A、The session ID is a 32-bit locally significant field used to identify the call on the destination or egresstunnel endport. The session ID will be negotiated by the control connection or statically defined if usingthe L2TP v3 data plane only

B、The cookie is a variable length（with a maximum of eight bytes），word-aligned optional field. The controlconnection can negotiate this as an additional level of guarantee beyond the regular session ID lookupto make sure that a data message has been directed to the correct session or that any recently reusedsession ID will not be misdirected

C、The cookie is a 32-bit locally significant field used to identify the call on the destination or egress tunnelendpoint. The cookie will be negotiated by the control connection or statically defined if using theL2TPv3 data plane only

D、The session ID is a variable length（with a maximum of eight bytes），word-aligned optional field the control connection can negotiate this as an additional level of guarantee beyond the regular cookielookup to make sure that a data message has been directed to the correct session or that any recentlyreused cookie will not be misdirected.