Subject: [rohc] A question about a chain of subheaders

From: [email-masked]
Date: Tue, 5 Nov 2002 16:41:02 -0000

Hi All,

In RFC 3095 section 5.7.7 there is the paragraph:

"The structure of a chain of subheaders is determined by each header
having a Next Header, or Protocol, field.  This field identifies the
type of the following header.  Each Static part below that is
followed by another Static part contains the Next Header/Protocol
field and allows parsing of the Static chain; the Dynamic chain, if
present, is structured analogously."

However, in the Initialization of UDP Header (5.7.7.5) there is no Next
Header or Protocol field. Can someone explain what the paragraph above
therefore means?

Thank you

Matthew Holmes
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From: "Lars-Erik Jonsson (EAB)" <[email-masked]>
Date: Tue, 5 Nov 2002 23:53:08 +0100

Matthew,

> However, in the Initialization of UDP Header (5.7.7.5) there 
> is no Next Header or Protocol field. Can someone explain what the
> paragraph above therefore means?

The UDP Header does not have a Next Header or Protocol field, but
this is not a problem since it can not be followed by any other
header (except for an RTP header). A static part of a UDP header
thus terminates the static chain. For the RTP profile, the UDP
header part is always (per definition) followed by an RTP header part.

Rgds,
/L-E

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From: [email-masked]
Date: Thu, 7 Nov 2002 08:26:19 -0000

Hi Micke

Yep I understand now thanks.

A sentence could be added stating "The exception is the UDP header which
does not contain a Next Header or Protocol field. Whether or not the UDP
header is followed by an RTP header is therefore determined by the profile."

Regards,

Matthew
 
-----Original Message-----
From: Mikael Degermark [mailto:[email-masked]]
Sent: 06 November 2002 19:58
To: [email-masked]
Subject: Re: [rohc] A question about a chain of subheaders

Hello Matthew, 

The UDP header itself does not have a Next Header
or Protocol field. Whether there is an RTP header, or 
any other header, after a UDP header is therefore
determined by the profile.

So: yes, the explanation could be better for  
the UDP header.

Do you understand how it is supposed to work now?

Do you have a suggestion on how to make this clearer?

Cheers, 

Micke Degermark