Cisco SPA303 Administration Manual page 250

Cisco SPA IP Phone Field Reference
SIP Tab
Cisco Small Business SPA300 Series, SPA500 Series, and WIP310 IP Phone Administration Guide
Parameter
RTP Packet Size
Max RTP ICMP Err
RTCP Tx Interval
No UDP Checksum
Symmetric RTP
Description
Packet size in seconds, which can range from 0.01 to
0. 1 6. Valid values must be a multiple of 0.01 seconds.
Defaults to 0.030.
Number of successive ICMP errors allowed when
transmitting RTP packets to the peer before the IP
phone terminates the call. If value is set to 0, the IP
phone ignores the limit on ICMP errors.
Defaults to 0.
Interval for sending out RTCP sender reports on an
active connection. It can range from 0 to 255 seconds.
During an active connection, the IP phone can be
programmed to send out compound RTCP packet on
the connection. Each compound RTP packet except
the last one contains a SR (Sender Report) and a SDES
(Source Description). The last RTCP packet contains an
additional BYE packet. Each SR except the last one
contains exactly 1 RR (Receiver Report); the last SR
carries no RR. The SDES contains CNAME, NAME, and
TOOL identifiers. The CNAME is set to <User
ID>@<Proxy>, NAME is set to <Display Name> (or
Anonymous if user blocks caller ID), and TOOL is set to
the Vendor/Hardware-platform-software-version (such
as Cisco/IP phone-1.0.31(b)). The NTP timestamp used
in the SR is a snapshot of the IP phone's local time, not
the time reported by an NTP server. If the IP phone
receives a RR from the peer, it attempts to compute the
round trip delay and show it as the <Call Round Trip
Delay> value (ms) in the Info section of IP phone web
page.
Defaults to 0.
Select yes if you want the IP phone to calculate the
UDP header checksum for SIP messages. Otherwise,
select no.
Defaults to no.
Enable symmetric RTP operation. If enabled, sends
RTP packets to the source address and port of the last
received valid inbound RTP packet. If disabled (or
before the first RTP packet arrives) sends RTP to the
destination as indicated in the inbound SDP.
Defaults to no.
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