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PPP Packet Formats        B


The following information describes the formats and configuration options for Point-to-Point Protocol (PPP). See "Debugging and Interpreting PPP Negotiation" on page 4-2 for information about displaying negotiation information that can be analyzed using the packet formats contained in this appendix, or by using the Decoder Ring located on the Lucent Remote Access website (http://www.livingston.com).

All values shown in the fields are in hexadecimal format. Adjacent frames can be separated by a single flag. Address and control bytes are omitted in non-Link Control Protocol (LCP) frames if Address-and-Control-Field-Compression is negotiated.

If the first byte of the Protocol field is zero, it is omitted in non-LCP frames if Protocol-Field-Compression is negotiated. On asynchronous links, special characters-flags, escape characters, and control characters selected in the negotiated remote Async-Control-Character-Map-between the flags are replaced by an escape character (7D) and the original byte with bit 6 inverted (XOR'ed with 0x20).

 Table B-1 shows values that can appear in the Protocol field of a PPP frame. The Network Control Protocol (NCP) value is used to establish a connection for the associated data transfer protocol. See RFC 1700, Assigned Numbers, for a complete list of protocol values.  
Table B-1 Protocol Values

Protocol

Value

NCP Value

Internet Protocol (IP)

0021

8021

OSI Network Layer

0023

8023

DECnet Phase IV

0027

8027

AppleTalk

0029

8029

Novell IPX

002B

802B

Van Jacobson Compressed TCP/IP

002D

 

Van Jacobson Uncompressed TCP/IP

002F

 

Banyan VINES

0035

8035

Link Control Protocol (LCP)

 

C021

Password Authentication Protocol (PAP)

 

C023

Link Quality Monitoring (LQM)

 

C025

Challenge Handshake Authentication Protocol (CHAP)

 

C223

Formats for LCP Packets

LCP Packet Formats

Configure-Request

01

ID

Length

Configuration Options

Configure-Nak

03

ID

Length

Configuration Options

Terminate-Request

05

ID

Length

Data

Code-Reject

07

ID

Length

Rejected-Packet

Echo-Request

09

ID

Length

Magic-Number

Data

Discard-Request

0b

ID

Length

Magic Number

Data

Configure-Ack

02

ID

Length

Configuration Options

Configure-Reject

04

ID

Length

Configuration Options

Terminate-Ack

06

ID

Length

Data

Protocol-Reject

08

ID

Length

Rejected-Protocol

Rejected-Info

Echo-Reply

0a

ID

Length

Magic-Number

Data

LCP Configuration Options

Maximum Receive Unit

01

04

MRU

Default is 1520 decimal

(MRU)

Authentication-Protocol

03

Length

Authentication

Protocol

Data

Default is no authentication

 

04

c0

23

 

PAP

 

05

c2

23

05

CHAP using MD5

 

05

c2

23

80

MS-CHAP

Magic-Number

05

06

Magic-Number

Default is no magic number

Address-and-Control-Field-Compression

08

02

Default is no compression

Async-Control-Character-Map

02

06

Async-Map

Default is FFFFFFFF

Quality-Protocol

04

Length

Quality

Protocol

Data

Default is no LQM

 

08

c0

25

Reporting-Period

 

Protocol-Field-Compression

07

02

Default is no compression

IPCP Configuration Options

The IP Control Protocol (IPCP) is similar to LCP except that only codes 1 through 7 are used.

IP-Addresses

01

0a

Source-IP-Address

Deprecated

Destination-IP-Address

 

 

IP-Address

03

06

IP-Address

No default

IP-Compression-Protocol

02

Length

Compression

Protocol

Data

Default is no compression

 

06

00

2d

Max-Slot-ID

Comp-Slot-ID

(Van Jacobson Compressed TCP/IP)

PAP Packet Formats

Authenticate-Request

01

ID

Length

IDLen

Peer-ID

PwLen

Password

 

 

Authenticate-Nak

03

ID

Length

MsgLen

Message

Authenticate -Ack

02

ID

Length

MsgLen

Message

CHAP Packet Formats

Challenge

01

ID

Length

ValSize

Value

Name

 

 

Success

03

ID

Length

Message

Response

02

ID

Length

ValSize

Value

Name

 

 

Failure

04

ID

Length

Message

Formats for IPXCP Packets

This section illustrates the packet formats and configuration options of IPX Control Protocol (IPXCP) that are found in the IPX NCP layer during the PPP negotiation process. More information on this subject can be found in RFC 1552, The PPP Internetwork Packet Exchange Control Protocol (IPXCP).

IPXCP Packet Formats

Configure-Request

01

ID

Length

Configuration Options

Configure-Ack

02

ID

Length

Configuration Options

Configure-Nak

01

ID

Length

Configuration Options

Configure-Reject

04

ID

Length

Configuration Options

Terminate-Request

05

ID

Length

Data

Terminate-Ack

05

ID

Length

Data

Code-Reject

06

ID

Length

Data

IPXCP Configuration Options

IPX-Network-Number

01

06

IPX-Network-Number

IPX-Node-Number

02

08

IPX-Node-Number

IPX-Compression-Protocol

03

Length

IPX-Compression-Protocol (2 bytes)

Data:

Formats for CCP Packets

The Compression Control Protocol (CCP) is similar to LCP with two additional codes.

CCP Packet Formats

Reset-Request

14

ID

Length

Configuration Options...

Reset-Ack

15

ID

Length

Configuration Options...

CCP Configuration Options

Type

Length

Values

Compression types:



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