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Using PPP Interfaces


This document provides information about the Point-to-Point Protocol (PPP), including PPP authentication protocols (PAP and CHAP), Multilink PPP (MP) and data compression over PPP. The document also explains how to configure PPP interfaces and describes the PPP commands. It includes the following topics:

PPP Overview

The PPP Link Control Protocol

The PPP Network Control Protocols

Multilink PPP

PAP and CHAP

Call-back Feature

Data Compression

Displaying the PPP Prompts

Configuring PPP

Configuring PAP

Configuring CHAP

PPP Commands

Displaying Statistics for PPP Interfaces

PPP Overview

Point-to-Point Protocol (PPP) is designed for simple links that transport packets between two peers. PPP provides a method for transmitting datagrams at the data link layer over serial point-to-point and ISDN links. PPP supports synchronous, asynchronous, and ISDN data transmission and provides the following services:

To establish data transmission over a link, the local and remote peers exchange LCP packets to configure and test the link. After the link is established, the peer can be authenticated, and then PPP sends NCP packets to choose and configure one or more network layer protocols. After PPP configures network layer protocols, PPP can send datagrams from each network layer over the link.

PPP Data Link Layer Frame Structure

PPP transmits data frames that have the same structure as High-level Data Link Control (HDLC) frames. PPP uses a bit-oriented, synchronous transmission method with a single-frame format for all data and control exchanges.

Figure 1 illustrates the PPP frame structure and a description of each field follows.

Figure 1 PPP Frame Structure

Table 1 PPP Frame Field Definitions

Field Definition
Flag The flag field begins and ends each frame with a unique pattern of 01111110. Generally a single flag ends one frame and begins the next. All active stations attached to the link continuously search for the flag sequence to synchronize the start of the next frame. The sending and receiving stations use a process called bit stuffing to avoid the loss of synchronization due to the arbitrary appearance of the 01111110 bit pattern within the data stream.

When bit stuffing, the sending station adds a 0 after the fifth 1 in a non-flag bit stream. Then the receiving station monitors the bit stream. If the receiver detects a bit pattern of five ones, it examines the sixth bit. If the sixth bit is a 0, the receiver deletes it. If the sixth bit is a 1 and the seventh bit is a 0, the receiver accepts the combination as the end of frame flag.

Address The address field is a single octet (8 bits) and contains the binary sequence 11111111 (0xff hexadecimal). This is known as the All-Station Address. PPP does not assign individual station addresses.

Control The control field is a single octet and contains the binary sequence 00000011 (0x03 hexadecimal). This sequence identifies the Unnumbered Information (UI) command with the P/F bit set to zero.

Protocol PPP defines the protocol field; it is not found in the true HDLC frame format. The protocol field is 2 octets (16 bits) and its value identifies the protocol datagram encapsulated in the Information field of the frame.

Protocol field values in the "cxxx" range indicate that datagrams belong to the Link Control Protocol (LCP). Values in the "8xxx" range indicate that datagrams belong to the Network Control Protocols (NCP). Values in the "0xxx" range identify the network protocol of specific datagrams.

Information The information field contains the datagram for the protocol specified in the protocol field. This is zero or more octets. This information field is present for all I-frames and only some U-frames.

When the protocol type is LCP, exactly one LCP packet is encapsulated in the information field of PPP data link layer frames.

Frame Check Sequence (FCS) The frame check sequence field is a 16-bit Cyclic Redundancy Check (CRC).

The PPP Link Control Protocol

The PPP Link Control Protocol (LCP) establishes, configures, maintains, and terminates the point-to-point link. This process is carried out in four phases:

1. Before exchanging any IP datagram, LCP first opens the connection through an exchange of Configure packets. (That is, each side must send a REQ and receive an ACK packet.) After this exchange is complete (with the reception of a Configure-ACK packet), the link enters the Open state. LCP handles only configuration parameters associated with the link; it does not handle configuration of any of the network layer protocols.

2. After the link enters the Open state, if authentication was requested in the Configuration Request, then the authentication protocol (PAP or CHAP) runs.

3. The appropriate NCP configures the network protocols and brings them up and takes them down. If LCP closes the link, the network layer protocols are first notified.

4. Finally, LCP has the ability to terminate the link at any time. This is usually done at the request of the user, but may occur because of the loss of a carrier or the expiration of an idle period timer.

LCP Packets

There are three classes of LCP packets:

Only one LCP packet is encapsulated in the information field of PPP Data Link Layer frames. In the case of LCP packets, the protocol field reads Link Control Protocol (0xC021 hexadecimal).

Figure 2 illustrates the structure of the LCP packet and a description of each field follows.

Figure 2 LCP Frame Structure

Code

The code field is one octet in length and identifies the type of LCP packet. The codes in Table 2 distinguish the packet types. They are described in more detail in later sections.

Table 2 LCP Packet Codes
Code Packet Type
1 Configure-Request (Link Establishment)

2 Configure-ACK (Link Establishment)

3 Configure-NAK (Link Establishment)

4 Configure-Reject (Link Establishment)

5 Terminate-Request (Link Termination)

6 Terminate-ACK (Link Termination)

7 Code-Reject (Link Termination)

8 Protocol-Reject (Link Maintenance)

9 Echo-Request (Link Maintenance)

10 Echo-Reply (Link Maintenance)

11 Discard-Request (Link Maintenance)

Identifier

The identifier field is one octet in length and is used to match packet requests and replies.

Length

The length field is two octets in length and indicates the total length (including the first and last fields) of the LCP packet.

Data (Optional)

The data field is zero or more octets as indicated by the length field. The format of this field is determined by the code.

Link Establishment Packets

Link Establishment Packets establish and configure a point-to-point link using the following packet types:

Configure-Request

LCP packet code field is set to 1. LCP transmits this packet type to open or reset a point-to-point link. Upon receiving a Configure-Request, a peer station's LCP entity must send an appropriate reply.

Configure-ACK

LCP packet code field is set to 2. The peer transmits this packet type when every configuration option in a Configure-Request packet is acceptable. Upon receiving the Configure-ACK (ACK = acknowledgment), the originating station checks the Identifier field. This field must match the one from the last transmitted Configure-Request or the packet is invalid.

Configure-NAK

LCP packet code field is set to 3. The peer transmits this packet type when some part of the configuration option in a Configure-Request packet is unacceptable. The Identifier field is copied from the received Configure-Request and the Data (optional) field is filled with the received unacceptable configuration options. The Identifier field must match the one from the last transmitted Configure-Request or the packet is invalid and the originator discards it.

When the originator receives a Configure-NAK packet, it sends a new Configure-Request packet that includes modified, acceptable configuration options.

Configure-Reject

LCP packet code field is set to 4. The peer transmits this packet type when some part of the configuration options in a Configure-Request packet is unacceptable. The Identifier field is copied from the received Configure-Request and the Data (optional) field is filled with the received unacceptable configuration options. The Identifier field must match the one from the last transmitted Configure-Request or the packet is invalid and the originator discards it.

When the originator receives a Configure-Reject packet, it sends a new Configure-Request packet that does not include any of the configuration options received in the Configure-Reject packet.

Link Termination Packets

Link Termination Packets close a link and include the following packet types:

Terminate-Request

LCP packet code field is set to 5. LCP sends this packet type when a point-to-point link needs to be closed. LCP sends these packets until a Terminate-ACK packet is sent back. If LCP does not receive an ACK after the configured number of REQs, the link is closed.

Terminate-ACK

LCP packet code field is set to 6. Upon receiving a Terminate-Request packet, this packet type must be transmitted. Reception of a Terminate-ACK packet that was not expected indicates that the link has been closed.

Link Maintenance Packets

Link Maintenance Packets manage and debug a link, and include the following packet types:

Code-Reject

LCP packet code field is set to 7. LCP sends this packet type to report that one of the communicating LCP entities is faulty or incomplete. LCP reports the error to the sender of the unknown code by sending an LCP packet with the code field set to 7. This situation ends in the closing of the link.

Protocol-Reject

LCP packet code field is set to 8. LCP transmits this packet type to indicate that a PPP frame that has been received contains an unsupported or unknown protocol. Upon receiving a Protocol-Reject packet, the peer stops transmitting the incorrect protocol.

