[Bier] Re: I-D Action: draft-ietf-bier-ping-23.txt

[Carlos Pignataro <[e-mail]>]

Hi, Tony,

Before the full careful review, could I please ask you to help me understand the wire formats for the BIER Echo packets?

Issue I:

Eyeing Figures 1 and 2, they seem to describe structurally mutually incompatible wire formats, likely simultaneously impossible to implement.

Figure 1 §3.1 shows a 64-bit "BIER OAM Header”, which includes a 6-bit MessageType.
Figure 2 §3.2 labels the "BIER OAM Header” as the top 64 bits. It includes an 8-bit "Echo Type”, and a shifted “Proto” field.
For both Figure 1’s “MessageType” (or “ Message Type") and Figure 2’s "Echo Type”, the document says that "Valid values are listed in Table 1."

So, @Tony, can you please help me figure out what happens when, for example, 6-bit MessageType and 8-bit "Echo Type” are, say, 1? — I am very sorry I am still confused and stuck on this point.


Issue II:

When I then try to further understand this by checking the IANA requests, I add to my confusion,
There is a "BIER OAM Message Type" (§5.2), which is for a 6-bit field, and includes a single value of 1 for "BIER Echo Request/Echo Reply”. BUT this Table 9 does not map Table 1 as per above.
There is then a "BIER Echo Request/Echo Reply Message Types” (§5.5.1), the Table 10 is called differently, "BIER Echo Types”, and values 1-2 seem to match Table 1 now.

@Tony, can you please show how these fields are mapped to the headers in Fig 1 and 2?

That is my main concern. Please help me understand, just trying to clarify.

Some other technical issues remain:


Issue III:

4.5.  Sending Echo Reply
   The Responder MUST set the Message Type as 2 and Return Code as Best-
   return-code.  The Proto field MUST be set to 0.

BUT

5.4.  BIER OAM Message Type
        +---------+-------------------------------+---------------+
        | 2 - 58  |           Unassigned          | This document |
        +---------+-------------------------------+---------------+


Issue IV:

3.4.8.  Erroneous Echo Request TLV
       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Type = 8              |       Length = variable       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

BUT

5.6.1.  TLVs
Table 14: TLVs

Reaches only until Type 7...


These seem to be relevant regressions:
https://author-tools.ietf.org/iddiff?url1=draft-ietf-bier-ping-17&url2=draft-ietf-bier-ping-18&difftype=--html#part-2
https://author-tools.ietf.org/iddiff?url1=draft-ietf-bier-ping-21&url2=draft-ietf-bier-ping-22&difftype=--html#part-5


As a process issue now, and not a technical one, before diving in: just confirming the full and careful review scope is -16 to -23, correct?
https://author-tools.ietf.org/iddiff?url1=draft-ietf-bier-ping-16&url2=draft-ietf-bier-ping-23&difftype=--html 
Please let me know if that's not right.


Thank you, and very best,

Carlos.


> On May 15, 2026, at 11:00 AM, Tony Przygienda <[e-mail]> wrote:
> 
> Yes, e'one please review this carefully. Document underwent clarifications w/o technical changes AFAIS and should incorporate all the comments in spades now. If no further comments I will conclude this respin end of next week and loop back to AD for further processing 
> 
> thanks 
> 
> -- tony 
> 
> On Wed, May 13, 2026 at 1:17 AM Greg Mirsky <[e-mail] <mailto:[e-mail]>> wrote:
>> 
>> Dear All,
>> updates in the new version address comments received from Carlos and the discussion with the WG Chairs.
>> 
>> Please share your questions and comments. Ready for the next step to progress this document to publication.
>> 
>> Regards,
>> Greg
>> 
>> ---------- Forwarded message ---------
>> From: <[e-mail] <mailto:[e-mail]>>
>> Date: Tue, May 12, 2026 at 3:19 PM
>> Subject: [Bier] I-D Action: draft-ietf-bier-ping-23.txt
>> To: <[e-mail] <mailto:[e-mail]>>
>> Cc: <[e-mail] <mailto:[e-mail]>>
>> 
>> 
>> Internet-Draft draft-ietf-bier-ping-23.txt is now available. It is a work item
>> of the Bit Indexed Explicit Replication (BIER) WG of the IETF.
>> 
>>    Title:   Bit Index Explicit Replication (BIER) Ping and Trace
>>    Authors: Nagendra Kumar
>>             Carlos Pignataro
>>             Mach Chen
>>             Greg Mirsky
>>    Name:    draft-ietf-bier-ping-23.txt
>>    Pages:   38
>>    Dates:   2026-05-12
>> 
>> Abstract:
>> 
>>    Bit Index Explicit Replication (BIER) is a multicast forwarding
>>    architecture designed to simplify and optimize multicast delivery.
>> 
>>    This document specifies the mechanism and basic BIER OAM packet
>>    format that can be used to perform failure detection and isolation on
>>    the BIER data plane without any dependency on other layers, like the
>>    IP layer.
>> 
>> The IETF datatracker status page for this Internet-Draft is:
>> https://datatracker.ietf.org/doc/draft-ietf-bier-ping/
>> 
>> There is also an HTML version available at:
>> https://www.ietf.org/archive/id/draft-ietf-bier-ping-23.html
>> 
>> A diff from the previous version is available at:
>> https://author-tools.ietf.org/iddiff?url2=draft-ietf-bier-ping-23
>> 
>> Internet-Drafts are also available by rsync at:
>> rsync.ietf.org::internet-drafts
>> 
>> 
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