A.topmost label exp value
B.customer marking
C.Innerrnost label exp value
D.Qos groups/discard class
E.remarked IP tos value
F.MDRR quantam

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.

A.Message Type
B.Calling Number
C.Assigned Session ID
D.Called Number
E.Call Serial Number

A.Extended IS neighbor TLV # 22
B.Extended IS name TLV #137
C.Extended IS resource TLV #138
D.Extended IS reachability TLV #135
E.Router ID TLV # 134

A.A value of 4 represents the "Implicit NULL Label."
B.A value of 0 represents the "IPv4 Explicit NULL Label."
C.A value of 1 represents the "Router Alert Label". The use of this label is analogous to the use of the"Router Alert Option" in IP packets （for example， ping with record route option）
D.A value of 2 represents the "IPv6 Explicit NULL Label"
E.A value of 1 represents the "IPv1 Explicit NULL Label"
F.A value of 3 represents the "Implicit NULL Label"