Path Computing and Signaling

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A path in a segment routing domain consists of a list of SIDs that identify the path from the source to the destination. A Path Computation Element (PCE) assists network nodes, known as Path Computation Clients (PCCs), by computing paths based on network topology information acquired from the IGP (IS-IS) and path computation constraints like the IGP metric. The path computation can be triggered by the PCE or the PCC, which are then correspondingly called PCE-initiated and PCC-initiated paths.

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In this test, two types of paths were computed, which are segment routing policy (SR-Policy) as defined in the draft "draft-ietf-pce-segment-routing-policy-cp" and segment routing traffic engineering (SR-TE) as defined in the "RFC8664". The test iterations also involved multiple scenarios, like using SR-MPLS and SRv6 (full SID and μSID) as the dataplane. Besides using PCEP for the path request and signaling, BGP was also utilized in some iterations to signal PCE-initiated paths to the PCC.

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The steps used to conduct the test were as follows

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*. Verify the PCEP status between the PCE and the PCC

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*. (PCEP) Trigger a path computation either by the PCC or the PCE

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*. (PCEP) Verify that the PCC reported the path instantiation to the PCE

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*. (BGP) Compute and signal a path from PCE to the PCC

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*. Verify the correct path instantiation on the PCC

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[[Figure 53: PCEP SR-Policy Computation and Signaling over SR-MPLS>>image:433488184811257857_SDN-1-PCEP-SR-MPLS-1-V1.png||alt="Figure 53" width="550"]]

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[[Figure 54: PCEP SR-Policy Computation and Signaling over SRv6 (full SID, μSID)>>image:433488185163841537_SDN-1-PCEP-SRv6-2-V1.png||alt="Figure 54" width="550"]]

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[[Figure 55: BGP SR-Policy Computation and Signaling over SR-MPLS>>image:433488184811388929_SDN-1-SR-MPLS-BGP-3-V1.png||alt="Figure 55" width="550"]]

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[[Figure 56: BGP SR-Policy Computation and Signaling over SRv6 μSID>>image:433488184811454465_SDN-1-uSID-BGP-4-V1.png||alt="Figure 56" width="550"]]

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[[Figure 57: PCEP SR-TE Computation and Signaling over SR-MPLS>>image:433488184811520001_SDN-30-SR-MPLS-5-V1.png||alt="Figure 57" width="550"]]

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|=PCE|=PCC|=Data Plane|=Target Address

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|Keysight IxNetwork|Nokia 7750 SR-1|SRv6 μSID|IPv4

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|Keysight IxNetwork|H3C CR16000-M1A|SRv6 μSID|IPv4

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|Keysight IxNetwork|H3C CR16000-M1A|SR-MPLS|IPv4

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|Nokia Network Services Platform (NSP)|H3C CR16005E-F|SR-MPLS|IPv4

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|Nokia Network Services Platform (NSP)|Keysight IxNetwork|SR-MPLS|IPv4

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|Nokia Network Services Platform (NSP)|Keysight IxNetwork|SR-MPLS|IPv6

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|Nokia Network Services Platform (NSP)|H3C CR16005E-F|SR-MPLS|IPv6

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Table 1: SR-Policy Computing and Signaling - BGP

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Table 2: SR-Policy Computing and Signaling - PCEP

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Table 3: SR-TE Computation and Signaling - PCEP

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