Subject: RE: RSVP on IP Phones

From: "Ramesh Pabbati" <[email-masked]>
Date: Wed, 3 May 2000 10:58:25 -0700

Hi,
 
1) On an device like IP telephone only a subset of RSVP functionality
needs to be implemented and implementing this subset of RSVP may not
increase in the cost of the phone. I have seen an implementation of this
already interoperating with Windows 2000 implementation. Since the IP
phones have a small number of active connections (<= 2) the amount of
RSVP state needed to keep will also be small hence will not increase the
memory needed on the IP phone. 
 
2) It is not feasible for some call manager (CM) to signal on behalf of
the IP telephone as it requires call manager to be physically connected
to all subnets for which CM needs to act as RSVP proxy. But CM can still
do the following.

*	a) During call setup time CM can generate the PATH message IP
phones needs to send out to the receiver and instruct the IP phone to
send it at regular intervals. 
*	b) Once the other party answers the phone, CM can generate the
RESV message and instruct the IP phone to send it towards the sender at
regular intervals.
*	c) At the end of the call CM can do the same with PathTear
messages.
*	d) Since the CM knows the Identity of the phone (like MAC
address or serial number etc) it can generate a identity of the device
originating the RSVP message. Since these CMs run a system with more h/w
and sw/ than the IP phones, CM can generate a secure identity to be
included in the RSVP messages. When the IP phones have SmartCard slots
in them the identity of the caller is known to the CM hence they can add
a secure user id to the RSVP messages (where by reduce the RSVP code
size of the IP phones).
*	Since CM can be managed centrally the Tspec by each IP phone can
be managed by CM as it generates the PATH message. 
*	When the IP phones get PathErr or ResvErr messages, CM can
translate them on so that IP phones can display proper message and take
appropriate action (busy tone etc)

So even though CM can not act as a proxy, it can play an important role
to reduce the complexity of the software on the IP phone.
 
Ramesh

-----Original Message-----
From: Dusan Sarvan [mailto:[email-masked]]
Sent: Wednesday, May 03, 2000 3:28 AM
To: [email-masked]
Subject: RSVP on IP Phones

Hi, 

I will be really appreciated if someone can answer my questions: 

1. Since RSVP is pretty complex technology, implementing RSVP on the end

devices such as an IP Phone makes this device pretty complex and
probably expensive. 
Could you tell me please if RSVP is  in implementation on IP phones and
is it 
implemented by some companies on IP phones? 

2. Is it feasible some centralized device such as a Call Manager to play
RSVP on a behalf 
of IP phones? 

Thanks a lot in advance.