Figure 82 End.OP SID used in an SRv6 SID-based ping
IPv6 SA=a, IPv6 DA=b
SRH[(c, op, b) SL=2]
ICMPv6 Echo Request
End.OP SID=op
Device A
SRv6 SID=a
Device B
SRv6 SID=b
Device C
SRv6 SID=c
IPv6 SA=b, IPv6 DA=op
SRH[(c, op, b) SL=1]
ICMPv6 Echo Request
SRv6 SID-based ping
SRv6 OAM supports segment-by-segment ping and end-to-end ping.
Segment-by-segment ping
Use segment-by-segment ping to detect connectivity of all SRv6 nodes in the SRv6 path. All SRv6 nodes will send an ICMPv6 echo reply to the source node.
In a segment-by-segment ping operation, do not specify the End.OP SID because some nodes might fail to send a reply.
Figure 83 Segment-by-segment ping
IPv6 SA=a, IPv6 DA=b
SRH[(d, b) SL=1]
ICMPv6 Echo Request
A
SRv6 SID=a
B
SRv6 SID=b
C D
SRv6 SID=d
IPv6 SA=b, IPv6 DA=d
SRH[(d, b) SL=0]
ICMPv6 Echo Request
Figure 83 shows the segment-by-segment ping process as follows:
1. Device A initiates a ping to Device D, with the SRv6 SIDs of Device B and Device D specified. It constructs an ICMPv6 echo request encapsulated with an SRH and then forwards the request.
2. Upon receiving the ICMPv6 echo request, the intermediate node performs relevant operations depending on whether it is SRv6 capable:
On an SRv6 capable node (such as Device B):
The node sends an ICMPv6 echo reply to Device A, and forwards the ICMPv6 echo request based on the SRH if the following conditions exist:
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−
The packet destination IPv6 address is the local SRv6 SID.
−
The O-flag is set in the packet SRH Flags field.
On an SRv6 incapable node (such as Device C):
The node forwards the ICMPv6 echo request according to routing table lookup without returning an ICMPv6 echo reply to Device A.
3. Upon receiving the ICMPv6 echo request with O-flag set and SL=0 in the SRH, Device D verifies the packet destination IPv6 address.
If the IPv6 address is the local SRv6 SID, the verification succeeds, and Device D sends an
ICMPv6 echo reply to Device A.
If the IPv6 address is not the local SRv6 SID, the verification fails, and Device D discards the ICMPv6 echo request.
4. Device A determines whether the destination node is reachable based on reception of the
ICMPv6 echo reply:
If the ICMPv6 echo reply is received before the specified timeout timer expires, the destination node is reachable.
If no ICMPv6 echo reply is received when the specified timeout timer expires, the destination node is unreachable.
End-to-end ping
Use end-to-end ping to detect connectivity of the destination node in the SRv6 path. Only the destination node sends an ICMPv6 echo reply to the source node.
Figure 84 End-to-end ping
IPv6 SA=a, IPv6 DA=b
SRH[(d, b) SL=1]
ICMPv6 Echo Request
A
SRv6 SID=a
B
SRv6 SID=b
C D
SRv6 SID=d
IPv6 SA=b, IPv6 DA=d
SRH[(d, b) SL=0]
ICMPv6 Echo Request
Figure 84 shows the end-to-end ping process as follows:
1. Device A initiates a ping to Device D, with the SRv6 SIDs of Device B and Device D specified. It constructs an ICMPv6 echo request encapsulated with an SRH and then forwards the request.
2. Upon receiving the ICMPv6 echo request, the intermediate node performs relevant operations depending on whether it is SRv6 capable:
On an SRv6 capable node (such as Device B):
The node forwards the ICMPv6 echo request based on the SRH if the packet destination
IPv6 address is the local SRv6 SID.
On an SRv6 incapable node (such as Device C):
The node forwards the ICMPv6 echo request according to routing table lookup.
3. Upon receiving the ICMPv6 echo request with SL=0 in the SRH, Device D verifies the packet destination IPv6 address.
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