Abstract: In some implementations, a network device may identify a segment routing traffic engineering (SR-TE) algorithm supported by the network device. The network device may determine, based on identifying the SR-TE algorithm, an identification value associated with the network device. The network device may generate an advertisement packet that includes the identification value and information identifying the SR-TE algorithm. The network device may send the advertisement packet to another network device to cause the other network device to update a data structure to indicate that the network device supports the SR-TE algorithm and that the network device is associated with the identification value. The other network device may determine, using the SR-TE algorithm, a forwarding path for a data packet that indicates the network device as a hop in the forwarding path.

Abstract: A node may receive a network topology message that identifies a first association of a first segment identifier (SID), relating to a loosely routed segment of a network, and an address of a first terminal interface associated with the loosely routed segment, or a second association of a second SID, relating to a strictly routed segment of the network, and an address of a second terminal interface associated with the strictly routed segment. The node may generate an entry in a segment translation table based on the first association or the second association. The node may route, according to the segment translation table, an internet protocol (IP) payload packet that has been encapsulated using an IPv6 transport header that has been extended with a compressed routing header of variable length.

Abstract: In some implementations, a network device may identify a segment routing traffic engineering (SR-TE) algorithm supported by the network device. The network device may determine, based on identifying the SR-TE algorithm, an identification value associated with the network device. The network device may generate an advertisement packet that includes the identification value and information identifying the SR-TE algorithm. The network device may send the advertisement packet to another network device to cause the other network device to update a data structure to indicate that the network device supports the SR-TE algorithm and that the network device is associated with the identification value. The other network device may determine, using the SR-TE algorithm, a forwarding path for a data packet that indicates the network device as a hop in the forwarding path.

Abstract: A network device may receive policy data identifying a first segment routing (SR) policy and a second SR policy. The first SR policy may be associated with a first path through a network and a first next hop, and the second SR policy may be associated with a second path through the network and a second next hop. The network device may advertise, to another device, reachability associated with the first next hop and the second next hop, and may receive, from the other device, a packet with a header. The network device may determine, from the header, data identifying the first next hop or the second next hop, without performing a lookup, and may cause the packet to be routed to a destination address, via the first path or the second path, based on the policy data associated with the first next hop or the second next hop.

Abstract: Ping or traceroute functionality is supported in a path spanning multiple autonomous systems (ASes) having segment routing (SR) enabled, the path including an ingress node in a first autonomous system (AS) and an egress node in an AS other than the first AS, using a reverse path label pair including (1) a node segment identifier (SID) corresponding to an AS Border Router (ASBR) of the second AS (second ASBR), and (2) an egress peer engineering (EPE) SID corresponding to a segment between the second ASBR to an ASBR of the first AS (first ASBR). Responsive to receiving a ping or traceroute request by a router in the second AS, the router generates a ping or traceroute reply including the reverse path label pair. The ping or traceroute reply is forwarded to the second ASBR using the node SID of the reverse path label pair. The ping or traceroute reply is then forwarded from the second ASBR to the first ASBR using the EPE SID of the reverse path label pair.

Abstract: This disclosure describes techniques for using Operations, Administration, and Management (OAM) operations when routing packets using micro SIDs in segment routing. For example, a network device comprises one or more processors configured to: receive a packet; determine whether the packet is encapsulated with one or more micro segment identifiers (SIDs); in response to a determination that the packet is not encapsulated with one or more micro SIDs, determine whether the packet has reached a segment routing tunnel endpoint; and in response to a determination that the packet has reached the segment routing tunnel endpoint, initiate Operations, Administration, and Maintenance (OAM).

Abstract: In general, various aspects of the techniques described in this disclosure provide a sequence number checksum for link state protocols. In one example, the disclosure describes an apparatus, such as a network device, having a control unit operative to obtain link state information describing links between pairs of the network devices in a network topology, the link state information being fragmented into a plurality of link state protocol (LSP) fragments; compute a sequence number checksum from sequence numbers of the link state protocol (LSP) fragments; receive an LSP data unit from another network device in the network; determine whether a sequence number checksum in the LSP data unit matches a sequence number checksum computed from the link state information; and configure a delay for processing the LSP data unit in response to determining a mismatch between the sequence number checksum of the LSP data unit and the sequence number checksum computed from the link state information.