Echo-Request Echo-Reply

LCP packet code fields are set to 9 and 10 respectively. LCP transmits these packet types to provide a Data Link Layer loopback mechanism for both directions on the link. This feature is useful in debugging, for example, a faulty link to determine link quality. LCP sends these packets only when the link is in the Open state.

Discard-Request

LCP packet code field is set to 11. LCP transmits this packet type to provide a data sink for Data Link Layer testing. A peer that receives a Discard-Request must throw away the packet. This is useful in debugging a link. LCP sends these packets only when the link is in the Open state.

The PPP Network Control Protocols

PPP has a family of Network Control Protocols (NCPs) that are responsible for configuring, enabling, and disabling the network layer protocols on both ends of the link. NCP packets cannot be exchanged until LCP has opened the connection and the link reaches the Open state.

PPP supports the Network Control Protocols in Table 3.

Table 3 Network Control Protocols

NCP Specified in RFC . . . OpenROUTE Software supports . . .
AppleTalk Control Protocol (ATCP) 1378

The AppleTalk-Address option.

The AppleTalk packet is encapsulated in the Information field of the PPP data frame. The encapsulated AppleTalk packet begins with an extended Datagram Delivery Protocol (DDP) header.

Bandwidth Allocation Control Protocol (BACP) 2125

Bandwidth Allocation Control Protocol (BACP) manages bandwidth between two peers on a point-to-point link. See BAP and BACP.

Bridging Network Control Protocol (BNCP) 1220

The IEEE 802.5 Line Identification Option and the Tinygram Compression Option.

IP Control Protocol (IPCP)

All IPCP options. They are

IPX Control Protocol (IPXCP) 1552

Does not send any IPXCP options. However, it accepts the following IPXCP options if the remote router sends them:

Multilink PPP

OpenROUTE supports standard Multilink PPP (MP) as defined in RFC 1990. MP combines multiple physical links between a fixed pair of systems into one logical link. This logical link is called a bundle, and it has greater bandwidth than any of the individual links.

You can use MP on multiple PPP devices that connect two systems. This includes ISDN, as well as serial connections. For example, on ISDN BRI devices, MP combines the two B channels into one logical link.

PPP negotiates MP in the LCP Configure Request. Once LCP transitions into the Open state, MP makes a determination: Does the new link join an existing bundle or start a new one? MP makes this determination based on information acquired about the peer's identity during authentication (if it was run) and by using an Endpoint Discriminator (EID), which was also negotiated in the LCP Configure Request.

Note: If authentication was not run, it is possible to get the peer's identity on ISDN calls that provide caller ID.

To use MP, enter the enable mp PPP configuration command. MP has several other configuration commands:

To set the . . . Use this command . . .
Endpoint Discriminator (EID) value that identifies the MP bundles that this peer creates.

set mp discriminator
Initial number of connections (or bundles) to use when OpenROUTE first makes a call to the remote router.

set mp initial-bundle-size
Maximum number of connections that MP can use. The default is 2.

For ISDN BRI devices, setting the maximum to 1 guarantees the remote router, when calling the local router, only gets one of the two available B channels. This is useful when the local router accesses two separate remote sites at once.

set mp max-bundle-size
Sequence number header format used in the MP encapsulation header to long or short.

set mp sequence-num-len

To set up Multilink PPP using more than one physical device, you need to add a manual stack to your router configuration.

Bandwidth-on-demand

Bandwidth-on-demand is a feature of MP that monitors the traffic utilization of calls and automatically opens additional connections when data traffic on the existing connections exceed a threshold that you configure. For ISDN BRI connections, bandwidth-on-demand is valuable when the telephone company charges separately for each B channel. You need to use the second B channel only during periods of heavy traffic.

OpenROUTE software determines traffic utilization by measuring the bytes per second passing the connection(s). It computes this measurement using a weighted average of traffic over the last 32 seconds. Three built-in sets of weights provide a Fast, Medium, or Slow response time to changes in traffic load. To enable bandwidth-on-demand enter set mp bandwidth-on-demand followed by Fast, Medium, or Slow.

MP decides to add or drop connections by comparing the traffic utilization to two thresholds that you set using the set mp high-utilization and set mp low-utilization commands. The default low and high utilization thresholds are 35% and 70%, respectively. When traffic on the interface exceeds 70% of its capacity, MP opens another link (if available) to provide more bandwidth. If traffic on the interface (counting across all connections currently in use) falls below 35%, then OpenROUTE drops the second connection. (OpenROUTE does not drop the first connection unless the dial-on-demand idle time expires).

Using Multilink PPP with Two OpenROUTE ISDN Routers

OpenROUTE software has sophisticated call collision logic within Multilink PPP (MP) that normally assembles a multilink bundle of two ISDN B channels even when two OpenROUTE routers call each other simultaneously. However, that software requires each router to know the identity of the other router. Therefore, when two routers are both enabled to place outbound calls to each other, you must have caller ID provisioned on your ISDN switch or have PPP PAP or CHAP enabled on the router, so the two routers can identify each other. Otherwise, one of the two calls is refused and call retries begin. This can cause some "thrashing" as call collisions continue to occur while the second B channel is brought up.

BAP and BACP

If you are using Multilink PPP (MP), you need to be able to manage bandwidth over MP. Bandwidth Allocation Protocol (BAP) and its associated protocol, Bandwidth Allocation Control Protocol (BACP), manage bandwidth between two peers on a point-to-point link.

BAP is a method for managing the dynamic bandwidth requirements of an MP bundle and defining datagrams for adding and removing individual links in the bundle. The local and remote peer use these datagrams to co-ordinate the addition and removal of Link Control Protocol (LCP) links to and from the MP bundle. BAP also specifies which peer is responsible for which decisions regarding managing bandwidth during a multilink connection. (See RFC 2125.)

BAP starts after the first link of the MP bundle is established.

BACP is the control protocol that negotiates the configuration BAP uses during each BAP session. It works essentially in the same way as LCP. It uses the same packet exchange mechanism as LCP. BACP negotiates after PPP has negotiated MP and reached the network-layer protocol phase. Packets received before this phase is reached are silently discarded. BACP is negotiated once per multilink bundle. When it is negotiated on any of the links in a multilink bundle, it is opened for all of the links in the bundle.

During the negotiation phase of BACP, a favored peer is determined. This is the only BACP configuration option currently defined (in RFC 2125). The favored peer is the originator of the first call.

When Bandwidth-on-demand is off, the router does not initiate BACP negotiation. When bandwidth-on-demand is on, BACP initiates BACP negotiation after the LCP link is established. All bandwidth increases and decreases are then negotiated with the peer, who either accepts or refuses the request.

PAP and CHAP

OpenROUTE provides two authentication methods, the Password Authentication Protocol (PAP) and the Challenge Handshake Authentication Protocol (CHAP). CHAP uses the RSA Data Security, Inc. MD5 Message-Digest Algorithm, Copyright, 1990.

This discussion of PAP and CHAP uses the following terms:
Local Router

This router.

Remote Router

The router to which you connect.

Authenticator

The router that initiates the authentication process by sending PAP or CHAP request packets. Either the local router or the remote router can be the authenticator.

Peer

The router that responds to the authentication request by identifying itself to other routers. Either the local router or the remote router can be the peer.

Selecting the Authentication Method

The authenticator and peer negotiate an authentication protocol during the Link Establishment phase of PPP. To do so, the authenticator requests the peer to use either PAP or CHAP. If the peer replies that it

The local router always responds to a request to use CHAP. The local router responds to requests to use PAP only if the local router originated the call and if the local router has a PAP password configured.

The local router does not respond to requests to use PAP from devices calling in to the local router. Doing so poses a security risk because PAP names and passwords are transmitted in clear text. An intruder could dial in to the router, obtain the router's name and PAP password, and then use that information to pose as the router.

Using Both PAP and CHAP

If an OpenROUTE Networks router is enabled to authenticate another router using PAP and CHAP, OpenROUTE requests CHAP first and then allows the remote router to use PAP if it does not support CHAP.

OpenROUTE cannot fall back from CHAP to PAP when another router is the authenticator because, by PPP specification, if a router supports CHAP, and the other router asks for CHAP, the first router must use CHAP.

This may cause confusion if you configure a PAP password on the OpenROUTE router and then enable the other router to authenticate using PAP and CHAP. When the other router asks for CHAP, OpenROUTE complies, but PPP authentication fails because OpenROUTE does not have a CHAP secret configured.

