IP Header Compression


IP Header Compression
 
 
This chapter provides information on configuring an enhanced, or extended, service. The product administration guides provide examples and procedures for configuration of basic services on the system. It is recommended that you select the configuration example that best meets your service model, and configure the required elements for that model, as described in the respective product administration guide, before using the procedures in this chapter.
 
Important: RoHC header compression is not applicable for SGSN and GGSN services.
This chapter includes the following procedures:
 
 
Overview
The system supports IP header compression on the PPP tunnels established over the EVDO-RevA A10 links and also over the GRE tunnel that is connected to the PCF to support EVDO-RevA Service Option 67 (SO67).
By default IP header compression using the VJ algorithm is enabled for subscribers using PPP.
Note that you can use the default VJ header compression algorithm alone, configure the use of RoHC header compression only, or use both VJ and RoHC IP header compression.
Van Jacobsen (VJ) - The RFC 1144 (CTCP) header compression standard was developed by V. Jacobson in 1990. It is commonly known as VJ compression. It describes a basic method for compressing the headers of IPv4/TCP packets to improve performance over low speed serial links.
RObust Header Compression (RoHC) - The RFC 3095 (RoHC) standard was developed in 2001. This standard can compress IP/UDP/RTP headers to just over one byte, even in the presence of severe channel impairments. This compression scheme can also compress IP/UDP and IP/ESP packet flows. RoHC is intended for use in wireless radio network equipment and mobile terminals to decrease header overhead, reduce packet loss, improve interactive response, and increase security over low-speed, noisy wireless links.
Important: Use of RoHC requires that a valid RoHC license key be installed. Contact your local Sales or Support representative for information on how to obtain a license.
In addition, you can configure RoHC profiles that define RoHC Compressor and Decompressor parameters. These RoHC profiles can be applied to subscribers.
You can also turn off all IP header compression for a subscriber.
The procedures in this chapter describe how to configure the IP header compression methods used, but for RoHC over PPP the Internet Protocol Control Protocol (IPCP) negotiations determine when they are used.
Implementing IP header compression provides the following benefits:
 
 
Configuring VJ Header Compression for PPP
By default, VJ IP header compression is enabled for subscriber sessions. When VJ header compression is configured all IP headers are compressed using the VJ compression algorithm.
 
Note that procedure described in this section is applicable only when VJ header compression is disabled.
Important: This section provides the minimum instruction set for configuring subscriber profile for header compression. For more information on commands that configure additional parameters and options, refer Subscriber Configuration Mode Commands chapter in Command Line Interface Reference.
To configure the system to enable VJ header compression to IP headers:
Step 1
Step 2
Step 3
Save your configuration as described in the Saving Your Configuration chapter.
 
Enabling VJ Header Compression
Use the following example to enable the VJ header compression over PPP:
configure
   context <ctxt_name>
      subscriber name <subs_name>
         ip header-compression vj
         end
Notes:
 
<ctxt_name> is the system context in which you wish to configure the subscriber profile. Typically this is an AAA context.
<subs_name> is the name of the subscriber in the current context that you want to enable VJ IP header compression for.
 
Verifying the VJ Header Compression Configuration
These instructions are used to verify the VJ header compression configuration.
Step 1
 
show subscriber configuration username subs_name
The output of this command is a concise listing of subscriber parameter settings as configured.
 
Configuring RoHC Header Compression for PPP
RoHC IP header compression can be configured for all IP traffic, uplink traffic only, or downlink traffic only. When RoHC is configured for all traffic, you can specify the mode in which RoHC is applied.
Important: Use of RoHC requires that a valid license key be installed. Contact your local Sales or Support representative for information on how to obtain a license.
Important: This section provides the minimum instruction set for configuring subscriber profile for header compression. For more information on commands that configure additional parameters and options, refer Subscriber Configuration Mode Commands chapter in the Command Line Interface Reference.
To configure the system to enable RoHC header compression to IP headers:
Step 1
Step 2
Step 3
Save your configuration as described in the Saving Your Configuration chapter.
 
Enabling RoHC Header Compression for PPP
Use the following example to enable the RoHC over PPP:
configure
   context <ctxt_name>
      subscriber name <subs_name>
         ip header-compression RoHC [ any [ mode { optimistic | reliable | unidirectional } ] | cid-mode { { large | small } [ marked-flows-only | max-cid | max-hdr <value> | mrru <value> ] } | marked flows-only | max-hdr <value> | mrru <value> | downlink | uplink ] }+
         end
Notes:
 
<ctxt_name> is the system context in which you wish to configure the subscriber profile. Typically this is an AAA context.
<subs_name> is the name of the subscriber in the current context that you want to enable RoHC header compression for.
 
