Jarno,
The diffserv architectire is the *result* of that discussion, with ISP
engineers, at the beginning of the diffserv effort, most specifically
at the interim WG meeting in June 1998. Comments below...
[EMAIL PROTECTED] wrote:
>
> Brian,
>
> I think this is the make or break question for the whole current flow label
> discussion:
>
> Has the validity of the scenario you describe (MF-classification between
> diffserv ISPs) been discussed somewhere?
>
> Some specific questions:
>
> (model: sender -> ... -> upstream ISP -> downstream ISP -> ... -> receiver)
>
> Q1: Why couldn't the ISP's agree on the DSCP-to-PHB mapping (SLA, "off-line
> signaling"), with the downstream ISP policing the traffic to the SLA (and
> possibly remarking)?
The ISPs specifically requested flexibility to *not* use the same mappings.
Of course the downstream will always police anyway.
>
> Q2: Why the downstream ISP would not "believe" the DSCP value, but would
> believe the flow label value?
That's a key question. With non-ESP traffic, you can equally ask why they
would believe the port and protocol numbers. It's really a question of
what the SLA says - if it doesn't say that they will honor the upstream
DSCP, they will use the rest of the header to reclassify the packet.
>
> Q3: Presumably the upstream ISP is transmitting traffic originated by his
> customers, so the upstream ISP has no control of the transport protocols and
> port numbers being transmitted. WHY would an SLA between two ISPs be based
> on port numbers (MF-classification) set by a third party (the packet
> originator)?
That's a business decision. The ISPs told us they wanted a standard that left
them free to make their business decisions.
>
> I see that the problem you have in the diffserv architecture is that the
> DSCP values are meaningless outside a diffserv domain, and that you'd like
> to utilize the flow-label field to carry the globally unique identifier of
> the PHB. IMO, this would be MUCH better than any traditional micro-flow
> MF-classification in the context of diffserv.
>
> But what I fail to understand is that, since SLAs between ISPs are needed
> anyway to specify the policy for each traffic aggregate (however the
> classification is done), why couldn't the DSCP->PHB mapping be a part of the
> same SLA?
It could, but the IETF has nothing to say about SLAs.
>
> In this model there would be NO question of anyone "believing" any values,
> as the downstream ISP would NOT CARE what any of the header values are, as
> all the traffic would be policed to the SLA, regardless of the actual
> contents of any headers above the IP header. It would be the responsibility
> of the upstream ISP to (re-)mark the DSCPs in the packets to get the best
> utilization of the SLA.
Indeed. If I was an ISP I might well do that. But they asked for the
flexibility to do other things too.
Brian
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