PLANET VIP-350PT User Manual
Page 105
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Expose SW Ver
Specify whether it should include “User-Agent” or “Server” SIP header in each SIP message.
These headers consist of product name and version. Default is checked (expose).
[On] / [Off]
Toggle between enable and disable this feature. Show check symbol ‘√’
in-line if enabled
[Back]
Return without any changes.
【
OK】
Save changes and return
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On/Off
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SIP Timer T1
By RFC3261, T1 timer is an estimated measure of network packet round-trip time, and default to
be 500-ms. However, if the network link is extremely slow, such as in a satellite link, and its round
trip time is more than 500-ms, you may increase T1 timer to reduce SIP messages retransmission
and increase the transaction timeout. However,
change of T1 will
affects 7 out of 11 SIP timers
(see below), which are Timer-(A, B, E, F, G, H and J). The foreseeable result of lengthen T1, such
as change it from 500-ms to 1-second, will double Timer-(B, F, H and J) as well, which in turn will
make the transaction timeout more time-consuming. For example, by default, at most 32 seconds
a user will wait for transaction timeout (such as dial a non-existed #), now it takes as long as 64
seconds for such timeout.
And below summarizes the meaning and defaults of the various timers used by RFC3261.
Timer
Value
Meaning
T1
500ms default
Round-Trip Time, RTT, Estimate
T2
4s
The maximum retransmit interval for non-INVITE
requests and INVITE responses
T4
5s
Maximum duration of a message will remain in the
network
Timer A
Initially T1, and
doubles for each retransmit
INVITE request retransmit interval, for UDP only.
Timer B
64*T1
INVITE transaction timeout timer
Timer C
> 3min
Proxy INVITE transaction timeout
Timer D
> 32s for UDP and
0s for TCP/SCTP
Wait time for response retransmits
Timer E
Initially T1, and
Doubles for each retransmit
Non-INVITE request retransmit interval, UDP only.