Table Of Contents
IP Header Compression Over Frame Relay for Interfaces Support
Prerequisites for Configuring IPHC on Frame Relay Interfaces
Restrictions for Configuring IPHC on Frame Relay Interfaces
Information About IPHC Support for Frame Relay Interfaces
Enabing IPHC Support for Frame Relay Interfaces
Loading Microcode on Line Card
Enabling Header Compression at Sub-Interface Level
Configuring Compression Connections at Sub-Interface Level
Configuring Maximum Packets for Receiving Full-Header
Configuring Maximum Size for Compressing IP Headers
Disabling Context Status Messages
frame-relay ip rtp header-compression
frame-relay ip rtp compression-connections
frame-relay ip tcp header-compression
frame-relay ip tcp compression-connections
hw-module slot x np mode feature
hw-module slot <slot> ip tcp compression-connections
hw-module slot <slot> ip rtp compression-connections
ip header-compression disable-feedback
ip header-compression max-header
ip header-compression max-period
show ip rtp header-compression
show ip tcp header-compression
Feature Information for IPHC Over Frame Relay
IP Header Compression Over Frame Relay for Interfaces Support
Part Number: OL-18313-01
First Published: November 10, 2008Table 1 Feature History
IP Header compression is a mechanism that compresses the protocol headers in a packet before the packet is transmitted. Header compression reduces network overhead and speeds up the transmission of both RTP and TCP packets.
The IP Header Compression (IPHC) Over Frame Relay feature enables efficient transmission of real time traffic such as voice and video by compressing and decompressing the packet header. IPHC Over Frame Relay is supported on Cisco 12000 Series Engine 5 based SPA Interface Processor (SIP)-401/501/601 line cards on FR interfaces. For FR, Cisco encapsulation type is the only encapsulation type on which this feature is supported. This feature is already supported on PPP/MLPPP interfaces.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for IPHC Over Frame Relay" section.
Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS, Catalyst OS, and Cisco IOS XE software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
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Prerequisites for Configuring IPHC on Frame Relay Interfaces
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Prerequisites for Configuring IPHC on Frame Relay Interfaces
Following are the prerequisites for configuring IPHC on FR interfaces:
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Restrictions for Configuring IPHC on Frame Relay Interfaces
Following are the restrictions for configuring IPHC on FR interfaces:
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Information About IPHC Support for Frame Relay Interfaces
The real-time transport protocol, RTP, as described in RFC 1889, is used to carry real-time data for voice and video applications. For a typical VoIP application, the payload portion of the packet can be much smaller than the headers. For example, using the G.729 Codec, the payload is 20 bytes but the IP/ UDP/RTP header is 40 bytes. It is inefficient to send the IP/UDP/RTP header on a slow link without compressing it. The IPHC feature addresses this inefficiency. The basic idea behind IPHC is that although several fields in the IP/ UDP/RTP header change from packet to packet, typically, the difference in these fields from packet to packet is constant. The compression scheme capitalizes on this characteristic. RFC 2508 describes the function of IPHC.
Following steps provide details for compressing, decompressing, and reconstructing an original packet:
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Enabing IPHC Support for Frame Relay Interfaces
This section explains the following procedures:
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Loading Microcode on Line Card
Enabling IPHC on Cisco 12000 Series Routers requires feature bundle microcode to be loaded on SIP-401/501/601 line card.
Note
To load and bundle microcode on each SIP-401/501/601 line card, perform the following required steps:
SUMMARY STEPS
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DETAILED STEPS
Enabling Header Compression at Sub-Interface Level
To enable the header compression at subinterface level, perform the following required steps:
SUMMARY STEPS
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DETAILED STEPS
Configuring Compression Connections at Sub-Interface Level
To configure the header compression connections that can exist at subinterface level, perform the following required steps:
SUMMARY STEPS
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DETAILED STEPS
Configuring Maximum Packets for Receiving Full-Header
Configure the number of packets after which a full-header (FH) is sent on the Cisco 12000 Series Routers. The full headers are sent based on the specified number of packets configured. A default value of 256 packets is considered, if the number of packets to receive full-header is not configured.
To configure the number of packets after which a full-header needs to be sent at subinterface level, perform the following steps (optional):
SUMMARY STEPS
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DETAILED STEPS
Configuring Maximum Size for Compressing IP Headers
To govern the IP headers of packets that need to be compressed, you can configure the maximum combined size of IP/UDP/RTP headers in the packet which needs to be compressed. The packets with header size more than the configured headers are sent uncompressed. The default size on Cisco 12000 Series Routers SIP-401/501/601 line card is 40 bytes.