Abstract: This disclosure describes techniques that include determining, at an egress node in an SRm6 network, how to process a packet that may arrive without a segment routing header and/or a compressed routing header. In one example, this disclosure describes a method that includes receiving, by an egress node of a segment routing network, segment routing advertisements; configuring, by the egress node and based on the segment routing advertisements, information enabling the egress node to recognize encapsulated packets arriving at the egress node without a compressed routing header; receiving, by the egress node, a packet that does not have a compressed routing header; and de-encapsulating, by the egress node and based on the stored information, the packet.

Abstract: Techniques are described for selectively pinging certain devices along a segment routing label switched path (LSP) to detect failures in the segment routing LSP. For example, an ingress device comprises one or more processors operably coupled to a memory that are configured to: in response to a request to verify connectivity of a segment routing LSP, configure a FEC stack specifying a stack of segment routing labels for the segment routing LSP; for each of the one or more devices identified from the FEC stack: generate a respective MPLS connectivity request packet for a respective device identified from an outermost FEC of the FEC stack; send the MPLS connectivity request packet to the respective device; receive an MPLS connectivity response packet that verifies connectivity of the respective device; and in response, update the FEC stack by removing the outermost FEC of the FEC stack that identifies the respective device.

Abstract: In some implementations, a first network device may receive an advertisement from a second network device. The advertisement may be associated with indicating that the second network device is configured to support a particular flex-algorithm. The first network device may identify, in the advertisement, an address of the second network device. The first network device may configure a routing table of the first network device to indicate that the second network device is capable of receiving traffic associated with the particular flex-algorithm based on the address. The first network device may perform, using the routing table, an action associated with routing the traffic associated with the particular flex-algorithm.

Abstract: A route reflector (e.g., a flex-algorithm optimal route reflector (ORR)) may receive an advertisement communication from a network device of a network associated with the route reflector and may identify, in the advertisement communication, information identifying one or more flex-algorithms that are supported by the network device. The route reflector may determine, based on the information identifying the one or more flex-algorithms that are supported by the network device, a set of routing paths associated with a flex-algorithm of the one or more flex-algorithms. The route reflector may update a data structure to include routing path information that indicates the set of routing paths associated with the flex-algorithm and may transmit a routing communication that includes routing information associated with the routing path information to the network device.

Abstract: Techniques are described for using route target constraint to filter routes advertised to a node in a seamless Multiprotocol Label Switching (MPLS) network. For example, a first router of a first network may generate a first border gateway protocol (BGP) message to advertise routing information for a first node of the first network, the first BGP message indicating a transport class and specifying an address-specific route target, the transport class comprising one or more tunnels to the first node that share common characteristics. In response to receiving a second BGP message originated by second node of a second network, the second BGP message comprising the address-specific route target, the first router sends the first BGP message to a second router of the second network for sending to the second node to cause the second node to import the routing information.

Abstract: Techniques are described for selectively pinging certain devices along a segment routing label switched path (LSP) to detect failures in the segment routing LSP. For example, an ingress device comprises one or more processors operably coupled to a memory that are configured to: in response to a request to verify connectivity of a segment routing LSP, configure a FEC stack specifying a stack of segment routing labels for the segment routing LSP; for each of the one or more devices identified from the FEC stack: generate a respective MPLS connectivity request packet for a respective device identified from an outermost FEC of the FEC stack; send the MPLS connectivity request packet to the respective device; receive an MPLS connectivity response packet that verifies connectivity of the respective device; and in response, update the FEC stack by removing the outermost FEC of the FEC stack that identifies the respective device.

