[c-nsp] MPLS best practices question

[Mounir Mohamed]

Please find my comments inline.

>
> On Tue, Jun 22, 2010 at 5:49 PM, <cisconsp at secureobscure.com> wrote:
>
>> Good morning everyone,
>>
>>
>>
>> If I may have a moment of your time, I'm approaching a small MPLS
>> deployment
>> (L3 VPN functionality only, no TE or L2VPN) on existing infrastructure
>> primarily 6500's & ASR1k's and would very much like the opinion of the
>> list
>> on some best practices. There are several technologies that I'm trying to
>> determine the appropriateness to activate or tune and I'm scared to
>> blindly
>> enable them without a good reason to do so as I haven't seen some of them
>> used in a production environment before.
>>
>>
>>
>> 1)       IGP LDP Sync. I am really looking for some direction as to where
>> it
>> makes sense or not to use. The same is also true for the IGP LDP startup
>> delay timers.
>>
>> A) The IGP LDP Sync feature is used to prevent blackhalling of labeled
>> traffic that you might face due to fast establishment of IS-IS adjacency in
>> contrast to LDP establishment in case of link failure, however it's not
>> widely deployed, GR and LDP Session protection is used instead.
>>
>
>
>>
>> 2)       OSPF timers or BFD? Currently my approach has been ospf timers of
>> 1/4, its fast and seems pretty compatible with everything I have tried it
>> on. All of my links are direct between routed ports so there are no
>> intermediate devices that would keep a link lit after equipment failure. I
>> know BFD makes sense but some of my code is old and linecards are flakey
>> so
>> I'm curious to know who has ditched low timers for BFD or vice versa.
>>
>
> A) BFD is used to fast up link failure detection, you may need to adjust
>> some default IGP timers to fast up the adaptation (Convergence)  as well,
>> these timers include (SPF, PRC, LSP Transmit), fortunately IOS and IOS-XE
>> (ASR1k OS) have the same default IGP timers values.
>
>
>
>> As Mark said, BFD on hardware-based platforms such as ASR working  perfectly
>> because it handles via line cards (SPAs).
>>
>>
>>
>> 3)       OSPF costing, automatic bandwidth-based or manual costing of PE-P
>> and P-P links? I have seen both used in production before, I do have 10gig
>> interfaces and 40gig port-channels so I would need to alter the ospf
>> reference bandwidth if auto-costing.
>>
>> A) TE gives you more control, but if it is not desired, adjust the
>> auto-ref bandwidth to reflect your links bandwidth.
>
>
>>
>> 4)       MTU on p2p gigabit ethernet links. Currently I have stolen
>> another
>> list members MTU settings using 1530 for global & mpls MTU, and 1524 as IP
>> MTU on all PE-P and P-P interfaces. I don't have any jumbo frame
>> requirements, but do have upstream providers that may not support jumbo so
>> I'm trying to keep the MTU fairly low.
>>
>> A)  Since L3VPN is the only running application 1530 is more than enough,
>> set the interface MTU to 1530 and let MPLS inherit it, but do not set the
>> MPLS MTU directly because some IOS codes may cause forwarding issues.
>>
>>
>> 5)       Other knobs and tweeks? I'm usually a minimalist, I go forward
>> with
>> the default settings and test, then alter as little as I need to meet any
>> special needs. With that in mind, I do expect to find things that are
>> necessary to modify but really would like to see wide adoption or clear
>> requirements in doing so.
>>
>>
>>
>> Thank you for your time, please feel free to share anything off list if
>> you
>> don't want to disclose it to the general public. I really value the
>> opinions
>> that list members have provided thus far,
>>
>>
>>
>> John
>>
>>
>>
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>>
>
>
>
> --
> Best Regards,
> Mounir Mohamed, CCIE No.19573 (R&S, SP)
> Senior Network Engineer, Core Team.
> NOOR Data Networks, SAE
> Mobile# +2-010-2345-956
> http://mounirmohamed.wordpress.com
> http://www.linkedin.com/in/mounirmohamed
>



-- 
Best Regards,
Mounir Mohamed, CCIE No.19573 (R&S, SP)
Senior Network Engineer, Core Team.
NOOR Data Networks, SAE
Mobile# +2-010-2345-956
http://mounirmohamed.wordpress.com
http://www.linkedin.com/in/mounirmohamed