Subject: Re: [lisp] IPv6 UDP checksum issue

From: [email-masked] (Noel Chiappa)
Date: Thu, 30 Jul 2009 16:22:39 -0400 (EDT)

> From: Lars Eggert <[email-masked]>

    > This is in direct conflict with what RFC2460 says, and I'd personally
    > would find it problematic to approve publication of an Experimental
    > protocol that did this, unless there was an IETF consensus on a
    > standards-track document that would update RFC2460 accordingly. Such a
    > document would IMO need to show extremely strong arguments for why this
    > change is needed.

This is for an inter-router packet carriage use, not end-end. Why the dickens
should there be a mandatory checksum on the data in the packet for sending a
packet from one router to another?

	Noel

---

From: Lars Eggert <[email-masked]>
Date: Fri, 31 Jul 2009 00:27:59 +0200

Hi,

> packet from one router to another?

Since we're up-levelling the discussion, I don't understand why one  
would use UDP as a router-router protocol in the first place,  
especially for IPv6, where the chance that the packet will hit a NAT  
are probably exactly zero.

What I'm saying is that *if* UDP us used, it needs to be used  
according to the RFCs that capture the IETF consensus on their use, or  
the IETF consensus must be revised.

Lars

---

From: Dino Farinacci <[email-masked]>
Date: Thu, 30 Jul 2009 15:33:04 -0700

> are probably exactly zero.

Because when you use tunnel encapsulation, core routers attached to  
LAGs will see packets from one flow and polarize traffic on one member  
of the LAG.

So if the encapsulator can modify the source port of the UDP header  
based on a 5-tuple hash of the inner header, then there can be evenly  
balanced LAGs.

Core routers today load-split traffic across members of LAGs by doing  
a 5-tuple hash. And the 5 tuple hash works for TCP and UDP protocol  
numbered packets only.

The LISP authors received a lot of good input from network operators  
to not create this LAG problem. Hence, LISP uses UDP encapsulation.

> according to the RFCs that capture the IETF consensus on their use,  
> or the IETF consensus must be revised.

And what we are are saying is to be practical (and sensible).

Dino

---

From: Fred Baker <[email-masked]>
Date: Fri, 31 Jul 2009 07:50:33 +0200

RIP is a router/router protocol and uses UDP...
SNMP is used to manage routers and uses UDP...

Yes, I wish UDP had never been invented so that people would write  
transports that actually did what they intended, but folks use UDP  
instead and build the transport in the application.

On Jul 31, 2009, at 12:27 AM, Lars Eggert wrote:

> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> [email-masked]
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------

---

From: "Manfredi, Albert E" <[email-masked]>
Date: Fri, 31 Jul 2009 16:57:06 -0400

> -----Original Message-----
> From: Fred Baker [mailto:[email-masked]] 

> instead and build the transport in the application.

Or an alternative wish, an IPv6 option of header checksum?

Bert