Re: [Tsv-art] Tsvart last call review of draft-ietf-lisp-gpe-05
Fabio Maino <fmaino@cisco.com> Fri, 28 September 2018 20:35 UTC
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To: Luigi Iannone <ggx@gigix.net>
Cc: Magnus Westerlund <magnus.westerlund@ericsson.com>, tsv-art@ietf.org, lisp@ietf.org, ietf@ietf.org, draft-ietf-lisp-gpe.all@ietf.org, Mirja Kühlewind <ietf@kuehlewind.net>
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From: Fabio Maino <fmaino@cisco.com>
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Subject: Re: [Tsv-art] Tsvart last call review of draft-ietf-lisp-gpe-05
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On 9/21/18 2:04 AM, Luigi Iannone wrote: > Hi Fabio, > > just one comment on the following sentence (section 1) > > LISP-GPE MAY also be used to extend the LISP Data-Plane header, that > has allocated all by defining a Next Protocol "shim" header that > implements new data plane functions not supported in the LISP header. > > Something is missing in this sentence. > > May be: LISP-GPE MAY also be used to extend the LISP Data-Plane > header, **since > all of the reserved bits have been allocated, ** by defining a > Next Protocol "shim" header that > implements new data plane functions not supported in the LISP header. > Ciao Thanks for catching this Luigi. It will be addressed in -07. Fabio > > L. > > > >> On 21 Sep 2018, at 07:12, Fabio Maino <fmaino@cisco.com >> <mailto:fmaino@cisco.com>> wrote: >> >> I have incorporated the changes as discussed, so hopefully rev 6. can >> be used by reviewers before the telechat: >> https://www.ietf.org/id/draft-ietf-lisp-gpe-06.txt >> >> Here is the diff: goo.gl/tCKD4A <http://goo.gl/tCKD4A> >> >> >> I believe the following comments are still open. I'll work with the >> respective authors to address them in the next rev of the document. >> >> >> A. [Deborah/Magnus] it is being discussed on a separate private >> thread if the following should be added to the IANA section: >> "To ensure that protocols that are encapsulated in LISP-GPE will work >> well from a transport interaction perspective, the registration of a >> new encapsulated payload MUST contain an analysis of how LISP-GPE >> SHOULD deal with outer UDP Checksum, DSCP mapping, and Explicit >> Congestion Notification (ECN) bits whenever they apply to the new >> encapsulated payload. The analysis for the new encapsulated payload >> registered in this document is in section 3.1." >> >> >> B. [Magnus] draft-ietf-tsvwg-ecn-encap-guidelines has expired >> yesterday, and cannot be referenced. I'll add it back to section 3.1 >> as soon as the draft is refreshed. >> >> C. [Magnus/Mirja] in 3.1.1 Payload Specific Transport Interactions >> for Ethernet Encapsulated Payloads >> >> >>>The UDP Checksum considerations specified in section 5.3 of >> [draft-ietf-lisp-rfc6830bis] apply to Ethernet Encapsulated Payloads. >> Implementors are encouraged to consider the UDP checksum usage >> guidelines in section 3.4 of [RFC8085] when it is desirable to >> protect UDP, LISP and Ethernet headers against corruption. >> >> So this is not the necessary documentation of the analysis that >> IP/UDP(with zero checksum)/LISP(with GPE)/Ethernet is a safe to use. >> There needs to be an analysis here to verify that this protocol >> combination do work. You will actually have to discuss how the >> Ethernet encapsulation fulfills the requirements listed in Section 4 >> of RFC 6936. >> >> https://datatracker.ietf.org/doc/rfc7510/ is an example where such an >> analysis was included. I would also note the applicability >> limitations this has. >> >> Which actually brings up an additional issue for Ethernet >> encapsulation. For IP the assumption is that the IP traffic that is >> encapsulated is congestion controlled. This assumption is even less >> certain when having Ethernet. Thus, some consideration of that issue >> is likely needed. >> >> >>>When a LISP-GPE router performs Ethernet encapsulation, the inner >> 802.1Q [IEEE.802.1Q_2014] priority code point (PCP) field MAY be >> mapped from the encapsulated frame to the Type of Service field in >> the outer IPv4 header, or in the case of IPv6 the 'Traffic Class' >> field as per guidelines provided by [RFC8325]. >> >> I don't know enough about IEEE and the various versions of Ethernet >> and WLAN here to be certain that 802.1Q PCP's can be mapped directly >> to the 802.11 User Priorities discussed in RFC8325. Please >> investigate if they are the same, and if they are the same >> priorities, then make a explicit statement that they are applicable. >> >> D. [Magnus] 3.1.2 Payload Specific Transport Interactions for NSH >> Encapsulated Payloads >> >> >>> The UDP Checksum considerations specified in section 5.3 of >> [draft-ietf-lisp-rfc6830bis] apply to NSH Encapsulated Payloads. >> Implementors are encouraged to consider the UDP checksum usage >> guidelines in section 3.4 of [RFC8085] when it is desirable to >> protect UDP, LISP, and NSH headers against corruption. >> >> Same as for Ethernet also the NSH header needs to have a documented >> analsysis of fulfillment of the requirements. >> >> >> Thanks, >> >> Fabio >> >> >> >> >> >> >> On 9/20/18 1:03 PM, Fabio Maino wrote: >>> Thanks Magnus, >>> I'll consolidate the changes we have agreed so far in the next rev >>> that I plan to publish later today. >>> >>> I'll then work on the comments on this email and will send you the >>> corresponding actions. >>> >>> Fabio >>> >>> On 9/20/18 2:39 AM, Magnus Westerlund wrote: >>>> >>>> Hi Fabio, >>>> >>>> Most of the below text is excellent. Some comments inline for >>>> needed clarifications and additions. >>>> >>>> On 9/18/2018 9:52 PM, Fabio Maino wrote: >>>>> Hi Magnus, >>>>> thanks for your comments. >>>>> >>>>> I think I see the points you are making. >>>>> >>>>> I'll add the section 3.1 below to specify the general transport >>>>> requirements for the registration of new LISP-GPE payloads, and I >>>>> will introduce two subsections to instantiate those requirements >>>>> for Ethernet and NSH (section 4.2 and 4.3 will be moved here). In >>>>> the "IANA Considerations" section I'll refer to this new section >>>>> 3.1 as a requirement for registration of new encapsulated payload. >>>>> >>>>> "3.1 Payload Specific Transport Interactions >>>>> >>>>> To ensure that protocols that are encapsulated in LISP-GPE will >>>>> work well from a transport interaction perspective, the >>>>> specification of a new encapsulated payload MUST contain an >>>>> analysis of how LISP-GPE SHOULD deal with outer UDP Checksum, DSCP >>>>> mapping, and Explicit Congestion Notification (ECN) bits whenever >>>>> they apply to the new encapsulated payload. >>>>> >>>>> For IP payloads, section 5.3 of [draft-ietf-lisp-rfc6830bis] >>>>> specifies how to handle UDP Checksums encouraging implementors to >>>>> consider UDP checksum usage guidelines in section 3.4 of [RFC8085] >>>>> when it is desirable to protect UDP and LISP headers against >>>>> corruption. Each new encapsulated payloads, when registered with >>>>> LISP-GPE, MUST be accompanied by a similar analysis. >>>>> >>>>> Encapsulated payloads may have a priority field that may or may >>>>> not be mapped to the DSCP field of the outer IP header (part of >>>>> Type of Service in IPv4 or Traffic Class in IPv6). Such new >>>>> encapsulated payloads, when registered