Use of Multicast Across Inter-Domain Peering Points
Summary: Has 4 DISCUSSes. Needs 2 more YES or NO OBJECTION positions to pass.
Ben Campbell Discuss
(This is related to Alissa's DISCUSS about logging of privacy-sensitive data. But since it's a little different, I'm entering my own DISCUSS.) In section 4.4 (operations) the bullet on problem notification states that AD2 will inform AD1 of, among other things, the locations of users. Is that intended to be geolocation, or network location? If the former, that's extremely sensitive information, and needs privacy guidelines.
Substantive Comments: - I support Alissa's and Kathleen's DISCUSS positions. - There seem to be quite a few implied assumptions about business models. I will call out some specifically, but I'm sure I didn't catch them all. These assumptions should either be removed or made explicit. - The lists of guidelines seem to mix guidelines with observations of fact. This makes it difficult to tell which parts are "best practices" (that is, recommendations) vs which parts simply state fact. -2: Is the assumption that the source is a service provider and the consumer is an end-user relevant? This seems to perpetuate the (often false) assumption that end users only consume content, but never produce it. It would be better to state this in the form of whatever assumptions are implied by the idea of SPs and EUs. For example, do you assume there is a one to many relationship between SPs and EUs? -3.2: Why does this section not rate a figure? I think it would be helpful to show the GRE tunnel as distinct from the native multicast. -3.5, paragraph after Figure 4: The large number of tunnels implies some assumptions about the cardinality between SPs and EUs that should be stated explicitly. (It would help to show this in the figures.) - 4.3.2: The idea that that AD1 has a need to identify users in AD2 seems to be based on some implied business model assumptions. Please state those explicitly. (Or if I missed where they are stated, please point out the text.) -4.3.3: This states that logging is necessary for delivery. Why is that? Again, this seems to make some implicit business model assumptions. This section also needs explicit privacy considerations. -4.4: The choice of monitoring, etc, seems to be up to the network operators to decide. Why does this document need to "expect" that? It might be helpful to describe how monitoring specific information could be useful (perhaps for troubleshooting), but the document does not go into that. The statements about compensation should be out of scope for an IETF document. -5: Can you define, or reference a definition for, "Looking-Glass style". -6: Please include a discussion of threat models. When might one choose to encrypt or not encrypt? What risks exist if you don't encrypt? -- : "DRM and Application Accounting, Authorization and Authentication should be the responsibility of the multicast application source" Why? This seems to imply some business model assumptions. Editorial Comments: - General: I find the heavy use of nested bullet lists hard to read. Much of the information in the lists would be better suited to paragraph form, especially when list entries span several sentences. Likewise, the inconsistent use of full sentences vs fragments makes it hard to read. (Maybe this is just me) -2: Please explain (s,g) before using, or even better spell it out. You do, in fact, explain it in 4.2.3, but it's used quite a bit before you get to there. -3.2, third bullet: "Ability to support only partial IP multicast deployments..." Does this mean "only able to support partial..." or "able to support partial..."? - 3.3, figure: The figures that involve tunnels would be easier to understand if you visually distinguished tunnels from non-tunneled links. - 3.3, e: "AMT tunnels will then configure dynamically" s/configure/"be configured" -3.4, d: " It is recommended that proper procedures are implemented such that the AMT Gateway at the End User device is able to find the correct AMT Relay..." Is that a recommendation or a requirement necessary to work at all? (Same construction appears in at least 3.5). -4.1: Please expand SLA on first use. -4.2.3: AMT Gateway: "The Gateway will reside on an End-Point - this may be a Personal Computer (PC) or a Set Top Box (STB)." Is that meant to be exhaustive? Surely there are endpoints that do not resemble PCs or STBs. -4.2.3, example procedures for gateway selection: The heavy use of passive voice in this section obscures the actors. (This is true to some degree throughout the document, but it seems more confusing here.) -4.3.2, 2nd bullet: Please don't use "/" as shorthand for conjunctions. (Pattern repeats throughout the rest of the draft.) -4.3.3, first paragraph: The first sentence is hard to parse. -6: Please expand DRM and CDN on first mention.
Alissa Cooper Discuss
Section 4.3.3 recommends that ADs generate and exchange extensive logging information, but the document says nothing about securing these logs or limiting the exchange of private or confidential information between the peers. This seems like it needs to be addressed in the BCP.
