[Dcpel] some comments on draft-vandenberghe-dcpel-basics-00.txt
"Hancock, Robert" <robert.hancock@roke.co.uk> Fri, 24 February 2006 16:05 UTC
Received: from [127.0.0.1] (helo=stiedprmman1.va.neustar.com) by megatron.ietf.org with esmtp (Exim 4.43) id 1FCfRW-00044J-4r; Fri, 24 Feb 2006 11:05:18 -0500
Received: from [10.91.34.44] (helo=ietf-mx.ietf.org) by megatron.ietf.org with esmtp (Exim 4.43) id 1FCfRU-00042q-J6 for dcpel@ietf.org; Fri, 24 Feb 2006 11:05:16 -0500
Received: from rsys001x.roke.co.uk ([193.118.201.108]) by ietf-mx.ietf.org with esmtp (Exim 4.43) id 1FCfRS-00089G-2p for dcpel@ietf.org; Fri, 24 Feb 2006 11:05:16 -0500
Received: from rsys005a.comm.ad.roke.co.uk (rsys005a [193.118.193.85]) by rsys001x.roke.co.uk (8.12.8/8.12.8) with ESMTP id k1OG54oW011810 for <dcpel@ietf.org>; Fri, 24 Feb 2006 16:05:04 GMT
X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0
Content-class: urn:content-classes:message
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Date: Fri, 24 Feb 2006 16:05:04 -0000
Message-ID: <A632AD91CF90F24A87C42F6B96ADE5C57EBE1F@rsys005a.comm.ad.roke.co.uk>
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
Thread-Topic: some comments on draft-vandenberghe-dcpel-basics-00.txt
Thread-Index: AcYYdS3TIGK+4Po8RAWdixxlqesEFAg0NmTA
From: "Hancock, Robert" <robert.hancock@roke.co.uk>
To: dcpel@ietf.org
X-MailScanner-rsys001x: Found to be clean
X-MailScanner-rsys001x-SpamCheck:
X-MailScanner-From: robert.hancock@roke.co.uk
X-Spam-Score: 0.0 (/)
X-Scan-Signature: 7fa173a723009a6ca8ce575a65a5d813
Subject: [Dcpel] some comments on draft-vandenberghe-dcpel-basics-00.txt
X-BeenThere: dcpel@ietf.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Mailing list for possible diffserv control plane elements WG <dcpel.ietf.org>
List-Unsubscribe: <https://www1.ietf.org/mailman/listinfo/dcpel>, <mailto:dcpel-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www1.ietf.org/pipermail/dcpel>
List-Post: <mailto:dcpel@ietf.org>
List-Help: <mailto:dcpel-request@ietf.org?subject=help>
List-Subscribe: <https://www1.ietf.org/mailman/listinfo/dcpel>, <mailto:dcpel-request@ietf.org?subject=subscribe>
Errors-To: dcpel-bounces@ietf.org
hi, i've been reading draft-vandenberghe-dcpel-basics-00.txt and draft-mendes-dcpel-requirements-00. i have some comments/questions on the first. leaving aside minor comprehensibility nits, my main questions are about trying to understand the scope in a bit more concrete terms. this email got rather long; sorry for that. r. 1. What is a "traffic aggregate"? This term is given in section 2, as the generalisation of a behaviour aggregate (which applies to a link) to a network. What I don't understand is the nature of the generalisation - does a traffic aggregate apply to a sequence of links along a path, or to all traffic within a network? (Both possibilities are listed in the previous section.) These would seem to me to be rather different concepts, especially once routing interactions are taken into account. The first is can be defined quite precisely by giving a specific (ingress, egress); for the second, is one expecting ({set of ingresses}, {set of egresses}), or {set of edge nodes}, or just to say 'all traffic passing a given AS'? Does a traffic aggregate have a direction? Would a service description assume/define particular traffic patterns within the aggregate, or would arbitrary distributions be expected? If there is a change in external connectivity (e.g. a BGP route switches from one egress to another) is the definition of the aggregate supposed to change, or are you supposed to renegotiate for a new aggregate? [The reason I ask is that there seems to be a big spectrum of complexity here in the range of possible sophistication of aggregate definition. And I'm not sure where the scope boundary is supposed to be.] Section 4.1 includes the phrase "There must be a non-path-specific option." but I can't tell what this means - does it refer to signalling mechanisms or to the definition of traffic aggregates themselves? 2. Interior vs. edge vs. exterior The document seems to distinguish three different aspects of a DiffServ network, but I'm not sure how they relate and/or overlap. - There is a fairly consistent message that the 'internals' of the network should not be exposed externally - There is a discussion of developing or being consistent with a universal inter-domain interface (which would presumably be independant of these 'internals') On the other hand, there are several places where it's asserted that certain sorts of operations should affect only edge and not interior nodes. This seems to be something that does more than just scope the problem but describes some fundamental aspect of the solution; does it mean that the edge nodes and interior nodes are going to be distinguished in some architectural sense? For example, does this distinction between edge and interior count as an aspect of the 'internals' which should not be exposed? 3. Role of PDBs and service descriptions [This may all be clear to people with a longer DS background than me.] I got continually confused by the relationship between PDBs and services. 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. A particular way of posing the question: would PDBs be visible in the inter-domain interface of a DS domain (e.g. as part of a service description)? If so, how would the use of PDBs to describe packet treatment relate to other syntax for describing packet treatment (e.g. ITU based)? Or are PDBs purely 'internal' language for a DCP to use in intra-domain communication between the various DCP elements? For example, the requirements draft indicates that the same inter-domain control interface should be applicable to non-DiffServ domains, which presumably wouldn't use PDBs at all. 4. SIP interactions I was confused by two aspects of the interaction with SIP. - SIP is mentioned as a possible instantiation of the inter-domain control mechanism, but I don't see how it would be relevant. If the idea is to piggyback the DifS signalling for a given flow on the SIP exchanges for a flow, this would imply that there is a constraint that the SIP signalling path and traffic path are the same (at the domain level), which does not need to be true. If the idea is to have totally different SIP interactions, I'm not clear how much of the SIP protocol machinery is relevant to the DCP problem space. - So far as I can tell, assuming that application interactions are handled by 3312 (SDP preconditions) is quite valid, but also means that there is no further relevance to the DCP work. As far as I understand, 3312 allows application endpoints to agree with each other which endpoint is taking responsibility for resource configuration, but the logic of the detailed interactions between the resource configuration and SIP/SDP signalling is internal to those endpoints. In other words, the fact that 3312 is being used should be entirely transparent to the resource configuration mechansisms between the endpoints. (But 4.2 implies there is some specific work to be done here.) 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. _______________________________________________ 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