Please add your name to the Virtual Blue sheet: Lou Berger Stewart Bryant Balazs Varga Jouni Korhonen Loa Andersson Toerless Eckert Jean-Yves Le Boudec Hao Wang Pascal Thubert Dan Romascanu Ethan Grossman Norman Finn János Farkas Damien Saucez Vishnu.N Recording: https://ietf.webex.com/ietf/ldr.php?RCID=e5116bc7db254c24a7bb3217bf202301 > Agenda for DetNet Virtual Interim Meeting February 14, 2018 > > Session Information: > > Webex: > https://ietf.webex.com/ietf/j.php?MTID=mca0b929db5297a5867bc7585429ad35b > Etherpad: > http://etherpad.tools.ietf.org:9000/p/notes-ietf-interim-2018-detnet-03 > Online Agenda and Slides at: > https://datatracker.ietf.org/meeting/interim-2018-detnet-03/session/detnet > > Duration: 90 min with 30 minute extra discussion time if needed > > The agenda is: > - Administrativa (chairs) > - Draft status update (authors) > see https://tools.ietf.org/html/draft-ietf-detnet-dp-sol > https://github.com/jounikor/draft-dt-detnet-dp-sol Agenda Bash Balasz contrib is about MPLS over IP which doesn't address point to point which is the main agenda this session so he will present second. Norm would like to talk Architetcure > - Contributions to address open issues (contributors) Lou: How to do end to end. CW as way to support PRE.F. Lou: 3 services all part of DetNet. Simplification to support IPv4 Norm: Transit node is PREF unaware Pascal :Transit node doing transport, relay node doing service Norm: PREF aware != DetNet aware - use phrase carefully Stewart: BW, Latency, just need alternate path (i.e. not necc PREF?) Pascal: Could provide transport services at higher layer but outside DetNet scope Loa: Should be "transport network" - to revisit in arch doc Lou: Expecting to be just presenting existing arch. TSN over DetNet slide: Lou: TSN over DetNet CW work not done yet. Norm: Do these cases cover subnet on each end, but detnet does not provide L2 connectivity - network too big to be bridged, want routed. Lou: That is IPvX end to end slide case. A DetNet relay node is always a router. Norm: No interworking? Lou: Don't need for DP-SOL. Currently focusing on how to do IP end to end. Stewart: Why interworking not just working? Lou: topic for later discusssion Toerless: Complexity is that IP can't use CW, only MPLS can, so always have to deal with two systems Lou: Proxy maps TSN CW into DetNet CW. Don't have spec for that proxy yet. Norm: OK to put that off for now. Lou: Good topic for future discussion once we have basics defined. Janos: Support Lou on doing basics first. Lou: Have DetNet CW and MPLS so can be used in both pictures. But as long as service is provided, don't absolutely have to use CW, e.g. router with dedicated service. Balazs: Lou: Not req'd to have MPLS. In IP wouldn't have PREF but could be provided at higher layer. (Focus Today's Discussion slide) Jouni slides: https://datatracker.ietf.org/doc/slides-interim-2018-detnet-03-sessa-ip-based-e2e-detnet-ts-flow-over-detnet-subnets/ Norm: If separate flows arrive separately do they have to have same seq num? Jouni: Somehow have to understand they are the same flow so would use TSN methods e.g. PREF Norm: Just making sure seq numbering is done before replication. Agree? Jouni: Yes. Stewart: Why interworking not just tunneling over MPLS? Norm: Not interworking. Jouni: At some point, we need to address how to handle two routers interconnecting IP subnets when replicated packets arrive at different routers Ethan: I though your were saying on a singl router could interconnect the routed subnets Stewart: Could bring multiple flows through domains? Isn't seq num put in by source? Lou: Agreed to table complex discussion of IP based PREF to the future. Do we need IP PREF to start? Can we go forward w/o IP PREF? Toerless: How would an IP application do PREF? Lou: Only within blue clouds, each may have its own PREF mechanism, independent of each other. Norm: Dual-homed host could generate two flows but would need seq numbering Stewart: Why do we need PREF in MPLS but not needed in IP? Lou: Issue is complexity of PREF over IP - just trying to simplify for now to go forward. Pascal - Could do at Layer 4 Jouni: Assuming DetNet aware endstation vs TSN aware endstation? At edge of domain, have weakness since not overall end to end reliability, but within domain can be made reliable. With this simplification is easier to make it