Abstract: Techniques are described by which a routing protocol, such as border gateway protocol (BGP), is extended to control propagation and importation of information using route targets (RTs) specified as bitmasks that encode link administrative group information. For example, a network control device (e.g., controller) is configured to allocate one or more subset of resources (e.g., nodes or links) of an underlay network to each of one or more virtual networks established over the underlay network. The controller generates a bitmask encoded with link administrative group information of the one or more links. The controller then outputs, to a plurality of provider edge (PE) routers that are participating in a respective virtual network, a routing protocol message to advertise the one or more subset of resources, wherein the routing protocol message includes a route target specified as the bitmask.

Abstract: Techniques are described for providing end-to-end segment routing paths across metropolitan area networks. For example, a method comprises receiving, by an area border router (ABR) connected to one or more metropolitan area networks and a core network, a packet including a segment routing label stack including at least a label of the ABR, a context label associated with a routing instance of the ABR, and a subsequent label identifying a device in the segment routing path, determining, from a lookup of the context label in the metro routing table, a table next hop to the core routing table (or metro routing table); in response to determining the table next hop, determining, from a lookup of the subsequent label in the core routing table (or metro routing table), a next hop in the segment routing path; and sending, by the ABR, the packet toward the device in the segment routing path.

Abstract: Techniques are described for advertising constraint-based path computation (e.g., flexible-algorithm) through a constrained network topology. For example, a network device comprises a memory and one or more programmable processors operably coupled to the memory, wherein the one or more programmable processors are configured to generate a packet including a segment identifier (SID) offset, wherein the SID offset is an offset value associated with the flexible-algorithm. The one or more programmable processors of the network device are also configured to send, to at least one other network device of the plurality of network devices, the SID offset to enable the at least one other network device to derive a node segment identifier for the at least one other network device to participate in the flexible-algorithm.

Abstract: A network device may receive topology data identifying a spine and leaf topology of network devices, and may set link metrics to a common value to generate modified topology data. The network device may remove data identifying connections from leaf network devices to any devices outside the topology from the modified topology data to generate further modified topology data, and may process the further modified topology data, with a model, to determine path data identifying paths to destinations. The network device may determine particular path data identifying shorter paths and longer paths to corresponding destinations, and may determine hop counts associated with the paths. The network device may determine whether the hop counts are all odd values, all even values, or odd and even values, and may perform actions based on whether the hop counts are all odd values, all even values, or odd and even values.

Abstract: Echo or traceroute functionality is supported in a path spanning multiple autonomous systems (ASes) having segment routing (SR) enabled, the path including an ingress node and an egress node, by: (a) obtaining a return label stack to reach the ingress node from either (A) the egress node, or (B) a transit node in the path; (b) obtaining a label stack to reach, from the ingress node, either (A) the egress node, or (B) the transit node; (c) generating a request message including the return label stack; and (d) sending the request message towards either (A) the egress node, or (B) the transit node using the label stack.

Abstract: Ping or traceroute functionality is supported in a path spanning multiple autonomous systems (ASes) having segment routing (SR) enabled, the path including an ingress node in a first autonomous system (AS) and an egress node in an AS other than the first AS, using a reverse path label pair including (1) a node segment identifier (SID) corresponding to an AS Border Router (ASBR) of the second AS (second ASBR), and (2) an egress peer engineering (EPE) SID corresponding to a segment between the second ASBR to an ASBR of the first AS (first ASBR). Responsive to receiving a ping or traceroute request by a router in the second AS, the router generates a ping or traceroute reply including the reverse path label pair. The ping or traceroute reply is forwarded to the second ASBR using the node SID of the reverse path label pair. The ping or traceroute reply is then forwarded from the second ASBR to the first ASBR using the EPE SID of the reverse path label pair.

Abstract: A first network device may determine that a link-state database (LSDB), associated with the first network device, includes a first link-state advertisement (LSA) instance associated with a second network device. The first network device may determine that the first network device has not received a second LSA instance, associated with the second network device, that does not include information identifying a fully adjacent link between the second network device and the first network device. The first network device may receive the second LSA instance associated with the second network device and may transmit, to the second network device, a third LSA instance, associated with the first network device, that includes the information identifying the fully adjacent link between the second network device and the first network device, only after the second LSA instance is received.