3.1.5.2 Control Message AV Pairs

Section 4 of [RFC2661] specifies control message AV pairs.

If a received message has an AV pair with

  • any of the reserved bits set to 1 or,

  • the M bit set and a non-IETF vendor-ID value or,

  • an unrecognized Attribute Value or,

  • the M and H bits set, and the AV pair has an attribute other than the following:

    • Proxy Authen Name

    • Proxy Authen Challenge

    • Proxy Authen Id

    • Proxy Authen Response

    • Called Number

    • Calling Number

    • Sub-Address

    • Initial Received LCP CONFREQ

    • Last Sent LCP CONFREQ

    • Last Received LCP CONFREQ

    • ACCM

    • Private Group ID

then

  • If the control message AV pair is in a control connection management message, the control connection MUST be torn down.

  • If the control message AV pair is in the call session management messages, the corresponding call session MUST be torn down.

The following AV pairs are ignored if they are hidden (H bit set to 1), even if the M bit is set.

  • Proxy Authen Name

  • Proxy Authen Challenge

  • Proxy Authen ID

  • Proxy Authen Response

  • Called Number

  • Calling Number

  • Sub Address

  • Initial Received LCP CONFREQ

  • Last Sent LCP CONFREQ

  • Last Received LCP CONFREQ:

  • ACCM

  • Private Group ID

None of the AV pairs sent by LAC/LNS have the H bit set to 1.

Section 4.4 of [RFC2661] provides a list of all L2TP AV pairs, some of which are hidden.