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Cisco Bug: CSCtb24325 - CUCM incorrectly handles H245 address collision, address comparison

Last Modified

Jan 29, 2017

Products (1)

  • Cisco Unified Communications Manager (CallManager)

Known Affected Releases


Description (partial)

H.245 negotiation fails to negotiate when facilities with h245address are sent after connect.  The CUCM has the numerically higher IP address than the device it is signaling with, and does not initiate a new connection.  Alternatively, it can have the lower connection and reset a current connection to switch to the higher IP address endpoint's open port.

This may cause certain features like fax and DTMF to fail, as well as call failure because of H.245 negotiation.

The CUCM algorithm for "numerically higher IP address" is also incorrect, and does not function correctly if both IP addresses are not either above 128 or below 128 in the octets that require comparison.

This happens with certain CUCM versions when fast start is initiated before connect, and H.245 happens after connect, particularly with Facility messages.  The H.245 collision is timing dependent, and may be an intermittent problem because of this.

This is the part of the H.323 specification that is not correctly implemented:

8.2.3 Snippet:
In the event that both endpoints simultaneously initiate the separate H.245 connection, the endpoint
with the numerically smaller h245Address shall close the TCP connection it opened and use the
connection opened by the other endpoint. For purposes of comparing the numeric values of
h245Address, each octet of the address shall be individually compared beginning with the first
octet of the OCTET STRING and continuing through the OCTET STRING left to right until
unequal numeric octet values are found. Comparison shall first be performed on the network-layer
address element of h245Address and, if found to be equal, then on the transport (port) address
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