with LISP-GPE, MUST be >>>>> accompanied by an analysis similar to the one performed in Section >>>>> 3.1.1 of this document for Ethernet payloads. >>>>> >>>>> Encapsulated payloads may have Explicit Congestion Notification >>>>> mechanisms that may or may not be mapped to the outer IP header >>>>> ECN field. Such new encapsulated payolads, when registered with >>>>> LISP-GPE, MUST be accompanied by a set of guidelines derived from >>>>> [draft-ietf-tsvwg-ecn-encap-guidelines] and [RFC6040]. >>>>> >>>>> The rest of this section specifies payload specific transport >>>>> interactions considerations for the two new LISP-GPE encapsulated >>>>> payloads specified in this document: Ethernet and NSH. >>>>> >>>>> 3.1.1 Payload Specific Transport Interactions for Ethernet >>>>> Encapsulated Payloads >>>>> >>>>> The UDP Checksum considerations specified in section 5.3 of >>>>> [draft-ietf-lisp-rfc6830bis] apply to Ethernet Encapsulated >>>>> Payloads. Implementors are encouraged to consider the UDP checksum >>>>> usage guidelines in section 3.4 of [RFC8085] when it is desirable >>>>> to protect UDP, LISP and Ethernet headers against corruption. >>>> >>>> So this is not the necessary documentation of the analysis that >>>> IP/UDP(with zero checksum)/LISP(with GPE)/Ethernet is a safe to >>>> use. There needs to be an analysis here to verify that this >>>> protocol combination do work. You will actually have to discuss how >>>> the Ethernet encapsulation fulfills the requirements listed in >>>> Section 4 of RFC 6936. >>>> >>>> https://datatracker.ietf.org/doc/rfc7510/ is an example where such >>>> an analysis was included. I would also note the applicability >>>> limitations this has. >>>> >>>> Which actually brings up an additional issue for Ethernet >>>> encapsulation. For IP the assumption is that the IP traffic that is >>>> encapsulated is congestion controlled. This assumption is even less >>>> certain when having Ethernet. Thus, some consideration of that >>>> issue is likely needed. >>>> >>>> >>>>> >>>>> When a LISP-GPE router performs Ethernet encapsulation, the inner >>>>> 802.1Q [IEEE.802.1Q_2014] priority code point (PCP) field MAY be >>>>> mapped from the encapsulated frame to the Type of Service field in >>>>> the outer IPv4 header, or in the case of IPv6 the 'Traffic Class' >>>>> field as per guidelines provided by [RFC8325]. >>>> >>>> I don't know enough about IEEE and the various versions of Ethernet >>>> and WLAN here to be certain that 802.1Q PCP's can be mapped >>>> directly to the 802.11 User Priorities discussed in RFC8325. Please >>>> investigate if they are the same, and if they are the same >>>> priorities, then make a explicit statement that they are applicable. >>>> >>>>> >>>>> When a LISP-GPE router performs Ethernet encapsulation, the inner >>>>> header 802.1Q [IEEE8021Q] VLAN Identifier (VID) MAY be mapped to, >>>>> or used to determine the LISP Instance ID field. >>>>> >>>>> 3.1.2 Payload Specific Transport Interactions for NSH Encapsulated >>>>> Payloads >>>>> >>>>> The UDP Checksum considerations specified in section 5.3 of >>>>> [draft-ietf-lisp-rfc6830bis] apply to NSH Encapsulated Payloads. >>>>> Implementors are encouraged to consider the UDP checksum usage >>>>> guidelines in section 3.4 of [RFC8085] when it is desirable to >>>>> protect UDP, LISP, and NSH headers against corruption. >>>> >>>> Same as for Ethernet also the NSH header needs to have a documented >>>> analsysis of fulfillment of the requirements. >>>> >>>> >>>>> >>>>> When a LISP-GPE router performs an NSH encapsulation, DSCP and ECN >>>>> values MAY be mapped as specified for the Next Protocol >>>>> encapsulated by NSH (namely