work. Toerless: W/o sender providing control word how can it send redundant streams? Lou: Two separate flows, done at transport. Toerless: How is that then part of DetNet service? Pascal: Part of service at layer 3, part at layer 4 Lou: Simplified version that works with IPv4/6 Toerless: Not worth discussing if orthogonal to DetNet. Get redundant transmission over diff't path - this could be done w/o control word. Only end-to-end service is Norm: Can do that now Toerless: Current in-scope solution - can't claim end to end sol'n w/o seq num Lou: Can provide rest of DetNet, just not guarantee end to end. Toerless: If can check timestamps can check if packets delivered on time. Else not. Lou: Congestion protection and explicit routes - our claim is that in this version we could do these two out of three. Toerless: If had timestamp like RTP could verify, not currently possible over MPLS. Want to make clear which services can be provided and which not Balazs: In figure, 3 domains. If each domain has its own seq num, can't PREF accorss domains. IF do have have seq num then can go across domains. Would prefer global option to place R&E anywhere - ultimate goal. Could have independent paths, only endpoints couild do elimination. If can correlate seq nums between domains then could coordinate. Norm: Agree with Balazs, this is interworking. End station in TSN station is doing IP, may or may not know if local cloud is bridged or routed - just puts packets onto ethernet. End station could put seq num into IP encap, 802.1CB fine with that. Could enable CB to . If not talking about seq num just have to recognize the flow. Lou: Fundamental question for group: Do we focus on delivering 2 of 3 services (congestion protection, latency control, explicit routes)(no pref, no in order delivery). Advantage we don't have to modify IP. Do we want to do that? Norm: DetNet doesn't have to do explicit routes, lots of that out there. Regarding latency bounds, done by IntServ long time ago. Balazs: If pushing Stewart: Concerned about too much complexity, should be doing layered sol'n. Independent of other layers. Agree already some already widely deployed, and issues in routing layer to make them usable and manageable. Norm: Do we need to do that? Stewart: Someone in IETF, maybe not us. Jouni: At left (in IPvx e-e service slide) . Is DetNet End system at left TSN aware? Lou: If want end to end guarantee then I Balazs: Layer 4 is only end to end systems Jouni: In this picture only have IP addr that system knows how to map to transport. End system is TSN aware. Assume for now transports are TSN aware. So packet goes out with duplicate streams. Hit first router, talks TSN to left, MPLS to right. Is that MPLS DetNet aware? Lou: Understands how to do congestion protection ,but doesn't know CW Jouni: So each domain would have own seq number? Norm: Duplicating at TSN layer at source, elim at end station? Jouni: Not neccessarily - would have to happen before exit domain. Norm: Guy who does elim has to be peer of who does sequencing. Either same encapsulation or interworking Stewart: Or proxy that helps. Norm: Can't replicate before adding seq num. Jouni: Restriction is have to terminate at single point before exit domain. Lou: Dotted lines are PREF domains. Dupl at ingress, elim at egress. That is the point of this picture (ipvx e-e service slide) Stewart: Need to call out layers individually, getting too munged together in these diagrams. Lou: Marked L4 transport to make it clearer. Pascal: in this topology ingress and egress routers are single point of failure. Jouni: Yes, but that gets hard to fix, and doesn't require header additions. Lou: So is this limitation acceptable for initial DetNet sol'n? Stewart: Exact proposal is? Lou: Jounis from last session. Service protection only provided within subnet. Stewart: Could have e-e PREF, everything, going through relay nodes. Lou: Could do that in follow-on. Stewart: Can do PREF etc within domains. Pat: Question being asked is can we get by without an end to end solution for service protection. Stewart: Could do at layer 4. Lou: yes, thus not part of DetNet. Just because doing it at layer 4 doesn't mean we don't do it in DetNet Jouni: For IPv6 have extensions that are handled at L4. That started to look ugly particularly with IPv4, that's why we came here. Stewart: IP extension