Verifying the Header Compression Configuration
These instructions are used to verify the header compression configuration.
Step 1
 
show subscriber configuration username subs_name
The output of this command is a concise listing of subscriber parameter settings as configured.
 
Configuring Both RoHC and VJ Header Compression
You can configure the system to use both VJ and RoHC IP header compression. When both VJ and RoHC are specified, the optimum header compression algorithm for the type of data being transferred is used for data in the downlink direction.
Important: If both RoHC and VJ header compression are specified, the optimum header compression algorithm for the type of data being transferred is used for data in the downlink direction.
Important: Use of RoHC requires that a valid license key be installed. Contact your local Sales or Support representative for information on how to obtain a license.
Important: This section provides the minimum instruction set for configuring subscriber profile for header compression. For more information on commands that configure additional parameters and options, refer Subscriber Configuration Mode Commands chapter in th Command Line Interface Reference.
To configure the system to enable both RoHC and VJ header compression to IP headers:
Step 1
Step 2
Step 3
Save your configuration as described in the Saving Your Configuration chapter.
 
Enabling RoHC and VJ Header Compression for PPP
Use the following example to enable the header compression over PPP:
configure
   context <ctxt_name>
      subscriber name <subs_name>
         ip header-compression vj RoHC [ any [ mode { optimistic | reliable | unidirectional } ] | cid-mode { { large | small } [ marked-flows-only | max-cid | max-hdr <value> | mrru <value> ] } | marked flows-only | max-hdr <value> | mrru <value> | downlink | uplink ] }+
         end
Notes:
 
<ctxt_name> is the system context in which you wish to configure the subscriber profile. Typically this is an AAA context.
<subs_name> is the name of the subscriber in the current context that you want to enable RoHC header compression for.
 
Verifying the Header Compression Configuration
These instructions are used to verify the header compression configuration.
 
show subscriber configuration username subs_name
The output of this command is a concise listing of subscriber parameter settings as configured.
 
Configuring RoHC for Use with SO67 in PDSN Service
This section explains how to set RoHC settings in the PDSN Service configuration mode. These settings are transferred to the PCF during the initial A11 setup and are used for the GRE tunnel that is connected to the PCF to support EVDO-RevA Service Option 67 (SO67). RoHC is enabled through an auxiliary SO67 A10 connection and the PCF signals this information when the auxiliary A10 is connected.
Important: This section provides the minimum instruction set for configuring subscriber profile for header compression. For more information on commands that configure additional parameters and options, refer PDSN Service Configuration Mode Commands chapter in Command Line Interface Reference.
To configure the system to disable the RoHC header compression feature at the PDSN Service over SO67:
Step 1
Step 2
Step 3
Save your configuration as described in the Saving Your Configuration chapter.
 
Enabling RoHC Header Compression with PDSN
Use the following example to disable the RoHC header compression with PDSN over SO67:
configure
   context <ctxt_name>
      pdsn-service <svc_name>
         ip header-compression RoHC
         cid-mode {large | small} max-cid integer
         mrru <num_octets>
         profile { [esp-ip] [rtp-udp] [udp-ip] [uncompressed-ip] }         end
Notes:
 
<ctxt_name> is the system context in which PDSN service is configured and you wish to configure the service profile.
<svc_name> is the name of the PDSN service in which you want to enable RoHC over SO67.
 
Verifying the Header Compression Configuration
These instructions are used to verify the header compression configuration.
Step 1
 
show configuration context ctxt_name
The output of this command is a concise listing of subscriber parameter settings as configured.
 
Using an RoHC Profile for Subscriber Sessions
You can configure RoHC profiles that specify numerous compressor and decompressor settings. These profiles can in turn be applied to a specific subscriber or the default subscriber. RoHC profiles are used for both RoHC over PPP and for RoHC over SO67.
Important: Use of RoHC requires that a valid license key be installed. Contact your local Sales or Support representative for information on how to obtain a license.
Important: This section provides the minimum instruction set for configuring subscriber profile for header compression. For more information on commands that configure additional parameters and options, refer Subscriber Configuration Mode Commands chapter in Command Line Interface Reference.
To configure the system to apply RoHC profile to a subscriber session:
Step 1
Step a
Step b
Step 2
Step 3
Step 4
Save your configuration as described in the Saving Your Configuration chapter.
 
Creating RoHC Profile for Subscriber using Compression Mode
Use the following example to create RoHC profile for a subscriber using compression mode:
configure
   RoHC-profile profile-name <RoHC_comp_profile_name>
      decompression-options
         [no] multiple-ts-stride
         rtp-sn-p <p_value>
         [no] use-ipid-override
         [no] use-optimized-talkspurt
         [no] use-optimized-transience
         [no] use-timer-based-compression
         end
Notes:
 
<RoHC_comp_profile_name> is the name of the RoHC profile with compression mode which you want to apply to a subscriber.
 
