Re: [Bier] BIER WG, Call For Agenda, Montreal IETF 105

["Jeffrey (Zhaohui) Zhang" <[e-mail]>]

Hi Jingrong,




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From: BIER <[e-mail]> On Behalf Of Xiejingrong
Sent: Friday, July 12, 2019 9:38 PM
To: Jeffrey (Zhaohui) Zhang <[e-mail]>; [e-mail]; BIER WG <[e-mail]>
Cc: '[e-mail]' <[e-mail]>; [e-mail]; [e-mail]; [e-mail]
Subject: Re: [Bier] BIER WG, Call For Agenda, Montreal IETF 105

Sorry there are some incorrect text inserted in wrong places.
Also I am not sure if the word 'meanful' is correct after I check in the dictionary.
Pls ignore these nits in the mail.
The comments are alright.

Zzh> No worries. I take it you meant “meaningful”. More below.


Thanks
Jingrong
发件人：Xiejingrong <[e-mail]<mailto:[e-mail]>>
收件人：Jeffrey (Zhaohui) Zhang <[e-mail]<mailto:[e-mail]>>;[e-mail] <[e-mail]<mailto:[e-mail]>>;BIER WG <[e-mail]<mailto:[e-mail]>>
抄 送：'[e-mail]' <[e-mail]<mailto:[e-mail]>>;[e-mail] <[e-mail]<mailto:[e-mail]>>;[e-mail] <[e-mail]<mailto:[e-mail]>>;[e-mail] <[e-mail]<mailto:[e-mail]>>
时间：2019-07-13 09:23:35
主 题：RE: [Bier] BIER WG, Call For Agenda, Montreal IETF 105

Thanks for the comments very much.
Meanful and helpful.
Please see my comments in line below.
发件人：Jeffrey (Zhaohui) Zhang <[e-mail]<mailto:[e-mail]>>
收件人：Xiejingrong <[e-mail]<mailto:[e-mail]>>;[e-mail] <[e-mail]<mailto:[e-mail]>>;BIER WG <[e-mail]<mailto:[e-mail]>>
抄 送：'[e-mail]' <[e-mail]<mailto:[e-mail]>>;[e-mail] <[e-mail]<mailto:[e-mail]>>;[e-mail] <[e-mail]<mailto:[e-mail]>>;[e-mail] <[e-mail]<mailto:[e-mail]>>
时间：2019-07-13 04:53:22
主 题：RE: [Bier] BIER WG, Call For Agenda, Montreal IETF 105

Hi Jingrong, Liang,
I have some questions and comments on two of the drafts.
draft-xie-bier-ipv6-encapsulation-02
·        Use of BIER multicast address FF0X::AB37 does not seem right to me. For example, on a LAN you can’t multicast BIER packets to multiple downstream BFRs – individual copies (with different BitString) must be unicast to those downstreams.
·        [XJR] Absolutely! The use of multicast DA can't support some very common usecases that may be assumed as Architecture of BIER. I agree with you to assume using a unicast DA. I will update the draft this way in next version.
·
·        Assuming that we agree that a unicast DA address must be used. What’s the rational of “Source Address field in the IPv6 header MUST be a routable IPv6 unicast address of the BFIR in any case”? Since the IPv6 header is only the outer encapsulation to get a packet from BFR1 to BFR2, why would you want to put the BFIR’s address in the outer encapsulation? If you could make both SA/DA of the IPv6 header to be the original SA/DA of the payload it may make some sense, but obviously you can’t do that.
·        [XJR] Yes, use of the address of the BFIR and keep it unchange when a packet fly through the BFRs is a key of the proposal. I think there is already examples of Source rooting that keep the source address unchange while change the DA in the fly. I would understand the BIER technology as a Multicast source routing!
Zzh> First of all, BIER is not source routing, even though BIER is the best multicast solution for SR because it does not have per-flow/tunnel/tree state in the core (yet BIER is independent of SR). Source routing means the source (router) determines the path of the packets. BIER is not like that. The BitString only specifies the set of BFERs.
Zzh> As I pointed out, the IPv6 header is only to get the packet from BFR1 (vs. BFIR) to BFR2 (whether they’re directly connected or not) – one-hop or multi-hop tunneling, so it makes sense to use the BFR1’s address as SA.
Zzh> Having said that, if you could convince everyone that the BFIR’s address should be used, then draft-zhang-bier-bierin6-03 could do the same.
·        With the above, I don’t see a real difference between this proposal and draft-zhang-bier-bierin6-03 – it’s just whether the BIER header is in the destination option or in the “payload” part of the IPv6 packet. Can you explain the pros and cons of two?
·        [XJR] there are more similarities since I (and you may also agree) want to use unicast DA only. but the difference is mainly two: one is use the address of BFIR without change in the fly as above point. one is use of a BIER specific ipv6 address in DA, which preceding any of the possible EHs and assume being the most efficient for fast path and most less impact on exist IPv6 functions.
Zzh> If you use unicast DA, what’s the BIER specific IPv6 address to use? How would it work for multi-hop tunnel? Why would that be most efficient and least impact existing IPv6 functions? To me using NH=BIER would be the most straightforward and least impactful to existing IPv6 functions.
Zzh> If I could ask a rhetorical question – would you put TCP or UDP header in an IPv6 Destination Option hdr?

