[Idr] AD Review of draft-ietf-idr-eag-distribution-15
Alvaro Retana <aretana.ietf@gmail.com> Tue, 30 March 2021 20:25 UTC
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From: Alvaro Retana <aretana.ietf@gmail.com>
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To: draft-ietf-idr-eag-distribution@ietf.org
Cc: Susan Hares <shares@ndzh.com>, idr-chairs@ietf.org, IDR List <idr@ietf.org>
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Subject: [Idr] AD Review of draft-ietf-idr-eag-distribution-15
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Dear authors: Here is my review of this document. I have some major comments (see inline below) that should be easy to address and that I would like to see reflected in the text before starting the IETF Last Call. Thank you for your work! Alvaro. [Line numbers from idnits.] 11 Distribution of Traffic Engineering Extended Admin Groups using BGP-LS [minor] s/Admin/Administrative 12 draft-ietf-idr-eag-distribution-15 14 Abstract 16 Administrative groups are link attributes (commonly referred to as 17 "colors" or "link colors") advertised by link state protocols (e.g. 18 ISIS or OSPF) and used for traffic engineering. These administrative 19 groups were initially defined as 32 bit masks. As network usage 20 grew, these 32 bit masks were found to constrain traffic engineering. 21 Therefore, link state protocols (ISIS, OSPF) were expanded to 22 advertise a variable length administrative group.This document 23 defines an extension to BGP-LS for advertisement of extended 24 administrative groups (EAGs) to allow to support a number of 25 administrative groups greater than 32, as defined in [RFC7308]. [minor] A couple of changes to simplify. The details can be found in the Introduction. Suggestion> Administrative groups are link attributes advertised used for traffic engineering. This document defines an extension to BGP-LS for advertisement of extended administrative groups (EAGs). ... 70 1. Introduction 72 Administrative groups (commonly referred to as "colors" or "link 73 colors") are link attributes that are advertised by link state 74 protocols like IS-IS [RFC5305], OSPFv2 [RFC3630] and OSPFv3 [RFC5329] 75 for traffic engineering use-cases. The BGP-LS advertisement of the 76 originally defined (non-extended) administrative groups is encoded 77 using the Administrative Group (color) TLV 1088 as defined in 78 [RFC7752]. [minor] "IS-IS [RFC5305], OSPFv2 [RFC3630] and OSPFv3 [RFC5329]" These references should point at the protocols themselves, not the TE extensions. Also, these references can be Informative. 80 These administrative groups are defined as a fixed-length 32-bit 81 bitmask. As networks grew and more use-cases were introduced, the 82 32-bit length was found to be constraining and hence extended 83 administrative groups (EAG) were introduced in the IS-IS and OSPFv2 84 link state routing protocols [RFC7308]. [minor] rfc7308 also includes OSPFv3. s/were introduced in the IS-IS and OSPFv2 link state routing protocols [RFC7308]./were introduced in [RFC7308]. ... 97 2. Advertising Extended Administrative Groups in BGP-LS 99 This document defines an extension that enable BGP-LS speakers to 100 signal the EAG of links in a network to a BGP-LS consumer of network 101 topology such as a centralized controller. The centralized 102 controller can leverage this information in traffic engineering 103 computations and other use-cases. When a BGP-LS speaker is 104 originating the topology learnt via link-state routing protocols like 105 OSPF or IS-IS, the EAG information of the links is sourced from the 106 underlying extensions as defined in [RFC7308]. The BGP-LS speaker 107 may also advertise the EAG information for the local links of a node 108 when not running any link-state IGP protocol e.g. when running BGP as 109 the only routing protocol. [minor] There is no defined mechanism to originate EAG information when not running a link-state protocol. Let's take the last sentence out. 111 The EAG of a link is encoded in a new Link Attribute TLV [RFC7752] 112 using the following format: 114 0 1 2 3 115 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 116 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 117 | Type | Length | 118 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 119 | Extended Administrative Groups (variable) // 120 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ [minor] Maybe use the same representation as rfc7308 for the format. ... 128 o Length: variable length which represents the total length of the 129 value field. The length value MUST be multiple of 4. If the 130 length is not a multiple of 4, the TLV MUST be considered 131 malformed. [major] "total length of the value field" What are the units? 133 o Value: one or more sets of 32-bit bitmasks that indicate the 134 administrative groups (colors) that are enabled on the link when 135 those specific bits are set. [major] rfc7308 talks about an "Extended Admin Group" (singular!), and not a set of groups. This TLV is then not in line with rfc7308. The whole document should be checked for (editorial) compliance with the concept of a single EAG. 137 The EAG TLV is an optional TLV. The originally defined AG TLV 1108 138 and the EAG TLV 1173 defined in this document MAY be advertised 139 together. The semantics of the EAG and the backward compatibility 140 aspects of EAG with respect to the AG are handled as described in the 141 Backward Compatibility section of [RFC7308], namely - If a node 142 advertises both AG and EAG, then the first 32 bits of the EAG MUST be 143 identical to the advertised AG. [minor] We don't really need this paragraph because any compatibility or checking is outside of what BGP-LS does (just transport). Please remove it. ... 158 4. Security Considerations 160 The extensions in this document advertise same administrative group 161 information specified via [RFC7752] but as a larger/extended value 162 and hence does not introduce security issues beyond those discussed 163 in [RFC7752] and [I-D.ietf-idr-rfc7752bis]. [major] No need to mention rfc7752bis -- at all! [major] Please take a look at the Security Considerations in rfc8814 and copy them here -- with appropriate modifications to talk about EAG instead of MSD, of course. [End of Review]
- [Idr] AD Review of draft-ietf-idr-eag-distributio… Alvaro Retana
- Re: [Idr] AD Review of draft-ietf-idr-eag-distrib… Jeff Tantsura
- Re: [Idr] AD Review of draft-ietf-idr-eag-distrib… Alvaro Retana
- Re: [Idr] AD Review of draft-ietf-idr-eag-distrib… Ketan Talaulikar (ketant)
- Re: [Idr] AD Review of draft-ietf-idr-eag-distrib… Les Ginsberg (ginsberg)
- Re: [Idr] AD Review of draft-ietf-idr-eag-distrib… Jeff Tantsura
- Re: [Idr] AD Review of draft-ietf-idr-eag-distrib… Alvaro Retana