Fast reroute for segment routing traffic
An apparatus and method are disclosed for fast reroute (FRR) for native segment routing (SR) traffic. In one embodiment, a node receives a packet that includes a segment routing (SR) segment identifier (ID) stack. The node determines what type of segment is designated as the active segment in the segment ID stack. Based, at least in part on the type of active segment, the node selects an update routine out of several possible update routines and performs the selected update routine. The update routine modifies the segment ID stack.
1. A method comprising:
receiving a packet, wherein
the packet comprises a segment routing (SR) segment identifier (ID) stack;
determining an active segment type of a plurality of segment types, wherein
the active segment type is associated with an active segment in the SR segment ID stack, and
the active segment type is one of nodal segment or adjacency segment;
selecting an update routine based, at least in part, on the active segment type; and
performing the update routine, wherein
the performing the update routine comprises modifying the SR segment ID stack.
2. The method of claim 1 , further comprising:
detecting a reroute condition, wherein
the determining is performed in response to the detecting; and
forwarding a packet along a backup path specified by the SR segment ID stack.
3. The method of claim 1 , further comprising:
determining a next segment type associated with a next segment in the SR segment ID stack.
4. The method of claim 3 , further comprising:
determining a position within the SR segment ID stack, wherein
the position is based on the active segment type and the next segment type; and
pushing a protection list onto the SR segment ID stack at the position.
5. The method of claim 1 , wherein the modifying comprises:
pushing at least one segment identifier onto the SR segment ID stack.
6. The method of claim 5 , wherein
the at least one segment identifier comprises a protection list.
7. The method of claim 1 , wherein the modifying comprises:
popping at least one segment identifier off of the SR segment ID stack.
8. The method of claim 1 , further comprising:
detecting that the SR segment ID stack comprises a plurality of adjacency segment identifiers followed by a nodal segment identifier; and
in response to the detecting, popping each of the adjacency segment identifiers of the plurality of adjacency segment identifiers off of the SR segment ID stack.
9. The method of claim 3 , further comprising:
detecting that the active segment type is nodal segment and the next segment type is nodal segment; and
in response to the detecting, popping the active segment identifier off of the SR segment ID stack.
10. A system comprising:
a first node configured to
receive a packet, wherein
the packet comprises a segment routing (SR) segment identifier (ID) stack;
determine an active segment type of a plurality of segment types, wherein
the active segment type is associated with an active segment in the SR segment ID stack, and
the active segment type is one of nodal segment or adjacency segment;
select an update routine based, at least in part, on the active segment type; and
perform the update routine, wherein
performing the update routine comprises modifying the SR segment ID stack.
11. The system of claim 10 , wherein the first node is further configured to:
detect a reroute condition, wherein
determining the active segment type is performed in response to detecting the reroute condition; and
forward a packet along a backup path specified by the SR segment ID stack.
12. The system of claim 10 , wherein the first node is further configured to:
determine a next segment type associated with a next segment in the SR segment ID stack.
13. The system of claim 12 , wherein the first node is further configured to:
determine a position within the SR segment ID stack, wherein
the position is based on the active segment type and the next segment type; and
push a protection list onto the SR segment ID stack at the position.
14. The system of claim 12 , wherein the first node is further configured to:
detect that the active segment type is nodal segment and the next segment type is nodal segment; and
in response to detecting the active segment type and the next segment type, pop the active segment identifier off of the SR segment ID stack.
15. The system of claim 10 , wherein the first node is further configured to:
detect that the SR segment ID stack comprises a plurality of adjacency segment identifiers followed by a nodal segment identifier; and
pop each of the adjacency segment identifiers of the plurality of adjacency segment identifiers off of the SR segment ID stack.
16. A non-transitory computer readable medium comprising executable instructions, wherein a method is implemented in response to executing the instructions, the method comprising:
receiving a packet, wherein
the packet comprises a segment routing (SR) segment identifier (ID) stack;
determining an active segment type of a plurality of segment types, wherein
the active segment type is associated with an active segment in the SR segment ID stack, and
the active segment type is one of nodal segment or adjacency segment;
selecting an update routine based, at least in part, on the active segment type; and
performing the update routine, wherein
the performing the update routine comprises modifying the SR segment ID stack.
17. The non-transitory computer readable medium of claim 16 wherein the method further comprises:
detecting a reroute condition, wherein
the determining is performed in response to the detecting; and
forwarding a packet along a backup path specified by the SR segment ID stack.
18. The non-transitory computer readable medium of claim 16 wherein the method further comprises:
determining a next segment type associated with a next segment in the SR segment ID stack.
19. The non-transitory computer readable medium of claim 18 wherein the method further comprises:
determining a position within the SR segment ID stack, wherein
the position is based on the active segment type and the next segment type; and
pushing a protection list onto the SR segment ID stack at the position.
20. The non-transitory computer readable medium of claim 16 wherein the method further comprises:
detecting that the active segment type is nodal segment and the next segment type is nodal segment; and
in response to the detecting, popping the active segment identifier off of the SR segment ID stack.