RoHC Profile Decompression Configuration
Mode Commands
The RoHC Profile Decompression
Configuration Mode is used to configure RoHC (Robust Header Compression)
Decompressor parameters.
IMPORTANT:
The availability of
commands, keywords and variables in this mode are dependent on platform
type, product version, and installed license(s).
accept-delayed-pkts
Accepts delayed packets
Syntax
[ default ] accept-delayed-pkts
default
Returns the command
to its default value of disabled.
Usage:
This command helps
reduce packet loss during context repair.
Example:
Use the following command
to enable the system to accept delayed packets:
accept-delayed-pkts
context-timeout
Ensures that no expired
contexts are used for data compression.
Syntax
context-timeout seconds
default context-timeout
default
Returns the command
to its default value.
seconds
Specifies the context
timeout value (in seconds) as an integer from 0 through 100.
Default: 20
Usage:
The RoHC stack should
periodically clean up expired contexts and release memory in case there
is no data activity for the call on this context. The context cleanup
period is internally calculated to be set to half of the value of
the context-timeout value. This will ensure that no expired contexts
are used for data compression.
Example:
The following command
sets the context-timeout parameter to 30 seconds:
context-timeout 30
crc-errors-fo
Sets the limits for
when a NACK message is sent while in the FO (First Order) state.
A NACK is sent whenever CRC errors are detected within a specified
number of packets.
Syntax
crc-errors-fo-k num_errors
crc-errors-fo-n num_packts
default crc-errors-fo-k
default crc-errors-fo-n
default
Returns the command
to its default value.
crc-errors-fo-k num_errors
Specifies the number
of received packets that trigger the sending of a NACK as an integer from
1 through 10.
Default: 1
IMPORTANT:
num_errors must
be less than or equal to the value specified with the crc-errors-fo-n command.
crc-errors-fo-n num_packts
Specifies the number
of packets to check for CRC errors as an integer from 1 through
10.
Default: 1
Usage:
Use this command to
set the parameters that trigger sending a NACK message when in the FO
state.
Example:
To configure a NACK
to be sent when 4 out of the last 10 packets have CRC errors when
in the FO state, use the following commands:
crc-errors-fo-k 4
crc-errors-fo-n 10
crc-errors-so
Sets the limits for
when a NACK message is sent while in the SO (Second Order) state.
A NACK is sent whenever CRC errors are detected within a specified
number of packets.
Syntax
crc-errors-so-k num_errors
crc-errors-so-n num_packets
default crc-errors-so-k
default crc-errors-so-n
default
Returns the command
to its default value.
crc-errors-so-k num_errors
Specifies the number
of received packets that trigger the sending of a NACK as an integer from
0 through 10.
Default: 1
IMPORTANT:
num_errors must
be less than or equal to the value specified with the crc-errors-so-n command.
crc-errors-so-n num_packets
Specifies the number
of packets to check for CRC errors as an integer from 1 through
10.
Default: 1
Usage:
Use this command to
set the parameters that trigger sending a NACK message when in the SO
state.
Example:
To configure a NACK
to be sent when 4 out of the last 10 packets have CRC errors when
in the SO state, use the following commands:
crc-errors-so-k 4
crc-errors-so-n 10
end
Exits the current
configuration mode and returns to the Exec mode.
Privilege:
Security Administrator,
Administrator
Usage:
Use this command to
return to the Exec mode.
exit
Exits the current
mode and returns to the parent configuration mode.
Privilege:
Security Administrator,
Administrator
Usage:
Use this command to
return to the parent configuration mode.
nack-limit
Sets the number of
unsuccessful decompressions allowed before a NACK is sent.
Syntax
nack-limit limit
default nack-limit
default
Returns the command
to its default value.
limit
Specifies the number
of unsuccessful decompressions allowed as an integer from 0 through 20.
Default: 0
Usage:
Use this command to
set the maximum number of unsuccessful decompressions before a NACK
message is sent.
Example:
The following command
sets the number of unsuccessful decompressions allowed to 10:
nack-limit 10
optimistic-mode-ack
When this command is
enabled and a type 2 IR-DYN packet is successfully decompressed,
an optional ACK is sent in U-mode.
Syntax
[ default | no ] optimistic-mode-ack
default
Returns the command
to its default value of enabled.
no
Disables the sending
of the optional ACK.