Note
To configure the maximum size of IP headers that need to be compressed at subinterface level, perform the following steps (optional):
SUMMARY STEPS
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DETAILED STEPS
Disabling Context Status Messages
Context status messages are sent by decompressor to compressor to inform about the context status. This context is used by decompressor to decompress received compressed packets correctly. When the path of the upward link is different from the path of the downward link, for example in case of satellite links, CONTEXT_STATUS messages are not useful. To disable feedback of context_status messages from subinterface or link this command is used.
To disable context_status messages at subinterface, perform the following steps (optional):
SUMMARY STEPS
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DETAILED STEPS
Additional References
The following sections provide references related to the IP Header Compressor Support for FR interfaces feature.
RFCs
RFC 1144
TCP/IP Header Compression
RFC 2507
IP Header Compression
RFC 2508
Compressed IP/UDP/RTP
RFC 2509
IP Header Compression for PPP
RFC 3544
IP Header Compression over PPP
Technical Assistance
Command Reference
The following commands are introduced or modified in the feature or features documented in this module. For information about all Cisco IOS commands, use the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or the Cisco IOS Master Command List, All Releases, at http://www.cisco.com/en/US/docs/ios/mcl/allreleasemcl/all_book.html.
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frame-relay ip rtp header-compression
To enable Real-Time Transport Protocol (RTP) header compression for all FR maps on a physical subinterface, use the frame-relay ip rtp header-compression command in subinterface configuration mode. To disable the compression, use the no form of this command.
Note
frame-relay ip rtp header-compression
no frame-relay ip rtp header-compression
Syntax Description
Not Applicable
Defaults
Disabled
Command Modes
Sub-Interface configuration
Command History
Usage Guidelines
When the frame-relay ip rtp header-compression command is used on the subinterface, it is only applicable on that particular subinterface. Header Compression needs to be configured explicitly on each subinterface for which IP header compression is desired.
Examples
The following example shows how to enable RTP header compression for all FR maps on a physical interface:
Router> enable
Router# configure terminal
Router(config)# interface Serial1/1/1:1.1
Router(config-if)# frame-relay ip rtp header-compressionRouter(config-if)# exit
Related Commands
Enables the TCP header decompression on the specified FR subinterface.
Displays RTP header compression statistics for FR.
frame-relay ip rtp compression-connections
To specify the maximum number of Real-Time Transport Protocol (RTP) header compression connections that can exist on a FR subinterface, use the frame-relay ip rtp compression-connections interface configuration command. To restore the default, use the no form of this command.
frame-relay ip rtp compression-connections number
no frame-relay ip rtp compression-connections
Syntax Description
Defaults
32 Compression Connections
Command Modes
Interface configuration
Command History
12.1(2)T
This command was introduced.
12.0(33)S2
This command was first supported on Cisco 12000 Series Routers.
Usage Guidelines
Before you can configure the maximum number of connections, RTP header compression must be configured on the interface using the frame-relay ip rtp header-compression command.
The number of RTP header compression connections must be set to the same value at each end of the connection.
Examples
The following example shows how to configure a maximum of 150 RTP header compression connections on serial subinterface 3/0/0.1/1/1/0.1:
Router(config)# interface Serial 3/0/0.1/1/1/0.1Router(config-if)# frame-relay ip rtp compression-connections 150Related Commands
Configures the maximum number of TCP header compression connections on a FR subinterface.
frame-relay ip tcp header-compression
To enable Transport Protocol (TCP) header decompression for all FR maps on a physical subinterface, use the frame-relay ip tcp header-compression command in subinterface configuration mode. To disable the compression, use the no form of this command.
Note
frame-relay ip tcp header-compression
no frame-relay ip tcp header-compression
Syntax Description
Not Applicable
Defaults
Disabled
Command Modes
Sub-Interface configuration
Command History
Usage Guidelines
When the frame-relay ip tcp header-compression command is used on the subinterface, it is only applicable on that particular subinterface. Header decompression needs to be configured explicitly on each subinterface for which TCP header decompression is desired.
Examples
The following example shows how to enable TCP header decompression for all FR maps on a physical interface:
Router> enable
Router# configure terminal
Router(config)# interface Serial1/1/1:1.1
Router(config-if)# frame-relay ip tcp header-compressionRouter(config-if)# exit
Related Commands
Enables RTP header compression on a FR subinterface.
Displays TCP header decompression statistics for FR.
frame-relay ip tcp compression-connections
To specify the maximum number of TCP header compression connections that can exist on a FR interface, use the frame-relay ip tcp compression-connections interface configuration command. To restore the default, use the no form of this command.
frame-relay ip tcp compression-connections number
no frame-relay ip tcp compression-connections
Syntax Description
Defaults
One (1) Compression Connection
Command Modes
Interface configuration
Command History
12.1(2)T
This command was introduced.
12.0(33)S2
This command was first supported on Cisco 12000 Series Routers.
