Previous post “Network Slice – Flex-Algo” explains how segment routing with flex also can help operators to create network slice and serve different type of business requirements.
In this post, I will be covering how to create network slice in service provider network by using segment routing. By default, IGP uses metric as constraint to calculate the shortest path tree. But while using flex-algo, delay will be used as metric to calculate end to end shortest path tree. Once the flex-algo topology will be created, after that we will be using link affinity to color the links and create constraints for flex-also also.
Have to follow below steps to create network slice:
1. Configure flex-algo(K) where K=128 in every router which will partipate in network slice.
2. Configure pre-fix sid for flex-algo(K). We already have prefix-sid configured for flex-algo(0) and now we have to configure one more value for flex-algo(K) where K=128. This is different from the previous prefix-sid but will be configured under same loopback.
3. Advertise fixed delay number to make the calulcations easy. I will be using delay as 100 micro seconds.
Apply link affinity to color the links and create constraints for flex-also.
1. Color links with any name like RED.
2. Exclude RED color links in Flex-algo
We will be using the above topology for creating network slice. Basic setup and configurations can be used from the segment routing post. Configuration to create network slice:
Apply the following configuration to all routers S1, S2, L3, L4, P5, P6 and PE7
router isis lab
flex-algo 128 -> Flex-Algo(128) will be created and advertised
metric-type delay -> Delay will be used for path calculation
address-family ipv4 unicast
prefix-sid index -> This is already configured. Please check the earlier post of Segment Routing – Control and Data Plane
prefix-sid algorithm 128 absolute 1700X -> Replace X with Router Number. E.g. S1 will be using 17001 and PE7 will be suing 17007
interface GigabitEthernet0/0/0/X -> Replace X with all the interfaces which will be advertising delay