Usage:
Use this command to
enable and disable the sending of an optional ACK in U-mode when a
type 2 IR-DYN packet is successfully decompressed.
Example:
To enable the sending
of the optional ACK, enter the following command:
optimistic-mode-ack
To disable the sending
of the optional ACK, enter the following command:
no optimistic-mode-ack
optimistic-mode-ack-limit
Sets the number
of packets for which to send ACKs.
Syntax
optimistic-mode-ack-limit num_pkts
default optimistic-mode-ack-limit
default
Returns the command
to its default value.
num_pkts
Specifies the number
of packets for which to send ACKs as an integer from 0 through 20.
Default: 3
Usage:
Use this command to
set the number of packets to send the optional ACK for when a type 2
IR-DYN packet is successfully decompressed.
Example:
Enter the following
command to set the number of packets to send and ACK for to 6:
optimistic-mode-ack-limit 6
Use the following command
to set the number of packets to send an ACK for back to the default
of 3:
default optimistic-mode-ack-limit
piggyback-wait-time
Specifies the time
in milliseconds to wait for a feedback packet to be picked up as piggybacked
feedback by the associated compressor.
Syntax
piggyback-wait-time m_secs
default piggyback-wait-time
default
Returns the command
to its default value.
m_secs
Specifies the time
(in milliseconds) to wait for a feedback packet to be picked up
as an integer value from 0 through 1000.
Default: 80
Usage:
Use this command to
set the time in milliseconds to wait for a feedback packet to be picked
up as piggybacked feedback by the associated compressor.
Example:
The following command
sets the wait time to 120 ms:
piggyback-wait-time 120
preferred-feedback-mode
Specifies the preferred
feedback mode to use between the compressor and the decompressor
Syntax
preferred-feedback-mode { bidirectional-optimistic | bidirectional-reliable | unidirectional }
default preferred-feedback-mode
default
Returns the command
to its default setting of bidirectional-optimistic.
bidirectional-optimistic
This mode is similar
to the Unidirectional mode, with the exception of a feedback channel used
to send error recovery requests from the decompressor to compressor.
This is the default
mode.
bidirectional-reliable
Reliable mode makes
extensive use of a feedback channel to avoid packet loss from context invalidation.
A secure reference model is used instead of the optimistic approach
used in the other modes. With the secure reference model, the confidence
of the compressor depends on acknowledgements from the decompressor
for every context updating packet.
Periodically the compressor
sends context updating packets repeatedly until an acknowledgement
is received from the decompressor.
unidirectional
Packets are sent in
only one direction, from the compressor to the decompressor.
Usage:
Use this command to
specify the preferred feedback method to use between the compressor
and the decompressor for the current RoHC profile.
Example:
Use the following command
to set the preferred feedback mode to bidirectional-reliable:
preferred-feedback-mode
bidirectional-reliable
rtp-sn-p
Specifies the value
of p in RTP SN (RTP Sequence Number) calculation. Least Significant
Bits (LSB) encoding is used for header fields whose values are usually
subject to small changes. With LSB encoding, the k least significant
bits of the field value are transmitted instead of the original
field value, where k is a positive integer. After receiving k bits,
the decompressor derives the original value using a previously received
value as reference (v_ref). The scheme is guaranteed to
be correct if the compressor and the decompressor each use interpretation
intervals as follows:
- In which the original
value resides
- And in which the original
value is the only value that has the exact same k least significant
bits as those transmitted.
The interpretation
interval can be described as a function:
f(v_ref, k).
Let f(v_ref, k) = [v_ref - p,
v_ref + (2^k - 1) - p]
Where p is an integer.
Syntax
rtp-sn-p value
default rtp-sn-p
default
Returns the command
to its default value.
value
Specifies the number
the value of p in the RTP SN calculation as an integer from 0 through 999.
Usage:
Use this command to
set the value to use for p when performing the RTP SN calculation.
Example:
The following command
sets the RTP Sequence Number integer “p” value
to 100:
rtp-sn-p 100
rtp-sn-p-override
Allows an override
of p in RTP SN calculation. This
is disabled by default.
Syntax
[ default | no ] rtp-sn-p-override
default
Returns the command
to its default value of disabled.
no
Disables overriding
p in RTP SN calculation.
Usage:
Use this command to
allow an override of p in RTP SN calculations.
