Re: [bess] Questions to draft-dawra-bess-srv6-services-02

[Gyan Mishra <[e-mail]>]

Hi Robert

in-line responses

Thank you

Gyan

On Thu, Oct 3, 2019 at 7:29 PM Robert Raszuk <[e-mail]> wrote:

> Hello Gyan,
>
> I have read your comment few times. but can't parse it.
>

    OK  let me try to clarify

>
> Is this a question ? A concern ? Just comment ?
>
>
    Question & Comment I guess let me try and rephrase


> You say:
>
> "Is that true and if so that is a major design concern for migration of
> customers to a SRv6 core."
>
> But what is that ? I am very happy to answer any questions you may have in
> honest way, but just need to understand what the question really is.
>
>     So "that" is the BGP services provided by an SRv6 service provider
that if AFI/SAFI  does not change for L3 VPN services and any underlying L3
protocols do not change then it does make SRv6 more viable without major
code rewriting and I believe that is what the purpose of this draft that it
is stating that the overlay services edges at the PE edge weather its L3
VPN vpnv4/vpnv6 6PE/6VPE, MVPN, EVPN whatever that service maybe all of
that will still work but now its just the flow is encapsulated in IPv6 SRv6
EH SRH header inserted by the source node and SID's copied hop by hop to
the destination for the hop by hop Ti-LFA traffic engineered path over the
service provider core.

In the draft I am talking about sections 3.1-vpnv4,3.2 vpnv6 ,3.3 ipv4,3.4
ipv6 4. evpn - that their AFI/SAFI remain the unchanged and will continue
to work as they do today providing seamless migration with what I said
swapping out the "topmost label" which is in MPLS terms but in the SRv6
world  instead of having an MPLS LDP shim now you have IPv6 encapsulation
of the L3 vpn services label using either RFC 4797 or RFC 7510 or new EH
encoding method.

So this is really the crux of it and critical for SRv6 to gain traction and
get of the ground  is having consensus on this draft as BESS WG is
providing the framework for existing technologies AFI/SAFI bgp "services"
to be used over SRv6.  So not having to reinvent the wheel and create a
request for IANA for any new AFI/SAFI for SRv6 as the existing address
families can all be "reused" with SRv6.  The main thing is figuring out
what encapsulation method to use for the L3 VPN label.

Regarding the L3 VPN service label and how that would get encapsulated in
SRv6 you mentioned existing methods using GRE/MPLS RFC 4797 or UDP/MPLS RFC
7510 or a new encoding of VPN label into SRH.  In the draft are you keeping
both options open for the operator to make a decision based on many factors
whichever works best for their environment?  With the later option encoing
VPN label into SRH would you save on overhead bytes from the encapsulation
I am guessing.  What is the benefit of one over the other.  Also when
encapsulating the L3 VPN service label traditionally in an MPLS
environement you only have the VPN label 4 byte shim added to the bottom of
the label stack but now with RFC 4797 with GRE you add extra 24 GRE/IP
bytes and with UDP/MPLS 8 bytes.


