>
> One of the reasons that IPv6 (rfc2460) dropped the header checksum
> that was in IPv4 is that with link layers all doing FCS it served no
> purpose.
> For the same reason TCP and UDP checksums server no purpose.
>
That's not what I understood, it is needed for endpoint delivery
verification. But in this case, TCP & UDP checksums incorporate the IP
address info in the pseudo header, and this was thought sufficient.
> The link layer checksum fails and the packet is dropped. Since this
> is usually not at the last hop (often a local Ethernet) but instead in
> a WAN link, the packet never arrives at the destination for anything
> to count IP header or TCP or UDP checksum errors.
>
Again, that presumes that everything above the link works flawlessly,
which isn't always the case.
> Also all of the following handle both data integrity and congestion
> avoidance the same way:
>
> UDP over IP over Ethernet
> UDP over IP over MPLS over Ethernet
> UDP over IP over MPLS over UDP over IP over Ethernet
> s/Ethernet/{POS,GFP,etc}/ for all of the above
> s/^UDP over IP/PW/ for all of the above
>
> In all of the above cases data integrity is handled by the link layer.
> In all of the above cases congestion avoidance is handled by the
> application (or not at all). Whether MPLS is carried directly over a
> link layer or over UDP/IP over a link layer makes no difference.
>
RFC 6936 section 3.1 says more about what happens when packets happen to
be mis-delivered to the wrong host or socket.
> Curtis
>
Gorry
> In message
> <290E20B455C66743BE178C5C84F1240847E63346BF@xxxxxxxxxxxxxxxxxxxxxx>
> l.wood@xxxxxxxxxxxx writes:
>
>> Really, you'd want to expose the pseudoheader check at endhosts; a
>> well-instrumented Linux box could tell you a lot
>> about checksum failures.
>>
>> But in this case, a router would be decapping UDP/MPLS tunnels as an
>> endpoint, so could report on checksum failures -
>> if the checksum wasn't zero.
>>
>> Lloyd Wood
>> http://about.me/lloydwood
>> ________________________________________
>> From: Dino Farinacci [farinacci@xxxxxxxxx]
>> Sent: 12 January 2014 21:37
>> To: Wood L Dr (Electronic Eng)
>> Cc: <mark.tinka@xxxxxxxxx>; <mpls@xxxxxxxx>; gorry@xxxxxxxxxxxxxx;
>> lisp@xxxxxxxx; david.black@xxxxxxx; randy@xxxxxxx; tsvwg@xxxxxxxx;
>> jnc@xxxxxxx; ietf@xxxxxxxx
>> Subject: Re: [lisp] [mpls] draft-ietf-mpls-in-udp was RE: gre-in-udp
>> draft (was: RE: [tsvwg] Milestones changed for tsvwg WG)
>>
>> > Do any routers count TCP/UDP checksum failures, much less
>> > expose the count via SNMP?
>>
>> Typically they do but only for packets destined to them. Much like hosts
>> would check the header checksum.
>>
>> Dino
>> _______________________________________________
>> mpls mailing list
>> mpls@xxxxxxxx
>> https://www.ietf.org/mailman/listinfo/mpls
>