[c-nsp] EoMPLS ?s

Jason LeBlanc jml at packetpimp.org
Thu Oct 13 12:00:50 EDT 2011


I may not be able to use this option then as I have no control of MTU 
between the sites, and I am assuming it is 1500 bytes.  No room for MPLS 
headers.  Not sure I can get the throughput with L2TPv3 unless this can 
be done in HW on some platform.

On 10/13/2011 09:19 AM, Ge Moua wrote:
> Once upon a time, we too did this between two sites about 90 miles 
> apart with:
> * a transport in the middle with a partner/service provider doing MPLS 
> CsC
> * on the edge sites with EoMPLS
>
> lesson learned:
> * as previously mentioned already, do as large MTU as possible for all 
> transit links
> * large MTU at the core
>
> we had a situation where we forgot to enable jumbo frame one of the 
> core transit links & needless to say traffic traversing that path was 
> being dropped if pkt size was greater than that specify MTU (which was 
> just the default of 1500); fix was to enable jumbo frame there too 
> then all was working
>
> MPLS is pretty unforgiving in that area (also as previously mentioned)
>
> -- 
> Regards,
> Ge Moua
> Univ of Minn Alumnus
> -- 
>
>
> On 10/12/11 3:02 PM, Arie Vayner (avayner) wrote:
>> Jason,
>>
>> There is no fragmentation in MPLS. Either you can forward the packet, or
>> it is dropped.
>> You need to either have a larger MTU on the core (usually the way it is
>> implemented today), or reduce MTU at both sides.
>> As this is a L2 link, you can't use things like MSS adjust etc...
>>
>> Arie
>>
>> -----Original Message-----
>> From: cisco-nsp-bounces at puck.nether.net
>> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Jason LeBlanc
>> Sent: Wednesday, October 12, 2011 20:53
>> To: cisco-nsp at puck.nether.net
>> Subject: [c-nsp] EoMPLS ?s
>>
>> We're considering using EoMPLS port mode to bridge two datacenters
>> together temporarily for a move using sup720-3BXL on both ends with 6724
>> blades, probably 2 or 4 gig links, possibly 10g if I can get them to buy
>> the HW.  The question I have primarily is with regard to MTU.  I have
>> heard there are issues with ensuring both sides match, not much concern
>> there.  But the network between the two facilities may be lower than the
>> 1518 bytes, causing fragmentation.  I know this gets punted to the RP,
>> and is going to be a problem.  Is there any work around?
>>
>> Thanks,
>> Jason
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