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Software User's Guide Version 3.3

Configuring and Monitoring Multilink PPP Protocol (MP)

This chapter describes how to configure specific Multilink PPP interfaces in a device. The chapter includes:

Accessing the MP Configuration Prompt

To access the MP config> prompt:

  1. Enter talk 6 at the * prompt.

  2. Enter net n, where n is the number of the dial circuit or MP interface that you enabled to use MP.
    Note:You are now configuring the Multilink PPP interface and not the PPP dial circuit that is part of the MP bundle.

MP Configuration Commands for Multilink PPP Interfaces

Table 66 lists the commands available at the MP config> prompt.

Table 66. MP Configuration Commands
Command Function
? (Help) Displays all the commands available for this command level or lists the options for specific commands (if available). See "Getting Help".
Disable Disables the negotiation of bandwidth on demand.
Enable Enables the negotiation of bandwidth on demand.
Encapsulator Places you in the PPP config> prompt so you can change the data-link protocol configuration.
List Displays the MP interface configuration parameters.
Set Configures MP interface for inbound or outbound traffic. Also allows you to set the idle timeout and other MP and BAP parameters.
Exit Returns you to the previous command level. See "Exiting a Lower Level Environment".

Disable

Use the disable command to disable the negotiation of bandwidth-on-demand (BOD). Disabling BOD prevents the link from allocating additional bandwidth when necessary.

Syntax:

disable
bod

Enable

Use the enable command to enable the negotiation of BOD. Enabling BOD allows the link to allocate additional bandwidth when necessary.

Syntax:

enable
bod

Encapsulator

Use the encapsulator command to access the PPP link-layer configuration for the Multilink PPP interface.

Syntax:

encapsulator
 
Example: 
encapsulator
Point-to-Point user configuration
PPP config>

List

Use the list command to display the current MP configuration.

Syntax:

list
 
Example: 
list
Idle timer = 0 (fixed circuit)
Outbound calls = allowed
Dialout MP Link net = 7
Max fragment size = 750
Min fragment size = 375
Maximum number of active links = 2
Links associated with this MP bundle:
net number 7
net number 8
BAP enabled
Add bandwidth percentage = 90
Drop bandwidth percentage = 70
Bandwidth test interval (sec) = 15

Idle timer
The setting of the idle timer for this circuit in seconds.

A setting of 0 indicates a fixed circuit. A nonzero setting configures a dial-on-demand MP circuit that will be brought down when the circuit is idle for the specified number of seconds The circuit is reactivated when network traffic resumes.

Outbound calls
Specifies whether the interface is configured to initiate outbound calls. If the interface cannot initiate outbound calls, this line is not displayed.

Inbound calls
Specifies whether the interface is configured to initiate inbound calls. If the interface cannot accept inbound calls, this line is not displayed.

Dialout MP link net
The dial circuit configured to place the first call for an outbound MP circuit.

Max fragment size
Specifies the largest number of bytes of data a packet can contain before the packet is fragmented to be sent over MP links.

Min fragment size
This is the minimum size of the fragments (in bytes) the software creates when a packet exceeds Max fragment size.

Maximum number of active links
Specifies the configured maximum number of links in the MP virtual link (also known as bundle).

Links associated with this MP bundle
Displays the links dedicated to this MP interface.

BAP enabled
Specifies whether BAP is enabled on this interface.

Add bandwidth percentage
The amount of bandwidth utilization at which the software will try to add a new link if BAP is enabled.

Drop bandwidth percentage
The amount of bandwidth utilization at which the software will remove a link from the MP bundle if BAP is enabled.

Bandwidth test interval
The time, in seconds, after which the software will check the bandwidth utilization to determine whether to add or drop a link from the bundle.

Set

Use the set command to configure:

Syntax:

set
bod parameters

calls

idle

mp parameters

bod parameters
Prompts you to specify the BOD add and drop bandwidth percentages and the BOD test interval.

Example: 

set bod parameters
Add bandwidth % [90]? 80
Drop bandwidth % [70]? 50
Bandwidth test interval (sec) [15]? 25

Add bandwidth %
The amount of bandwidth utilization at which the software will try to add a new link.

Valid Values: 1 to 99

Default Value: 90

Drop bandwidth %
The amount of bandwidth utilization at which the software will remove a link from the MP bundle.

Valid values: 1 to 99

Default value: 70

Bandwidth test interval (sec)
The time, in seconds, after which the software will check the bandwidth utilization to determine whether to add or drop a link from the bundle.

Valid Values: 10 to 200 seconds

Default Value: 15

calls
Specifies whether this MP interface will initiate outbound calls, only accept outbound calls, or participate in both types of calls.

Valid values: inbound, outbound, or both

Default value: inbound
Note:If you specify outbound or both, the software will request the net number of the dedicated MP link that will place the first call.

Example: 

set calls outbound
Dialout MP link net for this MP net []? 4

idle
Specifies the time period in seconds that an interface can have no protocol traffic at which the MP interface will end calls on all the links.

Valid Values: 0 to 65535

Default Value: 0

mp parameters
Prompts you to enter the maximum and minimum fragment sizes and the maximum number of active links.

