Enabling Segment Routing with XTC and JUNOS: A Packet Design How-to

Segment Routing is being widely adopted over RSVP-TE due to its simplicity in forwarding traffic over non-shortest paths for Traffic Engineering, protection against failures, BGP exit selection, SLA conforming service paths, and others. In this blog, we will go step by step into how to enable Segment Routing on Cisco XTC Controller, JUNOS and the Packet Design SDN Platform.


Cisco XTC

XTC is the acronym for XR Traffic Controller. The Controller software is provided as part of Cisco IOS XR operating system. XTC has a southbound interface to the network through multiple routing protocols: OSPF, IS-IS, BGP Link-State (BGP-LS). It also provides northbound interface for integration with other applications and products like the Packet Design Explorer Suite.

Southbound PCEP Interface

XTC has a PCE server that uses PCEP (Path Computation Element Communication Protocol) to push updates to the network. PCCs (Path Computation Client) can connect to the PCE server running in XTC to report their LSPs in a stateful manner. Using PCEP, XTC is able to update the attributes of the LSPs in PCC. XTC can create new LSPs in PCCs as well. The PCEP server can be enabled in IOS-XR supporting XTC functionality as below:

 address ipv4

Northbound REST Interface

XTC supports widely-used northbound interfaces like NETCONF/YANG, REST/JSON and gRPC. Packet Design’s SDN Platform has been integrated with XTC using the REST/JSON interface. Packet Design’s SDN applications viz the SDN Traffic Engineering App and SDN Path Provisioning App can provision, de-provision and update Segment Routed LSPs by making use of the rich analytics provided in the Explorer Suite.


JUNOS supports Segment Routing in its IGP. SPRING-TE (Source Packet Routing in Networking) is supported through the PCEP protocol. The Packet Design Explorer Suite’s independent and vendor-agnostic set of integrated technologies enables the real-time monitoring and analysis of Segment Routing in IGP as well as SPRING-TE.

JUNOS configurations for enabling Segment Routing in IGP and PCEP are given below:


isis { 
 source-packet-routing { 
  node-segment ipv4-index 251; 
 level 2 wide-metrics-only; 
 level 1 disable; 
 interface ge-0/0/0.0 { 
 interface lo0.0; 


pcep {
 pce xtc {
  destination-port 4189;
  pce-type active stateful;

Explorer SDN Platform

Packet Design’s Explorer SDN Platform is leading and embracing the evolution of SDN and Segment Routing. Recently, XL Axiata, one of Indonesia’s leading telecommunications service providers, deployed our SDN Platform in their production network – another proof point that adoption of SDN in the WAN is finally happening.

Request A Demo | More Resources | Follow us on Twitter