[j-nsp] bad packets

[sthaug at nethelp.no]

> My point of view in this case is the following:
> - the network should have standard MTU configured on both side of all
> links; should there be a non standard, this is a misconfiguration.

Agree about the "should" - however, the real world isn't always that
nice. In our case we have standardized on 4470 as the backbone MTU, 
but we have some links with an 1800 byte MTU due to limitations in a
specific vendor's Ethernet over SDH equipment. The long term plan is
obviously to get rid of these links.

> On this ground it is better to have LDP breaking due to MTU
> misconfiguration, because I can quite easily trouble-shoot it, rather
> that having LDP working and having problem on the dataplane such as
> latency due to fragmentation, high CPU usage on the router doing the
> fragmentation, customer packets being dropped..... all things that are a
> nightmare to troubleshoot!

In our case - since we *know* that the non-standard MTU links aren't
going away tomorrow, it is better to handle them, including fragmented
IP traffic.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no