This module provides information about Nonstop Routing (NSR), Stream Control Transmission Protocol (SCTP), Transmission Control Protocol (TCP), User Datagram Protocol (UDP
), and RAW Transports.
If you have specific requirements and need to adjust the NSR, SCTP, TCP, UDP, or
RAW values, refer to the Transport Stack Commands on Cisco IOS XR IP Addresses and Services Command
Reference for the Cisco XR 12000 Series Router.
Feature History for Configuring NSR, SCTP, TCP, UDP, and UDP RAW Transports on the Cisco IOS XR Software
Prerequisites for Configuring NSR, SCTP, TCP, UDP ,and RAW Transports
The following prerequisites are required to implement NSR, SCTP, TCP, UDP ,and RAW Transports:
You must be in a user group associated with a task group that includes the proper task IDs. The command reference guides include the task IDs required for each command. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Information About Configuring NSR, SCTP, TCP, UDP, and RAW Transports
To configure NSR, SCTP, TCP, UDP, and
RAW transports, you must understand the following concepts:
Nonstop Routing (NSR) is provided for Open Shortest Path First (OSPF) and Label
Distribution Protocol (LDP) protocols for the following events:
Route Processor (RP) or Distributed
Route Processor (DRP) failover
Process restart for either OSPF, LDP, or TCP
Minimum Disruption Restart (MDR)
In the case of the RP failover, NSR is achieved by for both TCP and the applications (OSPF
NSR is a method to achieve High Availability (HA) of the routing protocols. TCP connections
and the routing protocol sessions are migrated from the active RP to standby RP after the
RP failover without letting the peers know about the failover. Currently, the sessions
terminate and the protocols running on the standby RP reestablish the sessions after the
standby RP goes active. Graceful Restart (GR) extensions are used in place of NSR to
prevent traffic loss during an RP failover but GR has several drawbacks.
You can use the nsr process-failures switchover command to let
the RP failover be used as a recovery action when the active TCP or active LDP restarts.
When standby TCP or LDP restarts, only the NSR capability is lost till the standby
instances come up and the sessions are resynchronized but the sessions do not go down. In
the case of the process failure of an active OSPF, a fault-management policy is used. For
more information, refer to Implementing OSPF on Cisco IOS XR Routing Configuration Guide for the Cisco XR 12000 Series Router.
Stream Control Transmission Protocol (SCTP) is a reliable transport protocol that provides multihoming, stream support, and partial reliability. Multihoming occurs when one (or both) endpoints of a connection can consist of more than one IP address, which enables transparent failover between redundant network paths. SCTP can transport multiple message-streams.
TCP is a connection-oriented protocol that specifies the format of data and acknowledgments that two computer systems exchange to transfer data. TCP also specifies the procedures the computers use to ensure that the data arrives correctly. TCP allows multiple applications on a system to communicate concurrently, because it handles all demultiplexing of the incoming traffic among the application programs.
The User Datagram Protocol (UDP) is a connectionless transport-layer protocol that belongs to the IP family. UDP is the transport protocol for several well-known application-layer protocols, including Network File System (NFS), Simple Network Management Protocol (SNMP), Domain Name System (DNS), and TFTP.
Any IP protocol other than TCP, UDP, or SCTP is known as a RAW protocol.
For most sites, the default settings for the TCP, UDP, and RAW transports need not be changed.
How to Configure Failover as a Recovery Action for NSR
This task allows you to configure failover as a recovery action to process failures of
When the active TCP or the NSR client of the active TCP terminates or restarts, the TCP
sessions go down. To continue to provide NSR, failover is configured as a recovery
action. If failover is configured, a switchover is initiated if the active TCP or an
active application (for example, LDP, OSPF, and so forth) restarts or terminates.
For information on how to configure MPLS Label Distribution Protocol (LDP) for NSR,
refer to the
Cisco IOS XR
MPLS Configuration Guide for the Cisco XR 12000 Series Router.
For information on how to configure NSR on a per-process level for each
Open Shortest Path First (OSPF)
process, refer to the
Cisco IOS XR Routing Configuration Guide for the Cisco XR 12000 Series Router.
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.
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