Creating RoHC Profile for Subscriber using Decompression Mode
Use the following example to create RoHC profile for a subscriber using decompression mode:
configure
   RoHC-profile profile-name <RoHC_decomp_profile_name>
      decompression-options
         context-timeout <dur>
         max-jitter-cd <dur_ms>
         nak-limit <limit>
         optimistic-mode-ack
         optimistic-mode-ack-limit <num_pkts>
         piggyback-wait-time <dur_ms>
         preferred-feedback-mode { bidirectional-optimistic | bidirectional-reliable | unidirectional }
         rtp-sn-p <p_value>
         [no] rtp-sn-p-override
         [no] use-clock-option
         [no] use-crc-option
         [no] use-feedback
         [no] use-jitter-option
         [no] use-reject-option
         [no] use-sn-option
         end
Notes:
 
<RoHC_profile_name> is the name of the RoHC profile with decompression mode which you want to apply to a subscriber.
 
Applying RoHC Profile to a Subscriber
Once an RoHC profile has been created that profile can be specified to be used for a specific subscribers. Use the following example to apply the RoHC profile to a subscriber:
configure
   context <ctxt_name>
      subscriber name <subs_name>
         RoHC-profile-name <RoHC_profile_name>
         end
Notes:
 
<ctxt_name> is the system context in which you wish to configure the subscriber profile. Typically this is an AAA context.
<subs_name> is the name of the subscriber in the current context that you want to enable RoHC header compression for.
<RoHC_profile_name> is the name of the existing RoHC profile (created with compressed or decompressed mode) which you want to apply to a subscriber in the current context.
 
Verifying the Header Compression Configuration
These instructions are used to verify the header compression configuration.
Step 1
 
show subscriber configuration username subs_name
The output of this command is a concise listing of subscriber parameter settings as configured.
 
Disabling VJ Header Compression Over PPP
By default, VJ IP header compression is enabled for subscriber sessions. When VJ header compression is configured all IP headers are compressed using the VJ compression algorithm.
If you do not want to apply compression to any IP headers for a subscriber session you can disable the IP header compression feature.
Important: This section provides the minimum instruction set for configuring subscriber profile for header compression. For more information on commands that configure additional parameters and options, refer Subscriber Configuration Mode Commands chapter in Command Line Interface Reference.
To configure the system to disable VJ header compression to IP headers:
Step 1
Step 2
Step 3
Save your configuration as described in the Saving Your Configuration chapter.
 
Disabling VJ Header Compression
Use the following example to disable the VJ header compression over PPP:
configure
   context <ctxt_name>
      subscriber name <subs_name>
         no ip header-compression
         end
Notes:
 
<ctxt_name> is the system context in which you wish to configure the subscriber profile. Typically this is an AAA context.
<subs_name> is the name of the subscriber in the current context that you want to disable IP header compression for.
 
Verifying the VJ Header Compression Configuration
These instructions are used to verify the VJ header compression configuration.
Step 1
 
show subscriber configuration username <subs_name>
The output of this command is a concise listing of subscriber parameter settings as configured.
 
Disabling RoHC Header Compression Over SO67
If you do not want to apply compression to any IP headers for a subscriber sessions using the EVDO-RevA SO67 feature, you can disable the IP header compression feature at the PDSN Service.
Important: This section provides the minimum instruction set for configuring subscriber profile for header compression. For more information on commands that configure additional parameters and options, refer PDSN Service Configuration Mode Commands chapter in Command Line Interface Reference.
To configure the system to disable the IP header compression feature at the PDSN Service:
Step 1
Step 2
Step 3
Save your configuration as described in the Saving Your Configuration chapter.
 
Disabling RoHC Header Compression
Use the following example to disable the header compression over PPP:
configure
   context <ctxt_name>
      pdsn-service <svc_name>
         no ip header-compression RoHC
         end
Notes:
 
<ctxt_name> is the system context in which PDSN service is configured and you wish to configure the service profile.
<svc_name> is the name of the PDSN service in which you want to disable RoHC over SO67.
 
Verifying the Header Compression Configuration
These instructions are used to verify the header compression configuration.
 
show configuration context <ctxt_name>
The output of this command is a concise listing of subscriber parameter settings as configured.
 
Checking IP Header Compression Statistics
This section commands to use to retrieve statistics that include IP header compression information.
The following Exec mode commands can be used to retrieve IP header compression statistics:
For more information on these commands, refer to the Command Line Interface Reference.
 
RADIUS Attributes for IP Header Compression
This section lists the names of the RADIUS attributes to use for RoHC header compression. For more information on these attributes, refer to the AAA Interface Administration and Reference.
One of the following attributes can be used to specify the name of the RoHC profile to use for the subscriber session:
 
Any RoHC parameters not specified in the RoHC profile are set to their default values.
 

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