Segment Routing, Part I by Clarence Filsfils & Michielsen Kris & Talaulikar Ketan

Author:Clarence Filsfils & Michielsen,Kris & Talaulikar,Ketan [Filsfils, Clarence]
Language: eng
Format: azw3
Tags: SR, Segment Routing, SPRING
Published: 2016-10-06T04:00:00+00:00

HIGHLIGHT: BGP SR in Data Center

BGP Prefix SID brings improved Traffic Engineering capabilities in the DC.

The SR traffic steering capabilities can be utilized to solve existing problems in the DC.

Nodes in the DC can steer traffic (as flows or flowlets) to improve load-balancing efficiency, avoid hotspots, or use the best performing path.

SR OAM probes can be steered on any path through the network to validate path liveliness.

6.8 BGP Prefix-SID in Data Center

We have seen previously in sections 6.2 (“BGP Prefix-SID”) and 6.3 (“BGP Prefix-SID Advertisement”) how SR BGP extends the BGP-LU mechanism to also signal the Prefix-SID for BGP. Here we will look at an example of its application for enabling SR BGP in a Data Center.

In the Data Center topology of Figure 6-12, a single path from Node1 to Node3 is now examined, the path Node1→Node11→Node31→Node21→Node3. The path is represented as an unfolded path in Figure 6-18. Same as for the BGP-LU example used earlier in this chapter, External BGP sessions are established between the nodes. All nodes in the network have SR BGP enabled, using the same SRGB [16000-23999]. A Prefix-SID with SID index 3 is configured on Node3 for its loopback prefix 1.1.1.3/32. Node3 advertises prefix 1.1.1.3/32 to Node21 in BGP-LU, with label value 3 (implicit-null). The BGP nexthop for this prefix is the interface address 99.21.3.3. Node3 also adds the BGP Prefix-SID attribute to the update message, specifying Prefix-SID index 3. Notice that both a label value and a SID index are advertised with the prefix (Figure 6-18 (a)).

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