Re: [bess] Comments on <draft-dawra-bess-srv6-services-00>

Gaurav Dawra <gdawra.ietf@gmail.com> Mon, 08 July 2019 22:16 UTC

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From: Gaurav Dawra <gdawra.ietf@gmail.com>
Date: Mon, 8 Jul 2019 15:16:02 -0700
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To: "Swadesh Agrawal (swaagraw)" <swaagraw@cisco.com>
Cc: Xiejingrong <xiejingrong@huawei.com>, "draft-dawra-bess-srv6-services@ietf.org" <draft-dawra-bess-srv6-services@ietf.org>, "bess@ietf.org" <bess@ietf.org>
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Subject: Re: [bess] Comments on <draft-dawra-bess-srv6-services-00>
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Hi Jingrong,
I have updated -02 version to fix a typo and some minor nits. Rest of
comments are addressed in the latest version as mentioned by Swadesh as
well.
Cheers,
Gaurav


On Mon, Jul 8, 2019 at 1:47 PM Swadesh Agrawal (swaagraw) <
swaagraw@cisco.com> wrote:

> Hi Jingrong
>
>
>
> Thanks for reviewing and comments. Please see my response inline starting
> with [SA] .
>
>
>
> Regards
>
> Swadesh
>
>
>
> *From: *BESS <bess-bounces@ietf.org> on behalf of Xiejingrong <
> xiejingrong@huawei.com>
> *Date: *Thursday, June 27, 2019 at 7:51 PM
> *To: *"draft-dawra-bess-srv6-services@ietf.org" <
> draft-dawra-bess-srv6-services@ietf.org>gt;, "bess@ietf.org" <bess@ietf.org>
> *Subject: *[bess] Comments on <draft-dawra-bess-srv6-services-00>
>
>
>
> Hi
>
> I have read this documents several times.
>
> I think it is useful and stable to advance as a solution of L3VPN/EVPN
> service over IPv6 networks.
>
> Here are some minor comments:
>
>
>
>    SRv6 Service SID refers to an SRv6 SID that MAY be associated with
>
>    one of the service specific behavior on the advertising Provider
>
>    Edge(PE) router, such as (but not limited to), in the case of L3VPN
>
>    service, END.DT (Table lookup in a VRF) or END.DX (crossconnect to a
>
>    nexthop) functions
>
> [xjr] what are the things “but not limited to” ? Please specify explicitly
> or delete the words in this paragraph and other places.
>
> [SA] In future, new behaviors could be defined on Egress PE extension to
> network programming. So we don’t want to restrict behaviors.
>
>
>
>    To provide SRv6 service with best-effort connectivity, the egress PE
>
>    signals an SRv6 Service SID with the BGP overlay service route.  The
>
>    ingress PE encapsulates the payload in an outer IPv6 header where the
>
>    destination address is the SRv6 Service SID provided by the egress
>
>    PE.  The underlay between the PEs only need to support plain IPv6
>
>    forwarding [RFC2460].
>
> [xjr]“with best-effort connectivity” is not clear to me.
>
> [SA] Based on IGP shortest path reachability.
>
> [xjr] I suggest a section can be added to say about “not using color and
> SRH”, “using color and SRH” for easy-deployment and for path-optimization
> respectively.
>
> [SA] hopefully above response clarifies.
>
> [xjr] s/RFC2460/RFC8200/g
>
> [SA] Ack.
>
>
>
>    To provide SRv6 service in conjunction with an underlay SLA from the
>
>    ingress PE to the egress PE, the egress PE colors the overlay service
>
>    route with a Color extended
>
>    community[I-D.ietf-idr-segment-routing-te-policy].  The ingress PE
>
>    encapsulates the payload packet in an outer IPv6 header with an SRH
>
>    that contains the SR policy associated with the related SLA followed
>
>    by the SRv6 Service SID associated with the route.  The underlay
>
>    nodes whose SRv6 SID's are part of the SRH must support SRv6 data
>
>    plane.
>
> [xjr] see above suggestion.
>
>
>
> SRv6 Service Sub-TLV Type (1 octet): This field is set to 1 to
>
>       represent SRv6 SID Informaton Sub-TLV.
>
> [xjr] s/Informaton/information/g
>
> [SA] fixed in new version.
>
>
>
>    Egress PEs which supports SRv6 based L3 services advertises overlay
>
>    service prefixes along with a Service SID enclosed in a SRv6 L3
>
>    Service TLV within the BGP SID attribute.  This TLV serves two
>
>    purposes - first, it indicates that the egress PE is reachable via an
>
>    SRv6 underlay and the BGP ingress PE receiving this route MAY choose
>
>    to encapsulate or insert an SRv6 SRH; second ,it indicates the value
>
>    of the SID to include in the SRH encapsulation.
>
> [xjr] The two purposes I can see, the indication of the reachability to
> this PE, and the indication of a specific Service this SRv6 SID bound to.
>
> [xjr] Use of SRH or not is determined by Color Extended Community, or more
> precisely, the SR-policy installed on Ingress Node, not this TLV.
>
> [SA] Please refer to updated version which hopefully clarifies this
> comment. Further there is a typing error in new version. Last line of
> paragraph will be modified to below is next version.
>
>
>
> “second ,it indicates the value of the Service SID to be used in the
> encapsulation.”
>
>
>
> 4.6.  EVPN multicast routes (Route Types 6, 7, 8) over SRv6 core
>
>    These routes do not require the advertisement of SRv6 Service TLVs
>
>    along with them.  Similar to EVPN Route Type 4, the BGP Nexthop is
>
>    equal to the IPv6 address of egress PE.  More details may be added in
>
>    future revisions of this document.
>
> [xjr] is this determined that No SRv6 Service TLVs required ? the document
> <draft-xie-bier-ipv6-mvpn> had seen the use of SRv6 Service TLV in
> multicast VPN.
>
> [xjr] Suggest to say simply this is outside of this document, which I
> think covers unicast service only, and helpful to advance.
>
> [SA] This is specific to EVPN RT 6,7,8 and not MVPN (RT 6 and 7). This may
> be updated in future version of document based on future analysis.
>
>
>
> Thanks
>
> Jingrong
>
>
>