(1) Why does this document contain the copyright disclaimer for pre-RFC5378 work? (2) Section 4.4 says: "In the event of performance degradation (SLA violation), AD-1 may have to compensate the multicast application source per SLA agreement. As appropriate, AD-1 may seek compensation from AD-2 if the cause of the degradation is in AD-2's network." and "Faults in service could lead to SLA violation for which the multicast application source provider may have to be compensated by AD-1. Subsequently, AD-1 may have to be compensated by AD-2 based on the contract." These bullets seem out of scope for this BCP. I would recommend deleting them. (3) Section 6 says: "DRM and Application Accounting, Authorization and Authentication should be the responsibility of the multicast application source provider and/or AD-1. AD-1 needs to work out the appropriate agreements with the source provider. Network has no DRM responsibilities, but might have authentication and authorization obligations. These though are consistent with normal operations of a CDN to insure end user reliability, security and network security." I find these two paragraphs somewhat contradictory and vague. The first paragraph makes it sound like DRM could be the responsibility of AD-1. The second paragraph makes it sound like AD-1 (assuming it counts as "network") would never be responsible for DRM. Then later on the text says: "Authentication and authorization of EU to receive multicast content is done at the application layer between the client application and the source. This may involve some kind of token authentication and is done at the application layer independently of the two AD's." Is this differentiating authentication and authorization of the application source from that of the end user? It's not clear. I would suggest revising this whole section to be clear about which security functions are the responsibility of which parties.
Mirja Kühlewind (was No Objection) Discuss
Sorry for this last minute discuss but I would like to emphasize the points made in the tsv-art review on congestion/rate control (Thanks Yoshi!): Please provide stronger guidance (MUST) on the use of rate/congestion control in these two cases: In Section 3.1: " If the peering point between AD-1 and AD-2 is a controlled network environment, then bandwidth can be allocated accordingly by the two domains to permit the transit of non- rate adaptive multicast traffic. If this is not the case, then it is recommended that the multicast traffic should support rate-adaption." In Section 4.1, "When determining the appropriate bandwidth allocation, parties should consider use of a multicast protocol suitable for live video streaming that is consistent with Congestion Control Principles [BCP41]."
Minor questions/comments: 1) Section 3.4 also says: "Highly efficient use of bandwidth in AD-1." But aren't packets eventually duplicated in this case in AD-1? I guess it's more efficient than replicating them at the network border but might be still less efficient than native multicast in the whole network, no? 2) section 4.3.3 says: "The two AD's may supply additional security logs..." This seems to be a general action not specific to multicast or the scenarios described in this doc. 3) I don't think the conclusion section (8) is helpful or needed. If you want to keep it at all, this text could be moved into the introduction.
Kathleen Moriarty Discuss
Thanks for your work on this draft. I'd like to see some text clarifications on security recommendations that should not be difficult to resolve. Section 4.4 - the exchange of supporting information could be sensitive, are there security requirements on the exchange? I don’t see them in this section. Section 6 - For the following text, it would be helpful to see some recommendations: “DRM and Application Accounting, Authorization and Authentication should be the responsibility of the multicast application source provider and/or AD-1. AD-1 needs to work out the appropriate agreements with the source provider.”
I agree with and support Alissa's Discuss and comments. Since she already holds a discuss on this point, here are my comments: Section 4.3.3 clearly refers to different types of logs, some have well known methods of delivery (syslog) and authentication, but setting a minimum requirement for secure exchange including encryption and authentication should be included in this section. The protocols and options may vary between the log types.
