Re: [PWE3] 答复: [Technical Errata Reported] RFC4385 (1743)

[Stewart Bryant <stbryant at cisco.com>]

TDM uses a circular space, the others use a space with a gap at zero.
With these PWs, zero is used to indicate that sequence numbering
is not enabled.

Stewart

jiang.xiaowei at zte.com.cn wrote:
>
> SAToP [RFC4335] might be 4553, right?
> and 1 more question, I do not quite understand the difference b/w TDM
> PW seq and non-TMD PW sequence #
>
> In SAToP RFC, it says:
> "
> Sequence number - used to provide the common PW sequencing function
> as well as detection of lost packets. It MUST be generated in
> accordance with the rules defined in Section 5.1 of [RFC3550] for
> the RTP sequence number:
>
> o Its space is a 16-bit unsigned circular space
> o Its initial value SHOULD be random (unpredictable).
>
> It MUST be incremented with each SAToP data packet sent in the
> specific PW.
> "
>
>
>
>
> *RFC Errata System <rfc-editor at rfc-editor.org>*
> 发件人: pwe3-bounces at ietf.org
>
> 2009-03-27 04:23
>
> 	
> 收件人
> 	stbryant at cisco.com, swallow at cisco.com, lmartini at cisco.com,
> danny at arbor.net, rdroms at cisco.com, jari.arkko at piuha.net,
> townsley at cisco.com, stbryant at cisco.com, matthew.bocci at alcatel-lucent.com
> 抄送
> 	yaakov_s at rad.com, pwe3 at ietf.org, rfc-editor at rfc-editor.org
> 主题
> 	[PWE3] [Technical Errata Reported] RFC4385 (1743)
>
>
>
> 	
>
>
>
>
>
>
> The following errata report has been submitted for RFC4385,
> "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an
> MPLS PSN".
>
> --------------------------------------
> You may review the report below and at:
> http://www.rfc-editor.org/errata_search.php?rfc=4385&eid=1743
>
> --------------------------------------
> Type: Technical
> Reported by: Yaakov (J) Stein <yaakov_s at rad.com>
>
> Section: 4, 4.1, 4.2
>
> Original Text
> -------------
> The sequence number mechanism described here uses a circular unsigned
> 16-bit number space that excludes the value zero.
> ...
> o The sequence number that follows 65535 (maximum unsigned 16-bit
> number) is one.
> ...
> o If the sequence number on the packet is zero, the sequence
> integrity of the packets cannot be determined. In this case, the
> received packet is considered to be in order.
>
> Corrected Text
> --------------
> The sequence number mechanism for all PW types except the TDM PWs
> SAToP [RFC4335], CESoPSN [RFC5086], and TDMoIP [RFC5087] use a
> circular unsigned 16-bit number space that excludes the value zero.
> The TDM PWs include the value zero.
> ...
> o For all non-TDM PWs the sequence number that follows 65535
> (maximum unsigned 16-bit number) is one.
> ...
> o If the sequence number on a non-TDM-PW packet is zero, the sequence
> integrity of the packets cannot be determined. In this case, the
> received packet is considered to be in order.
>
> Notes
> -----
> While the fact that the TDM PWs always require the sequence number and
> thus do not give a zero value special meaning was well-known and
> documented in the relevant RFCs. However, this was forgotten in this
> document and is causing confusion to implementers.
>
> Instructions:
> -------------
> This errata is currently posted as "Reported". If necessary, please
> use "Reply All" to discuss whether it should be verified or
> rejected. When a decision is reached, the verifying party (IESG)
> can log in to change the status and edit the report, if necessary.
>
> --------------------------------------
> RFC4385 (draft-ietf-pwe3-cw-06)
> --------------------------------------
> Title : Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use
> over an MPLS PSN
> Publication Date : February 2006
> Author(s) : S. Bryant, G. Swallow, L. Martini, D. McPherson
> Category : PROPOSED STANDARD
> Source : Pseudo Wire Emulation Edge to Edge
> Area : Internet
> Stream : IETF
> Verifying Party : IESG
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