Subject: [PWE3] AD Evaluation of draft-ietf-pwe3-wildcard-pw-type-02.txt

From: Mark Townsley <[email-masked]>
Date: Mon, 15 Jan 2007 19:14:42 +0100

Before sending this to IETF Last Call, I'd like to understand how 
possible race-conditions are avoided or resolved with the new PW Type. 
The document is clear that it is a configuration error to have both 
sides send the wildcard PW Type. However, does it follow that this is 
fixed in advance?

For example, is it desirable to allow this sort of case...

"PE A can accept any type of PW (i.e., it is in wildcard mode by 
default), but if PE B sends a wildcard PW Type, PE A will fallback and 
choose its preferred non-wildcard PW mode of (as an example) ethernet."

If these kinds of dynamic configurations are expected, then there may be 
some deadlock or non-deterministic situations where one side waits on 
the other to initiate, or the decision is left up to chance based on 
which side receives a message first, etc.

Thanks,

- Mark

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From: Stewart Bryant <[email-masked]>
Date: Wed, 17 Jan 2007 13:26:38 +0000

> choose its preferred non-wildcard PW mode of (as an example) ethernet."

The draft says:

    If the PW Type cannot be supported or is "wildcard" it MUST respond
    to this message with a Label Release message with an LDP Status Code
    of "Generic Misconfiguration Error".  Further actions are beyond the
    scope of this document but could include notifying the associated
    application (if any) or notifying network management.

Maybe the draft needs to be more explicit, but surely a mutual
wildcard request is the same as a wildcard response to a wildcard
request.

> which side receives a message first, etc.

I don't think that there was any initial intent to ever support
wildcard wildcard, and as you say if you do allow it the result is
unpredictable.

- Stewart