Usage Guidelines
Before you can configure the maximum number of connections, TCP header compression must be configured on the interface using the frame-relay ip tcp header-compression command.
The number of TCP header compression connections must be set to the same value at each end of the connection.
Examples
The following example shows how to configure a maximum of 150 RTP header compression connections on serial subinterface 3/0/0.1/1/1/0.1:
Router(config)# interface Serial 3/0/0.1/1/1/0.1Router(config-if)# frame-relay ip rtp compression-connections 150Related Commands
Configures the maximum number of RTP header compression connections on a FR subinterface.
hw-module slot x np mode feature
To work in IPHC load the microcode on SIP-401/501/601 line card, which enables you to work in feature mode from Turbo mode. This is specifically used for working on IPHC.
hw-module slot x np mode feature
Syntax Description
x
Slot number in which SIP-401/501/601 line card is installed and on which you want to load the microcode and enable feature mode.
Command Modes
Global Configuration mode
Defaults
Turbo mode
Command History
Examples
The following example shows how to configure feature mode on both ingress and egress data paths on the network processor (NP):
Router> enableRouter# configure tRouter(config)# hw-module slot 2 np mode featureRelated Commands
no hw-module slot x np mode feature
Selects Turbo mode on the NP.
show controllers ise slot x np mode
Displays the microcode mode on the NP.
hw-module slot <slot> ip tcp compression-connections
To configure the maximum number of TCP context per line card, use the hw-module slot <slot> ip tcp compression-connections command. The default value is 4000 for the maximum number of connections.
hw-module slot <slot> ip tcp compression-connections <maximum number of connections>
Syntax Description
Command Modes
Global Configuration mode
Defaults
4000
Command History
Examples
The following example shows how to configure the maximum number of TCP context per line card:
Router> enableRouter# configure tRouter(config)# hw-module slot 2 ip tcp compression-connections 2000Related Commands
hw-module slot <slot> ip rtp compression-connections
To configure the maximum number of non-TCP (cRTP) context per line card, use the hw-module slot <slot> ip rtp compression-connections command. This command requires explicit user configuration for IPHC compression and decompression to work.
hw-module slot <slot> ip rtp compression-connections <maximum number of connections>
Syntax Description
Command Modes
Global Configuration mode
Defaults
20480
Command History
Examples
The following example shows how to configure feature mode on both ingress and egress data paths on the network processor (NP):
Router> enableRouter# configure tRouter(config)# hw-module slot 2 ip rtp compression-connections 2000Related Commands
ip header-compression disable-feedback
To disable CONTEXT_STATUS feedback messages from the interface or link, use the ip header-compression disable-feedback command in interface configuration mode. To enable CONTEXT_STATUS feedback messages from the interface or link, use the no form of this command.
ip header-compression disable-feedback
no ip header-compression disable-feedback
Syntax Description
This command has no arguments or keywords.
Defaults
CONTEXT_STATUS feedback messages are enabled by default.
Command Modes
Interface configuration
Command History
12.3(2)T
This command was introduced.
12.0(33)S2
This command was introduced for the first time on Cisco 12000 Series Routers for SIP-401/501/601 line card.
Usage Guidelines
The ip header-compression disable-feedback command is designed for use with satellite links where the path for the upward link is different from the path for the downward link. When the paths are different, CONTEXT_STATUS messages are not useful.
The ip header-compression disable-feedback command can be used with either Real-Time Transport Protocol (RTP) or TCP header compression.
Examples
The following example shows how to disable the CONTEXT_STATUS messages on the Serial2/0/0:0.1 subinterface:
Router> enable
Router# configure terminal
Router(config)# interface Serial2/0/0:0.1
Router(sub-if)# ip header-compression disable-feedback
Router(sub-if)# exit
Related Commands
Specifies the maximum size of the compressed IP header.
Specifies the maximum number of compressed packets between full headers.
ip header-compression max-header
To specify the maximum size of the compressed IP header, use the ip header-compression max-header command in interface configuration mode. To return the size of the compressed IP header to the default value, use the no form of this command.
ip header-compression max-header max-header-size
no ip header-compression max-header max-header-size
Syntax Description
max-header-size
Size of the IP header, in bytes. The size of the IP header can be in the range of 20 to 168 bytes.
Defaults
40 bytes for Cisco 12000 Series Routers on a SIP-401/501/601 line card
Command Modes
Interface configuration
Command History
12.3(2)T
This command was introduced.
12.0(33)S2
This command was introduced for the first time on Cisco 12000 Series Routers for SIP-401/501/601 line card.
Usage Guidelines
The max-header-size argument of the ip header-compression max-header command can be used to restrict the size of the header to be compressed.
Examples
The following example shows how to configure the maximum IP header size of the packet. In this configuration, the maximum IP header size is 100 bytes.
