The MPLS-OPS Archive

[Stefano Novello <stefano.novello@parc-technologies.com>]

What Harish asks for is not possible with 2 attribute bits, but if you have a spare attribute bit C, that you always set to C = (A or B)

then you can set the mask and affinity on tunnels such that they only use links where C is set.

 

Stefano Novello

Parc Technologies Limited
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-----Original Message-----
From: Harish Kumtakar [mailto:harish_hsk@yahoo.com]
Sent: 21 January 2004 06:26
To: mpls-ops@mplsrc.com
Subject: [MPLS-OPS]: MPLS-TE tunnel's AFFINITY and MASK configuration

I've a question for Cisco ppl on the list or anybody who knows Cisco's MPLS-TE configuration.

The question is related to the configuration of a MPLS-TE tunnel's 'AFFINITY' and 'MASK' parameters.

Cisco Press book on MPLS-TE (By Eric Osborne) says that "during CSPF path calculation a link considered a match if it satisfies the relation ((AFFINITY & MASK) = = (LINK_ATTRIBUTE & MASK))", where AFFINITY, MASK and LINK_ATTRIBUTE are 32 bit fields (Note: MASK is a collection of do-care bits; this means that if a bit is set to 1 in the MASK, you do care that the bit set in the tunnel AFFINITY string matches the LINK_ATTRIBUTE flags). LINK_ATTRIBUTE flags for a link can be configured using the command 'mpls traffic-eng attribute-flags <0x0-0xFFFFFFFF>'. MPLS-TE tunnel's AFFINITY and MASK parameters can be configured using the command 'mpls traffic-eng affinity <0x-0xFFFFFFFF> [mask <0x-0xFFFFFFFF>]'

Now, suppose that rightmost 2 bits of LINK_ATTRIBUTE represent the attributes 'attr A' and 'attr B' respectively. Consider simple n/w topology with 3 nodes,

X-----Y-----Z,

wherein the link X to Y has only 'attr A' bit set and link Y to Z has only 'attr B' bit set. I want to have a MPLS-TE tunnel from X to Z that must pass through only those links which have either 'attr A' bit or 'attr B' bit or both bits set. I could not find any values for AFFINITY and MASK parameters meeting my requirement and satisfying the above mentioned relation (may be I'm weak in bitwise operations :-)). I would appreciate if you could tell me the values for my tunnel's AFFINITY and MASK parameters.

Thanks, cheers,

-Harish

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