SRv6 OAM Extensions
As SRv6 simply adds a new type of routing extension header to implement forwarding based on the IPv6 data plane, ICMPv6 ping & tracert can be directly used on an SRv6 network for continuity check based on common IPv6 addresses, without requiring any changes to hardware or software. ICMPv6 ping and tracert both support packet forwarding to a destination address over the shortest path, thereby checking the reachability to the destination.
If the destination address is an SRv6 SID, the check can be performed through either ICMPv6 ping & tracert or SRv6 OAM extensions. Currently, SRv6 OAM extensions are implemented by setting the O-bit (OAM bit) in the SRH or by inserting an End.OP SID at an appropriate place in the SRH.
SRH O-bit
O-bit is located in the Flags field of the SRH shown in Figure 1. Figure 1 shows the format of the Flags field.
O-bit indicates that the local packet is an OAM packet. If O-bit is set, each SRv6 endpoint node needs to copy the received data packet, add a timestamp to the packet, and then send the packet to the control plane for further processing, for example, for analysis by an analyzer. To prevent reprocessing the same packet, the control plane does not need to respond to upper-layer IPv6 protocol operations, such as ICMPv6 ping & tracert.
As each SRv6 endpoint node needs to process ICMPv6 packets carrying the O-bit, segment-by-segment detection can be implemented based on the O-bit.
End.OP SID
End.OP SID is a variant of the End function. It instructs a data packet to be sent to the control plane for OAM processing. For details about the function of the End.OP SID, see End.OP SID.
Only the SRv6 endpoint node that generates an End.OP SID can process ICMPv6 packets. Therefore, end-to-end detection can be implemented based on the End.OP SID.