Re: [Idr] 6PE-Alt draft

"Vishwas Manral" <vishwas.ietf@gmail.com> Sun, 03 February 2008 23:43 UTC

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Date: Sun, 03 Feb 2008 15:45:14 -0800
From: Vishwas Manral <vishwas.ietf@gmail.com>
To: raszuk@juniper.net
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Subject: Re: [Idr] 6PE-Alt draft
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Hi Robert,

I am unaware of the ASIC's you work on, but I guess the entire idea is
that micro-flows do not get reordered and yet use load balancing.

I will update the 6PE-Alt draft with the information you have given.

Thanks,
Vishwas

On Feb 3, 2008 3:02 PM, Robert Raszuk <raszuk@juniper.net> wrote:
> Hi Vishwas,
>
> Unfortunately it is not configurable ... as it is done at the forwarding
> layer in hardware ASICs in some implementations I am familiar with.
>
> In fact some just hash on first and last label in stack some indeed
> could hash only on first two or three and some could go up to the IP
> header (if this is IP which is a big question at the P router).
>
> Cheers,
> R.
>
>
> >
> >  Hi Robert/ Martin,
> >
> > That is an interesting point you bring out.  What you say does make sense.
> >
> > I agree if load balancing is based on the labels it will not help load
> > share in case of 6PE-Alt - if we use a constant label. Anyway I would
> > assume the load sharing mechanism is configurable (what fields to use
> > to hash) and works within the scope of the router.
> >
> > Thanks,
> > Vishwas
> >
> > On Feb 3, 2008 1:28 PM, Robert Raszuk <raszuk@juniper.net> wrote:
> >  > Hi Vishwas,
> >  >
> >  >  > The P device works on the outer Tunnel label and its functionality
> >  >  > will not change in my view.
> >  >
> >  > I must say that your view here is incorrect.
> >  >
> >  > There are hardware implementations just like Martin pointed out which
> >  > take not the only top most but _entire_label_stack_ in the mpls packets
> >  > into considerations when hashing in P routers for load sharing purposes.
> >  >
> >  > As far as I can see your proposal breaks this as the second label will
> >  > be always the same thus all packets going to single PE will always take
> >  > the same path.
> >  >
> >  > To address this you would need to change implementations of those P
> >  > routers mpls switching vectors to also consider IPv6 header which is a
> >  > non starter operationally.
> >  >
> >  > Cheers,
> >  > R.
> >  >
> >  >
> >  > > Hi Martin,
> >  > >
> >  > > The load sharing and everything else on the of P devices will still
> >  > > work the same way. So we would have for example LDP running on the P
> >  > > routers giving out labels for FEC's just the same way. The P device
> >  > > works on the outer Tunnel label and its functionality will not change
> >  > > in my view.
> >  > >
> >  > > There is a case of having different labels for preventing one IPv6
> >  > > lookup in some cases but in case we had the ECMP case we would have to
> >  > > use the IPv6 header lookup and use the inner label as an IPv6 Explicit
> >  > > NULL label.
> >  > >
> >  > > Do let me know if I missed the point?
> >  > >
> >  > > Thanks,
> >  > > Vishwas
> >  >
> >  >
> >
>
>
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