Re: [lisp] Review of RFC6833bis
Alberto Rodriguez-Natal <rodrigueznatal@gmail.com> Wed, 29 November 2017 18:04 UTC
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From: Alberto Rodriguez-Natal <rodrigueznatal@gmail.com>
Date: Wed, 29 Nov 2017 10:04:18 -0800
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To: Dino Farinacci <farinacci@gmail.com>
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Subject: Re: [lisp] Review of RFC6833bis
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Thanks for the responses Dino. I'll get back to you later this week. Alberto On Tue, Nov 28, 2017 at 5:12 PM, Dino Farinacci <farinacci@gmail.com> wrote: >> Hi all, >> >> Wanted to send this before the meeting on Friday. I just completed a >> review of 6833bis, you can find my comments below. Like last time, >> extracts from the draft are copied and followed by my comments. >> >> Thanks, >> Alberto > > Thanks again Alberto for your comments. See my responses inline and a -07 diff file. > >> Map-Resolver: A network infrastructure component that accepts LISP >> Encapsulated Map-Requests, >> >> • [AR] We could remove "Encapsulated" and just use "Map-Requests". >> A Map-Resolver may accept non-encapsulated Map-Requests as well. > > No, they are “control-plane” encapsulated. I’ll make that more clear. > >> Map-Register message: A LISP message sent by an ETR to a Map-Server >> to register its associated EID-Prefixes. In addition to the set of >> EID-Prefixes to register, the message includes one or more RLOCs to be >> used by the Map-Server when forwarding Map-Requests (re-formatted as >> Encapsulated Map-Requests) received through the database mapping >> system. >> >> • [AR] This may give the impression that the RLOCs on the >> Map-Register are only to forward Map-Requests, which is not the case >> in proxy-reply mode. I would suggest we rephrase this text as follows: >> "In addition to the set of EID-Prefixes to register, the message >> includes one or more RLOCs to be used to reach the ETR. The Map-Server >> uses these RLOCs when it has to forward Map-Requests (potentially >> re-formatted as Encapsulated Map-Requests) received through the >> database mapping system.” > > I reworded. > >> Map-Notify message: A LISP message sent by a Map-Server to an ETR >> >> • [AR] I would replace "ETR" with "xTR" so we cover the PubSub >> behavior as well. > > Can’t do that because an ITR does not get Map-Notifies as a response to a Map-Register. But I will add that ITRs get Map-Notifies to inform them of RLOC-set changes (for pubsub and signal-free-multicast use-cases). > >> >> For definitions of other terms -- notably Map-Request, Map-Reply, >> Ingress Tunnel Router (ITR), and Egress Tunnel Router (ETR) -- please >> consult the LISP specification [I-D.ietf-lisp-rfc6830bis]. >> >> • [AR] I think that the definitions for Map-Request and Map-Reply >> should be moved here, and probably we should include the definition >> for Map-Notify-Ack as well. 6830bis should reference 6833bis for >> control-plane messages, not the other way around. > > They did. But the text you identified above was not changed. Changed now. > >> A Map-Register message contains a list of EID-Prefixes plus a set of >> RLOCs that can be used to reach the ETR when a Map-Server needs to >> forward a Map-Request to it. >> >> • [AR] Since proxy-reply is a common case, I'd not constrain the >> meaning of the RLOCs in the Map-Register. I'd remove the last part of >> the sentence that says "when a Map-Server needs to forward a >> Map-Request to it.” > > Agree. > >> A Map-Resolver receives Encapsulated Map-Requests from its client ITRs >> and uses a mapping database system to find the appropriate ETR to >> answer those requests. >> >> • [AR] A MR can receive Map-Requests that don't come from ITR >> and/or that are not encapsulated. If we don't want to change the text, >> at least I'd add at the beginning: "In a common scenario, a >> Map-Resolver…" > > I don’t think we should change this. The lig document indicates that a lig client can send Map-Requests. This document is for support of a data-plane. > >> Note that while it is conceivable that a non-LISP-DDT Map-Resolver >> could cache responses to improve performance, >> >> • [AR] The discussion on caching or not at the Map-Resolver goes >> beyond DDT. We could rephrase this removing the mention to >> "non-LISP-DDT”. > > Agree. Changed. > >> The LISP UDP-based messages are the Map-Request and Map-Reply >> messages. When a UDP Map-Request is sent, the UDP source port is >> chosen by the sender and the destination UDP port number is set to >> 4342. When a UDP Map-Reply is sent, the source UDP port number is set >> to 4342 and the destination UDP port number is copied from the source >> port of either the Map-Request or the invoking data packet. >> >> • [AR] I would remove the first sentence and re-phrase this >> paragraph as follows: "When a UDP LISP control message is sent and is >> not a direct reply to a previous control message, the UDP source port >> is chosen by the sender and the destination UDP port number is set to >> 4342. When a UDP LISP control message is sent as a direct reply to a >> previous message, the source UDP port number is set to 4342 and the >> destination UDP port number is either set to 4342 or copied from the >> source port of the invoking LISP control message. See the following >> subsections for details.” > > This is not really true. There are too many cases with respect to NAT-traversal that make things more complicated. I think we need to be specific about each message and not generalize it. Plus, Map-Notify messages are response and unsolicited so they vary on whether the destination or source port is 4342. > > I have added text to identify each message that follow the Map-Request and Map-Reply port rules. > >> The UDP checksum is computed and set to non-zero for