Tom,
Not an expert by any means, but I believe here's how you explain it:-
Well known mandatory - is attributes that is ALWAYS present (eg. ORIGIN,
AS-PATH, NEXT-HOP)
Well known discretionary - is attributes that are optionally
added/configured (eg. Local Preference)
There is no bit that specifically indicated mandatory/discretionary - well
known attributes are pre-defined as per the protocol specifications and thus
should be recognized by all implementations. Well known attributes are
always transitive.
Regards,
Adrian
"Tom Pruneau" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Greetings All
>
> I have a fairly Arcane BGP question, so any help will be appreciated
>
>
> I'm specifically looking at the flags in the attribute type field of the
> update packet.
>
> Bit 0 is the optional/well known bit
> Bit 1 is the transitive/non-transitive bit
>
> What I can't figure out is what determines whether a well known attribute
> is a
> "well known mandatory" or a "well known discretionary"
>
> mandatory and discretionary don't seem to be the same thing as transitive
> and non-transitive (although they do seem similar)
> but there is no bit (at least according to the documentation I'm
> referenceing (internet routing architectures by halabi and BGP 4 by John
> Stewart) which specifically states whether a well knonw is mandatory or
> discretionary.
>
>
> Any Help?
>
>
> Thanks Tons
>
> Tom Pruneau
> Trainer Network Operations
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