Re: [bess] draft-hao-bess-inter-nvo3-vpn-optionc

[<[e-mail]>]

2015-11-19, Henderickx, Wim (Wim):
> WH> I vote for a an evolution of switches/TORs that have proper
> support for this. I hope some HW vendors of TOR chips shime in, but I
> am told the MPLS solution is possible in the next generation chips
> they are working on.

Well, it looks like the key questions are:
- when would ToR chips support MPLS/MPLS/UDP ?  (the generation that has 
been released recently but not present in most shipping ToRs yet, the 
next one ?)
- do we want an interim VXLAN-based solution ? (that will involve at 
best a performance penalty with existing chips, and at worse impossible 
to implement -- we haven't seen clear information in this thread)

-Thomas


>> Zhuangshunwan  :
>>>
>>> Hi Diego,
>>>
>>> Thanks for your comments. Pls see inline with [Vincent].
>>>
>>> Vincent
>>>
>>> *发件人:*BESS [mailto:[e-mail]] *代表 *Diego Garcia del
>>> Rio *发送时间:*2015年11月18日14:25 *收件人:*[e-mail] *主题:*Re: [bess]
>>> draft-hao-bess-inter-nvo3-vpn-optionc
>>>
>>> Some comments from my side, I think the draft makes quite a few
>>> assumptions on specific implementation details that are way too
>>> general to be considered widely available. Most of the TOR
>>> devices today already pay a double-pass penalty when doing
>>> routing of traffic in/out of vxlan-type tunnels. Only the newest
>>> generation can route into tunnels without additional passes. And
>>> are definitively limited in being able to arbitrary select UDP
>>> ports on a per tunnel basis. In fact, most are even limited at
>>> using more than one VNID per "service" of sorts. [Vincent]: Yes,
>>> the new generation BCM chipset has already supported VXLAN
>>> routing without additional passes. For OVS/TOR, VXLAN
>>> encapsulation is more popular than MPLSoGRE/UDP, and has better
>>> performance. The IP-addressed based implementation which would, I
>>> assume, imply assigning one or more CIDRs to a loopback interface
>>> on the ASBR-d is also quite arbitrary and does not seem like a
>>> technically "clean" solution. (besides burning tons of IPs). As a
>>> side-note, most PE-grade routers i've worked with were quite
>>> limited in terms of IP addresses used for tunnel termination and
>>> it wasn't that just a simple pool can be used. [Vincent]: I think
>>> the larger VTEP IP address range on ASBR-d has no limitations.
>>> For the hardware on ASBR-d, it has capability to terminate
>>> multiple VXLAN tunnels with arbitrary destination VTEP IP
>>> addresses. Wim's mentions on cases where the Application itself,
>>> hosted in a datacenter, would be part of the option-C
>>> interconnect, was dismissed without much discussion so far,
>>> while, if we look in detail at the type of users which will even
>>> consider a complex topology like model-C its most likely users
>>> and operators very familiar with MPLS VPNs in the WAN. Those type
>>> of operators will most likely be very interested in deploying
>>> MPLS or WAN-grade applications (i.e., virtual-routers or other
>>> VNFs) in the DC and thus its highly likely that the interconnect
>>> would not terminate at the NVE itself but rather the TS (the
>>> virtual machine). Also, the use of UDP ports at random would
>>> imply quite complex logic on the ASBR-d IMHO. Im not saying its
>>> impossible, but since the received packet now not only has to be
>>> received on a random (though locally chosen) UDP port and this
>>> information preserved in the pipeline to be able to do the
>>> double-tunnel-stitching, it sounds quite complex. I am sure
>>> someone in the list will mention this has already been