IPv4, IPv6 and Ethernet)." >>>>> >>>>> >>>>> I will also add a paragraph to "Iana Considerations" that says: >>>>> >>>>> >>>>> "To ensure that protocols that are encapsulated in LISP-GPE will >>>>> work well from a transport interaction perspective, the >>>>> registration of a new encapsulated payload MUST contain an >>>>> analysis of how LISP-GPE SHOULD deal with outer UDP Checksum, DSCP >>>>> mapping, and Explicit Congestion Notification (ECN) bits whenever >>>>> they apply to the new encapsulated payload. The analysis for the >>>>> new encapsulated payload registered in this document is in section >>>>> 3.1." >>>>> >>>>> Please, let me know if this address your comments. >>>>> >>>>> Thanks, >>>>> Fabio >>>>> >>>>> >>>>> >>>>> On 8/29/18 2:17 AM, Magnus Westerlund wrote: >>>>>> Reviewer: Magnus Westerlund >>>>>> Review result: Not Ready >>>>>> >>>>>> This document has been reviewed as part of the transport area directorate's >>>>>> ongoing effort to review key IETF documents. These comments were written >>>>>> primarily for the transport area directors, but are copied to the document's >>>>>> authors and WG for their information and to allow them to address any issues >>>>>> raised. >>>>>> >>>>>> When done at the time of IETF Last Call, the authors should consider this >>>>>> review together with any other last-call comments they receive. >>>>>> Please always CCtsv-art@ietf.org if you reply to or forward this review. >>>>>> >>>>>> Issue A. >>>>>> >>>>>> The reason I state Not Ready has to do with this documents failure to consider >>>>>> the use of zero checksum for IPv6 when tunneling other things than IP. The none >>>>>> GPE version is limited to tunnel IP for which the analysis for use of zero >>>>>> checksum has been done. Each of the new tunneled protocols that are specified >>>>>> in this document, i.e. ethernet and NHS, will need to perform the analysis if >>>>>> they are safe to use zero checksum or not, and if not disallow zero checksum >>>>>> for IPv6/UDP. The documetn also need a requirement in the registration >>>>>> requirements to perform this analysis and defined if zero checksum is >>>>>> acceptable or not. >>>>>> >>>>>> Citing Section 5.3 of draft-ietf-lisp-rfc6830bis >>>>>> >>>>>> UDP Checksum: The 'UDP Checksum' field SHOULD be transmitted as zero >>>>>> by an ITR for either IPv4 [RFC0768] and IPv6 encapsulation >>>>>> [RFC6935] [RFC6936]. When a packet with a zero UDP checksum is >>>>>> received by an ETR, the ETR MUST accept the packet for >>>>>> decapsulation. When an ITR transmits a non-zero value for the UDP >>>>>> checksum, it MUST send a correctly computed value in this field. >>>>>> When an ETR receives a packet with a non-zero UDP checksum, it MAY >>>>>> choose to verify the checksum value. If it chooses to perform >>>>>> such verification, and the verification fails, the packet MUST be >>>>>> silently dropped. If the ETR chooses not to perform the >>>>>> verification, or performs the verification successfully, the >>>>>> packet MUST be accepted for decapsulation. The handling of UDP >>>>>> zero checksums over IPv6 for all tunneling protocols, including >>>>>> LISP, is subject to the applicability statement in [RFC6936]. >>>>>> >>>>>> The issue is that when LISP encapsulate other protocols the impact of a >>>>>> missdelivered tunnel packet to the wrong ETR can have different impacts. As >>>>>> well as errors in the headers of the encapsulated packet that may be assumed to >>>>>> be protected by the encapsulating layer. Thus, individual analysis of each >>>>>> protocol that are tunneled are needed. >>>>>> >>>>>> B.) 4.2. Type of Service >>>>>> >>>>>> When a LISP-GPE router performs Ethernet