If PAP authentication is required, then the other router (of any brand) must only request PAP. OpenROUTE complies and returns the PAP password that you configured.

How PAP Works

PAP is a simpler protocol than CHAP because it uses a two-way handshake and does not encrypt the password that identifies the peer to the authenticator. The PAP authentication process is as follows:

1. When authentication begins, the peer sends a PAP packet that contains its name and its password. If the peer

2. The authenticator waits a configurable period of time for a PAP packet.

How CHAP Works

CHAP uses a three-way handshake to verify the identity of the peer. CHAP does this upon initial link establishment and may repeat the handshake any time after PPP establishes the link. The local router authenticates the remote router only once when the link is established. However, the local router replies to a CHAP authentication request whenever it receives one.

The CHAP authentication process is as follows:

1. After the Link Establishment phase, the authenticator sends a challenge message to the peer and waits for a response. The challenge contains the name of the authenticator.

If the authenticator does not receive a response after a configurable time, it retransmits the challenge. The authenticator can repeat this a configurable number of times until it gives up and terminates the connection.

2. Upon receiving a challenge packet, the peer uses the authenticator's name in the challenge to look up a secret.

The peer then encrypts the message contained in the challenge using this secret and transmits the encrypted result back to the authenticator in a response packet that contains the peer's name.

CHAP does not transmit the secret over the link. You must configure the same secret on both routers.

3. The authenticator uses the peer's name in the response packet to look up a secret. It uses the secret to check the response against its own encryption of the message.

If the values match, the authenticator transmits a success packet and brings up the Network Control Protocols (NCPs); otherwise, it transmits a failure packet and terminates the connection.

4. If the peer does not receive a success or failure acknowledgment packet, it waits a configurable period of time and then retransmits its last response.

About CHAP Names and Secrets

The two routers (peer and authenticator) share the secret. The peer has a table that contains the authenticator's name and secret. The authenticator has a table that contains the peer's name and the same secret.

CHAP depends on knowing the name of the remote router. The local router uses the remote router's name, which is contained in the CHAP challenge, to look up the secret that it uses to reply to the remote router. However, you may not know that name because some ISPs or network administrators provide only your account name and the CHAP secret that you must use to log into that account. They may not provide the remote router name.

OpenROUTE includes a feature that simplifies CHAP when the local router places a call to a remote router. If the local router does not know the name that the remote router sends in the CHAP challenge, the local router uses the CHAP secret configured for the dial destination.

For example, if you configure an interface with a destination of Boston, and the remote router identifies itself in its CHAP challenge with a different name that is unknown to the local router, then OpenROUTE uses the CHAP secret configured for Boston to build a CHAP response.

Therefore, if you do not know the name of the remote router, add a CHAP secret (using the add secret command) for the remote router's destination address name that you entered using the set destination command at the Circuit Config <NET-#> prompt.

Call-back Feature

The Call-back feature causes a local router to use an incoming call as a signal to call back a remote router. OpenROUTE uses the Link Control Protocol (LCP) Callback option, as defined in RFC 1570, to control Call-back processing. Call-back is typically used with dial-on-demand.

The default is to have Call-back disabled. If the remote router requests Call-back and Call-back is disabled on the local router, the local route rejects the request.

Using the Call-back Feature on an ISDN Interface

On an ISDN interface, you can set up Call-back so that the local router does not answer the incoming call, and the remote router does not incur the expense of placing the call. This feature is sometimes called D-channel Call-back.

D-channel Call-back only works on the first call received from the caller. If the calling router calls a second time after one call is already established, the receiving router answers the second call momentarily, and then drops the call. Then, the receiving router makes a second call-back.

To work around this problem, configure the remote router (that is, the router making the call) to call only once.

If you're using Multilink PPP (MP), configure the router receiving the call to bring up the second call either by enabling Bandwidth-on-Demand or by setting the MP initial-bundle-size to two.

Identifying the Call-back Destination

The local router never calls back a caller that it cannot identify or that fails authentication. It calls only destinations that you set at the Circuit Config <NET-#> prompt. Ideally, you should set up your router to use Caller-ID, PAP, or CHAP so that it can identify which destination to call. If you set up Call-back on an ISDN interface using the Always option, described below, the router does not answer the incoming call. Therefore, it is preferable to use Caller-ID to identify the caller.

Using Caller-ID with Call-back assures the following:

When you use Call-back on an interface that does not have Caller-ID, PAP, or CHAP, the router does not know which destination to call back. Therefore, it performs a Call-back using every interface on the physical device that has Call-back enabled. If this happens, only the lower number circuits can place a call because higher number circuits find the physical device busy.

Configuring Call-back

This feature has three separate, mutually exclusive options when you enable Call-back. The following sections describe these options. In each of the examples below, the interface you are configuring has dial-on-demand enabled by setting the idle time to a nonzero value, that is Circuit Config <NET-#> set idle 60

Request

This option causes the local router to request the remote router to call back. If the remote router agrees, then the local router hangs up the call and waits for the return call. If the remote router rejects the Call-back request, then the local router leaves the line connected as if it never requested the Call-back.

This option is useful for a telecommuter who configures a router to call an employer in order to reverse the charges back to the employer. In the following example, the remote destination router is called my-job.

Config>network 1
Circuit Config <NET-1>set destination
Assign destination address name [ ]?my-job
Circuit Config <NET-1> set idle
Idle timer (seconds, 0 means always active) [ ]? 60
Circuit Config <NET-1> ppp
Point-to-Point user configuration

PPP Config <NET-1> enable call-back request

Accept

With this option, if the remote router requests a Call-back, the local router accepts the request and acknowledges to the remote router that it will call back. The local router disconnects the call and places a Call-back.

You can use Caller-ID, PAP, or CHAP with the accept option to identify the caller.

This option supports the Internet Service Provider (ISP) who wants to connect to the local router. The ISP can request a Call-back from the local router to the ISP, my-isp, so the local router bears the cost of the call. The local router only calls back the ISP if the ISP requests a Call-back.

Config>network 1
Circuit Config <NET-1>set destination
Assign destination address name [ ]?my-isp
Circuit Config <NET-1> set idle
Idle timer (seconds, 0 means always active) [ ]? 60
Circuit Config <NET-1> ppp
Point-to-Point user configuration

PPP Config <NET-1> enable call-back accept

Always

This option causes OpenROUTE to call back the remote router unconditionally. If you use this option on an ISDN interface, the local router does not answer the incoming call, and the remote router does not incur the expense of placing the call. Since the local router does not answer the call, you cannot use PAP or CHAP to identify the caller; you need to use Caller-ID.

If you enable this option, you must have outbound calls enabled using Circuit Config <NET-1>enable outbound

Timing problems can occur if the Call-back is performed too quickly or too slowly. The set lcp parameters command lets you define how long the local router waits between hanging up the telephone and making the Call-back to the remote router. The following example shows an interface configured to always call back the remote router, my-isp, whenever the local router receives a call from the ISP.

Config>network 1
Circuit Config <NET-1>set destination
Assign destination address name [ ]?my-isp
Circuit Config <NET-1> enable outbound
Circuit Config <NET-1> set idle
Idle timer (seconds, 0 means always active) [ ]? 60
Circuit Config <NET-1> ppp
Point-to-Point user configuration

PPP Config <NET-1> enable call-back always

Data Compression

Data compression lets the router software pack more data into the packets moving through router interfaces. If the rate of packet transfer stays constant, the data transfer rate (throughput) for the router increases proportionately.

Character Sequence Substitution

The data compression software works by replacing frequently-occurring character sequences with single characters that represent the sequences. The sequences can be words, blank spaces, numbers, or any other string in the data stream. The substitution characters are called index characters.

For example, the character sequences that make up the words "the" and "computer" may appear separately throughout an ASCII text file in a data stream. The data compression software substitutes a single character for each of the words. Further, if the words appear together as "the computer," a different index character replaces the phrase. This substitution scheme in effect compresses the data.

Histories (Dictionaries)

Data compression histories maintain an association between each repeatedly occurring sequence and its index character. The histories must be the same at the sending and receiving routers to ensure accurate compression and decompression. Compression protocol messages implement the history coordination and the router must closely monitor the link between the routers to maintain the coordination. If a packet is lost, the history is reset. The longer you build a history, the higher the compression ratio.

