This Attribute indicates the tunneling protocol(s) to be used (in
the case of a tunnel initiator) or the the tunneling protocol in
use (in the case of a tunnel terminator). It MAY be included in
Access-Request, Access-Accept and Accounting-Request packets. If
the Tunnel-Type Attribute is present in an Access-Request packet
sent from a tunnel initiator, it SHOULD be taken as a hint to the
RADIUS server as to the tunnelling protocols supported by the
tunnel end-point; the RADIUS server MAY ignore the hint, however.
A tunnel initiator is not required to implement any of these
tunnel types; if a tunnel initiator receives an Access-Accept
packet which contains only unknown or unsupported Tunnel-Types,
the tunnel initiator MUST behave as though an Access-Reject had
been received instead.
If the Tunnel-Type Attribute is present in an Access-Request
packet sent from a tunnel terminator, it SHOULD be taken to
signify the tunnelling protocol in use. In this case, if the
RADIUS server determines that the use of the communicated protocol
is not authorized, it MAY return an Access-Reject packet. If a
tunnel terminator receives an Access-Accept packet which containsone or more Tunnel-Type Attributes, none of which represent the
tunneling protocol in use, the tunnel terminator SHOULD behave as
though an Access-Reject had been received instead.
A summary of the Tunnel-Type Attribute format is shown below. The
fields are transmitted from left to right.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
| Type | Length | Tag | Value
Value (cont) |
64 for Tunnel-Type
The Tag field is one octet in length and is intended to provide a
means of grouping attributes in the same packet which refer to the
same tunnel. Valid values for this field are 0x01 through 0x1F,
inclusive. If the Tag field is unused, it MUST be zero (0x00).
The Value field is three octets and contains one of the following
values, indicating the type of tunnel to be started.
1 Point-to-Point Tunneling Protocol (PPTP)
2 Layer Two Forwarding (L2F)
3 Layer Two Tunneling Protocol (L2TP)
4 Ascend Tunnel Management Protocol (ATMP)
5 Virtual Tunneling Protocol (VTP)
6 IP Authentication Header in the Tunnel-mode (AH)
7 IP-in-IP Encapsulation (IP-IP)
8 Minimal IP-in-IP Encapsulation (MIN-IP-IP)
9 IP Encapsulating Security Payload in the Tunnel-mode (ESP)
10 Generic Route Encapsulation (GRE)
11 Bay Dial Virtual Services (DVS)
12 IP-in-IP Tunneling