Specifications

Engineering Guidelines
270
T.38 UDP, Low Speed Redundancy = 8, High Speed Redundancy = 3
T.38 Alarms
T.38 load alarm
For Release MCD 5.0 SP2 a new alarm has been added called ‘T.38 Load Alarm’. The purpose
of this alarm is to indicate if there is an issue with the T.38 software/hardware/configuration
when the system starts up. For example this alarm will be set if a DSP II card is not installed
in the system or if the DSP II card is defective and the system is unable to load software onto
the DSP II card.
DSP resource exhaustion alarm
If DSP resources are not available for a T.38 call a generic DSP resource exhaustion alarm will
be raised and the call will be handled as G.711 pass through.
T.38 Frequently Asked Questions
The following answers to frequently asked questions are provided for persons deploying T.38
in their networks.
Q: Why is the maximum number of T.38 Fax sessions set at 64?
A: 64 is the maximum number of T.38 Fax licenses that are allowed through AMC. In practice
for a single DSP II card, the maximum number of sessions is 56 since one of the DSP devices
is needed for V.21 FAX Tone detection.
Q: Does this mean the 3300 can only support 64 T.38 Fax machines?
A: No, 64 is the maximum number of T.38 CODECs supported on the ICP. Since Fax machines
are typically not busy all of the time, it is possible to support more than 64 Fax machines. This
is similar to the way that subscribers and trunks are allowed to be oversubscribed based on
traffic patterns.
Q: How can an installer see how many active T.38 sessions are in progress?
A: The command line entry of 'e2tShow' will cause a line to be output such as:
'T2E crypto/clear/T.38 Channels active 0/0/0(high 1/0/1)'
The first numeric field indicates the number of currently active T.38 sessions. The second
numeric field, in brackets indicates the maximum number of T.38 sessions that were ever active.
Packet Loss Jitter End-to-End Delay
< 7% < 1000 ms < 6000 ms Green = Go
< 10% < 2000 ms Yellow = Caution
> 10% > 2000 ms > 6000 ms Red = Stop