Compression Protocols and Algorithms

The router implements the following data compression protocols and algorithms. The data compression software runs in the router's data link layer.

Data Compression on the Router

The following sections and Figure 3 describe the data compression process on the router.

Negotiating a Compression Algorithm

When the router brings up a PPP link, it initiates an exchange of CCP packets as part of the link establishment. The router negotiates with its peer router to set the compression algorithm.

Compressing Data

The router performs PPP network layer encapsulation and then hands the data stream to the compression algorithm interface. The interface manipulates the PPP packet for compression by the compression algorithm.

The compression algorithm uses its compression history (dictionary) to carry out the compression of the data stream.

Transmitting the Compressed Data

The router sends the compressed datagram to the MAC layer. If Multilink PPP is enabled, one of the physical channels is selected. Then the HDLC software generates a physical frame to be transmitted to the WAN link. See Figure 3.

The compression process is reversed at the peer router on the WAN link. The negotiated compression algorithm and the compressor algorithm interface decompress the data in the packet.

Figure 3 Data Compression on the Router

Displaying the PPP Prompts

To display the PPP configuration prompt

1. Enter list interfaces at the Config> prompt to display a list of interfaces.

2. Enter network followed by the number of the PPP interface you want to configure.

Config>network
What is the network number [0]? 1
Circuit Configuration

Circuit Config <NET-1>

3. Enter ppp.

Circuit Config <NET-1> ppp
Point-to-Point user configuration

PPP Config <NET-1>

To display the PPP monitoring prompt

1. Enter list interface at the + prompt to see a list of interfaces configured on the router.

+list interface
Self-Test Self-Test Maintenance
Nt Interface Passed Failed Failed
0 Eth/0 2 0 0
1 PPP/0 0 0 0
2 PPP/1 0 0 0

2. Enter network followed by the number of the PPP interface at the + prompt.

+network 1
Circuit <NET-1>

3. Enter ppp.

Circuit <NET-1>ppp
Point-to-Point Console

PPP <NET-1>

Configuring PPP

To configure PPP, Multilink PPP (MP), and data compression, do the following procedure. If the default values are acceptable, you can omit steps 2, 3, and 4. The next sections describe how to configure PAP and CHAP.

Note: If you enable a PPP interface for bridging, OpenROUTE Networks recommends that you enable Bandwidth Reservation System.

1. Display the PPP configuration prompt.

Config>network
What is the network number [0]? 1
Circuit Configuration

Circuit Config <NET-1> ppp
Point-to-Point user configuration

PPP Config <NET-1>

2. Set Link Control Protocol (LCP) options and parameters.

If you are running bridging, enter Yes to set the MRU automatically. Bridging cannot run on PPP interfaces if the MRU is less than the maximum Ethernet frame size. Setting the MRU to automatic prevents this problem.

PPP Config <NET-1>set lcp options
Set Maximum Receive Unit (MRU) automatically? [Yes]:
Magic Number [no]:
Async Control Char. Map (ACCM) [0x0]?
Protocol Field Compression(PFC) [yes]:
Address/Control Field Compression(ACFC) [yes]:

PPP Config <NET-1>set lcp parameters
Config tries [10]?
NAK tries [5]?
Terminate tries [2]?
Retry timer (mSec) [3000]?
Callback Delay (mSec) [600]?

3. Set IP Control Protocol options for the link.

PPP Config <NET-1>set ipcp
IP COMPRESSION [yes]?
Number of Slots [16]?
Send our IP address [no]?
Request their IP address [no]?

4. Set Network Control Protocol (NCP) parameters for all PPP NCPs.

PPP Config <NET-1>set parameters
Config tries [10]?
NAK tries [5]?
Terminate tries [2]?
Retry timer (mSec) [3000]?

5. If needed, enable MP.

PPP Config <NET-1>enable mp

6. If you enable MP, set MP parameters. See Multilink PPP for more information on configuring MP.

PPP Config <NET-1>set mp ?
DISCRIMINATOR
SEQUENCE-NUM-LEN
BANDWIDTH-ON-DEMAND
INITIAL-BUNDLE-SIZE
MAX-BUNDLE-SIZE
HIGH-UTILIZATION
LOW-UTILIZATION

7. If you want it, enable the Call-back feature. See Call-back Feature for a choice of options.

PPP Config <NET-1>exit
Circuit Config <NET-1>set destination
Assign destination address name [ ]?my-isp
Circuit Config <NET-1> set idle
Idle timer (seconds, 0 means always active) [ ]? 60
Circuit Config <NET-1> ppp
Point-to-Point user configuration

PPP Config <NET-1> enable call-back always

Note: You must enable PAP or CHAP on any interface that you configure the Call-back feature.

8. If you want it, enable data compression.

PPP Config <NET-1>enable ccp

9. If necessary, change CCP options.

PPP Config <NET-1>set ccp options
STAC: # histories [1]?
STAC: check mode (0=none, 1=LCB, 2=CRC, 3=Seq) [3]?

10. To use dynamic IP addressing on the PPP interface, do the following:

a. Display the IP Config> prompt.
PPP Config <NET-1>exit
Circuit Config <NET-1>exit
Config> protocol ip
IP Config>
b. Enter add address.
c. Enter an unnumbered serial address (0.0.0.n), where n is the interface number.
d. Respond Yes to the prompt that asks if you want to allow dynamic address assignment.
e. Enter an address mask. The default should be sufficient for connections to most Internet Service Providers.
IP config>add address
Which net is this address for [0]? 1
New address [0.0.0.0]? 0.0.0.1
Allow dynamic address assignment(Yes or [No]): yes
Address mask [255.255.255.0]?
11. Restart the router to activate the new configuration.

Config> Ctrl P
*restart
Are you sure you want to restart the gateway? (Yes or [No]):yes

Configuring PAP

Follow these steps to configure PAP.

1. Configure the router's host name. Enter the user account name that your ISP or network administrator assigned to you.

Config>set hostname
What is the new host name []?GTlocal

2. Display the PPP configuration prompt.

Config>network
What is the network number [0]? 1
Circuit Configuration

Circuit Config <NET-1> ppp
Point-to-Point user configuration

PPP Config <NET-1>

3. If the local router, as the peer, must authenticate its identity to other routers, add a PAP password for the name that identifies this router to others. The ISP or remote system administrator assigns this password to you.

PPP Config <NET-1>add password
Router name []? GTlocal
Router password []? localpw

4. If the local router must authenticate other routers, add the name and PAP password of those other routers. These are passwords that you assign for each remote router you allow to call in to your local router.

PPP Config <NET-1>add password
Router name []? GTremote
Router password []? remotepw

5. To restrict the remote routers that can connect to this interface, specify the names of up to eight remote routers that you want to allow to connect.

The default is to allow any router that passed authentication to connect. You must have previously used the add password command to define a password for each router you enter.

You create the access list at the Circuit Config <NET-#> prompt.

PPP Config <NET-1>exit
Circuit Config <NET-1>set access-list
Enter 1st name: ? GT70remote1
Enter 2nd name: ? GT70remote2
Enter 3rd name: ?

6. To authenticate the identity of other routers, enable PAP to enable the local router's role as authenticator. If CHAP answering-calls is also enabled, then the local router uses CHAP first. If the remote router does not support CHAP, the local router then uses PAP.

PPP Config <NET-1>enable pap answering-calls

7. If necessary, set PAP parameters.

PPP Config <NET-1>set pap parameters
Max Request Timeouts [20]?
Request Timeout (mSec) [15000]?
Retry Timeout (mSec) [3000]?

8. Exit from the PPP Config <NET-1> prompt and restart the router to activate the new configuration.

PPP Config <NET-1> exit
Circuit Config <NET-1> exit
Config> Ctrl P
*restart

Are you sure you want to restart the gateway? (Yes or [No]):yes

Configuring CHAP

Follow these steps to configure CHAP.

1. Configure the router's host name. Enter the user account name that your ISP or network administrator assigned to you.

Config>set hostname
What is the new host name []?GTlocal

2. Display the PPP configuration prompt.

Config>network
What is the network number [0]? 1
Circuit Configuration

Circuit Config <NET-1> ppp
Point-to-Point user configuration

PPP Config <NET-1>

3. To use a name other than the host name to identify this PPP interface, use the set chap local-name command. The local router uses the local name only when making a call. It always uses the host name when it receives a call.