encapsulation, the inner >>>>>> 802.1Q [IEEE.802.1Q_2014] priority code point (PCP) field MAY be >>>>>> mapped from the encapsulated frame to the Type of Service field in >>>>>> the outer IPv4 header, or in the case of IPv6 the 'Traffic Class' >>>>>> field. >>>>>> >>>>>> Any recommendation about how to perform that mapping? Maybe parts of >>>>>> https://datatracker.ietf.org/doc/rfc8325/ are relevant in this context. >>>>>> >>>>>> C. General case of 4.2: >>>>>> >>>>>> I expect other protocols than Ethernet may have a priority field that may or >>>>>> may not be mapped to the DSCP field of the tunnel packet. >>>>>> >>>>>> I would expect that for new protocol registration in the LISP-GPE Next Protocol >>>>>> Registry should consider this. Thus, it would be good to note that such >>>>>> considerations are needed and part of what should be evaluated for new >>>>>> registrations. >>>>>> >>>>>> D. ECN handling >>>>>> >>>>>> Section 5.3 of draft-ietf-lisp-rfc6830bis states: >>>>>> >>>>>> o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 >>>>>> of the IPv6 'Traffic Class' field) requires special treatment in >>>>>> order to avoid discarding indications of congestion [RFC3168]. >>>>>> ITR encapsulation MUST copy the 2-bit 'ECN' field from the inner >>>>>> header to the outer header. Re-encapsulation MUST copy the 2-bit >>>>>> 'ECN' field from the stripped outer header to the new outer >>>>>> header. >>>>>> >>>>>> The above rules may not be applicable for all transport protocols. Thus I think >>>>>> it is required that one do protocol specific considerations of ECN. TSVWG are >>>>>> working on recommendations for tunnels handling of ECN here, see: >>>>>> https://datatracker.ietf.org/doc/draft-ietf-tsvwg-ecn-encap-guidelines/ Thus, >>>>>> my expectation would be to ensure that the registered protocols have defined >>>>>> ECN handling, explicitly or by reference. Secondly that registration >>>>>> requirement states the need for this consideration. >>>>>> >>>>>> Summary: To ensure that future added protocols that are encapsulated will work >>>>>> well from a transport interaction perspective there need to be a requirement on >>>>>> new registration to consider and define how they use zero checksum, any DSCP >>>>>> mapping and ECN bits. In addition the current document needs to ensure these >>>>>> things are clearly specified for the encapsulated protocols in this document. >>>>>> >>>>>> >>>>> >>>> -- >>>> >>>> Magnus Westerlund >>>> >>>> ---------------------------------------------------------------------- >>>> Network Architecture & Protocols, Ericsson Research >>>> ---------------------------------------------------------------------- >>>> Ericsson AB | Phone +46 10 7148287 >>>> Torshamnsgatan 23 | Mobile +46 73 0949079 >>>> SE-164 80 Stockholm, Sweden | mailto:magnus.westerlund@ericsson.com >>>> ---------------------------------------------------------------------- >>> >>> >> >
- [Tsv-art] Tsvart last call review of draft-ietf-l… Magnus Westerlund
- Re: [Tsv-art] Tsvart last call review of draft-ie… Fabio Maino
- Re: [Tsv-art] Tsvart last call review of draft-ie… BRUNGARD, DEBORAH A
- Re: [Tsv-art] Tsvart last call review of draft-ie… Magnus Westerlund
- Re: [Tsv-art] Tsvart last call review of draft-ie… Magnus Westerlund
- Re: [Tsv-art] Tsvart last call review of draft-ie… BRUNGARD, DEBORAH A
- Re: [Tsv-art] Tsvart last call review of draft-ie… Magnus Westerlund
- Re: [Tsv-art] Tsvart last call review of draft-ie… Fabio Maino
- Re: [Tsv-art] Tsvart last call review of draft-ie… Fabio Maino
- Re: [Tsv-art] Tsvart last call review of draft-ie… Luigi Iannone
- Re: [Tsv-art] Tsvart last call review of draft-ie… Fabio Maino