RE: [[e-mail]: Re: BGP4 stuff: Local Preference Computation]

["John G. Scudder" <[e-mail]>]

[cc list trimmed]

At 12:43 PM -0600 9/9/96, NITTMANN Michael (MSMail) wrote:
>MED should be transitive and mandatory on all ebgp connections; doesn't look
>so difficult to me.

I disagree that MED should be transitive/mandatory.  That is, I agree with
Curtis.  The question is not whether it is difficult, but whether it's
useful/needed.  (Well, there's also a question of whether it's
interoperable with current implementations.)

>these 4 bits, what's the purpose at all? Are the property bits for
>attributes in fact part of the transmitted protocol message (transitive,
>etc....)?

Yes, every BGP Path Attribute has an 8-bit FLAGS field.  (Perhaps a
read-through of the RFC (or I-D) would be in order before continuing this
dialogue.)

>Any real use transmitting protocol definition elements in run time PEs?

The transitive bit tells a BGP implementation if it should propagate an
unrecognized attribute to external peers.  It's clearly useful at runtime.

The optional bit, if not set, tells a BGP implementation that there's a big
problem if it receives a non-optional attribute which it doesn't recognize.
(The need for this one is open to question, but it doesn't hurt.)

The partial bit tells a BGP implementation if the entire path supports the
given attribute.  I don't know if anyone uses this for anything, but one
can certainly see how it may be useful.

The extended length bit's utility should be obvious to the most casual reader.

Regards,

--John

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