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PM36035: SIP RE-SENDS CANCEL WHEN RECEIVING 2ND PROVISIONAL RESPONSE

Fixes are available

7.0.0.19: WebSphere Application Server V7.0 Fix Pack 19
7.0.0.21: WebSphere Application Server V7.0 Fix Pack 21
8.0.0.2: WebSphere Application Server V8.0 Fix Pack 2
8.0.0.3: WebSphere Application Server V8.0 Fix Pack 3
7.0.0.23: WebSphere Application Server V7.0 Fix Pack 23
8.0.0.4: WebSphere Application Server V8.0 Fix Pack 4
7.0.0.25: WebSphere Application Server V7.0 Fix Pack 25
8.0.0.5: WebSphere Application Server V8.0 Fix Pack 5
7.0.0.27: WebSphere Application Server V7.0 Fix Pack 27
8.0.0.6: WebSphere Application Server V8.0 Fix Pack 6
7.0.0.29: WebSphere Application Server V7.0 Fix Pack 29
8.0.0.7: WebSphere Application Server V8.0 Fix Pack 7
8.0.0.8: WebSphere Application Server V8.0 Fix Pack 8
7.0.0.31: WebSphere Application Server V7.0 Fix Pack 31
7.0.0.27: Java SDK 1.6 SR13 FP2 Cumulative Fix for WebSphere Application Server
7.0.0.33: WebSphere Application Server V7.0 Fix Pack 33
8.0.0.9: WebSphere Application Server V8.0 Fix Pack 9
7.0.0.35: WebSphere Application Server V7.0 Fix Pack 35
8.0.0.10: WebSphere Application Server V8.0 Fix Pack 10
7.0.0.37: WebSphere Application Server V7.0 Fix Pack 37
8.0.0.11: WebSphere Application Server V8.0 Fix Pack 11
7.0.0.39: WebSphere Application Server V7.0 Fix Pack 39
8.0.0.12: WebSphere Application Server V8.0 Fix Pack 12
7.0.0.41: WebSphere Application Server V7.0 Fix Pack 41
8.0.0.13: WebSphere Application Server V8.0 Fix Pack 13
7.0.0.43: WebSphere Application Server V7.0 Fix Pack 43
8.0.0.14: WebSphere Application Server V8.0 Fix Pack 14
7.0.0.45: WebSphere Application Server V7.0 Fix Pack 45
8.0.0.15: WebSphere Application Server V8.0 Fix Pack 15
PM36035; 7.0.0.17: sip re-sends cancel when receiving 2nd provisional response
7.0.0.19: Java SDK 1.6 SR9 FP2 Cumulative Fix for WebSphere Application Server
7.0.0.21: Java SDK 1.6 SR9 FP2 Cumulative Fix for WebSphere
7.0.0.23: Java SDK 1.6 SR10 FP1 Cumulative Fix for WebSphere
7.0.0.25: Java SDK 1.6 SR11 Cumulative Fix for WebSphere Application Server
7.0.0.27: Java SDK 1.6 SR12 Cumulative Fix for WebSphere Application Server
7.0.0.29: Java SDK 1.6 SR13 FP2 Cumulative Fix for WebSphere Application Server
7.0.0.45: Java SDK 1.6 SR16 FP60 Cumulative Fix for WebSphere Application Server
7.0.0.31: Java SDK 1.6 SR15 Cumulative Fix for WebSphere Application Server
7.0.0.35: Java SDK 1.6 SR16 FP1 Cumulative Fix for WebSphere Application Server
7.0.0.37: Java SDK 1.6 SR16 FP3 Cumulative Fix for WebSphere Application Server
7.0.0.39: Java SDK 1.6 SR16 FP7 Cumulative Fix for WebSphere Application Server
7.0.0.41: Java SDK 1.6 SR16 FP20 Cumulative Fix for WebSphere Application Server
7.0.0.43: Java SDK 1.6 SR16 FP41 Cumulative Fix for WebSphere Application Server

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APAR status

  • Closed as program error.

Error description

  • Product Version:  7.0.0.13
    Operating System and Additional Information:
    Linux, version 2.6.18-194.17.4.el5
    
    Example scenario:
    
    UAC          Proxy          UAS
    |             |             |
    1  |-- INVITE -->|             |
    2  |<-- 100 I ---|-- INVITE -->|
    3  |             |<-- 180 I ---|
    4  |<-- 180 I ---|             |
    |             |             |
    5  |-- CANCEL -->|             |
    6  |<-- 200 C ---|-- CANCEL -->|
    7  |             |<-- 100 I ---|
    8  |             |-- CANCEL -->|
    |             |             |
    9  |             |<-- 200 I ---|
    10  |<-- 200 I ---|             |
    11  |             |<-- 200 C ---|
    |             |             |
    12  |             |<-- 200 I ---|
    13  |<-- 200 I ---|             |
    
    Note the problem starts at message (7) where the UAS sends a
    provisional response after it received a CANCEL. This is not a
    bug, it is a race condition in the network, where the downstream
    CANCEL request (6) and the upstream Trying response (7) cross
    each other on the wire.
    However, this exposes a bug in the Session Initiation Protocol
    (SIP) container, which re-sends the CANCEL in (8). The
    container should not re-send the CANCEL just because it
    received another provisional response.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:  Session Initiation Protocol (SIP) users     *
    *                  of IBM WebSphere Application Server V7.0    *
    ****************************************************************
    * PROBLEM DESCRIPTION: CANCEL is sent out twice                *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    The problem occurs in a call flow such as this.
    
       UAC          Proxy          UAS
        |             |             |
     1  |-- INVITE -->|             |
     2  |<-- 100 I ---|-- INVITE -->|
     3  |             |<-- 100 I ---|
     4  |-- CANCEL -->|             |
     5  |<-- 200 C ---|-- CANCEL -->|
     6  |             |<-- 180 I ---|
    
    There is a "race condition" between steps 5 and 6 - sending a
    CANCEL (5) and receiving a second provisional response (6).
    These two steps are run in two different threads. Each thread
    first checks if a CANCEL was already sent, then sends out the
    CANCEL, and then updates the state machine about having sent
    the CANCEL. Because of a bug, this procedure is not
    "synchronized", that is, it is not guaranteed to run as one
    atomic operation. As a result, specific thread timing
    conditions may cause both threads to send out the CANCEL,
    concurrently.
    

Problem conclusion

  • The bug is fixed in the SIP container. With this fix, the race
    condition is eliminated, and the CANCEL is sent out once only,
    irrespective of thread or timing.
    
    The fix for this APAR is currently targeted for inclusion in
    fix pack 7.0.0.19.  Please refer to the Recommended Updates
    page for delivery information:
    http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM36035

  • Reported component name

    WEBS APP SERV N

  • Reported component ID

    5724H8800

  • Reported release

    700

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2011-03-31

  • Closed date

    2011-05-18

  • Last modified date

    2011-06-18

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

    PM36185

Fix information

  • Fixed component name

    WEBS APP SERV N

  • Fixed component ID

    5724H8800

Applicable component levels

  • R700 PSY

       UP



Document information

More support for: WebSphere Application Server
General

Software version: 7.0

Reference #: PM36035

Modified date: 18 June 2011