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SRv6 OAM
SRv6 Operation, Administration, and Maintenance (OAM) monitors SRv6 path connectivity and rapidly detects faults. SRv6 OAM is implemented using IPv6 ping and tracert.
SRv6 Ping
In Figure 3-7, nodes A, D, G,
and Z have SRv6 capabilities. An SRv6 tunnel is established between
nodes A and Z.
Node A pings the SRv6 tunnel. The process is as follows:
- Node A constructs an IPv6 Echo Request packet that carries whole IPv6 link information <Z, G, D>. The IPv6 DA is set to node D. A searches the IPv6 routing table and forwards the packet to node B.
- SRv6-incapable node B cannot process this packet and searches the IPv6 routing table to transparently transmit the packet to node D.
- Upon receipt of the packet, node D finds that itself is the IPv6 DA. Node D updates the IPv6 DA and SL information and searches the IPv6 routing table to forward the packet to node F.
- SRv6-incapable node F processes the packet in the same way as node B.
- Upon receipt of the packet, node G finds that itself is the IPv6 DA and the SL is reduced to 0, indicating that node G is the penultimate node. Node G updates the IPv6 DA, deletes IPv6 link information <Z, G, D>, and searches the IPv6 routing table to send the packet to node Z.
- Upon receipt of the packet, node Z processes the received IPv6 packet and sends it to the host transceiver module for processing. Then, node Z returns an IPv6 Echo Reply packet to node A.
- Node A receives the IPv6 Echo Reply packet and generates SRv6 ping results. If node A does not receive IPv6 Echo Reply packets, the tracert operation fails.
SRv6 Tracert
The tracert mechanism is similar to the ping mechanism. Tracert first sends a packet with the TTL value of 1. Each time a tracert packet is sent, the TTL increases by one. Tracert checks whether a network connection is reachable and where a fault occurs.
In Figure 3-7, node A initiates
a tracert operation on an SRv6 tunnel. The process is as follows:
- Node A continuously constructs IPv6 Echo Request packets and forwards them to node D.
- Node D checks whether TTL-1 is 0:
- If TTL-1 is 0, the packets are sent to the host transceiver for processing after the TTL times out.
- If TTL-1 is greater than 0, node D updates the IPv6 DA and SL information, searches the IPv6 routing table, and forwards the packets to the next-hop node G.
- Node G processes them in the same way as D. G checks whether TTL-1
is 0:
- If TTL-1 is 0, the packets are sent to the host transceiver for processing after the TTL times out.
- If TTL-1 is greater than 0, node G updates the IPv6 DA and SL information, searches the IPv6 routing table, and forwards the packets to the next-hop node Z.
- After common IPv6 packets arrive at node Z, node Z sends the packet to the host transceiver for processing and returns IPv6 Echo Reply packets to node A.
- After node A receives IPv6 Echo Reply packets, it generates SRv6 tracert results. If node A does not receive IPv6 Echo Reply packets, the tracert operation fails.
