|
| |
IP-LCP
Reference standard: RFC 1331 updated by RFC 1661 and RFC 1570.
PPP provides a Link Control Protocol which is used for establishing,
configuring, and testing the data-link connection (to automatically agree
upon the encapsulation format options, handle varying limits on sizes of
packets, detect a looped-back link and other common misconfiguration errors, and
terminate the link).
Exactly one LCP packet is encapsulated in the PPP Information field, where
the PPP Protocol field indicates type hex c021 (Link Control Protocol).
Packet structure: fields
| bits 0 _ _ _ _ _ _ 7 |
field |
| octet 1 |
Code |
| octet 2 |
Identifier
The identifier field aids in matching requests and replies. |
| octets 3-4 |
Length
The length field indicates the length of the LCP packet including the
Code, Identifier, Length and Data fields. |
| octets 5-n |
Data (as an example Configuration
Options)
The data field is zero or more octets. |
Bit 0 is the most significant bit.
| bits 0 _ _ _ _ _ _ 7 |
Dec |
Code designation |
|
|
Link Configuration packets |
| 0 0 0 0 0 0 0 1 |
1 |
Configure Request |
| 0 0 0 0 0 0 1 0 |
2 |
Configure Ack |
| 0 0 0 0 0 0 1 1 |
3 |
Configure Nack |
| 0 0 0 0 0 1 0 0 |
4 |
Configure Reject |
|
|
Link Termination packets |
| 0 0 0 0 0 1 0 1 |
5 |
Terminate Request |
| 0 0 0 0 0 1 1 0 |
6 |
Terminate Ack |
|
|
Link Maintenance packets |
| 0 0 0 0 0 1 1 1 |
7 |
Code Reject |
| 0 0 0 0 1 0 0 0 |
8 |
Protocol Reject |
| 0 0 0 0 1 0 0 1 |
9 |
Echo Request |
| 0 0 0 0 1 0 1 0 |
10 |
Echo Reply |
| 0 0 0 0 1 0 1 1 |
11 |
Discard Request |
| 0 0 0 0 1 1 0 0 |
12 |
Reserved |
| bits 0 _ _ _ _ _ _ 7 |
field |
| octet 1 |
Configuration Option type. |
| octet 2 |
Length
The length field indicates the length of the Configuration Option
including the Type, Length and Data fields. |
| octets 3-n |
Data
The data field is zero or more octets, and contains information specific
to the Configuration Option. |
| bits 0 _ _ _ _ _ _ 7 |
Dec |
Type designation |
| 0 0 0 0 0 0 0 0 |
0 |
Reserved |
| 0 0 0 0 0 0 0 1 |
1 |
Maximum-Receive-Unit |
| 0 0 0 0 0 0 1 0 |
2 |
Async-Control-Character-Map |
| 0 0 0 0 0 0 1 1 |
3 |
Authentication-Protocol |
| 0 0 0 0 0 1 0 0 |
4 |
Quality-Protocol |
| 0 0 0 0 0 1 0 1 |
5 |
Magic-Number |
| 0 0 0 0 0 1 1 1 |
7 |
Protocol-Field-Compression |
| 0 0 0 0 1 0 0 0 |
8 |
Address-and-Control-Field-Compression |
| 0 0 0 0 1 0 0 1 |
9 |
FCS-Alternatives |
|
