SEGMENT ROUTING IPV6 EXTENSION TO SUPPORT MULTICAST IN RAN AND PC
Point-to-Multipoint (p2mp) delivery of data in a SRv6 network for multicast/p2mp data delivery. Function and Argument bits are encoded Segment Routing (SRv6) as a Last Significant Bit in an IPv6 address. An SRv6 node can be encoded with a Segment ID to tunnel multicast through a node that does not support Bit Index Explicit Replication (BIER) SRv6 forwarding.
1 . A method comprising:
providing an Internet Protocol Version (IPv6) index format including a bitstring configured to address egress routers in a Bit Index Explicit Replication (BEIR) subdomain for Point-to-Multipoint delivery of data for Segment Routing (SR), the bitstring being a Bit-Index-6 format (BI6) configured to identify each of the egress routers with a Bit-Forwarding Router id (BFR-id), wherein the BFR-id translates to a Set Identifier (SI) and bitstring, wherein the SI is identified by a SI Locator, the SI Locator is a routable prefix configured to reach a specific set of the egress routers in the SI, and the IPv6 index format includes a Function bit and an Argument bit each configured as a Last Significant Bit (LSB) in an IPv6 address.
2 . The method of claim 1 , wherein the bitstring is encoded in a bitstring part of the BI6.
3 . The method of claim 1 , wherein the format comprises multiple Segment IDs (SIDs), wherein the multiple SIDs are for one or more of:
sending a packet though a predefined path to a first router of the egress routers in the BIER subdomain;
sending a packet though a legacy device that does not support BI6; or
sending a packet on to a node that is reachable over a transit LAN.
4 . The method of claim 1 , wherein the SI Locator is present in a destination address in an IPv6 header that provides a map of a Segment Routing Header (SRH).
5 . The method of claim 4 , wherein the SRH comprises an SID vector.
6 . The method of claim 4 , wherein the SRH comprises:
a Next Header configured identify a type of header immediately following ta Routing header;
a Segments Left configured to list the number of route segments remaining;
a Last Entry comprising the index in the Segment List including SID of the last element of the Segment List; and
a Segment List [0 . . . n] configured for the 128-bit IPv6 addresses representing the nth segment in the Segment List, wherein the Segment List is encoded starting from the last segment of an SR Policy.
7 . The method of claim 6 , further comprising:
encoding an SID stack to specify a multihop routing chain to the SRH, and
encoding the bitstring in initial SID locations of the SRH for a BIER bitmap.
8 . The method of claim 7 , wherein the bitstring length is any multiple of 128, the value of Segments Left are set to a length of the bitstream divided by 128 plus the number of elements present in the Segment List and, after the bitstring, a BI6 top-SID follows, which includes the SI Locator bit, an Argument bit and a Function bit.
9 . The method of claim 8 , wherein the SI Locator bit has a size of 48 for a maximum BI6 addressing space of an 80 bit length, and wherein the bit-index string length is determined by a Solicitor prefix length, the Argument bit and the Function bit.
10 . The method of claim 1 further comprising an ingress router that is programmed to execute ingress replication of packets to multiple BIER subdomains, wherein the ingress router is configured to introduce a path vector as an SID list on each of the packets.
11 . The method of claim 7 , wherein the SRH comprises Flags to mark presence of the BIER Bitmap in the SRH.
12 . A method comprising:
obtaining at a router a notice of a Bit-Index-6 format (BI6) capability of a neighboring device;
forming a map of a Bit-Forwarding Egress Router BFER to the nearest Bit-Forwarding Router (BFR) in an egress path; and
if a BFR is not connected, inserting the non-connected BFR's Segment ID (SID) into a packet SRH prior to forwarding the packet.
13 . The method of claim 12 , further comprising:
obtaining at the router a notice of a BI6 capability of all routers in an Interior Gateway Protocol (IGP) area;
forming a map of adjacent BFRs;
if an adjacent BFR is reachable over legacy nodes, and if the adjacent BFR is not directly connected, computing a list of the legacy nodes that must be passed through to reach the adjacent BFR;
maintaining by the BFR an SID vector to reach the adjacent BFR; and
when the packet is forwarded to the adjacent BFR, inserting an SID vector in the packet after forwarding updates in the bitmap.
14 . The method of claim 12 , further comprising:
receiving at a router an BI6 packet with a penultimate SID being that of itself;
stripping the SRH of all SIDs other than the SID of the BI6 packet; and
forwarding the packet.
15 . An apparatus comprising:
a router configured to at least obtain a notice of a Bit-Index-6 format (BI6) capability of a neighboring device; form a map of a Bit-Forwarding Egress Router BFER to the nearest Bit-Forwarding Router (BFR) in an egress path; and if a BFR is not connected, inserting the non-connected BFR's Segment ID (SID) into a packet SRH prior to forwarding the packet.
16 . The apparatus of claim 12 , wherein the router is further configured to at least:
obtain a notice of a BI6 capability of all routers in an Interior Gateway Protocol (IGP) area;
form a map of adjacent BFRs;
if an adjacent BFR is reachable over legacy nodes, and if the adjacent BFR is not directly connected, computing a list of the legacy nodes that must be passed through to reach the adjacent BFR;
maintain by the BFR an SID vector to reach the adjacent BFR; and
when the packet is forwarded to the adjacent BFR, insert an SID vector in the packet after forwarding updates in the bitmap.
17 . The apparatus of claim 12 , wherein the router is further configured to at least:
receive at a router an BI6 packet with a penultimate SID being that of itself;
strip the SRH of all SIDs other than the SID of the BI6 packet; and
forward the packet.