RE: Thoughts and comments

["Walmsley, Clive" <Clive.Walmsley@dsto.defence.gov.au>]

Patrick,

good answer: but please see additional comments.

R/Clive

-----Original Message-----
From: Patrick Cipiere [mailto:Patrick.Cipiere@sophia.inria.fr]
Sent: Tuesday, April 13, 1999 10:13 PM
To: Walmsley, Clive
Cc: udlr@sophia.inria.fr
Subject: Re: Thoughts and comments


Clive,

> 1) Why does the standard consider the problem of receiver to receiver
> communications?

My understanding is:

- If you want to emalutate the bidirectional behaviour of a 
  unidirectional link, this scenario has to be solved.

CW: I disagree. 

- Even if the 2 receivers are connected by a BDL, the IP adress of
  their interface on that link is different from the adress they have
  on the UDL interface.

CW: true and accepted, but I don't see how this changes my point. I
assumed that a receiver will have have at least two interfaces: a UDL
and a BDL. Further that the BDL is part of the (an) IP routed network.
Why does the UDL standard have to consider a receiver to receiver
scenario when the normal routing architecture on the BDL interface
should be able to derive the route between two UDL interfaces. 

Note that I have assumed that a receiver would not distribute routing
information stating that had access to a route to its own UDL interface
or traffic arriving on that interface. Further that the send only feed
would distribute on its BDL interface the fact that it had routes to all
the receivers UDL and BDL addresses. I am not certain how these would be
derived at present by the send only feed. 

If this is true then I don't need to consider the receiver to receiver
communications on either UDL or BDL interfaces.

IP is network level protocol and nowhere in the standard does it state
that trafic between two IP addresses need to travel the same route.
Therefore by using the routing architecture on the BDL interfaces,
receiver to reciever communications can be assumed to exist.

This arguement falls down if you try and use some of the options in IP
such as source routing where you try and force packets to follow a
certain route. The introduction of a UDL service could make this
difficult. 

Not certain what impact these idea will have with IPV6. 

  Depending on the destination address (and routing) you are using,
  the packets will go thru the BDL or UDL interface.

Patrick.