Warren Kumari Yes
Deborah Brungard No Objection
Benoit Claise No Objection
Spencer Dawkins No Objection
Thanks for doing this work. I have comments, but they're all editorial. In this text, o AD-1 and AD-2 are assumed to adopt compatible protocols. The use of different protocols is beyond the scope of this document. "compatible protocols" isn't helpful without some context. Is this talking about "compatible multicast protocols", or complete protocol stacks from IP on up, or something else? I'm also noticing that the terms "should" and "recommended" appear a few times in this document. This is a BCP and doesn't reference BCP 14, which is all fine, but the wording is likely to lead readers in one direction. I wonder if it's helpful to say these things differently, so that (for instance) Hence, in the case of inter-domain peering, it is recommended to use only SSM protocols; the setup of inter- domain peering for ASM (Any-Source Multicast) is not in scope for this document. might become Hence, this document assumes that in the case of inter-domain peering, only SSM protocols are used; the setup of inter- domain peering for ASM (Any-Source Multicast) is not in scope for this document. Nit: "out of cope" This text, packet streams will be part of a suitable multicast transport protocol. didn't parse for me - was it saying packet streams will be carried by a suitable multicast transport protocol. or something else? In this text, Note that domain 2 may be an independent network domain (e.g., Tier 1 network operator domain). Alternately, domain 2 could also be an Enterprise network domain operated by a single customer. The peering point architecture and requirements may have some unique aspects associated with the Enterprise case. The Use Cases describing various architectural configurations for the multicast distribution along with associated requirements is described in section 3. Unique aspects related to the Enterprise network possibility will be described in this section. Section 4 contains a comprehensive list of pertinent information that needs to be exchanged between the two domains in order to support functions to enable the application transport. it wasn't easy for me to tie "some unique aspects" in the first paragraph to "will be described in this section" in the second - if the last sentence in the first paragraph was moved to be the second paragraph, so the text was Note that domain 2 may be an independent network domain (e.g., Tier 1 network operator domain). Alternately, domain 2 could also be an Enterprise network domain operated by a single customer. The Use Cases describing various architectural configurations for the multicast distribution along with associated requirements is described in section 3. The peering point architecture and requirements may have some unique aspects associated with the Enterprise case. These unique aspects will be described in this section. Section 4 contains a comprehensive list of pertinent information that needs to be exchanged between the two domains in order to support functions to enable the application transport. that would have been easier for me to follow. It's also worth mentioning that I'm guessing that "section 3" is "this section" in that text, and I'm pretty sure "this section" isn't "section 2", which is actually where the sentence appears, but it might be easier for the reader to say "will also be described in section 3". The first sentence in e. The interconnection of AD-1 and AD-2 should, at a minimum, follow guidelines for traffic filtering between autonomous systems [BCP38]. Filtering guidelines specific to the multicast control-plane and data-plane are described in section 6. just seems odd ("this BCP says you should do that BCP"). ISTM that if there are multicast-specific reasons to do BCP38 in addition to the usual reasons, that would be a fine thing to say here, of course. If your audience doesn't already know o The GRE tunnel is often left pinned up. (and if they don't, thank you for telling them), you might want to add a few words explaining why that's a disadvantage. In this text, The advantage for such a chained set of AMT tunnels is that the total number of unicast streams across AD-2 is significantly reduced, thus freeing up bandwidth. Additionally, there will be a single unicast stream across the peering point instead of possibly, an unacceptably large number of such streams per Use Case 3.4. However, this implies that several AMT tunnels will need to be dynamically configured by the various AMT Gateways based solely on the (S,G) information received from the application client at the EU device. A suitable mechanism for such dynamic configurations is therefore critical. is there a good reference for "suitable mechanism(s)"?
Suresh Krishnan No Objection
Eric Rescorla No Objection
I support Kathleen's and Alissa's discusses I'm concerned about whether the practices described adequately capture the notion of user consent to receive the data. Specifically, we're talking about sending large streams of data to people. Do the protocols in question adequately ensure that the addresses in question wish to receive the data. Specifically, the issue I am concerned with is whether I can cause you to get a large video stream. I'm filing this as a Comment rather than a Discuss because it doesn't seem like an issue for this BCP but rather for the protocols it documents. Please define S,G at first use.
Alvaro Retana No Objection
Adam Roach No Objection
I support Alissa's and Kathleen's DISCUSSes; and (as a separate concern), I support Ben's DISCUSS. Most of the comments I noted in my review of this document have been made by other reviewers, and I will not reiterate most of them. I would, however, like to draw particular attention to Ben's comments regarding charging, billing, and settlement -- I believe these issues should either be fleshed out in significantly more detail, or removed (with a simple statement in the introduction that such issues are generally out of scope for the entire document). ___ Section 4.2.3 contains the following text: (Note that in IPv6 there is a specific Anycast format and Anycast is inherent in IPv6 routing, whereas in IPv4 Anycast is handled via provisioning in the network. Details are out of scope for this document.) It would be helpful to the reader if the "out of scope" statement were accompanied by a pointer to BCP 126/RFC 4786. ___ Section 5 contains the following text: It is expected that multicast diagnostics will be collected according to currently established practices [MDH-04]. I believe this statement makes [MDH-04] normative, as it is required to understand its contents to implement the recommendations in this BCP.