>>> implemented somewhere, and I won't argue with that. And let's
>>> not even bring into account what this would do to any DC
>>> middlebox that now has to look at vxlan over almost any random
>>> port. We have to go back to the "is it a 4 or is it a 6 in byte
>>> x" heuristics to try to guess whether the packet is vxlan or just
>>> something entirely different running over IP. [Vincent]: Using NP
>>> or multi-core CPU hardware technology, it can be implemented
>>> although deeper packet inspection is needed to perform UDP port
>>> and MPLS stitching. In general I feel the proposed solution seems
>>> to be fitting of a specific use-case which is not really detailed
>>> in the draft and does not describe   a solution that would
>>> "elegantly" solve the issues at hand. It just feels like we're
>>> using any available bit-space to stuff data into places that do
>>> not necesarily belong. Yes, MPLS encapsulations on virtual
>>> switches are not yet fully available, and there can be some
>>> performance penalty on the TORs, but the solutions are much
>>> cleaner from a control and data plane point of view. Maybe I'm
>>> too utopic. [Vincent]: I think pure VXLAN solution has its
>>> scenario, it's general rather than specific. We can't require all
>>> OVS/NVEs support VXLAN + MPLSoGRE at the same time. Best
>>> regards, Diego
>>> ---------------------------------------------------------------------------------
>>>
>>>
Hi,
>>> The problem we are trying to solve is to reduce data center
>>> GW/ASBR-d's forwarding table size, the motivation is same as
>>> traditional MPLS VPN option-C. Currently, the most common
>>> practise on ASBR-d is to terminate VXLAN encapsulation, look up
>>> local routing table, and then perform MPLS encapsulation to the
>>> WAN network. ASBR-d needs to maintain all VM's MAC/IP. In
>>> Option-C method, only transport layer information needed to be
>>> maintained at GW/ASBR-d, the scalability will be greatly
>>> enhanced. Traditonal Option-C is only for MPLS VPN network
>>> interworking, because VXLAN is becoming pervasive in data center,
>>> the solution in this draft was proposed for the heterogeneous
>>> network interworking. The advantage of this solution is that only
>>> VXLAN encapsulation is required for OVS/TOR. Unlike Wim's
>>> solution, east-west bound traffic uses VXLAN encap, while
>>> north-south bound traffic uses MPLSoGRE/UDP encap. There are two
>>> solutions in this draft: 1. Using VXLAN tunnel destination IP for
>>> stitching at ASBR-d. No data plane modification requirements on
>>> OVS or TOR switches, only hardware changes on ASBR-d. ASBR-d
>>> normally is router, it has capability to realize the hardware
>>> changes. It will consume many IP addresses and the IP pool for
>>> allocation needs to be configured on ASBR-d beforehand. 2. Using
>>> VXLAN destination UDP port for stitching at ASBR-d. Compared with
>>> solution 1, less IP address will be consumed for allocation. If
>>> UDP port range is too large, we can combine with solution 1 and
>>> 2. In this solution, both data plane modification changes are
>>> needed at OVS/TOR and ASBR-d. ASBR-d also has capability to
>>> realize the hardware changes. For OVS, it also can realize the
>>> data plane changes. For TOR switch, it normally can't realize
>>> this function.  This solution mainly focuses on pure software
>>> based overlay network, it has more scalability. In public cloud
>>> data center, software based overlay network is the majority
>>> case. Whether using solution 1 or 2 depends on the operators real
>>> envionment. So I think our solution has no flaws, it works fine.