OpenROUTE Networks recommends that you do not use this command to override the default of using the host name to identify the PPP interface. Use this command only if the local router needs to identify itself differently on different PPP interfaces.

PPP Config <NET-1>set chap local-name
Local router name? [GT70local]? gt70

4. If the local router is a CHAP peer or authenticator, use the add secret command to define the secret shared between the local and remote routers. The secret is associated with the name of the remote router (the name provided by the remote router in the CHAP Challenge packet).

If you do not know the name of the remote router, then add a secret for the destination address name you entered for the remote router using the set destination command at the Circuit Config <NET-#> prompt. The local router uses the secret you define for the destination address name if it cannot find a secret for the name in the remote router's CHAP challenge packet.

PPP Config <NET-1>add secret
Router name []? GT70remote
Router secret []? remotesecret

5. To restrict the remote routers that can connect to this interface, specify the names of up to eight remote routers that you want to allow to connect.

The default is to allow any router that passed authentication to connect. You must have previously used the add secret command to define a secret for each router you enter.

You create the access list at the Circuit Config <NET-#> prompt.

PPP Config <NET-1>exit
Circuit Config <NET-1>set access-list
Enter 1st name: ? GT70remote1
Enter 2nd name: ? GT70remote2
Enter 3rd name: ?

6. To authenticate the identity of other routers, enable the local router's role as authenticator. You can enable CHAP when the router answers a call and/or when it originates a call.

PPP Config <NET-1>enable chap answering-calls
PPP Config <NET-1>enable chap originating-calls

Note: Typically, you should enable CHAP when the local router answers an incoming call. If you enable CHAP when the local router originates a call, you should be aware that some routers refuse to reply to CHAP requests from a remote caller.

7. If necessary, set CHAP parameters.

PPP Config <NET-1>set chap parameters
Challenge tries [10]?
Challenge timeout (mSec) [15000]?
Response timeout (mSec) [3000]?

8. Exit from the PPP Config <NET-1> prompt and restart the router to activate the new configuration.

PPP Config <NET-1>exit
Circuit Config> Ctrl P
*restart

Are you sure you want to restart the gateway? (Yes or [No]):yes

PPP Commands

Table 4 lists the PPP commands.

Not all parameters apply to all router platforms. Press Space twice after you type a command to display the available parameters for each command for your router. Enter help for information about using the command line interface.

[C] means the command is available at the PPP Config <NET-#> prompt.

[M] means the command is available at the PPP<NET-#> prompt.

Table 4 PPP Commands

Command Function
Add [C] Adds a PAP password or CHAP secret.

Change [C] Changes a PAP password or CHAP secret.

Clear [M] Clears all statistics from PPP interfaces.

Delete [C] Deletes a PAP password or CHAP secret.

Disable [C] Disables Call-back, Echo, Multilink PPP, PAP and CHAP, and data compression on this PPP interface.

Enable [C] Enables Call-back, Echo, Multilink PPP, PAP and CHAP, and data compression on this PPP interface.

Exit [C] [M] Returns to the previous prompt.

List [C] [M] Lists the PPP configuration, statistics, and counters.

Set [C] Sets PPP parameters and the parameters and/or options for BNCP, CCP (data compression), PAP, CHAP, IPCP, LCP, and MP.

Add [C]

Adds an entry to the tables of PAP passwords and CHAP secrets that the router uses during authentication. The local router uses the remote router's name to search these tables to find the corresponding password or secret that authenticates connections from that router. The router also uses these tables to store the password and/or secret that authenticates the local router to others.

A router name can have both a secret and a password associated with it. If you define both, the router can use either PAP or CHAP to authenticate that remote router.

The router shares the table of passwords and secrets among all PPP interfaces. Once you enter a password or secret, it is available to all interfaces.

To modify an existing password or secret, use the change command

Syntax: add

password
secret

password

Add a name and password for:

Example: add password

Router name []? GT70remote1
Router password []? remotepw

secret

Add a name and secret for all remote routers that the local router must authenticate (or be authenticated by) using CHAP. The secret is associated with the name of the remote router (the name that the remote router provides in the CHAP Challenge packet).

If you do not know the name of the remote router, add a secret using the destination address name you entered for the remote router using the set destination command at the Circuit Config <NET-#> prompt. The local router uses the secret you define for the destination address name if it cannot find a secret for the name in the remote router's CHAP challenge packet.

Example: add secret

Router name []? GT70remote1
Router secret []? remotesecret

Change [C]

Modifies the PAP password or CHAP secret associated with a remote router name.

Syntax: change

password
secret

password

Changes a password.

Example: change password

Router name []?mygt70
Router password []?rtc

secret

Changes a secret.

Example: change secret

Router name []?remote70
Router secret []?wilder

Clear [M]

Clears all statistics from PPP interfaces.

Syntax: clear

Example: clear

Delete [C]

Deletes a remote router's PAP password or CHAP secret. There are two reasons to delete a password or secret:

Syntax: delete

password
secret

password

Deletes a PAP password.

Example: delete password

Router name []? GT70remote

secret

Deletes a CHAP secret.

Example: delete secret

Router name []? GT70remote

Disable [C]

Disables Call-back, data compression, CHAP and PAP, Multilink PPP, and LCP echos on this PPP interface.

Syntax: disable

call-back
ccp
chap
mp
pap
echo

call-back

Disables the Call-back feature on this interface. This is the default.

Example: disable call-back

ccp

Disables the Compression Control Protocol (CCP) on this interface.

Example: disable ccp

chap answering-calls

Disables the local router from requiring CHAP authentication from a remote router when the local router answers a call.

Example: disable chap answering-calls

chap originating-calls

Disables the local router from requiring CHAP authentication from a remote router when the local router places a call.

Example: disable chap originating-calls

mp

Disables Multilink PPP (MP) on this interface. If you disable MP, the local router does not initiate MP negotiation. However, if the remote router initiates MP negotiation, the local router does negotiate MP.

Example: disable mp

pap answering-calls

Disables the local router from requiring PAP authentication from a remote router when the local router answers a call.

Example: disable pap answering-calls

echo

Disables sending LCP maintenance packets. Disabling echo may improve performance slightly.

Example: disable echo

Enable [C]

Enables data compression, CHAP and PAP, Multilink PPP, and LCP echos on this PPP interface.

Syntax: enable

call-back
ccp
chap
mp
pap
echo

call-back request or accept or always

Enables the Call-back feature on this interface. See Configuring Call-back for more information on this command.

Example: enable call-back accept

ccp

Enables the Compression Control Protocol (CCP) on this interface.

Example: enable ccp

chap answering-calls

Enables the local router to require CHAP authentication from a remote router when the local router answers a call. This is the typical use of CHAP.

Example: enable chap answering-calls

chap originating-calls

Enables the local router to require CHAP authentication from a remote router when the local router places a call. Normally, you would not enable this option because the local router identifies the remote router by the telephone number that the local router calls.

Example: enable chap originating-calls

mp

Enables Multilink PPP (MP) on this interface. Enabling MP causes the local router to initiate MP negotiation in LCP Configure Request packets.

Example: enable mp

pap answering-calls

Enables the local router to require PAP authentication from a remote router when the local router answers a call. This option is disabled by default.

Example: enable pap answering-calls

echo

Enables sending LCP maintenance packets. This helps the local router to verify that the remote router is functioning properly.

Example: enable echo

Exit [C] [M]

Returns to the previous prompt.

Syntax: exit

Example: exit

List [C] [M]

The next sections describe the list commands available at the PPP Config <NET-#> prompt and the PPP <NET-#> prompt.

List [C]

At the PPP Config <NET-#> prompt, list displays information related to the PPP interface and its protocol parameters and options.

Syntax: list

all
bncp
ccp
chap
ipcp
lcp
mp
pap
parameters
password
secret

all

Lists all options and parameters related to the PPP interface.

