The MPLS WG Archive

[Jeremy Lawrence <jlawrenc@cisco.com>]

Paul,

My reading is that this paragraph amounts to
"The combination of Downstream Unsolicited mode and conservative label
retention is a bad idea and should not be implemented." 

Less flippant answers follow inline...

At 07:45 02/20/2001 -0800, Paul Billinghurst wrote:

>Regarding the scenario discussed in Section 3.5.7.1.4. of RFC 3036 
>
>"The combination of Downstream Unsolicited mode and conservative label
>   retention can lead to a situation where an LSR releases the label for
>   a FEC that it later needs.  For example, if LSR Rd advertises to LSR
>   Ru the label for a FEC for which it is not Ru's next hop, Ru will
>   release the label.  If Ru's next hop for the FEC later changes to Rd,
>   it needs the previously released label "
>
>The section says the following "To deal with this situation either Ru can
>explicitly request the
>label when it needs it, or Rd can periodically readvertise it to Ru ".
>
>Does this mean that even though during session initialization Ru stated it
>was configured for downstream unsolicited it is allowed to send a label
>request message. Have I understood this correctly ?

Yes.

>and does this mean the
>downstream will accept a request from an upstream router that has signaled
>that it is configured for Du ?

Yes.

>The latter mentioned solution i.e. periodically readvertise, is this
>inferring periodic label refresh ?

Yes, though it does seem a silly thing to imply.

Regards,

Jeremy Lawrence