[Isis-wg] ISIS MIB question

[Jim Halpin]

> -----Original Message-----
> From:	bhazen@xedia.com [SMTP:bhazen@xedia.com]
> Sent:	Tuesday, November 30, 1999 7:54 PM
> To:	isis-wg@juniper.net
> Subject:	RE: [Isis-wg] ISIS MIB question
> 
> 
> I understand that you can have multiple adjacencies on
> a LAN interface. But my question is why do you need to
> 'assign' an AdjIndex to distinguish adjacencies when 
> there seems to be enough other information to uniquely
> identify an adjacency without it?  Specifically, why can't
> you use isisISAdjNeighSNPAAddress in combination with the
> circuit attributes to distinguish an adjacency?  Are SNPA
> addresses not unique?
	[JJH>]  
		From a purely SNMP/MIB-only point of view, you really don't
want to use
	something like a SNPA Address (defined as an OCTET STRING (0..20) I
believe) as
	the index of a table. Because its a variable length string, its
length must be encoded
	into the OID every time you reference an entry in the table. You'll
be adding somewhere
	between 1 to 21 sub-ids to every object reference in this table.
Mixing it in with a couple
	other INDEX objects only makes it worse. 

	Variable length strings are also a pain to deal with when doing
GetNext lookups in the
	MIB at run-time. For ease of implementation, you'll want to avoid
complex INDEX clauses.
	Which is why so many tables have simple, "meaningless" integer index
objects like
	"ifIndex".