Configuring Serial Interfaces on the Cisco ASR 9000 Series Router
Information About Configuring Serial Interfaces
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Cisco ASR 9000 Aggregation Services Router Interfaces and Hardware Component Configuration Guide
OL-26061-03
Table 22 shows the IPHC features, the values of the features, and their defaults:
Currently, only IPv4 unicast packets with UDP in the protocol field of the IP header are compressed.
IPHC is configured on an interface as follows:
• Configure the IPHC slot level command
• Create an IPHC profile
• Configure IPHC attributes in the profile
• Attach the profile to an interface
IPHC profiles must contain the rtp command to enable Real Time Protocol (RTP) on the interface, or
the profile is not enabled. The refresh rtp command must be used to enable the configured refresh
settings for RTP packets. By default, refresh RTP is disabled and only the first packet in the flow is sent
as a ‘full-header’ packet.
If some attributes, such as feedback messages, maximum refresh period size, maximum refresh time
period, and maximum header size, are not configured in the profile, the default values for those attributes
apply when the profile is enabled on the interface.
Currently, IPHC is supported only on serial interfaces with PPP encapsulation and on multilink with PPP
encapsulation interfaces.
IPHC is typically configured between the Customer Edge (CE) and Provide Edge (PE) ends of an
interface and must be configured at both ends of the interface to work. The PPP protocol negotiates the
IPHC specific parameters between the two ends of the interface and settles on the lowest value
configured between the two ends.
QoS and IPHC
An IPHC profile can be enabled on an interface so that the IPHC profile applies only to packets that
match a Quality of Service (QoS) service policy. In this case, the QoS service-policy class attributes
determine which packets are compressed. This allows users to fine tune IPHC with greater granularity.
Policy maps are attached to an interface using the service-policy command. IPHC action applies only to
output service policies. IPHC is not supported on input service policies.
Table 22 IPHC features and default setttings
IPHC Feature Values Defaults
TCP contexts 0 to 255 1
Non-TCP contexts 1 to 6000 16
Compression Format Options IETF or IPHC —
Feedback Messages Enable or Disable Enabled
Maximum Refresh Period Size 1 to 65535 packets 256
Maximum Refresh Time Period 0 to 255 seconds 5
Maximum Header Size 20 to 40 bytes 40
Real Time Protocol (RTP) Enable or Disable Enabled
Refresh RTP Enable or Disable Disable
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