Example: list all

LCP Parameters
--------------
Config Request Tries: 10 Config Nak Tries: 5
Terminate Tries: 2 Retry Timer: 3000
Callback Mode: Accept Callback Delay: 600

LCP Options
-----------
Max Receive Unit: 1500 Magic Number: No
Async Control Char. Map(ACCM): 0
Protocol Field Comp(PFC): Yes Addr/Cntl Field Comp(ACFC): Yes
Echo Requests: DISABLED

CHAP Parameters
---------------
CHAP on Call Answer: Enabled
CHAP on Call Originate: Disabled
Local Name: gt70local
Challenge tries: 10
Challenge timeout(mSec): 15000
Response timeout(mSec): 3000
Challenge Algorithm:RSA Data Security,Inc. MD5 Message-Digest Algorithm

CHAP Secrets
Router Secret
------ ------
boise etc

PAP Parameters
--------------
PAP on Call Answer: Enabled
Local Name: gt70local
Local Password: localpw
Max Request Timeouts: 20
Request Timeout(mSec): 15000
Retry Timout(mSec): 3000

PAP Passwords
Router Password
------ --------
local localpassword
my_gt70 localpassword
remoterouter remotepassword
mygt70 xxx
gt70local localpw

NCP Parameters
---------------
Config Request Tries: 20 Config Nak Tries: 10
Terminate Tries: 10 Retry Timer: 3000

IPCP Options
------------
IPCP Compression: None
IP Address: Don't Send or Request

Multilink PPP Configuration
---------------------------
MP: Enabled
Initial MP bundle size: 2
Maximum MP bundle size: 2
Discriminator: Default
Sequence Number Length: Long
Bandwidth-on-Demand: Off
High-Utilization Threshold: 70%
Low-Utilization Threshold: 35%

CCP Options
-----------
Data Compression enabled
Algorithm list: Stac-LZS
Stac: histories 1
Stac: check_mode SEQ

LCP Parameters

Config Request
Tries

Number of times LCP sends configure-request packets to a peer station while attempting to open a PPP link. Exceeding the count halts configure-request transmission.

Terminate Tries

Number of times LCP sends terminate-request packets to a peer station to close a PPP link. Exceeding the count halts terminate-request transmission.

Callback Mode

Displays the configuration of the Call-back feature. See Call-back Feature for a description of the modes.

Config Nak Tries

Number of times LCP sends configure-nak (nak=not acknowledged) packets to a peer station while attempting to open a PPP link.

Retry Timer

Amount of time, in milliseconds, that elapses before LCP's transmission of configure-request (to open the link) and terminate-request (to close the link) packets is timed out. This timer is the time to wait before retransmitting configure-request and terminate-request packets.

Callback Delay

Amount of time, in milliseconds, the local router waits between the hanging up of the telephone and subsequently making the call-back to the remote router.

LCP Options

Max Receive Unit

Maximum size of the information field in a PPP frame.

Magic Number

Indicates whether the magic number loopback detection option is enabled or disabled.

Async Control
Char. Map
ACCM

Provides a method to negotiate the use of control characters transparently on an asynchronous link.

Protocol Field
Comp (PFC):

Indicates whether Protocol Field Compression is enabled or disabled. See Protocol Field Compression (PFC).

Addr/Cntl Field
Comp (ACFC)

Indicates whether Address/Control Field Compression is enabled or disabled. See Addr/Cntl Field Compression (ACFC).

Echo Requests

Indicates whether sending of LCP maintenance packets is enabled or disabled. Disable if running a large volume of traffic. Enable when first setting up network configuration.

CHAP Parameters

CHAP on Call
Answer

Indicates whether CHAP is enabled or disabled when answering calls.

CHAP on Call
Originate

Indicates whether CHAP is enabled or disabled when originating calls.

Local Name

Name that this interface uses to identify itself to other devices. The default is the host name of the router. Otherwise, this field shows the name you entered using the set chap local-name command.

Challenge Tries

The number of times the local router, as authenticator, transmits a CHAP challenge packet. If the router does not receive a CHAP response after this number of tries, it closes the connection. The range is 1 to 100. The default is 20.

Challenge
Timeout (mSec)

Sets how long the local router, as peer, waits for a CHAP challenge packet from the remote router. When this time expires, authentication fails and the local router closes the connection.

The range is 200 to 150000 milliseconds. The default is 15000.

Response Timeout
(mSec)

If the local router is the

The range is 200 to 30000 milliseconds. The default is 3000.

Challenge
Algorithm

MD5 Message-Digest Algorithm. Copyright© RSA Data Security, Inc.

CHAP Secrets

Lists the CHAP secret for each router.

PAP Parameters

PAP on Call
Answer

Indicates whether PAP is enabled or disabled when the local router answers a call.

Local Name

Name that this interface uses to identify itself to other devices. The default is the host name of the router. Otherwise, this field shows the name you entered using the set pap local-name command.

Local Password

Password on the local router. This is the password that the local router sends to the remote router during PAP authentication.

Max Request
Timeouts

The number of times the local router, as authenticator, waits to receive a PAP Request packet. If it does not receive a PAP request after this number of tries, it closes the connection. The range is 1 to 100. The default is 20.

Request Timeout
(mSec)

How long the local router, as authenticator, waits for a PAP Request packet. This timer starts at the end of the Link Establishment phase of PPP. If the router does not receive a PAP Request packet after this timer expires, it waits again. It repeats this process until the Max Request Timeouts counter counts down to zero. The range is 200 to 150000 milliseconds. The default is 15000.

Retry Timeout
(mSec)

How long the local router, as the peer, waits for a PAP ACK or NAK after it sends a PAP Request packet. When this timer expires, the local router retransmits the PAP Request. The local router keeps trying as many times as are set in the Max Request Timeouts parameter. The range is 200 to 30000 milliseconds. The default is 3000.

PAP Passwords

Lists the PAP password for each router.

NCP Parameters

Config Request
Tries

Number of times NCP sends configure-request packets to a peer station while attempting to open an NCP connection. Exceeding the count halts configure-request transmission.

Terminate Tries

Number of times NCP sends terminate-request packets to a peer station to close an NCP connection. Exceeding the count halts terminate-request transmission.

Config Nak tries

Number of times NCP sends configure-nak (nak=not acknowledged) packets to a peer station while attempting to open an NCP connection.

Retry Timer

Amount of time, in milliseconds, that elapses before NCP's transmission of configure-request (to open the link) and terminate-request (to close the link) packets is timed out. This timer is the time to wait before retransmitting configure-request and terminate-request packets.

IPCP Options

IPCP Compression

Displays whether or not IPCP is using Van Jacobson TCP/IP Header Compression. You should enable this option when the link is running at a low baud rate.

IP Address

Displays whether or not IPCP is configured to send the local IP address to the remote end of the link or to request the IP address from the remote end of the link.

In order to properly establish the link, the software overrides the setting for sending the local IP address in two cases:

The display of the IPCP options shows what you configured, it does not reflect any overrides.

Multilink PPP Configuration

MP

Indicates whether Multilink PPP is enabled or disabled.

Initial MP Bundle
Size

Number of MP bundle member links requested on an outbound call.

Maximum MP
Bundle Size

Number of member links to accept in a bundle. This is also the limit on how many links MP can use when dynamic bandwidth allocation is enabled.

Discriminator

Indicates whether a discriminator is set to default or to be generated.

Sequence Number
Length

Indicates whether the long or short sequence number header format is used in MP packets.

Bandwidth-on-
Demand

Type of dynamic bandwidth allocation to be used. The choices are Off (none), Slow, Medium, and Fast. The last three choices control how quickly the local router responds to changes in bandwidth.

High-Utilization
Threshold

When the average utilization of the entire Multilink bundle exceeds this threshold, MP opens another circuit to add more bandwidth.

Low-Utilization
Threshold

If more than one circuit is open, when the average utilization of the entire Multilink bundle falls below this threshold, MP drops one circuit.

CCP Options

Data
Compression

Shows whether data compression is currently enabled or disabled on this interface.

Algorithm list

Displays the current compression algorithms followed by the options configured using the set ccp options command.

Stac: histories

The number of separate compression histories to maintain. The valid options are 0 and 1.

Stac: check_mode

There are three methods for detecting lost packets: LCB (Longitudinal Check Byte), CRC (Cyclical Redundancy Check), and SEQ (Sequence number). SEQ is the default.

bncp

Lists the Bridging Network Control Protocol (BNCP) options.

Example: list bncp

BNCP Options
------------
Tinygram Compression: DISABLED

ccp

Lists the current Compression Control Protocol options and algorithms.

