Subject: Re: ipNetToMediaPhysAddress

From: [email-masked]
Date: Wed, 19 Nov 97 09:11:17 EST

Paul,

>I remember reading something somewhere, but I can't find it anymore...

>The question is: what does one find in the ipNetToMediaPhysAddress
>object?   The obvious answer is an ATM address, but there are two
>issues: (1) it can be either an AESA (20 byte NSAP format address) or
>an E.164 address, and (2) there can be a subaddress along with the
>address.

>Some vague memory suggests one would concatenate address and
>subaddress (potentially yielding a 40 byte value) but that is still
>not enough to answer point (1).

I disagree. Take a look at the textual convention that is used to
define this object:

IpoaAtmAddr ::= TEXTUAL-CONVENTION
   DISPLAY-HINT "1x"
   STATUS  current
   DESCRIPTION
     "The ATM address used by the network entity.
      The address type can be determined by the
      OCTET STRING size. IpoaAtmAddr can be comprised
      of both an ATM Address and a subaddress. The
      ATM Address portion is required and must be
      first in the OCTET STRING.

      An implementation must use BCD encoding to
      represent a E.164 address as a MIB object."
   SYNTAX   OCTET STRING (SIZE(0..40))

Clearly subaddress follow address if present and the size of the octet
string determines what's present.

>Given that the IPOA MIB document at least talks about the ipNetToMedia
>table in the context of IPOA, it seems like the best place for this
>question to be answered.

>So... what is the answer?  And could it be added to the IPOA MIB
>document?

Back in March there were numerous notes on the ion mailing list
discussing this object. It was agreed that the size of the octet
string would determine its content:

   Structure  Octets  Type
      -         0     no address
      1        20     NSAP
      2         8     E.164 encoded in BCD format
      2        15     E.164 encoded in native format
      3        28     BCD encode E.164 + NSAP sub-addr
      3        35     native E.164 + NSAP sub-addr"
      -        40     NSAP + NSAP sub-addr

This was also discussed in the ATOMMIB working group. The agreement
was that the atm2tc internet-draft's AtmAddr would be updated to
handle up to 40 octets. I just checked the September version and
it still doesn't:

 AtmAddr ::= TEXTUAL-CONVENTION
                       DISPLAY-HINT "1x"
                       STATUS  current
                       DESCRIPTION
                           "The ATM address used by the network entity.
                           The address types are: no address (0 octets),
                           E.164 (8 octets), and NSAP (20 octets).
                           Note: The E.164 address is encoded in BCD
                           format."
                      SYNTAX   OCTET STRING (SIZE(0º8º20)

At this time I prefer to see if I can add some comments to the
description clause of the IpoaAtmAddr and forget about attempting
to import AtmAddr as part of the review process.

Ken