Cisco 6821 Administration Guide

DescriptionParameter
Sets if the phone uses IPv4 or IPv6.
Default: IPv4.
SIP IP Preference
SIP Timer Values (sec)
DescriptionParameter
RFC 3261 T1 value (RTT estimate) that can range
from 0 to 64 seconds.
Default: 0.5 seconds
SIP T1
RFC 3261 T2 value (maximum retransmit interval for
non-INVITE requests and INVITE responses) that
can range from 0 to 64 seconds.
Default: 4 seconds
SIP T2
RFC 3261 T4 value (maximum duration a message
remains in the network), which can range from 0 to
64 seconds.
Default: 5 seconds.
SIP T4
INVITE time-out value, which can range from 0 to
64 seconds.
Default: 16 seconds.
SIP Timer B
Non-INVITE time-out value, which can range from
0 to 64 seconds.
Default: 16 seconds.
SIP Timer F
INVITE final response, time-out value, which can
from 0 to 64 seconds.
Default: 16 seconds.
SIP Timer H
ACK hang-around time, which can range from 0 to
64 seconds.
Default: 16 seconds.
SIP Timer D
Non-INVITE response hang-around time, which can
range from 0 to 64 seconds.
Default: 16 seconds.
SIP Timer J
INVITE request Expires header value. If you enter 0,
the Expires header is not included in the request.
Ranges from 0 to 2000000.
Default: 240 seconds
INVITE Expires
Cisco IP Phone 6800 Series Multiplatform Phones Administration Guide
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Phone Troubleshooting
SIP Timer Values (sec)

Cisco 6821 Specifications

General

Resolution	320 x 240 pixels
Speakerphone	Yes
Headset Port	Yes
Protocols	SIP
USB Port	No
Wireless	No
Bluetooth	No
Video Support	No
Conference Capabilities	Yes
Wall Mountable	Yes
Display	3.5-inch grayscale
Ethernet	10/100 Ethernet
Line Keys	2
PoE	IEEE 802.3af Power over Ethernet (PoE)
Codecs	G.711, G.722, G.729, iLBC
Weight	2.0 lb (0.91 kg)