MPLS Network and Ethernet Jumbo Frame Questions
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08-18-2016 12:24 AM - edited 03-05-2019 04:31 AM
Hello Experts,
I have a customer that would like a L2 VPN pseudowire between his two sites. He also states that jumbo frames are a requirement as well and I expect to receive jumbo frames from the customer attachment circuit. However, all of my MPLS backbone circuits were designed for a three label deep system mtu = 1534. It is my understanding that if I enable jumbo frames on the attachment circuit to my customer and indeed receive a jumbo frame, when the PE routers tries to label switch it out across its back bone link(s) towards the remote site, given the back bone link system mtu= 1534, the ethernet frame cannot be fragmented and will be dropped as a result. Q1: Is this correct?
Q2: If all of the devices in the MPLS network CAN support jumbo frames, is there *** ANY *** disadvantage (or any reason NOT) to enable jumbo frames throughout the MPLS network as a general rule? The only thing that I can come up with is the possibility of buffer exhaustion or having to tune buffers given all the frames are now 9k+ in size vice the default 1518 bytes. Any insights, comments or recommendations would be much appreciated.
Thank you,
Brett
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08-24-2016 04:29 PM
If Ethernet in the network is GE or above then it can support MTU size of 9000 bytes.
Fragmentation should be supported on the router for PW but MTU-management is a better route:
http://www.rfc-base.org/txt/rfc-4623.txt
HTH.
