Re: [Dcpel] some comments on draft-vandenberghe-dcpel-basics-00.txt
Kathleen Nichols <nichols@pollere.com> Fri, 24 February 2006 22:48 UTC
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Date: Fri, 24 Feb 2006 14:48:49 -0800
From: Kathleen Nichols <nichols@pollere.com>
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Subject: Re: [Dcpel] some comments on draft-vandenberghe-dcpel-basics-00.txt
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Robert, First, I apololgize for the "minor comprehensibility nits" but 1) we wanted to get something out for comment and 2) we figured that things might change a lot after discussion, so a lengthy editing pass seemed okay to skip. This is a fairly short reply. I can send more later or let others reply in detail. > 1. What is a "traffic aggregate"? > I thought that we said we were using the 3086 definition of taffic aggregate. Anyway, that is: Traffic Aggregate: a collection of packets with a codepoint that maps to the same PHB, usually in a DS domain or some subset of a DS domain. A traffic aggregate marked for the foo PHB is referred to as the "foo traffic aggregate" or "foo aggregate" interchangeably. This generalizes the concept of Behavior Aggregate from a link to a network. > 2. Interior vs. edge vs. exterior So, again, we are following the diffserv architecture. See, for example section 2.1.1 of RFC2475. "edge", "boundary" and "border" are somewhat interchangeable, but normally "border" is used for the edge of an AS where boundary or edge might be at the edge of a DS domain that is not administratively separate from the adjoining one. We should probably avoid "exterior". The same distinction between interior and edge/boundary/border shows up in RFC3086. > 3. Role of PDBs and service descriptions > ...PDBs apparently define the treatment that a set of packets > will receive from a DS domain; that sounds like a service to (certainly > in the way that IntServ talks about service elements). Elsewhere the > document indicates that multiple services might use (implement? > provide?) the same PDB, but with different policy constraints, which > implies that 'service' means something more like an SLS (e.g. in the > Tequila sense). It might be nice to have a definition of 'service' and > some examples. So, I think you have it correct. RFC3086 says in the abstract: The next step is to formulate examples of how forwarding path components (PHBs, classifiers, and traffic conditioners) can be used to compose traffic aggregates whose packets experience specific forwarding characteristics as they transit a differentiated services domain. The WG has decided to use the term per-domain behavior, or PDB, to describe the behavior experienced by a particular set of packets as they cross a DS domain. A PDB is characterized by specific metrics that quantify the treatment a set of packets with a particular DSCP (or set of DSCPs) will receive as it crosses a DS domain. A PDB specifies a forwarding path treatment for a traffic aggregate and, due to the role that particular choices of edge and PHB configuration play in its resulting attributes, it is where the forwarding path and the control plane interact. The measurable parameters of a PDB should be suitable for use in Service Level Specifications at the network edge. And says later that a PDB might be specified in an SLA (e.g. if it is a "well-known PDB") or perhaps just the measurable parmeters of the PDB. I believe part of the work of dcpel can be to work out what are the right ways to exchange this information. But the point is well-taken that all of this will need to be made clearer. > 4. SIP interactions The quick response is that we didn't plan to change SIP or 3312 but to use that as a guideline for our framework, that is, our framework should have a way to interoperate in the 3312 sense. It was suggested as a starting point (and maybe sufficient) for application interaction. > 5. Is development of signalling protocols in scope or not? > > 4.1.2 says that "...definition of an interdomain QoS signaling protocol > is considered as future work for the proposed DCPEL WG", but 4.2 only > lists interworking with existing protocols. This seems contradictory. So I think this is a language failure. I think we meant something more like "selection" instead of "definition" subject to the state of the art at the time interdomain is being considered. But perhaps others have a different opinion. Kathie _______________________________________________ Dcpel mailing list Dcpel@ietf.org https://www1.ietf.org/mailman/listinfo/dcpel
- [Dcpel] some comments on draft-vandenberghe-dcpel… Hancock, Robert
- Re: [Dcpel] some comments on draft-vandenberghe-d… Kathleen Nichols
- Re: [Dcpel] some comments on draft-vandenberghe-d… Paulo Mendes
- RE: [Dcpel] some comments on draft-vandenberghe-d… Hancock, Robert
- RE: [Dcpel] some comments on draft-vandenberghe-d… Hancock, Robert