Re: rtg-dir review: dpapadimitriou, prz: draft-ietf-mpls-oam-requirements-04.txt
dimitri papadimitriou <dpapadimitriou@psg.com> Sun, 10 October 2004 19:04 UTC
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Date: Sun, 10 Oct 2004 20:57:54 +0200
From: dimitri papadimitriou <dpapadimitriou@psg.com>
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Subject: Re: rtg-dir review: dpapadimitriou, prz: draft-ietf-mpls-oam-requirements-04.txt
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hi alex, you will find here below my comments on the above referenced document 1) Technical and 2) Editorial - see below: 1) Technical ------------ 0. Section 3 "This leads to inconsistent and inefficient applicability across the MPLS architecture, and/or requires significant modifications to operational procedures and systems in order to provide consistent and useful OAM functionality." -> How to ensure that the proposed OAM techniques will not create more inconsistencies than those apparently occurring with the existing ad hoc methods/solutions (those that are not currently part of the proposed framework) - as a matter of fact these techniques are already deployed ? 1. Section 4.1 Distinction between failure and defect is not clearly reflected, it is therefore difficult to understand the requirement behind detection of a "broken LSP" 2. Section 4.1 In the sentence "... this function SHOULD be automated and performed from the origination of that LSP." does not say until which point this operation has to be performed 3. Section 4.1 The sentence "As an example of a false positive, consider the case where the MPLS data plane flows through a network node using a different output line card than the data plane does to each the next neighbor." is mispelled which understanding of the false positive difficult as per [LSP-PING] "MPLS echo request are sent along the same data path as other packets belonging to this FEC. An MPLS echo request also carries information about the FEC whose MPLS path is being verified. This echo request is forwarded just like any other packet belonging to that FEC. In "ping" mode (basic connectivity check), the packet should reach the end of the path, at which point it is sent to the control plane of the egress LSR, which then verifies whether it is indeed an egress for the FEC." 4. Section 4.1 Is there any specific requirement for the return path of unidirectional LSPs to avoid "false negative" ? as this is not explicitly mentioned as part of this section 5. Section 4.2 The sentence "... and any mid-point LSR" does not specify what has to be traced inlight with the above statement "Diagnosis of defects and isolation of the failed component is best accomplished via a path trace function which can return the the entire list of LSRs and links used by a certain LSP (or at least the set of LSRs/links up to the location of the defect) is required." 6. Section 4.3 Second bullet mentions "externally visible aspects" and then points to "specific algorithms" - the term "externally visible" should thus refer to what "external" refers to ? 7. Section 4.4 This section dedicated to "performance measurement" requires more specific i.e. more formal definition of LSP availability (than "service is considered to be available") There is no specific reference to the "one-hop delay" experienced by labeled packets (that included the switching delay and the transmission delay) and "queuing/buffering delay" creates variation in the delay experienced by labeled packets - more accurate definitions could thus be provided to describe the exact OAM&P mechanism to be supported (example there are several methods to take the jitter into account) In the sentence "... so as to accurately reflect the latency ..." what is the expected measurement accuracy expected as part of the present requirements ? 8. Section 4.5 The following sentence "The capability to synchronize OAM operations is desired as to permit consistent measurement of service level agreements." should be more prescriptive than "is desired" does it mean optional and this synchronization is not available how it impacts the overall OAM operations 9. Section 4.5 (Alarm Suppression) To what the term "device" is referring here ? The relationship between the reduction of the "emitted notifications" and the "fault notifications" flowing to the LSP egress is not described ? 10. Section 4.7 This section does not detail what is the object of the failure and the subject of the recovery ? nor the scope of the requirement - does it apply on inter-provider basis (ingress and egress belonging to separate networks) 2) Editorial ------------ 0. As the document has less than 15/20 pages a ToC is not required but if one ToC is included suggestion is made to complete it with sub-sections 1. Section 2. This section should better be split into a "Terminology" section that includes conceptual overview of the terms used in the document (some of them can be more accurately defined as part of the document) and a "Abbreviation and Acronyms" section 2. Section 2. The term "head-end LSR" is introduced but the core of the document make use of the terms "ingress LSR" are these equivalent ? or different ? -> suggestion is made (if they are equivalent) to use a single terminology either ingress/egress LSR or head-end/tail-end LSR 3. Section 3. Spell out acronyms RSVP (isn't RVSP-TE ?) and LDP 4. Section 4.1 The term "path liveliness" has not been defined in Section 2/referenced The term "LSP problem" has not been defined in Section 2/referenced 5. Section 4.1 Add reference to ICMP-based Ping 6. Section 4.2 Sentence "The tracing capability SHOULD include the ability to trace recursive paths, such as when nested LSPs are used, or when LSPs enter and exit traffic-engineered tunnels" is the latter case not covered by the previous one ? 7. Section 4.3 Is the first bullet (TTL models) meant to address RFC 3443 - in this case suggestion is made to add this RFC as reference what the "data/control plane OAM capabilities" means ? this would clarify the scope of the sentence 8. Section 4.4 suggestion is made to clarify the sentence "measure the qualitative aspects of OAM probing" and define the term "OAM probing" 9. Section 4.5 numbering appears twice 10. Section 4.6 Spell out AIS acronym and include as part of the "Abbreviation" section 11. Section 4.9 Include DoS acronym as part of the "Abbreviation" section "control planes" instead of "control plaes" 12. Section 4.10 Include SP acronym as part of the "Abbreviation" section "information" instead of "informationr" "inter-AS" instead of "inter-as" 13. Section 4.10.1 "For example, the LSR might ..." is meant for "For example, the LSR MAY ..." ? what the etc. stands for that other methods exist or what's described is only part of the process ? --- Alex Zinin wrote: > Loa asked me for an early rtg-dir review of this draft. > > skill-specific: dimitri > round-robin: tony > > http://www.ietf.org/internet-drafts/draft-ietf-mpls-oam-requirements-04.txt > > >> Title : OAM Requirements for MPLS Networks >> Author(s) : T. Nadeau, et al. >> Filename : draft-ietf-mpls-oam-requirements-04.txt >> Pages : 13 >> Date : 2004-9-2 >> >>As transport of diverse traffic types such as voice, frame >> relay, and ATM over MPLS become more common, the ability to detect, >> handle and diagnose control and data plane defects becomes >> critical. >> >> Detection and specification of how to handle those defects is not >> only important because such defects may not only affect the >> fundamental operation of an Multi-Protocol Label Switching network, >> but also because they MAY impact service level specification >> commitments for customers of that network. > >
- rtg-dir review: dpapadimitriou, prz: draft-ietf-m… Alex Zinin
- Re: rtg-dir review: dpapadimitriou, prz: draft-ie… Dimitri.Papadimitriou
- Re: rtg-dir review: dpapadimitriou, prz: draft-ie… dimitri papadimitriou
- Re: rtg-dir review: dpapadimitriou, prz: draft-ie… Alex Zinin