Map-Request, >> Map-Reply, Map-Register, and Encapsulated Control Message (ECM) >> control messages. >> >> • [AR] Shouldn't it be computed for all LISP control messages? > > Yes. Added text. > >> EID-Prefix: This prefix is 4 octets for an IPv4 address family and 16 >> octets for an IPv6 address family. When a Map-Request is sent by an >> ITR because a data packet is received for a destination where there is >> no mapping entry, the EID-Prefix is set to the destination IP address >> of the data packet, and the 'EID mask-len' is set to 32 or 128 for >> IPv4 or IPv6, respectively. >> >> • [AR] We should probably rephrase this to don't limit it to IPv4/6 > > Good point. Generalized the text a bit. > >> For the latter two cases, the destination IP address used for the >> Map-Request is one of the RLOC addresses from the Locator-Set of the >> Map-Cache entry. >> >> • [AR] To refresh map-caches before TTL expiration, the >> destination IP of the Map-Request can be the address of the Map-Server >> if in proxy-reply. This should be considered here. > > This is not true. The Map-Request has an IP header but it is encapsulated in an ECM and that IP header destination address is the *Map-Resolvers*. > >> If the ITR erroneously provides no ITR-RLOC addresses, the Map-Replier >> MUST drop the Map-Request. >> >> • [AR] This could probably be a SHOULD since we use AFI = 0 as >> ITR-RLOC to unsubscribe in PubSub. > > An AFI=0 Is an RLOC address. > >> EID-Prefix: This prefix is 4 octets for an IPv4 address family and 16 >> octets for an IPv6 address family. >> >> • [AR] We should mention the possibility for address families >> other than IPv4/6. > > Have that covered. > >> The RLOCs in the Map-Reply are globally routable IP addresses of all >> ETRs for the LISP site. >> >> • [AR] We should remove "globally" here. Maybe also add a >> "Generally" at the beginning since we might have LCAFs with AFI = 0 >> (LISP-VPN encoding of Home-IID for instance). > > Removed “globally”. I don’t understand your other “Generally” comment. > >> For example, a requester with two cached EID-Prefixes that are covered >> by a Map-Reply containing one less-specific prefix replaces the entry >> with the less-specific EID-Prefix. >> >> • [AR] Not sure if I follow here. Does this mean that a >> less-specific received in a Map-Reply will erase from the map-cache >> previously cached more-specifics that are covered by the >> less-specific? > > Yes, because if the Map-Reply returned a more-specific with the less-specific, then it would be replaced so the less-specific replaces the more-specifics that ARE NOT in the Map-Reply. > >> When more than one EID-Prefix is returned, all SHOULD use the same >> Time to Live value so they can all time out at the same time. When a >> more-specific EID-Prefix is received later, its Time to Live value in >> the Map-Reply record can be stored even when other less-specific >> entries exist. >> >> • [AR] We should explain in which cases a more-specific can be >> received later. > > I don’t follow. Each EID-record will contain a TTL for the length prefix that is encoded. So the new Map-Reply TTL will be used for any length entry (and in this case the more-specific). > >> The Locator-Set MUST be sorted in order of ascending IP address where >> an IPv4 locator address is considered numerically 'less than' an IPv6 >> locator address. >> >> • [AR] LCAF addresses (maybe with AFI=0) should be discussed here as well. > > It is discussed in the LCAF draft. Don’t want to repeat it. > >> Nonce: This 8-octet 'Nonce' field is set to 0 in Map-Register messages. >> >> • [AR] Since there may be future cases that benefit from having a >> non-zero nonce on the Map-Register, I would suggest to rephrase this >> sentence to add a CAN. > > Not until we identify and describe the use-case. No point to speculate. But note, if a Map-Notify is returned, the nonce should be non-zero. I’ll fix that. > >> E: This is the to-ETR bit. When set to 1, the Map-Server's intention >> is to forward the ECM to an authoritative ETR. >> >> • [AR] Can M and E be set at the same time? > > It can. M bit is set to indicate to avoid DDT procedures. The E bit tells the Map-Server what to do with the Map-Request. > >> LCM: The format is one of the control message formats described in >> this section. At this time, only Map-Request messages are allowed to >> be encapsulated. >> >> • [AR] Shall we mention the NAT traversal draft? > > No, this is an ECM, not a data-encapsulated control-message. > >> A Map-Server's configuration must also include a list of the >> EID-Prefixes for which each ETR is authoritative. >> >> • [AR] There may be certain cases where this does not need to be >> pre-configured. I suggest we replace the "must" with a "should". Note >> that this requirement is already a "should" in section 6. > > Agree. > >> See [I-D.ietf-lisp-rfc6830bis] for details on how the Map-Server sets >> certain flags (such as those indicating whether the message is >> authoritative and how returned Locators should be treated) when >> sending a Map-Reply on behalf of an ETR. >> >> • [AR] It may be useful to discuss at least some of those details here. > > It does following this. > > I also made the document RFC2119 compliant where the terms for not capitalized. There were a few places. > > Thanks again, > Dino > > > > > >
- [lisp] Review of RFC6833bis Alberto Rodriguez-Natal
- Re: [lisp] Review of RFC6833bis Dino Farinacci
- Re: [lisp] Review of RFC6833bis Alberto Rodriguez-Natal
- Re: [lisp] Review of RFC6833bis Dino Farinacci
- Re: [lisp] Review of RFC6833bis Alberto Rodriguez-Natal
- Re: [lisp] Review of RFC6833bis Victor Moreno (vimoreno)
- Re: [lisp] Review of RFC6833bis Dino Farinacci
- Re: [lisp] Review of RFC6833bis Alberto Rodriguez-Natal
- Re: [lisp] Review of RFC6833bis Dino Farinacci
- Re: [lisp] Review of RFC6833bis Alberto Rodriguez-Natal