>>> Thanks, weiguo ________________________________ From: BESS
>>> [[e-mail] <mailto:[e-mail]>] on behalf
>>> of John E Drake [[e-mail] <mailto:[e-mail]>]
>>> Sent: Wednesday, November 18, 2015 2:49 To: Henderickx, Wim
>>> (Wim); EXT - [e-mail]
>>> <mailto:[e-mail]>; BESS Subject: Re: [bess]
>>> draft-hao-bess-inter-nvo3-vpn-optionc Hi, I think Wim has
>>> conclusively demonstrated that this draft has fatal flaws and I
>>> don’t support it.  I also agree with his suggestion that we first
>>> figure out what problem we are trying to solve before solving
>>> it. Yours Irrespectively, John From: BESS
>>> [mailto:[e-mail] <mailto:[e-mail]>] On
>>> Behalf Of Henderickx, Wim (Wim) Sent: Tuesday, November 17, 2015
>>> 12:49 PM To: EXT - [e-mail]
>>> <mailto:[e-mail]>; BESS Subject: Re: [bess]
>>> draft-hao-bess-inter-nvo3-vpn-optionc — Snip — No, the spec as it
>>> is can be implemented in its VXLAN variant with existing
>>> vswitches (e.g. OVS allows to choose the VXLAN destination port,
>>> ditto for the linux kernel stack). (ToR is certainly another
>>> story, most of them not having a flexible enough VXLAN dataplane
>>> nor support for any MPLS-over-IP.) WH> and how many ports
>>> simultaneously would they support? For this to work every tenant
>>> needs a different VXLAN UDP destination port/receive port. There
>>> might be SW elements that could do some of this, but IETF defines
>>> solutions which should be implemented across the board HW/SW/etc.
>>> Even if some SW switches can do this, the proposal will impose so
>>> many issues in HW/data-plane engines that I cannot be behind this
>>> solution. To make this work generically we will have to make
>>> changes anyhow. Given this, we better do it in the right way and
>>> guide the industry to a solution which does not imply those
>>> complexities. Otherwise we will stick with these specials forever
>>> with all consequences (bugs, etc). - snip - From:
>>> "[e-mail]
>>> <mailto:[e-mail]><mailto:[e-mail]
>>> <mailto:[e-mail]>>" <[e-mail]
>>> <mailto:[e-mail]><mailto:[e-mail]
>>> <mailto:[e-mail]>>> Organization: Orange Date:
>>> Tuesday 17 November 2015 at 01:37 To: Wim Henderickx
>>> <[e-mail]
>>> <mailto:[e-mail]><mailto:[e-mail]
>>>
>>>
<mailto:[e-mail]>>>, BESS <[e-mail]
>>> <mailto:[e-mail]><mailto:[e-mail]
>>> <mailto:[e-mail]>>> Subject: Re: [bess]
>>> draft-hao-bess-inter-nvo3-vpn-optionc Hi Wim, WG, 2015-11-16,
>>> Henderickx, Wim (Wim): 2015-11-13, Henderickx, Wim (Wim): Thomas,
>>> we can discuss forever and someone need to describe requirements,
>>> but the current proposal I cannot agree to for the reasons
>>> explained. TM> Well, although discussing forever is certainly not
>>> the goal, the reasons for rejecting a proposal need to be
>>> thoroughly understood. WH> my point is what is the real driver
>>> for supporting a plain VXLAN data-plane here, the use cases I
>>> have seen in this txt is always where an application behind a
>>> NVE/TOR is demanding option c, but none of the NVE/TOR elements.
>>> My understanding is that the applications  are contexts where
>>> overlays are present is when workloads (VMs or baremetal) need to
>>> be interconnected with VPNs. In these contexts, there can be
>>> reasons to want Option C to reduce the state on ASBRs. In these
>>> context, its not the workload (VM or baremetal) that would
>>> typically handle VRFs, but really the vswitch or ToR. WH2> can it
>>> not be all cases: TOR/vswitch/Application. I would make the
>>> solution flexible to support all of these not? 2015-11-13,
>>> Henderickx, Wim (Wim): TM> The right trade-off to make may in
>>> fact depend on whether you prefer: (a) a new dataplane stitching
>>> behavior on DC ASBRs (the behavior specified in this draft) or
>>> (b) an evolution of the encaps on the vswitches and ToRs to
>>> support MPLS/MPLS/(UDP or GRE) WH> b depends on the use case I
>>> don't get what you mean by "b depends on the use case". WH> see
>>> my above comment. If the real use case is an application behind
>>> NVE/TOR requiring model C, than all the discussion on impact on
