Subject: RE: Usage of IPv6 flow label

From: "Thomas Eklund" <[email-masked]>
Date: Mon, 4 Dec 2000 18:36:22 +0100

Hi Brian,

> There are several misunderstandings of diffserv here.

> There is nothing about "traffic trunks" in the diffserv
> model. At a stretch,
> you can think of a DSCP as labelling a "service class", but formally
> it simply labels a "traffic aggregate", i.e. all the traffic
> that receives
> the same QOS treatment on a given hop.
so if you call your traffic aggregates something else thats fine with me.

> owever, we *do* assume in the
> model that DSCP values are invariant across an entire domain, with the
> routers in the domain being centrally configured. That configuration
> may be done using COPS, or SNMP, or HTTP, or telnet, or by telefax
> for that matter - it's of no importance for this discussion.
Well I think its VERY relevant, and I'm not the only one that thinks that it
has to be more clear how diffserv is managed over a domain.

>
> DSCP mutability applies at diffserv domain boundaries, which will
> typically be ISP/ISP boundaries or customet/ISP boundaries.
Which is exactly what I have said.

> As of today, there is *no* defined relationship between DSCP and
> Flow Label. But I tend to agree with Jim that defining the Flow Label
> as immutable across domain boundaries (as well as being visible
> in encrypted packets) has distinct advantages.

And who had said anything else that not having it visible? The flowlabel is
visible since it is part of the basic header. But then one might ask - what
happen when we use IP sec in tunneling mode? Is it a MUST to copy the flow
label into the new tunnel header or not? etc.

All I said was that it is very nice on paper - but in reality it will have
problem with acceptence from the service providers!

And to say that there is no relationship between MPLS and diffserv is
strange because they represent two different aproaches to achieve QoS in you
network which has many overlaps and many things that differs them (dont get
me wrong here I love diffserv).

Today I know many operators using mpls and not many that uses diffserv.

What I was speaking about was to have a QoS model that include intserv,
diffserv and mpls into an optimal ipv6 arhitechure...

-- thomas

-- thomas

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From: Jim Bound <[email-masked]>
Date: Mon, 04 Dec 2000 12:47:39 -0500

thomas,

yes the tunnel endpoints would copy the flow label.

on MPLS what do you want to do with MPLS and diff serv and why did you
not bring this up in diff serv?  

thanks
/jim

---

From: Francis Dupont <[email-masked]>
Date: Wed, 06 Dec 2000 15:25:01 +0100

In your previous mail you wrote:

=> I agree this is reasonnable thing to do (copy the flow label
or any information that can be useful and should not be hiden
accounding to the security policy) but this makes the unicity
guarantee impossible (because the encapsulator hasn't the choice
of the flow label). IMHO it doesn't really matter but according
to your previous mail (and Steve's one) this is an issue.

Thanks

[email-masked]

PS: I believe the flow label should be reserved for IntServ stuff
then SHOULD be set by the source, MAY be copied over tunnels,
SHOULD NOT be rewritten by routers. If we agree about the default
behaviour (ie. default value is zero or random) then we can be a
bit stronger, for instance MUST NOT be rewritten if the value is
not zero/default.
Things we cannot ask for are:
 - a MUST for copying (security)
 - a MUST NOT for rewriting (not protected by IPsec)
 - a strong guarantee for unicity (we'll get only a best effort unicity)
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