headers are layer 3. Jouni: Trying to cover IPv4 thus had to drop use of extension headers. Pascal: DetNet incapsulating one flow inside another. IP matches transport services. If L4 provides service layer, then if tunnel that through MPLS which is DetNet aware and provides service, then fits nicely. Norm: Agree, saying that for IP only not doing PREF, seq numbers. OK with that. No conflict with L4 xport, people can use dual paths at L4, we are not making that illegal, but not part of DetNet. OK with our DP sol'n not including PREF and seq num aspects of DetNet. Pascal: Yes, agree. (Balazs slides) https://datatracker.ietf.org/doc/slides-interim-2018-detnet-03-sessa-ip-psns/ Balazs: (slide 3) RFC3985 Stewart : How to carry IP over MPLS? Balazs: Have encapsulation w/ magic enet addrs + CW. Stewart: Encapsulate IP over Ethernet, then Ethernet over MPLS. Is that the best thing? Assume OK for now. Lou: Think there is a defintion of IP w/ control word but no Ethernet Stewart: Not sure but could create it. That RFC was done to solve a different problem. Balazs: Do we need different DN PW format for IP and MPLS? Why? Balazs: Industrial example: Don't already have MPLS. Would like to put PREF points anywhere. Don't need interworking at border of domains. Stewart: With PW, a connection accross MPLS domain, know context of Seq Num. Do we know this in IP PSN example? Balazs: Edge node will create CW and seq num. Stewart: Creating a point to point tunnel so have all context Balazs: Yes Stewart: Stitch tunnels across domains. Lou: Don't care how tunnel across networks? Could aggregate or have flow per tunnel. Janos: As Lou explains, has boundaries at edge of domains. Pascal: Packet source/dest IP from source Balazs: In Lou: green triangle is not edge node - is PE. So how to get e-e DetNet service? Balazs: If in single box then get this service. Lou: If have a LAN with DetNet aware hosts, single IP subnet - do we get e-e service, one hop? Balazs: Yes, using PW and CW Lou: Where is PW CW get inserted? B: Between application and IP L: So socket would have param to specify this? Norm: Wherever you do sequencing has to either have encapsulation or interworking. Can have either peers or interworking. Multiple layers involved in sequencing and elim. Janos: Agree Norm: Likes IP over CW Lou: We are doing DetNet CW so just context and CW. Moved away from this kind of complexity on host. Norm: If want end station must do seq num before replicate. I.e. has to do encaps. Stewart: Agree. Lou: Existing encaps include CW, label, always uses UDP? Stewart: If doing at PW layer need label. Lou: 64-bit wide field. Stewart: yes. Prob with upper (IP PSN) example: Firewall and NAT won't like it. Balazs: with firewall second example is better. But might be OK to assume no firewall given engineered network. Norm: App PDU contains IP header? Lou: Not if comes from "green triangle" Stewart: IP pushed to socket layer Norm: IP next fields says MPLS, IANA code point. Lou: IP dest addrs is green triangle Norm: what is label sequence: . . . (?) Lou: Host stack harder to implement than router stack, Norm: 802 has notion of encap shim - can tell host what encaps know how to handle. Host will then use one of them. Taken care of stripping out before hitting IP layer, e.g. seq num. Jouni: Balazs said appl PDU also contains IP header? Balazs: Only true if ... Jouni: What happens if end system talks app PDU over IP? LOU: Case where CW is stripped: PE reaches into packet? Why not layer that? Please repeat: Balazs: PW and an MPLS label (3x32-bit?) Lou: Next protocol is MPLS? Stewart: Why not re-encapsulate? Would simplify? Jouni: Multiple flows into MPLS domain via diff't PEs, want to do PREF inside domain. Stewart: Would have to reach in to get CW? Janos: If appl puts seq num, then requires Stewart: Dangerous, better to do in separate layers Jouni: Then we're back to same proposal before this preso. Balazs: Same domain, then can do seq numbering. Norm: Yes, main reason to do this. But if doing e-e with source doing repl and end stn doing elim, don't need detnet, since other systems do this. Lou: Let's try to recap, get impressions of group Stewart: Only have 20 bits of PW, so need context as identifier Balazs: yes. Lou: Unified ipvx e-e service slide. PREF domain end to end, multiple routers. Requires seq num Other sol'n means lose PREF but no