A network administrator is planning a new network with a segment-routing architecture using a distributed control plane. How is routing information distributed on such a network?
A.
Each segment is signaled by a compatible routing protocol, and each segment makes its own steering decisions based on SR policy.
B.
Each segment is signaled by MPLS, and each segment makes steering decisions based on the routing policy pushed by BGP.
C.
Each segment is signaled by an SR controller, but each segment makes its own steering decisions based on SR policy.
D.
Each segment is signaled by an SR controller that makes the steering decisions for each node.
I think it should be A based on the following documentation.
https://www.cisco.com/c/en/us/support/docs/multiprotocol-label-switching-mpls/mpls/215215-segment-routing-overview-and-migration-g.html
These gains are achieved by eliminating resource-intensive control plane signaling protocols of MPLS and moves intelligence to the headend device in distributed deployment vs to a centralized controller in a centralized deployment hence reducing the complexity from the network to a greater extend.
The distributed intelligence of the network is used to build these segments at the ingress node, adaptable to any network topology change and pre-calculated backup path against node or link failures that can be activated within sub-milliseconds. The centralized intelligence can focus on network resource optimization by pushing optimum end-to-end paths in the network by a centralized entity.
I think so
A headend can learn different candidate paths of an SR Policy via different available means like via local configuration, via Path Computation Element Communication Protocol (PCEP) or BGP SR-TE. In a distributed control-plane environment, the candidate path is likely to be learned by the headend via local configuration or automated solution such as Cisco NSO. In a centralized control-plane environment, the candidate path is likely to be learned by the headend from the controller via BGP SR-TE or PCEP.
https://www.cisco.com/c/en/us/support/docs/multiprotocol-label-switching-mpls/mpls/215215-segment-routing-overview-and-migration-g.html#anc8
Excerpt >
In a distributed scenario, the segments are allocated and signaled by IS-IS or OSPF or BGP. A node individually decides to steer packets on an SR Policy (e.g., pre-computed local protection [RFC8355]). A node individually computes the SR Policy.
https://www.cisco.com/c/en/us/support/docs/multiprotocol-label-switching-mpls/mpls/215215-segment-routing-overview-and-migration-g.html
It seems that besides the "distributed control plane" phrase, it's refering SR with SDN Controller:
This article confirms it's A. "The Segment Routing control plane can run purely as a distributed control plane, or it can use a hybrid approach where more complex forwarding paradigms (such as inter-domain routing) are required."
Distributed control plane = no SDN controller.
i go for A! Distributed control plane is the contrary of controller...
upvoted 3 times
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