Re: [Bier] Questions regarding <draft-zhang-bier-bierin6-03>

Xiejingrong <> Fri, 12 July 2019 11:25 UTC

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From: Xiejingrong <>
To: Antoni Przygienda <>, "Jeffrey (Zhaohui) Zhang" <>, "" <>, BIER WG <>
Thread-Topic: Questions regarding <draft-zhang-bier-bierin6-03>
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Date: Fri, 12 Jul 2019 11:19:43 +0000
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Subject: Re: [Bier] Questions regarding <draft-zhang-bier-bierin6-03>
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Hi Tony,

Exactly, the whole v6 extension headers(EH) and the v6 options consideration is basically a first stab!

Once a judgement is based on the "Upper-layer Protocol", the last next header of a chain, then a walk through the chain is unavoidable, to "dig out" the right format that need to be processed in fast-path.

The difficulty with a "regular" IPv6 DA is that, normal things like TCP/UDP/ICMPv6 packet must be handled without much impact on it.

Use a "XXX specific IPv6 DA" is not only the SRv6-NetworkProgramming concept, but also the ISO NSAP address as I learned from a book and found in the WIKI

The NSEL (Network-Selector) is a field in the NSAP address that identifies the network layer<> service to which a packet should be sent.

BIER forwarding seems match very much a "network layer service" in my opinion, and the "AB37" in "2019::AB37" is very similar to a NSEL too.


From: Antoni Przygienda []
Sent: Friday, July 12, 2019 12:02 AM
To: Jeffrey (Zhaohui) Zhang <>et>; Xiejingrong <>om>;; BIER WG <>
Subject: Re: Questions regarding <draft-zhang-bier-bierin6-03>

2.1.  IPv6 Options Considerations

   RFC 8200 section 4, defines the IPv6 extension headers.  Currently

   there are two defined extension headers, Hop-by-Hop and Destination

   options header, which can carry a variable number of options.  These

   extension headers are inserted by the source node.

   For directly connected BIER routers, IPv6 Hop-by-Hop or Destination

   options are irrelevant and SHOULD NOT be inserted by BFIR on the

   BIERin6 packet.  In this case IPv6 header, Next Header field should

   be set to TBD.  Any IPv6 packet arriving on BFRs and BFERs, with

   multiple extension header where the last extension header has a Next

   Header field set to TBD, SHOULD be discard and the node should

   transmit an ICMP Parameter Problem message to the source of the

   packet (BFIR) with an ICMP code value of TBD10 ('invalid options for


[XJR Q6]: You have to walk the ext header chain and get the last NH to judge if this packet need to be discard, right? For example for an incoming packet(ipv6hdr+RoutingHeader+DestOptHdr<nh!=TBD>), you have to walk the whole extension header chain until you know the last NH, to execute the above "discard" action. Right?

prz> topic for discussion. The whole v6 options consideration is basically a first stab.

   This also indicates that for disjoint BIER routers using IPv6

   encapsulation, there SHOULD NOT be any IPv6 Hop-by-Hop or Destination

   options be present in a BIERin6 packet.

[XJR Q7]: What does "disjoint BIER router" mean?

prz> non-adjacent, good catch