Subject: RSVP PathError and ResvError messages

From: Dusan Sarvan <[email-masked]>
Date: Tue, 19 Sep 2000 19:24:45 +0200

Hi,

I am considering to use RSVP as a signaling protocol at the end user
side
(telephone Gateway).
I've studied carefully RFC 2205 spec, but there is a point where I am
not
completely clear from the end user prospective. So if some of you
clarify
the following questions, I will be really appreciated.

1. Let's consider the following scenario:

SENDER ---> Router_1 ---> Router_2 ---> Router_N ---> RECEIVER

a)  Sender sends PATH message which is processed by the "admission
control" and
"process control" modules on each router downstream along a data path.
If the
PATH message fails some of these controls, PathError message will be
generated
and sent back to the SENDER. So SENDER will examine ERROR_SPEC object
and
will know what has caused the fail of reservation process. This is clear
to me, so there
is no question about this.

b)  If RESV message sent from the RECEIVER fails "admission control" or
"process control" on some of the routers, ResvError message will be sent
to the
RECEIVER. In this case the SENDER will never receive the RESV message
and will
never know what has caused the fail, for example no enough bandwidth,
PATH or RESV
messages are lost somewhere between SENDER and RECEIVER due to the
unreliable
delivery mechanism of these messages, or something else.

QUESTION:  How to handle this case on the SENDER side? Whether to setup
time out for
the RESV message at the time of sending the PATH message, or to use some
other RSVP
mechanism which I probably have not read correctly in the RFC spec?
Should gateway try to repeat this process once more by sending new
PATH message, or
to start sending data packets with unreserved bandwidth (?????), or to
refuse the call setup
and to play busy tone?

c)   This question relates probably more to the Policy and Network
Management then to
the RSVP problem, but probably someone can answer.

SENDER and RECEIVER are connected to the routers which belong to the
different
network domains or ISPs. SENDER is RSVP capable, RECEIVER doesn't
support RSVP.

QUESTION: How SENDER knows RECEIVER's RSVP capabilities? It will
retrieve that
information from the Policy /Network Manager
OR
SENDER will initiate the RSVP signaling without having any knowledge
about RECEIVERS
RSVP capabilities, with setting time out for the RESV message? After
this time out (RESV has
not been received - RECEIVER is not RSVP capable, or PATH/RESV are
lost),  SENDER
will start sending traffic with unreserved bandwidth?

Thank you very much for your time, and I appreciate your answers in
advance.

Dusan Sarvan
SW Designer
Ascom Business Systems AG
Switzerland