Example:
The following command
enables the override of p in the RTP SN calculation:
rtp-sn-p-override
sliding-window-ts
Computes jitter as
described in RFC 3095,[4.5.4]
Syntax
sliding-window-ts size
default sliding-window-ts
default
Returns the command
to its default value of 4.
size
Sets the size of the
sliding window. size must
be an integer from 1 through 1000.
Default: 4
Usage:
Use this command to
set the size of the sliding window used to compute jitter for the current
RoHC profile.
Example:
The following command
sets the sliding window size to 500:
sliding-window-ts 500
use-clock-option
Controls usage of the
RoHC clock option. The clock option informs the compressor of the
clock resolution of the decompressor. This allows the compressor
to estimate the jitter introduced by the clock of the decompressor
when doing timer-based compression of the RTP timestamp.
Syntax
[ default | no ] use-clock-option
default
Returns the command
to its default value of enabled.
no
Disables use of the
RoHC clock option.
Usage:
Use this command to
enable and disable the use of the RoHC clock option.
Example:
The following command
enables RoHC clock option usage:
use-clock-option
The following command
disables RoHC clock option usage:
no use-clock-option
use-crc-option
Controls usage of the
RoHC cyclic redundancy check (CRC) option. The CRC option contains
an 8-bit CRC computed over the entire feedback payload, without
the packet type and code octet, but including any CID fields,
Syntax
[ default | no ] use-crc-option
default
Returns the command
to its default value of enabled.
no
Disables use of the
CRC option.
Usage:
Use this command to
enable and disable the use of the RoHC CRC option.
Example:
The following command
enables RoHC CRC option usage:
use-crc-option
The following command
disables RoHC CRC option usage:
no use-crc-option
use-feedback
Controls use of the
feedback channel. A feedback channel sends error recovery requests
and (optionally) acknowledgments of significant context updates
from the decompressor to the compressor.
Privilege:
Security Administrator,
Administrator
Syntax
[ default | no ] use-feedback
default
Returns the command
to its default value of disabled.
no
Disables use of the
feedback channel.
Usage:
Use this command to
enable and disable the use of the RoHC feedback channel.
Example:
The following command
enables RoHC feedback channel usage:
use-feedback
The following command
disables RoHC feedback channel usage:
no use-feedback
use-jitter-option
Controls usage of RoHC
jitter option. The jitter option allows the decompressor to report
the maximum jitter it has observed
Syntax
[ default | no ] use-jitter-option
default
Returns the command
to its default value of enabled.
no
Disables use of the
jitter option.
Usage:
Use this command to
enable and disable the use of the RoHC jitter option.
Example:
The following command
enables RoHC jitter option usage:
use-jitter-option
The following command
disables RoHC jitter option usage:
no use-jitter-option
use-reject-option
Controls usage of RoHC
reject option. The reject option informs the compressor that the
decompressor does not have sufficient resources to handle the flow.
Syntax
[ default | no ] use-reject-option
default
Returns the command
to its default value of disabled.
no
Disables use of the
reject option.
Usage:
Use this command to
enable and disable the use of the RoHC reject option.
Example:
The following command
enables RoHC reject option usage:
use-reject-option
The following command
disables RoHC reject option usage:
no use-reject-option
use-sn-not-valid-option
Controls usage of the
RoHC SN not valid option. The sn-not-valid option indicates that
the SN of the feedback is not valid. A compressor must not use the
SN of the feedback to find the corresponding sent header when this
option is present.
Syntax
[ default | no ] use-sn-not-valid-option
default
Returns the command
to its default value of enabled.
no
Disables use of the
sn-not-valid option.
Usage:
Use this command to
enable and disable the use of the RoHC sn not valid option.
Example:
The following command
enables RoHC sn not valid option usage:
use-sn-not-valid-option
The following command
disables RoHC sn not valid option usage:
no use-sn-not-valid-option
use-sn-option
Controls usage of RoHC
sn option. The sn option provides eight additional bits of SN (Sequence
Number, usually the RTP Sequence Number.)
Syntax
[ default | no ] use-sn-option
default
Returns the command
to its default value of enabled.
no
Disables use of the
SN option.
Usage:
Use this command to
enable and disable the use of the RoHC SN option.
Example:
The following command
enables RoHC SN option usage:
use-sn-option
The following command
disables RoHC SN option usage:
no use-sn-option