Reason: preemption ;cause=2 ;text=reserved resourced preempted
Call-ID: 3848276298220188511@pc33.usmc.example.mil
CSeq: 6187 BYE
Contact: <sip:bob@usmc.example.mil>
When Alice’s UA receives this message, her UA terminates the call,
sends a 200 OK to Bob to confirm reception of the BYE message, and
plays a preemption tone to Alice the user.
The RESV message from Dave successfully traverses R2, and Carol’s UA
receives it. Just as with the Alice-to-Bob call setup, Carol sends
an UPDATE message to Dave, confirming she has QoS "e2e" in "sendrecv"
directions. Bob acknowledges this with a 200 OK that gives his
current status (QoS "e2e" and "sendrecv"), and the call setup in SIP
continues to completion.
In summary, Alice set up a call to Bob with RSVP at a priority level
of Routine. When Carol called Dave at a high priority, their call
would have preempted any lower priority calls if there were a
contention for resources. In this case, it occurred and affected the
call between Alice and Bob. A router at this congestion point
preempted Alice’s call to Bob in order to place the higher-priority
call between Carol and Dave. Alice and Bob were both informed of the
preemption event. Both Alice and Bob’s UAs played preemption
indications. What was not mentioned in this appendix was that this
document RECOMMENDS that router R2 (in this example) generate a
syslog message to the domain administrator to properly manage and
track such events within this domain. This will ensure that the
domain administrators have recorded knowledge of where such events
occur, and what the conditions were that caused them.
Authors’ Addresses
Fred Baker
Cisco Systems
1121 Via Del Rey
Santa Barbara, California 93117
USA
Phone: +1-408-526-4257
Fax: +1-413-473-2403
EMail: fred@cisco.com
James Polk
Cisco Systems
2200 East President George Bush Turnpike
Richardson, Texas 75082
USA
Phone: +1-817-271-3552
EMail: jmpolk@cisco.com
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