Router> enable
Router# configure terminal
Router(config)# interface Serial2/0/0:0.1
Router(sub-if)# ip header-compression max-header 100
Router(sub-if)# exit
Related Commands
Disables CONTEXT_STATUS feedback messages from the interface or link.
Specifies the maximum number of compressed packets between full headers.
ip header-compression max-period
To specify the maximum number of compressed packets between full headers, use the ip header-compression max-period command in interface configuration mode. To return the number of compressed packets to the default value, use the no form of this command.
ip header-compression max-period number-of-packets
no ip header-compression max-period number-of-packets
Syntax Description
number-of-packets
Specifies a number of packets between full headers. The number can be in the range of 0 to 65535 packets.
Defaults
256 packets
Command Modes
Interface configuration
Command History
12.3(2)T
This command was introduced.
12.0(33)S2
This command was introduced for the first time on Cisco 12000 Series Routers for SIP-401/501/601 line card.
Usage Guidelines
With the ip header-compression max-period command, full IP packet headers are sent every 'x' number of compressed packets configured using this command.
Examples
The following example shows how to configure the number of packets between full header packets. In this configuration, the packet number specified is 160.
Router> enable
Router# configure terminal
Router(config)# interface Serial2/0/0:0.1
Router(sub-if)# ip header-compression max-period 160
Router(sub-if)# exit
Related Commands
Disables CONTEXT_STATUS feedback messages from the interface or link.
Specifies the maximum size of the compressed IP header.
show ip rtp header-compression
To display the Real-Time Transport Protocol (RTP) header compression statistics, use the show ip rtp header-compression command from EXEC mode.
show ip rtp header-compression <interface>
Syntax Description
interface
Indicates the interface on the SIP-401/501/601 line card for which you want to view the RTP header compression statistics.
Defaults
Not Applicable
Command Modes
EXEC mode
Command History
Usage Guidelines
Use the show ip rtp header-compression command is used to view the RTP header compression statistics.
Examples
The following shows the RTP header compression statistics. The command output in bold indicates the statistics supported on Cisco 12000 Series Routers:
Router# show ip rtp header-compression
RTP/UDP/IP header compression statistics:
DLCI 200 Link/Destination info: point-to-point dlci
Interface Serial1/1/1:1.1 DLCI 200 (compression on, Cisco, RTP)
Distributed fast switched:
9 seconds since line card sent last stats update
Rcvd: 0 total, 0 compressed, 0 errors, 0 status msgs
0 dropped, 0 buffer copies, 0 buffer failures
Sent: 1001 total, 996 compressed, 0 status msgs, 996 not predicted
34855 bytes saved, 25205 bytes sent
2.38 efficiency improvement factor
Connect: 16 rx slots, 16 tx slots,
5 misses, 0 collisions, 0 negative cache hits, 32 free contexts
99% hit ratio, five minute miss rate 0 misses/sec, 0 ma
Related Commands
Enables RTP header compression on a FR subinterface.
Displays TCP header decompression statistics for FR.
show ip tcp header-compression
To display the TCP header decompression statistics, use the show ip tcp header-compression command from EXEC mode.
show ip tcp header-compression <interface>
Syntax Description
interface
Indicates the interface on the SIP-401/501/601 line card for which you want to view the TCP header decompression statistics.
Command Default
Not Applicable
Command Modes
EXEC mode
Command History
Usage Guidelines
Use the show ip tcp header-compression command is used to view the TCP header decompression statistics.
Examples
The following example shows the TCP header decompression statistics. The command output in bold indicates the statistics supported on Cisco 12000 Series Routers:
Router# show ip tcp header-compression
TCP/IP header compression statistics:
DLCI 200 Link/Destination info: point-to-point dlci
Interface Serial1/1/1:1.1 DLCI 200 (compression on, VJ)
Distributed fast switched:
6 seconds since line card sent last stats update
Rcvd: 0 total, 0 compressed, 0 errors, 0 status msgs
0 dropped, 0 buffer copies, 0 buffer failures
Sent: 0 total, 0 compressed, 0 status msgs, 0 not predicted
0 bytes saved, 0 bytes sent
Connect: 1 rx slots, 1 tx slots,
0 misses, 0 collisions, 0 negative cache hits, 1 free contexts
Related Commands
Enables TCP header decompression on a FR subinterface.
Displays RTP header compression statistics for FR.
Feature Information for IPHC Over Frame Relay
IPHC Over FR enables efficient transmission of delay sensitive traffic such as voice and video by compressing and decompressing the IP/UDP/TCP packets. This feature is applicable on Cisco 12000 series routers and only on Engine 5 based SIP-401/501/601 line cards on FR interfaces having Cisco as the encapsulation type.
Table 2 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS, Catalyst OS, and Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
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Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.
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