change required to host in terms of data plane. Would need control plane changes. Layer 4 not the domain of DetNet. Could be used but we don't specify here, now. Opinions from the group: Options: Which to focus on? Put response in chat: Focus on end systems. unified (8 for slide 8) (modified host, CW + PW, but get e-e and nested, laddered service protection). simplified (7 slide 7) can do 7 now 8 later (no mods to host DP, no e-e service protection, only sausage approach) Norm: If doing 7, do we need to specify anything at all? Lou: Service params to be specified on host, maybe mapping to TSN Pascal: D-CW is Jouni: Sol'n 8 is original proposal. Janos: Yes. As proposed by design team. Stewart: Does 8 require interaraction between domains? So vote for 8 doesn't commit to poking around in packet to make it work? Lou: correct, just more discussion. (some votes not cast yet, meeting time is over). Jouni: For HW based stack is harder. (NIC w/ HW offload) Stewart: Suspect will have to do 7 then do 8 as perf agreement. 8 is complex, should push this out. Norm: Would not do 8 w/o 7. Lou: Can we live with "only" 7? If only had one, could you live with it? Norm: Doesn't make sense - are we saying end station can't provide a seq num? Lou: Agree, that was a failed idea. Add new option: 7 now 8 later. Stewart. If do 7 only, then any end station can do what they want at appl layer e.g. PREF. Norm: But can't do e.g. Ladder. Pascal: But is much nicer if network can provide e-e service. Stewart: Only peek as far as the ports. So go deeper than just 5 tuple Norm: Must do 7 no matter what. Do we do 8 now or later? Stewart: If 8 done at L4, we're done Norm: Don't need to define that in DetNet, various ways to do it. Norm: Do we do 8 now or later? Lou: Have not made enough progress in our drafts, would prefer to complete 7 before doing 8. Norm: Agree. Stewart: Why can't we leave service protection to L4? Norm: I'll explain it to you later. Stewart: If we do 7 w/o accounting for 8 in advance will we risk boxing ourselves into a corner? Norm: No, 8 is already in arch. Lou: Do authors feel they have enough bandwidth to document 7? What text do you need? Lou: No response from authors. do you want anything from anyone on the call to document 7? Jouni: Send me anything you have. Lou: Can we come back in 2 weeks and have a proposal for 7? Jouni: Unlikely for Jouni to do alone, travelling one week. Lou: Designate someone to take lead on 7? Balazs: Will take lead on 8 Lou: Cutoff date for drafts is in 4 weeks. Can't hae another interim. March 5 cutoff, during 802 meeting so no 802 people likely to work on it. Jouni to take lead on 7 Jouni: OK. Lou: could do separate subsections for now, split doc later. Norm: Anything to be done to Arch other than make sure network coding back in, and separate PR and EF. Rename transport, need better term. Pascal: Flow inside another flow - maybe could desrcribe that more? Norm: Mention that must aggregate to scale Pascal: Jouni's doc adds more? Lou: Propose on list Pascal: Already did? Norm: Don't want to add new concepts to Arch. Put suggestions on list. Pascal: Endorsing what is in data plane draft. Norm: Is this the last interim? Lou: Correct, no time according to IETF process. Lou: In London, only on Friday, same day as regular session. Stewart: Clashes on time? Lou: Told no clashes on what they requested. Norm: 802 Interim in Pittsburgh, could join? Talk to Glenn Parsons to arrange? Pat: Would have to pay IEEE fee for whole week, might be able to work out. 5 day meeting using all days. Would have to be before or after. Just useful for co-location. Pat: Maybe nearby hub city, e.g. Wash DC Janos: Could host in Budapest To be discussed offline. > - Next steps, including future meetings > > [1] https://tools.ietf.org/html/draft-ietf-detnet-dp-sol-01 > > [2] IETF 100 open issues: > https://datatracker.ietf.org/meeting/100/materials/slides-100-detnet-3-detnet-data-plane-encapsulation-resolving-open-issues/ > > [3] IETF 100 open issues - PREF: > https://datatracker.ietf.org/meeting/100/materials/slides-100-detnet-3a-detnet-data-plane-encapsulation-resolving-open-issues-pref/ > > [4] 1st DetNet Interim: > https://datatracker.ietf.org/meeting/interim-2018-detnet-01/session/detnet > > [5] 2nd DetNet Interim: > https://datatracker.ietf.org/meeting/interim-2018-detnet-02/session/detnet > > >