This feature adds support of the Target FEC Stack TLV of type BGP Labeled IPv4 /32 Prefix as defined in RFC 8029.
The new TLV is structured as shown in Figure: Target FEC stack TLV for a BGP labeled IPv4 and IPv6 prefixes.
The user issues a LSP ping using the existing CLI command and specifying a new type of prefix:
oam lsp-ping bgp-label prefix ip-prefix/mask [src-ip-address ip-address] [fc fc-name [profile {in | out}]] [size octets] [ttl label-ttl] [send-count send-count] [timeout timeout] [interval interval] [path-destination ip-address [interface if-name | next-hop ip-address]] [detail]
This feature supports BGP label IPv4 prefixes with a prefix length of 32 bits only and supports IPv6 prefixes with a prefix length of 128 bits only.
The path-destination option is used to exercise specific ECMP paths in the network when the LSR performs hashing on the MPLS packet.
Similarly, the user issues a LSP trace using the following command:
oam lsp-trace bgp-label prefix ip-prefix/mask [src-ip-address ip-address] [fc fc-name [profile {in | out}]] [max-fail no-response-count] [probe-count probes-per-hop] [size octets] [min-ttl min-label-ttl] [max-ttl max-label-ttl] [timeout timeout] [interval interval] [path-destination ip-address [interface if-name | next-hop ip-address]] [detail]
The following is the process to send and respond to an LSP ping or LSP trace packet. This process is valid when the downstream mapping is set to the DSMAP TLV. The detailed procedures with the DDMAP TLV are presented in Using DDMAP TLV in LSP stitching and LSP hierarchy.
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The next-hop of a BGP label route for a IPv4 /32 or an IPv6 /128 can be resolved to either an IPv4 transport tunnel or to an IPv6 transport tunnel. Thus, the sender node encapsulates the packet of the echo request message with a label stack which consists of the transport label stack as the outer labels and the BGP label as the inner label.
If the packet expires on a node which acts as an LSR for the outer transport LSP, and does not have context for the BGP label prefix, the outer label in the stack is validated and if the validation is successful it replies as in the case when it receives an echo request message for an LDP FEC which is stitched to a BGP IPv4 label route. In other words, it replies with return code 8 Label switched at stack-depth <RSC>.
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An LSR node which is the next-hop for the BGP label prefix as well as the LER node which originated the BGP label prefix have full context for the BGP IPv4 or IPv6 target FEC stack and can therefore perform full validation of it.
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If a BGP IPv4 label route is stitched to an LDP FEC, the egress LER for the resulting LDP FEC does not have context for the BGP IPv4 target FEC stack in the echo request message and replies with return code 4 Replying router has no mapping for the FEC at stack- depth <RSC>. This is the same behavior as that of an LDP FEC which is stitched to a BGP IPv4 label route when the echo request message reaches the egress LER for the BGP prefix.
Note that only BGP label IPv4 /32 prefixes and BGP IPv6 /128 prefixes are supported because only these are usable as tunnels on the Nokia router platforms. The BGP IPv4 or IPv6 label prefix is also supported with the prefix SID attribute if BGP segment routing is enabled on the routers participating in the path of the tunnel.
The responder node must have an IPv4 address to use as the source address of the IPv4 echo reply packet. SR OS uses the system interface IPv4 address. When an IPv4 BGP label route resolves to an IPv6 next-hop and uses an IPv6 transport tunnel, any LSR or LER node which responds to an lsp-ping or lsp-trace message must have an IPv4 address assigned to the system interface or the reply is not sent. In the latter case, the lsp-ping or lsp-trace probe times out at the sender node.
Similarly, the responder node must have an IPv6 address assigned to the system interface so that it gets used in the IPv6 echo reply packet in the case of a BGP-LU IPv6 label route when resolved to an IPv4 or an IPv4-mapped IPv6 next-hop which itself is resolved to an IPv4 transport tunnel.