RE: [RRG] The use of UDP in LISP

[<jarno.rajahalme@nsn.com>]

Few points on this:
- The issue with having to sum all the data in the packet is moot, since
you do not have to do this with UDP-Lite
- There is no way you can require L2 error detection from all links
between the tunnel endpoints. You can maybe hope. Also L2 errors are not
the only possible source of bit errors.
- For the intended load-balancing effect you should be able to use the
flow label field of the encapsulating IPv6 header. Routers ought to be
able to take that into the hash in addition of the IP addresses.
- If your router can't take the IPv6 flow label into the hash you could
still use multiple addresses per (IPv6) ETR

But I have to agree that I can't see why checksumless IPv6/UDP
encapsulation would be any more dangerous than IPv6 encapsulation
without UDP. But for the purpose being discussed here UDP is really not
needed at all, since you have the flow label in the IPv6 header anyway.

Regards,

	Jarno

>-----Original Message-----
>From: owner-rrg@psg.com [mailto:owner-rrg@psg.com] On Behalf 
>Of ext Dino Farinacci
>Sent: 12 December, 2007 02:24
>To: Brian E Carpenter
>Cc: Marshall Eubanks; Iljitsch van Beijnum; Stephen Sprunk; 
>Routing Research Group list
>Subject: Re: [RRG] The use of UDP in LISP
>
>>
>>> Dino Farinacci has suggested this text :
>>> o When a IPv6 router is using a UDP header as part of a tunnel 
>>> encapsulation,  it MAY compute a UDP checksum. The IPv6 
>router on the 
>>> other side of the  tunnel receives a UDP checksum of 
>non-zero it MUST 
>>> compute the checksum  according to [UDP-spec]. When an IPv6 router 
>>> uses a UDP header for tunnel  encapsulation and sets the 
>UDP checksum 
>>> field to 0, the IPv6 router on the  other side of the 
>tunnel MUST not 
>>> compute the checksum on the received  packet. This procedure allows 
>>> tunnel routers to behave the same for  tunnel encapsulating 
>IPv4 and 
>>> IPv6 packets.
>>> At the least AMT and LISP would require this, and I suspect that 
>>> there will be others.
>>
>> I don't actually understand the "require". If you'd written "People
>
>Required in the sense if you want to get the protocols into product.
>
>> coding AMT and LISP would find this convenient" I'd understand it,
>
>And it isn't the code, it is the gates.  ;-)
>
>> but surely the tunnel end-points will know whether they are 
>generating 
>> or receiving IPv4 or IPv6 packets?
>
>Yes, but what is your point?
>
>> I also don't understand why it would be considered safe, in the 
>> absence of a header checksum - are you deeming that the tunnel must 
>> have error detection at layer 2?
>
>Yes. As well as the low probably of bit-error rates, matching 
>sockets and mis-routing, all that would have to work in unison 
>to have a real problem.
>
>Dino
>
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