Subject: DCL Comments on ATM-08

From: "J. G. Dudley (444/4358)" <[email-masked]>
Date: Mon, 4 Nov 96 09:21:02 EST

Josh,

>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.

You are correct.  ATM addresses are universally unique.  Ok, I'll
make this clarification.

>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?

First, remember that NOF configuration is a product option.

If there is more than one gateway, each gateway would have its own
address.  Furthermore, each gateway could be attached to different
public wide-area networks.  Use of different gateway addresses on a
TG basis could be a means for load distribution across the gateways.
It also could be a means for indicating a preferred transit network;
you'll notice that transit network selection is also defined on a
CN 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).

Native E.164 addresses are a max of 8 bytes in the APPN topology
database and RSCVs, but they are a max of 15 bytes at the UNI.

>- 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?

You are correct.

Regards,
Gary Dudley