>>> NVE/TOR is void. As such I want to have a discussion on the real
>>> driver/requirement for option c interworking with an IP based
>>> Fabric. Although I can agree than detailing requirements can
>>> always help, I don't think one can assume a certain application
>>> to dismiss the proposal. WH> for me the proposal is not
>>> acceptable for the reasons explained: too much impact on the
>>> data-planes I wrote the above based on the idea that the encap
>>> used in MPLS/MPLS/(UDP or GRE), which hence has to be supported
>>> on the ToRs and vswitches. Another possibility would be
>>> service-label/middle-label/Ethernet assuming an L2 adjacency
>>> between vswitches/ToRs and ASBRs, but this certainly does not
>>> match your typical DC architecture. Or perhaps had you something
>>> else in mind ? WH> see above. The draft right now also requires
>>> changes in existing TOR/NVE so for me all this discussion/debate
>>> is void. No, the spec as it is can be implemented in its VXLAN
>>> variant with existing vswitches (e.g. OVS allows to choose the
>>> VXLAN destination port, ditto for the linux kernel stack). (ToR
>>> is certainly another story, most of them not having a flexible
>>> enough VXLAN dataplane nor support for any MPLS-over-IP.) WH> and
>>> how many ports simultaneously would they support? WH> and
>>> depending on implementation you don’t need to change any of the
>>> TOR/vswitches. Does this mean that for some implementations you
>>> may not need to change any of the TOR/vswitches, but that for
>>> some others you may ? WH> any proposal on the table requires
>>> changes, so for me this is not a valid discussion See above, the
>>> proposal in the draft does not necessarily need changes in
>>> vswitches. Let me take a practical example : while I can quite
>>> easily see how to implement the procedures in
>>> draft-hao-bess-inter-nvo3-vpn-optionc based on current vswitch
>>> implementations of VXLAN, the lack of MPLS/MPLS/(UDP, GRE)
>>> support in commonplace vswitches seems to me as making that
>>> alternate solution you suggest harder to implement. WH> I would
>>> disagree to this. Tell me which switch/TOR handles multiple UDP
>>> ports for VXLAN ? I mentioned _v_switches, and many do support a
>>> variable destination port for VXLAN, which is sufficient to
>>> implement what the draft proposes. -Thomas From: Thomas Morin
>>> <[e-mail]
>>> <mailto:[e-mail]><mailto:[e-mail]
>>> <mailto:[e-mail]>>> Organization: Orange Date:
>>> Friday 13 November 2015 at 09:57 To: Wim Henderickx
>>> <[e-mail]
>>> <mailto:[e-mail]><mailto:[e-mail]
>>>
>>>
<mailto:[e-mail]>>>
>>> Cc: "[e-mail] <mailto:[e-mail]><mailto:[e-mail]
>>> <mailto:[e-mail]>>" <[e-mail]
>>> <mailto:[e-mail]><mailto:[e-mail]
>>> <mailto:[e-mail]>>> Subject: Re: [bess]
>>> draft-hao-bess-inter-nvo3-vpn-optionc Hi Wim, I agree on the
>>> analysis that this proposal is restricted to implementations that
>>> supports the chosen encap with non-IANA ports (which may be hard
>>> to achieve for instance on hardware implementations, as you
>>> suggest), or to context where managing multiple IPs would be
>>> operationally viable. However, it does not seem obvious to me how
>>> the alternative you propose [relying on 3-label option C with an
>>> MPLS/MPLS/(UDP|GRE) encap] addresses the issue of whether the
>>> encap behavior is supported or not (e.g. your typical ToR chipset
>>> possibly may not support this kind of encap,  and even
>>> software-based switches may not be ready to support that today).
>>> My take is that having different options to adapt to various
>>> implementations constraints we may have would have value. (+ one
>>> question below on VXLAN...) -Thomas 2015-11-12, Henderickx, Wim
>>> (Wim): On VXLAN/NVGRE, do you challenge the fact that they would
>>> be used with a dummy MAC address that would be replaced by the
>>> right MAC by a sender based on an ARP request when needed ? Is
>>> the above the issue you had in mind about VXLAN and NVGRE ? WH>
>>> yes I you don't mind me asking : why do you challenge that ?
>>>

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