Drafat H.450.8

[Sakae OKUBO]

Steve,

But H.323, the referencing document via H.225.0 of RFC 1889, says that
bandwidth for the open logical channel bitrate and ARQ is calculated _without_
headers. We cannot change this, because it would break existing
implementations. Are you suggesting that flowControlCommand should do it
differently, i.e., include at least the RTP header? The value in consistently
using the same, although arguably flawed, bandwidth calculations outweighs the
benefit of having a mix of calculations.

Paul Long
Smith Micro Software, Inc.

        -----Original Message-----
        From:   Stephen Casner [SMTP:casner at CISCO.COM]
        Sent:   Wednesday, May 05, 1999 10:20 PM
        To:     ITU-SG16 at MAILBAG.INTEL.COM
        Subject:        Re: flowControlCommand and packet overhead

        On Wed, 28 Apr 1999, Paul Long wrote:

        > Therefore, clarification text to the following effect should be
added to
        > 6.2.11.2 (in v2) of H.323:
        >
        >         "flowControlCommand applies to the information streams which
are the
        > content of logical channel(s), not including RTP headers, RTP
payload headers,
        > network headers and other overhead."

        I'm mostly a lurker on this list, but I thought I would offer another
        perspective.  The RTP spec, RFC 1889, says the following:

           Bandwidth calculations for control and data traffic include lower-
           layer transport and network protocols (e.g., UDP and IP) since that
           is what the resource reservation system would need to know. The
           application can also be expected to know which of these protocols
are
           in use. Link level headers are not included in the calculation
since
           the packet will be encapsulated with different link level headers
as
           it travels.

        At a minimum, I would expect the RTP payload header to be included
        because that is specific to the encoding and would not be known by
        lower layers.  The difficulty in pushing this problem off to lower
        layers is that they need to know the packet rate in order to know how
        much overhead the additional headers will add.
                                                                -- Steve