draft-geng-bier-ipv6-inter-domain-00
·        Can you elaborate the following?
Note: Use of the IPv6 address configured on PE1 to identify an MVPN
instance can eliminate the need for BFR-id configuration on PE1x,
which otherwise has to be configured from the space of a sub-domain.
·        For the “peering multicast”, how many BIER sub-domain do you have?
·        [XJR] haven't evaluate that so far.I initiate this idea when I found a recent rfc8313 and thought of the tenant spanning multiple DCs. Also I assume the multicast as a service draft for this case.
·        Zzh> If I understand it correctly, the draft seems to assume only a single sub-domain.
·
·        What’s the real difference between “hierarchical multicast” and “peering multicast”, once you take away the color and MVPN aspects that I believe are orthogonal here?
·        [XJR] the hierarchical one is a P2MP case like IPTV in service provider. The peering one is an MP2MP case where the multicast source may be more unpredictable.
Zzh> From BIER point of view, there is no difference, right?
·
·        What’s the significance of “inter-domain” here, that requires this new draft?
·        [XJR] there is still no inter-domain BIER underlay construction, which I would think comparable to the so called non-segmented mvpn solution. It is the idea in my mind since the first presentation in ietf102 to deploy inter-domain BIER underlay. Also impressed by the points of multicast as a service you proposed.
Zzh> The reason I asked that question is that, in this single sub-domain scenario, there is really nothing new wrt inter-domain. You can use IGP signaling, BGP signaling, draft-zwzw-bier-prefix-redistribute, and draft-zzhang-bier-multicast-as-a-service procedures together to signal and build BIFTs. You can of course use static configuration, but that also applies to intra-domain and does not seem to warrant a specific spec for “inter-domain”.
·        What’s the uniqueness of IPv6 here?
·        [XJR] I found it difficult to construct the inter-domain BIFTs since the BIER-MPLS label is dynamic. Use of a static SRGB label as BIER-MPLS of a BR(border router) is waste ful, while use the SRGB for the entire domain seems not welcome in ietf102.
Zzh> I don’t follow. BIER label is indeed completely local and dynamic, but whether it is intra or inter-domain is irrelevant? Not sure why SRGB was brought up here.
Zzh> Besides, how does IPv6 solve this problem? You still have BIFT-ID, which could be dynamic just like MPLS label or could be hardcoded but that can work without IPv6 as well.
Zzh> Jeffrey
·        Thanks.
·        Jingrong.

Thanks!
Jeffrey
From: BIER <[e-mail]<mailto:[e-mail]>> On Behalf Of Xiejingrong
Sent: Monday, July 8, 2019 9:30 PM
To: [e-mail]<mailto:[e-mail]>; BIER WG <[e-mail]<mailto:[e-mail]>>
Cc: '[e-mail]' <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Subject: Re: [Bier] BIER WG, Call For Agenda, Montreal IETF 105
We’d like to request 35-40 minutes for the presentation of the following BIERv6 drafts.  I will be the speaker (may have some adjustment before the session).
BIERv6 Encapsulation // draft-xie-bier-ipv6-encapsulation-02, 15min
BIERv6 via IS-IS // draft-xie-bier-ipv6-isis-extension-00  10min
MVPN using BIERv6 // draft-xie-bier-ipv6-mvpn-01            5min
Inter-domain Multicast Deployment using BIERv6  // draft-geng-bier-ipv6-inter-domain-00 10min
Thanks
Jingrong on behalf of the authors
From: BIER [mailto:[e-mail]] On Behalf Of Greg Shepherd
Sent: Tuesday, July 09, 2019 3:37 AM
To: BIER WG <[e-mail]<mailto:[e-mail]>>
Subject: [Bier] BIER WG, Call For Agenda, Montreal IETF 105
Please send agenda items with title, draft, speaker name, and requested time to this thread.
Thanks,
Shep
(chairs)

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