Subject: ATM gateway address questions

From: Josh Mason <[email-masked]>
Date: Fri, 1 Nov 1996 09:53:20 -0000

We have a few questions on ATM-08, regarding use of the gateway (E.164)
ATM address for SVC setup across public networks which do not understand
private ATM address formats.

Destination address matching
----------------------------

ATM-08 section 2.11.1 (Sharing of TGs) says that for a CN TG to share an
active regular TG, both TGs must have the same destination ATM address.
As well as the destination ATM address, there may also be a destination
gateway (E.164) address associated with the TG (configured on DEFINE_LS
for the regular TG, supplied on ACTIVATE_ROUTE for the CN TG).  If the
regular TG and CN TG have different destination gateway addresses (or
one has a destination gateway address and the other doesn't), but have
the same destination ATM address, presumably it is still OK for the CN
TG to share the active regular TG.  Is this correct?  If so then we
would recommend clarifying the specification on this point.

Gateway address on DEFINE_CN_TG
-------------------------------

For CN TGs, the local ATM address is configured on DEFINE_PORT (or
learned during port activation), but the local gateway address is
configured on DEFINE_CN_TG.  What is the benefit of configuring the
local gateway address on a per TG basis?

Size of ATM address information
-------------------------------

We are trying to determine the size of the ATM address information
needed to locate a destination across a public network.  Our
understanding is that the address format is either non-E.164 NSAP (20
bytes), E.164 in NSAP format (20 bytes) or native E.164 (up to 8 bytes
long), and that these formats are used according to the following (based
on Annex A of the UNI 3.1 spec).

- At the private UNI, when the destination supports private ATM
addresses, use an NSAP format address as the called party address (no
subaddress).
- At the private UNI, when the destination only supports native E.164
format, use an E.164 in NSAP format address as the called party address
(no subaddress).
- At a public UNI which supports NSAP format, use a non-E.164 or E.164
in NSAP format address as the called party address (no subaddress).
- At a public UNI which does not support NSAP format, use a native E.164
format (gateway) address as the called party address, with an NSAP
format (destination) address as the called party subaddress.

Our conclusion is that the address information required to locate a
destination across an ATM network can be either one 20 byte address, or
a 20 byte address with an 8 byte address, but never two 20 byte
addresses together.  Is this conclusion correct?

Thanks in advance for your help.

Josh Mason

==============================================================
Josh Mason ([email-masked])           http://www.datcon.co.uk
SNA Products Group                     phone: +44 181 366 1177
Data Connection Limited (DCL)          fax:   +44 181 363 4478
==============================================================