Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard

[Curtis Villamizar <[e-mail]>]

We are continuing to stray off topic, but...

Router vendors focus on real needs identified by customers.  If this
were to become something customers were bugging them about, then
they'll do it.  OTOH, most hardware in the field today can only track
one 32 bit FCS, given that only one L2 header would need this.  The
ability to run on existing hardware is important.

Perhaps you missed this:

> When a critical mass of routers hash on this new protocol number and
> port space we'll let you know and the MPLS WG can obsolete MPLS over
> UDP and replace it with MPLS over this new protocol.

Providers and router vendors are also aware that most routers look
only for protocol numbers 6 and 17 for load balancing on port
numbers.  So if the motivation of MPLS over UDP is an interim solution
to get ECMP, then not using UDP is not an option.

Curtis


In message <[e-mail]>
[e-mail] writes:
> 
> Yes, it would be unreasonable for the router vendors themselves to design
> something with a trailing checksum and pseudo-header check that would meet
> their forwarding needs while ensuring reliability.
>  
> Lloyd Wood
> http://about.me/lloydwood
> ________________________________________
> From: Curtis Villamizar [[e-mail]]
> Sent: 17 January 2014 18:05
> To: Wood L  Dr (Electronic Eng)
> Cc: [e-mail]; [e-mail]; [e-mail]; [e-mail]; [e-mail]
> Subject: Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard
>  
> In message <[e-mail]>
> [e-mail] writes:
>  
> > There's an opportunity to define a simple generic IPv6 encapsulating
> > mechanism a la UDP, but with a payload checksum of varying coverage
> > (header only, partial payload, full payload) and with the (stronger
> > than UDP) checksum placed at the end of the packet.
> >
> > Lloyd Wood
> > http://about.me/lloydwood
>  
>  
> Go for it!
>  
> When a critical mass of routers hash on this new protocol number and
> port space we'll let you know and the MPLS WG can obsolete MPLS over
> UDP and replace it with MPLS over this new protocol.
>  
> Thanks for offering to write this.
>  
> Curtis
>  
>  
> > ________________________________________
> > From: ietf [[e-mail]] On Behalf Of Stewart Bryant [[e-mail]]
> > Sent: 16 January 2014 17:35
> > To: Eggert, Lars; Joel Jaeggli
> > Cc: [e-mail]; IETF discussion list
> > Subject: Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard
> >
> > On 16/01/2014 17:19, Eggert, Lars wrote:
> > > Hi,
> > >
> > > On 2014-1-16, at 18:06, joel jaeggli <[e-mail]> wrote:
> > >> These tunnels are stateless
> > > yep. (But they don't have to be.)
> > Ah, they do if they are to scale. State at speed is really hard. The sort
> > of systems we are talking about do things like pipeline counters
> > and it is loooooots of packets later before the counter is actually
> > incremented.
> > >>   The endpoints not the encapsulators have visibility into the
> > >> end-to-end loss latency properties of the path.
> > > Yep. But when you tunnel some L2 in UDP, apps that were limited to L2 domains - where not reacting to congestion may be OK - can now go over the wider Internet, where this is not OK.
> > >
> > > I'd be great if those apps would change. But in the meantime, it's the duty of the encapsulator - who enables this traffic to break out of an L2 domain and go over the wider net - to make sure the traffic it emits conforms to our BCPs.
> > >
> > >>   the encapsulator is an intermediate hop, similar to any other router
> > >> in the path.
> > > It's not. For the rest of the network, that encapsulator is indistinguishable from any other app that sends UDP traffic.
> > >
> > > UDP is a transport-layer protocol, and we have practices how it is to be used on the net. If you want to use it for encapsulation, you bind yourself to these BCPs.
> > >
> > > Look at it the other way: if transport area folks would want to send MPLS packets into the network in some problematic way, I'm sure the routing and ops folks would not be amused.
> > The root cause of the problem here is that UDP, has bifurcated into
> > a general purpose encapsulation.
> >
> > Stewart