Cisco Cisco IOS XR Software Release 4.0

Cisco Session Border Controller (SBC) is not supported on any platform in Cisco IOS XR Software 
Release 4.0.1. Cisco IOS XR Software Release 3.7 is the last release that supports SBC.

The following new software features were introduced in Cisco IOS XR Software Release 4.0.1 on the 
Cisco XR 12000 Series Router platform:

IP Fast Reroute (IPFRR)—The following commands are introduced on the Cisco IOS XR Software 
Release 4.0.1:

ipfrr lfa

ipfrr lfa exclude interface

The following commands are modified to support this feature:

fast-reroute per-link

fast-reroute per-link exclude interface

For more information about these commands, refer to the Cisco IOS XR Routing Command 
Reference documentation.

IPHC Over Frame Relay for Interface Support—IP header compression over Frame Relay is 
supported on the Cisco XR 12000 Series Router in Cisco IOS XR software Release 4.0.1.

Inverse Multiplexing over ATM (IMA)—This feature is now supported on the 24-Port Channelized 
T1/E1 ATM CEoP SPA.

Policy Based Tunnel Selection (PBTS) Default Class—PBTS directs traffic into TE tunnels based 
on incoming packets TOS/EXP bits.

For more information about this feature, refer to the PBTS section of the Cisco IOS XR MPLS 
Configuration Guide for the Cisco XR 12000 Series Router.

Ingress ATM QoS and CEoPs L2 QoS on E5—ATM Layer 2 QoS support was added for Circuit 
Emulation over Packet Shared Port Adapters (CEoPs).

Ingress policing support was added for ATM AAL5SNAP, AAL5MUX, and AAL5NLPID 
encapsulated packets, for all 10 Gbps IP Services Engine (Engine 5) ATM SPAs.

For more information about this feature, refer to the Modular QoS Deployment Scenarios on Cisco 
IOS XR Software section of the Cisco IOS XR Modular Quality of Service Configuration Guide for 
the Cisco XR 12000 Series Router. 

FPD Upgrade—By default, the FPD image is not automatically upgraded. Generally you must 
manually upgrade the FPD image running on the SPA or SIP when you upgrade the Cisco IOS XR 
software image. Cisco IOS XR Release 4.0.1 introduces the following new command:

For more information about FPD upgrades, refer to the FPD Image Upgrade section of the Cisco 
IOS XR System Management Configuration Guide for the Cisco XR 12000 Series Router.

BFD Echo Latency Detection—Beginning in Cisco IOS XR 4.0.1, you can configure BFD sessions 
on non-bundle interfaces to bring down a BFD session when it exceeds the configured echo latency 
tolerance.