Example: list ccp

CCP Options
-----------
Data Compression enabled
Algorithm list: Stac-LZS
Stac: histories 1
Stac: check_mode SEQ

chap

Lists the CHAP parameters. These parameters are described under the list all command.

Example: list chap

CHAP Parameters
---------------
CHAP on Call Answer: Enabled
CHAP on Call Originate: Enabled
Local Name: gt70local
Challenge tries: 10
Challenge timeout(mSec): 15000
Response timeout(mSec): 3000
Challenge Algorithm:RSA Data Security,Inc. MD5 Message-Digest Algorithm

ipcp

Lists the Internet Protocol Control Protocol (IPCP) options. These fields are described under the list all command.

Example: list ipcp

IPCP Options
------------
IPCP Compression: None
IP Address: Don't Send or Request

lcp

Lists parameters and options for the Link Control Protocol (LCP). These fields are described under the list all command.

Example: list lcp

LCP Parameters
--------------
Config Request Tries: 10 Config Nak Tries: 5
Terminate Tries: 2 Retry Timer: 3000
Callback Mode: Accept Callback Delay: 600

LCP Options
-----------
Max Receive Unit: 1500 Magic Number: No
Async Control Char. Map(ACCM): 0
Protocol Field Comp(PFC) Yes Addr/Cntl Field Comp(ACFC) Yes
Echo Requests: DISABLED

mp

Lists the Multilink PPP (MP) configuration parameters and options. These parameters are described under the list all command.

Example: list mp

Multilink PPP Configuration
---------------------------
MP: Enabled
Initial MP bundle size: 1
Maximum MP bundle size: 2
Discriminator: Default
Sequence Number Length: Long
Bandwidth-on-Demand: Fast
High-Utilization Threshold: 70%
Low-Utilization Threshold: 35%

pap

Lists the PAP parameters. These parameters are described under the list all command.

Example: list pap

PAP Parameters
--------------
PAP on Call Answer: Enabled
Local Name: gt70local
Local Password: localpw
Max Request Timeouts: 20
Request Timeout(mSec): 15000
Retry Timout(mSec): 3000

parameters

Lists parameters for all Network Control Protocols (NCPs).

Example: list parameters

NCP Parameters
---------------
Config Request Tries: 10 Config Nak Tries: 5
Terminate Tries: 2 Retry Timer: 3000

password

Lists the PAP password for each router.

Example: list password

PAP Passwords
Router Password
------ --------
gt70local localpw

secret

Lists the CHAP secret for each router.

Example: list secret

CHAP Secrets
Router Secret
------ ------
gt70remote sample secret

List [M]

Displays information and counters related to the PPP interface and PPP parameters and options. You can display specific groups of information by listing the information for that group only.

Syntax: list

all
ap2
atcp
bacp
bncp
ccp
chap
compression
control
errors
ip
ipcp
ipx
ipxcp
lcp
mp
mp-bundle
pap

all

Lists all information and counters related to the PPP interface and PPP options and parameters. For a description of the fields displayed, see the individual list commands in the following sections.

Example: list all

ap2

Lists statistics on the AppleTalk Phase 2 (AP2) packets received and transmitted over the PPP interface.

Example: list ap2

AP2 Statistic In Out
------------ -- ---
Packets: 349 351
Octets: 128488 129412
Prot Rejects: 0

atcp

Lists statistics for the AppleTalk Control Protocol (ATCP).

Example: list atcp

ATCP Statistic In Out
--------------- -- ---
Packets: 0 0
Octets: 0 0
Prot Rejects: 0 -

bacp

Lists statistics for the Bandwidth Allocation Control Protocol (BACP).

Example: list bacp

BACP Statistic In Out
------------- -- ---
Packets: 2 2
Octets: 20 20
Prot Rejects: 0 -

bncp

Lists statistics for the Bridging Network Control Protocol (BNCP).

Example: list bncp

BNCP Statistic In Out
--------------- -- ---
Packets: 0 0
Octets: 0 0
Prot Rejects: 0 -

ccp

Lists statistics on CCP packets and shows the compression algorithm in use, if any.

Example: list ccp

CCP Statistic In Out
------------- -- ---
Packets: 746703 746703
Octets: 4480326 4480326
Reset Reqs: 120 72
Reset Acks: 72 120
Prot Rejects: 0 -
Max size of transmit compression dictionary: 8398
Local (transmit) compressor: Stac-LZS
Local (transmit) compressor statistics:
Recent compression ratio: 2.1:1
Size of receive decompression dictionary: 4424
Remote (receive) compressor: Stac-LZS
Remote (receive) decompressor statistics:
Recent compression ratio: 1.6:1

chap

Lists CHAP statistics.

Example: list chap

CHAP Statistics In Out
--------------- -- ---
Packets: 6 14
Octets: 130 801
Challenges: 0 8
Responses: 6 0
Successes: 0 4
Failures: 0 2

compression

Lists details of PPP packet statistics for data compression.

Example: list compression

Compression Statistic In Out
--------------------- -- ---
Packets: 0 0
Octets: 0 0
Compressed Octets: 0 0
Incompressible Packets: 0 0
Discarded Packets: 0 0
Copied Packets: 0 0
Prot Rejects: 0 -

control

Lists information and counters related to the specified control protocol.

Syntax: list control

atcp
bacp
bncp
ccp
chap
ipcp
ipxcp
lcp
mp
pap
Example: list control atcp

ATCP State: Closed
Previous State: Closed
Time Since Change: 6 hours, 27 minutes and 7 seconds
AppleTalk Address Info:
Common network number = 12
Local node ID = 49
Remote node ID = 76

The ATCP State fields are the same as those described under the list control lcp command.

AppleTalk Address Info

Common Network Number

Network number of the two ends of the PPP link. (You must statically configure both ends of the link to have the same network number.)

Local Node ID

Unique node number of the local end of the link.

Remote Node ID

Unique node number of the remote end of the link.

Example: list control bacp

BACP State: Open
Previous State: Ack Sent
Time Since Change: 21 minutes and 53 seconds

BACP Option Local Remote
___________ _____ ______
Favored Peer: 0xFFFFFFFF 0x1

Example: list control bncp

BNCP State: Closed
Previous State: Closed
Time Since Change: 5 hours, 25 minutes and 3 seconds

BNCP Option Local Remote
----------- ----- ------
Tinygram Compression DISABLED DISABLED

Source-route Info:
Remote side does not support source-route bridging

The BNCP State fields are the same as those described under the list control lcp command.
BNCP Option

Tinygram Compression

Displays whether or not Tinygram Compression is enabled or disabled on the local and remote ends of the link.

Source-route
Info

Displays whether or not source route bridging is enabled for the local and remote ports that correspond to this interface.

Example: list control ccp

CCP State: Open
Previous State: Ack Sent
Time Since Change: 43 seconds
Local (transmit) compressor: Stac-LZS histories 1, check_mode SEQ
Remote (receive) compressor: Stac-LZS histories 1, check_mode SEQ

The CCP State fields are the same as those described under the list control lcp command.

Example: list control chap

CHAP Option
-----------
CHAP on Call Answer: Enabled
CHAP on Call Originate: Enabled

Local Name: gt70-2
Remote Router Name: gt70-1
Max Challenges: 20
Challenge timeout 15000
Response timeout 3000
Challenge Algorithm:RSA Data Security,Inc. MD5 Message-Digest Algorithm

CHAP State: Opened
Previous State: Success Sent
Time Since Change: 1 minute and 28 seconds

Example: list control ipcp

IPCP State: Listen
Previous State: Closed
Time Since Change: 20 seconds

IPCP Option Local Remote
----------- ----- ------
IP Address 128.189.209.20 None
Compression Slots None None

The IPCP State fields are the same as those described under the list control lcp command.
IPCP Option

IP Address

The IP address of the local and remote ends of the link, if available.

Compression Slots

The number of IP headers saved for reference to determine the type of compression that is enabled.

Example: list control ipxcp

IPXCP State: Closed
Previous State: Closed
Time Since Change: 2 hours, 9 minutes and 2 seconds

The IPXCP State fields are the same as those described under the list control lcp command.

