Subject: [AVT] RE: Q about draft-ietf-avt-rtp-new-12

From: "Oren Peleg" <[email-masked]>
Date: Tue, 17 Jun 2003 20:13:49 +0300

It is mentioned that it is "included in the length field". This could be interpreted as if padding exists only for 1 octet - still the Length will be increased by one - rounded to 32bit size. It could be that Im just blowing some wind, but it did cause my suspicious level to rise.

Thanks for clearing it up to me,

Oren P.

-----Original Message-----
From: Stephen Casner [mailto:[email-masked]]
Sent: Tuesday, June 17, 2003 7:46 PM
To: Oren Peleg
Cc: [email-masked]; [email-masked]
Subject: Re: Q about draft-ietf-avt-rtp-new-12

On Tue, 17 Jun 2003, Oren Peleg wrote:

> In the draft-ietf-avt-rtp-new-12 it is mentioned that the RTCP
> packet MUST end on a 32-bit boundary. At the RTCP Padding section,
> it is mentioned that the padding is done octet based - length value
> is at the last padding octet:
>
> "If the padding bit is set, this individual RTCP packet
>              contains some additional padding octets at the end which
>              are not part of the control information but are included in
>              the length field.  The last octet of the padding is a count
>              of how many padding octets should be ignored, including
>              itself (it will be a multiple of four)."
>
> As I understand it, the Padding MUST be 32-bit aligned. Is my
> assumption correct? if it is, shouldn't it be mentioned at the
> Padding part? If this will be misunderstood, it could cause reading
> of a garbage octet as the padding length ...

This text seems clear to me.  The padding must fit within the length
field, which is in units of 32-bit words; it is appended to the
contents of an RTCP packet, which must end on a 32-bit boundary for
all packet types; and the padding count is a multiple of four.

What construction did you envision that complies with those
requirements and is not 32-bit aligned?

                                                        -- Steve

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