the assumptions were based on published
RFCs, ROHC doesn't even have that for context transfer/compressor
restart with new state.

>3) Connectivity to the mobiles shall not be interrupted in the presence of
>the failure of regional registration agents

The regional agents need to function more like routers, and exhibit
the same kind of fail-over and self-healing. I think it needs to be
a requirement that the regional registration scheme include this
as a basic part of the protocol, not as a future study item.

>4) Regional registration shall scale to support millions of nodes in a
>visited network

This requirement is too broad. What does this mean in terms of the
properties of the protocol? See below for more  on this.

>5) Regional registration shall be secure against malicious behavior from
>visiting mobiles

Yes, this is important.

>6) Regional registration shall allow multiple levels of hierarchy

Absolutely critical. In our OpenRAN study, this was a deficiency we
identified with HMIP basic mode. Mobile operators need to have
the freedom to configure localized signalling according to their
own needs. Also, being able to support multiple levels of hierarchy
may help with supporting mobile routers, see below.

>7) Regional registration shall support fast handoffs

This is important, but it should not be part of the design. It should
be possible to keep the fast handoff design orthogonal from the RegReg
design, so that fast handoff can be used for straight MIPv6 as well.
Perhaps the requirement should be restated as:

	Regional registration shall not impose any additional requirements
	on fast handoff beyond what is required by basic MIPv6.

>8) Regional registration shall not require changes to the mobile node, the
>home agent, or correspondent nodes

Yes, keeping the mobile node unchanged is important. Ideally, a standard
MIPv6 mobile node would work with a regional scheme without any change.
Perhaps that is too optimistic.

An additional requirement in this area is:

	Regional registration shall minimize the involvement of the
	mobile node in routing beyond what is in the basic MIPv6
	protocol. Preferences, load balancing, and other complex schemes
	requiring heavy mobile node involvement in choosing routes 
	should be avoided, since experience with IP networks has
	shown that routing decisions are best left to routers.

>9) Regional registration shall not introduce host routes in routing tables
>

This relates to 4) above and is a specific consequence of scalability.
However, I would say that the requirement should be:

	Regional registration shall assure that router state scales
	linearly with the number of mobile nodes registered, and
	that the increase in router state is confined to those
	routers involved in implementing the regional registration
	protocol.
	
This covers any router state, including such MIP specific items as
binding caches, not just host routes.

I would also add the following requirement:

	Regional registration shall not degrade support for mobile
	routers beyond what basic MIPv6 supports, and should provide
	additional support if possible.

		jak

---

From: Michael Thomas <[email-masked]>
Date: Tue, 10 Apr 2001 09:38:05 -0700 (PDT)

James Kempf writes:
 > overhead. 

   Crucial for whom? The alternative is to require FA
   functionality in the access routers which is not
   without its own set of issues. Just because 3G is
   bandwidth starved -- which in the long run will be
   a transient problem -- doesn't mean we should    
   optimize for it at all costs. We already have an
   L2 shipping right now -- 802.11 -- for which this
   issue is a big ho-hum. It needs to be given equal
   standing when the requirements are evaluated.
   
 > 	on fast handoff beyond what is required by basic MIPv6.

   What about your ROHC constraint? It looks like 
   it conflicts.

		Mike