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  1. #1
    Registered User
    Join Date
    Mar 2003
    Posts
    3

    SAR, Permanent vs. Temporary "Session Mode" & d/l issues

    Gang, here are several Q's, bear with me.

    1. If both ? the WAP Gateway and the Nokia Phone ? are SAR enabled, does the "session mode" setting matter anymore or is it ignored?

    2. Is it true that if "session mode" is set to "permanent" the gateway requires confirmation for each packet, hence all the packets are guaranteed to arrive in the order they were sent?

    3. If "session mode" is set to "temporary" does this mean that the order of arrival is not guaranteed and packets may be lost?

    All downloads work if session mode is set to "permanent" on both gateways (Ericsson - OPERATOR A and CMG - OPERATOR B). No downloads work on OPERATOR B and only some (smaller file size) work on OPERATOR A with "temporary" session mode.

    On OPERATOR B for all files requested over a "temporary" session the message is the same: "Invalid file" and is displayed after a few seconds;

    4. Can we conclude that the gateway limits the response to a certain size discarding larger files?

    On OPERATOR A we noticed empirically that only for files larger than a size in the interval 30-39KB the download will not complete over a "temporary" session. However, the behavior is different: the download starts and stops after 3-5 minutes with the same message "Connection lost, try again".

    5. Can we assume that we have the same limitation as in question 4) or packets have been lost (the likelihood for packet loss for larger files thus increasing)?

    Hope this is the right place to ask, just passing over Q's from the real developers.

    10x in advance. gorgeoux
    DC Communication

  2. #2
    Regular Contributor
    Join Date
    Mar 2003
    Posts
    466

    RE: SAR, Permanent vs. Temporary "Session Mode" & d/l issues

    Hi!

    I would recommend you to take a look at the "Segmentation and Re-assembly in the Wireless Transaction Protocol" document at the Forum Nokia web site (http://www.forum.nokia.com/documents). The document provides valuable information about the SAR technology. SAR is used to split large WTP messages into a number of smaller datagrams and selectively retransmit failed datagrams. To use SAR, it must be supported by both of the communicating parties: WAP gateway and WAP browser. It is known that SAR can not be used in Connectionless (temporary) mode and in that case the maximum data transfer size through WAP smaller than in Connection-oriented (permanent) mode.

    Kind regards,
    Satu/Forum Nokia Developer Support

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