> Thx,
> R.
>
> On Fri, Oct 4, 2019 at 1:03 AM Gyan Mishra <[e-mail]> wrote:
>
>>
>> Hi Robert
>>
>> In-line question
>>
>> Sent from my iPhone
>>
>> On Oct 3, 2019, at 11:01 AM, Robert Raszuk <[e-mail]> wrote:
>>
>> Hi Linda,
>>
>> Nope. Nodes except egress have any reason to look at VPN label. That
>> label has only local significance on egress.
>>
>> Thx,
>> R.
>>
>>
>> Robert
>>
>> From an operator perspective ease of implementation and migration is
>> critical to deployment.
>>
>> So just as with SR-MPLS where you can prefer SR over mpls and it’s a swap
>> of the “topmost label” in the label stack and all VPN services label at the
>> bottom of the stack remain unchanged.  Drawing an analogy to SRv6 scenario
>> that would it be exactly the same it sounds like that L3 VPN vpn label
>> remains intact for vpnv4 vpnv6 scenario and IP native native IPv4 / IPv6
>> encapsulation IP/MPLS remains the same no change and it’s just the
>> “topmost” label gets swapped out from either legacy mpls LDP/TE to either
>> SR-MPLS or now SRv6 topmost label. The services bottom label are only
>> imposed by ingress PE as with legacy mpls and per SRv6 End SID programming
>> is either PSP or USP popped similar to legacy mpls PHP UHP and VPN label is
>> then processed by the egress PE identical to how it’s done with SR-MPLS or
>> legacy mpls.
>>
>> So from an operator perspective such as Verizon that does make it
>> attractive and an easy swap out migration or new green field implementation
>> to migrate to SRv6 as all the customer Edge PE-CE protocols and
>> encapsulation VPN related services L3 VPN. MVPN EVPN PBB VPWS e-tree e-lan
>> e-line does not change for any services bottom labels.
>>
>> Is that true and if so that is a major design concern for migration of
>> customers to a SRv6 core.
>>
>> With SR-TE now we would have native TE capabilities with SRv6 over
>> SR-MPLS so that we can individually color each per vpn  flow to an SR-TE
>> tunnel over SRv6 core.  I am stating that correctly that is the major
>> benefit of SRv6 over SR-MPLS.
>>
>> Gyan
>> Verizon Communications
>> Cell phone [phone]
>>
>>
>> On Thu, Oct 3, 2019 at 4:45 PM Linda Dunbar <[e-mail]>
>> wrote:
>>
>>> Robert,
>>>
>>>
>>>
>>> Thank you very much for the explanation.
>>>
>>> With the L3VPN case,  there are nodes between Egress and Ingress PEs
>>> that do look into the VPN label carried by the packets for VRF & IP lookup,
>>> correct?
>>>
>>> I was just confused of the statement about “all nodes between Egress &
>>> Ingress PE are SR unaware plain IP forwarding nodes”.
>>>
>>>
>>>
>>> Thanks,
>>>
>>>
>>>
>>> Linda
>>>
>>>
>>>
>>> *From:* Robert Raszuk <[e-mail]>
>>> *Sent:* Thursday, October 03, 2019 3:50 AM
>>> *To:* Linda Dunbar <[e-mail]>
>>> *Cc:* [e-mail]; [e-mail]
>>> *Subject:* Re: [bess] WG adoption and IPR poll for
>>> draft-dawra-bess-srv6-services-02
>>>
>>>
>>>
>>> Linda,
>>>
>>>
>>>
>>> SRv6 services is just a general term used here. Imagine one of such
>>> service is L3VPN. VPN label (or pointer to it) is needed to be carried
>>> somewhere in the packet as address space may be overlapping between VPN
>>> customers and simple IP lookup will not be sufficient to determine VRF or
>>> exit interface.
>>>
>>>
>>>
>>> One option which has been done and deployed is to encode it natively in
>>> the packet and on ingress simply apply prodecures of IPv4 or IPv6
>>> encapsulation - RFC4797 and RFC7510
>>>
>>>
>>>
>>> The other new option is to take the VPN label or VPN demux value and
>>> encode it in SRH or in DO.
>>>
>>>
>>>
>>> Now which option to choose is left for the operator to decide likely
>>> depending on a lot of other factors involved.
>>>
>>>
>>>
>>> Thx,
>>>
>>> R.
>>>
>>>
>>>
>>> On Thu, Oct 3, 2019 at 5:52 AM Linda Dunbar <[e-mail]>
>>> wrote:
>>>
>>> I support WG adoption of the draft, with the following questions. Hope
>>> authors can help to explain:
>>>
>>>
>>>
>>> Section 1 Introduction states that the underlay between the Ingress and
>>> Egress only needs to support plain IPv6
>>>
>>> Forwarding. Those plain IPv6 routers don't need to understand the SR
>>> policies encoded in the payload, correct?
>>>
>>> Why need Ingress PE to encapsulate the policy sent by egress PE if all
>>> the nodes between them are plain IPv6 routers?
>>>
>>>
>>>
>>> Which PE is to enforce the SR policy?
>>>
>>> If the policies are for the egress to enforce, why can't the egress PE
>>> simply enforce the policy instead of asking ingress node to encapsulate the
>>> policy in the packet header? Which has the drawback of extra header bits in
>>> packets.
>>>
>>>
>>>
>>> Linda Dunbar
>>>
>>>
>>>
>>>
>>>
>>> *From: *"Bocci, Matthew (Nokia - GB)" <[e-mail]>
>>> *Date: *Friday, September 27, 2019 at 4:00 AM
>>> *To: *"[e-mail]" <
>>> [e-mail]>, "[e-mail]" <[e-mail]
>>> >
>>> *Subject: *WG adoption and IPR poll for
>>> draft-dawra-bess-srv6-services-02
>>> *Resent-From: *<[e-mail]>
>>> *Resent-To: *<[e-mail]>, <[e-mail]>, <
>>> [e-mail]>, Swadesh Agrawal <[e-mail]>, <
>>> [e-mail]>, <[e-mail] <[e-mail]>>,
>>> <[e-mail]>, <[e-mail]>, <[e-mail]>, <
>>> [e-mail]>, <[e-mail]>, <
>>> [e-mail]>
>>> *Resent-Date: *Friday, September 27, 2019 at 4:00 AM
>>>
>>>
>>>
>>> Hello,
>>>
>>>
>>>
>>> This email begins a two-weeks WG adoption poll for
>>> draft-dawra-bess-srv6-services-02 [1] .
>>>
>>>
>>>
>>> Please review the draft and post any comments to the BESS working group
>>> list.
>>>
>>>
>>>
>>> We are also polling for knowledge of any undisclosed IPR that applies to
>>> this Document, to ensure that IPR has been disclosed in compliance with
>>> IETF IPR rules (see RFCs 3979, 4879, 3669 and 5378 for more details).
>>>
>>>
>>>
>>> If you are listed as an author or a contributor of this document, please
>>> respond to this email and indicate whether or not you are aware of any
>>> relevant undisclosed IPR, copying the BESS mailing list. The document won't
>>> progress without answers from all the authors and contributors.
>>>
>>> Currently, there are no IPR disclosures against this document.
>>>
>>>
>>>
>>> If you are not listed as an author or a contributor, then please
>>> explicitly respond only if you are aware of any IPR that has not yet been
>>> disclosed in conformance with IETF rules.
>>>
>>>
>>>
>>> This poll for adoption closes on Friday 11th October 2019.
>>>
>>>
>>>
>>> Regards,
>>>
>>> Matthew and Stephane
>>>
>>>
>>>
>>> [1] https://datatracker.ietf.org/doc/draft-dawra-bess-srv6-services/
>>> <https://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fdraft-dawra-bess-srv6-services%2F&data=02%7C01%7Clinda.dunbar%40futurewei.com%7Ccda46858450b47cddd2908d747deab0f%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637056893990134792&sdata=KplKMUlBMxL1hSt2ZMbYHpChddEsDhTRrUOLH7e7gaQ%3D&reserved=0>
>>>
>>>
>>>
>>>
>>>
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-- 

Gyan S. Mishra

IT Network Engineering & Technology

Verizon Communications Inc. (VZ)

13101 Columbia Pike FDC1 3rd Floor

Silver Spring, MD 20904

United States

Phone: [phone]

Email: [e-mail]

www.linkedin.com/in/GYAN-MISHRA-RS-SP-MPLS-IPV6-EXPERT