Example: list control lcp

Version: 1
LCP State: Listen
Previous State: Req Sent
Time Since Change: 8 seconds

LCP Option Local Remote
---------- ----- ------
Max Receive Unit: 2048 1500
Async Control Char Map: FFFFFFFF FFFFFFFF
Authentication: CHAP CHAP
Magic Number: B87DA37F None
Echo Requests: DISABLED
Protocol Compr: No No
Addr/Cntl Compr: No No
Link Discriminator: 1 1
32-Bit Checksum: No No

LCP State

Displays the current state of the point-to-point link. These states include the following:

Open— A connection has been made and data can be sent. The retry timer does not run in this state.
Closed— The link is down and there is no attempt being made to open it. In this state, all connection requests from peers are rejected.
Listen— The link is down and there is no attempt being made to open it. In contrast to the Closed state, however, all connection requests from peers are accepted.
Request-Sent— An active attempt is being made to open the link. A Configure-request packet has been sent but a Configure-Ack has not yet been received nor has one been sent. The retry timer is running at this time.
Ack-Received— A Configure-request packet has been sent and a Configure-Ack packet has been received. The retry timer is still running since a Configure-Ack packet has not been transmitted.
Ack-Sent— A Configure-Ack packet and a Configure-request packet have been sent but a Configure-Ack packet has not been received. The retry timer always runs in this state.

Closing— An attempt is being made to close the connection. A Terminate-request packet has been sent but a Terminate-Ack packet has not been received. The retry timer is running in this state.
Previous State

The state of the point-to-point link prior to the state displayed in the LCP State field. These states are the same as those described in the LCP State field.

Time Since Change

Amount of time the link has been in the present state.

LCP Option

Max receive unit

The maximum packet size set for both the local and remote end of the link.

Async control character map

Not applicable to all platforms. PPP accepts this option but ignores it.

Authentication

PAP and CHAP currently supported.

Echo Requests

Echo-request packets.

Magic number

The current magic number for both the local and remote end of the link.

Protocol Compr

Whether or not Protocol Field Compression (PFC) is enabled or disabled for both the local and remote ends of the link. If local PFC is Yes, this interface expects the protocol field to be compressed. If remote is Yes, this interface sends a compressed protocol field per the PPP RFC 1661 specification.

Addr/Cntl Compr

Whether or not Address/Control Field Compression (ACFC) is enabled or disabled for both the local and remote ends of the link. If local ACFC is Yes, this interface expects the address/control field to be compressed. If remote is Yes, this interface sends a compressed address/control field per the PPP RFC 1661 specification.

Link Discriminator

A unique identifier used to indicate a particular link in a multilink bundle.

32-bit checksum

Not currently supported. PPP rejects this option.

Example: list control mp

Breakdown per LCP
-----------------
LCP 1:
------
Version: 1
Time Since Change: 1 minute and 21 seconds

MP Option Local Remote
--------- ----- ------
Max Rcv Recon Units: 2048 2048
Discriminator: class: 1 class: 0
addr: 0114872C addr:
Sequence Number Format: 12 bits 24 bits

LCP 2:
------
Version: 1
Time Since Change: 51 seconds

MP Option Local Remote
--------- ----- ------
Max Rcv Recon Units: 2048 2048
Discriminator: class: 1 class: 0
addr: 0114872C addr:
Sequence Number Format: 12 bits 24 bits

Breakdown per LCP

Version

Version of LCP software running.

Time Since
Change

How long this LCP link has been established.

Max Rcv Recon
Units

The Maximum Received Reconstructed Units is the maximum size the final packet can be after the MP fragmented packets are put back together.

Discriminator

The local side uses the remote Endpoint Discriminator to identify the MP bundle. The remote side uses the local Endpoint Discriminator to identify the MP bundle. A discriminator of class 0 and no address indicates the default discriminator.

Sequence Number
Format

The length in bits of the Multilink sequence numbers.

Example: list control pap

PAP Option
----------
PAP on Call Answer: Disabled

Local Name: gt70-5029
Local Password: Unknown
Remote Router Name: gt70-2
Max Request Timeouts: 20
Request Timeout(mSec): 15000
Retry Timout(mSec): 3000
PAP State: Opened
Previous State: Listen
Time Since Change: 2 minutes and 11 seconds

errors

Lists information related to all error conditions tracked by the PPP software.

Example: list errors

Error Type Count Last One
---------- ----- --------
Bad Address: 0 0
Bad Control: 0 0
Unknown Protocol: 0 0
Invalid Protocol: 0 0
Config Timeouts: 0 0
Terminate Timeouts: 0 0

Error Type

Bad Address

Bad addresses encountered over the link.

Bad Control

Bad control packets encountered over the link.

Unknown
Protocol

Unknown protocol packets encountered by the link.

Invalid Protocol

Invalid protocol packets encountered by the link.

Config
Timeouts

Configuration timeouts experienced by the link.

Terminate
Timeouts

Link termination timeouts experienced by the link.

ip

Lists statistics on the IP packets received (in) and transmitted (out) over the PPP interface.

Example: list ip

Ip Statistic In Out
------------ -- ---
Packets: 349 351
Octets: 128488 129412
Prot Rejects: 0

Ip Statistic

Packets

IP packets transmitted (out) and received (in) over the interface.

Octets

Bytes in octets.

Prot Rejects

Protocol-reject packets.

ipcp

Lists statistics on the IPCP packets received and transmitted over the PPP interface.

Example: list ipcp

Ipcp Statistic In Out
-------------- -- ---
Packets: 2 2
Octets: 14 14
Prot Rejects: 0 -

ipx

Lists statistics on the IPX packets received and transmitted over the PPP interface.

Example: list ipx

IPX Statistic In Out
------------ -- ---
Packets: 0 0
Octets: 0 0
Prot Rejects: 0 -

ipxcp

Lists statistics for the IPX control protocol.

Example: list ipxcp

IPXCP Statistic In Out
-------------- -- ---
Packets: 0 0
Octets: 0 0
Prot Rejects: 0 -

lcp

Lists statistics on Link Control Protocol packets received (in) and transmitted (out) over the current point-to-point interface.

Example: list lcp

LCP Statistic In Out
------------- -- ---
Packets: 0 3833
Octets: 0 53662
Cfg Req: 0 3833
Cfg Ack: 0 0
Cfg Nak: 0 0
Cfg Rej: 0 0
Term Req: 0 0
Term Ack: 0 0
Echo Req: 0 0
Echo Resp: 0 0
Disc Req: 0 0
Code Rej: 0 0

LCP Statistic

Packets

Packets

Octets

Bytes in octets

Cfg Req

Configure-request packets

Cfg Ack

Configure-ack (acknowledged) packets

Cfg Nak

Configure-nak (not acknowledged) packets

Cfg Rej

Configure-reject packets

Term Req

Terminal-request packets

Term Ack

Terminal-ack (acknowledged) packets

Echo Req

Echo-request packets

Echo Resp

Echo-response packets

Disc Req

Discard-request packets

Code Rej

Code-reject packets

mp

Displays statistics for the MP bundle as a whole and for the individual links that make up the bundle.

Example: list mp

MP Statistic In Out
------------- -- ---
Packets: 9 204
Octets: 311 9623
Lost Fragments: 0
Discarded Fragments: 0

Breakdown per LCP
-----------------
LCP 1: In Out
------ -- ---
MP Fragments: 9 174
MP Octets 311 8001

LCP 2: In Out
------ -- ---
MP Fragments: 0 30
MP Octets 0 1622

MP Statistics

Packets

The number of PPP MP packets coming into and going out of the MP bundle.

Octets

The number of PPP MP octets (8 bits) coming into and going out of the MP bundle.

Lost Fragments

The number of times it was detected that at least one MP packet was lost.

Discarded
Fragments

The actual number of MP packets lost.

Breakdown Per LCP

MP Fragments

The number of fragmented or whole PPP MP packets coming into and going out on this link of the MP bundle.

MP Octets

The number of octets contained in fragmented or whole PPP MP packets coming into and going out on this link of the MP bundle.

mp-bundle

Displays information about the current running state of the MP bundle in this channel configuration.

Example: list mp-bundle

MP Bundle Statistic
--------------------
PPP Name: 1
Discriminator: Class: 0 Addr:
Number Member Links: 2
Init Member Links: 2
Max Member Links: 2
Dest Name: operoute
MRRU: 2048
Rcv Sequence Number Length:12
Snd Sequence Number Length:24