Example: 

set mp parameters
Max frag size [750]? 675
Min frag size [375]? 300
Max number of active links [2]? 4

Max frag size
Specifies the largest of number of bytes of data a packet can contain before the packet is fragmented to be sent over MP links.

Valid Values: 100 to 3 000

Default Value: 750

Min frag size
This is the minimum size of the fragments (in bytes) the software creates when a packet exceeds Max fragment size.

Valid Values: 100 to 3 000

Default Value: 375

Max number of active links
Specifies the configured maximum number of links in the MP virtual link (also known as bundle).

Valid Values: 1 to 64

Default Value: 2

Monitoring MP Interface Status

To determine the status of all the MP interfaces in your device, use the configuration command in talk 5 (see "Configuration").

Accessing the MP Monitoring Commands

To access the MP monitoring commands:

  1. Enter talk 5 at the * prompt.

  2. Enter net n, where n is the number of the MP interface that was created in talk 6 using add device multilink-ppp command.

Multilink PPP Protocol Monitoring Commands

Table 67 shows the monitoring commands available for an MP interface.

Table 67. MP Monitoring Commands
Command Function
? (Help) Displays all the commands available for this command level or lists the options for specific commands (if available). See "Getting Help".
List Displays BAP, BACP, BOD, and MP statistics, errors, and other information.
Exit Returns you to the previous command level. See "Exiting a Lower Level Environment".

List

Use the list command to display information about the MP interface including bandwidth allocation statistics.

Syntax:

list
bacp

bap

control bacp

control bod

control mp

mp
Note:The examples that follow assume that the MP interface on this device is net number 6.

bacp
The list bacp command lists the statistics for bandwidth allocation control packets which have been sent or received on this MP circuit.

Example: 

PPP 6> list bacp
 
BACP Statistic             In           Out
-------------              --           ---
Packets:                   6            8
Octets:                    60           80
Rejects:                   0            -

bap
The list bap command lists the statistics for bandwidth allocation protocol packets which have been sent or received on this MP circuit.

Example: 

PPP 6> list bap
 
BAP Statistic                In           Out
-------------                --           ---
Packets:                     3            3
Octets:                      22           37
Call Requests:               1            0
Call Response(ACK):          0            1
Call Resp(NK & FLLNK):       0            0
Call Response(Rej):          0            0
Callback Requests:           0            0
Callback Response(ACK):      0            0
Cllbck Resp(NK & FLLNK):     0            0
Callback Response(Rej):      0            0
Drop Requests:               0            1
Drop Response(ACK):          1            0
Drop Resp(NK & FLLNK):       0            0
Drop Response(Rej):          0            0
Call Status(Success):        1            0
Call Status(Fail):           0            0

There are four different responses to a peer's request: ACK, NAK, FULL-NAK, and REJECT.

ACK
Indicates the peer's request has been granted.

NAK (NK)
Indicates that the peer's request is supported but not desired at this time. Try again later.

FULL-NAK (FLLNK)
Indicates that the peer s request is supported but because of a resource condition, cannot be granted at this time. The request should not be sent again until the total bandwidth across the MP bundle changes.

REJECT (REJ)
Indicates that the request is not supported.

control bacp
The list control bacp command lists the current state of the BACP state-machine within PPP. The state information is identical to that produced for all of the PPP control protocols. Information about favored peer is also listed. Favored peer is used to alleviate BAP packet collisions (when both sides simultaneously initiate requests). During BACP negotiations, each side sends a magic-number and the one with the smallest magic number is the favored peer and should take precedence in the event of a collision. Typically, the call initiator will choose a magic number of X'1' and the call receiver will choose a magic number of X'FFFFFFFF' establishing the call initiator as the favored peer. 
PPP 6> list control bacp
 
BACP State:                Open
 
BACP Option                Local                      Remote
----------                 -----                      ------
Magic Number:              FFFFFFFF                   1
Favorite Peer:             NO                         YES

control bod
The list control bod command lists the current state of bandwidth-on-demand (BOD). This information includes BAP state, configured bandwidth-on-demand parameters for adding and subtracting bandwidth, current bandwidth, and information from the last bandwidth poll.

Valid BAP states are:

Closed
BACP is not opened - BAP is either not enabled or not supported by the peer.

Ready
BACP is opened and there is no outstanding request being processed.

Call Req Sent
There is an outstanding call-request that was sent from the local machine.

Callback Req Sent
There is an outstanding callback-request that was sent locally.

Call Placed
As a result of a BAP request to add bandwidth, a call has been placed.

Retry Status Sent
The outgoing call failed to join the MP bundle, a retry status was sent.

No Retry Status Sent
The outgoing call either succeeded or exhausted all retries, a no retry status was sent.

Drop Req Sent
There is an outstanding drop request that was sent locally.

Configured bandwidth-on-demand parameters include add percentage, drop percentage, maximum number of active links in the MP bundle, and the bandwidth polling interval.

A BAP request to add a link to the bundle will be initiated if both the following conditions are met:

A BAP request to drop a link from the MP will be initiated if both the following conditions are met:

Bandwidth can be polled only when BAP is in the ready state. The information listed from the previous poll will give you an idea of the bandwidth utilization across the MP bundle.

These two sets of information are displayed when a drop can be initiated:

To prevent thrashing, the second set of information is used when determining whether to drop a link.

Example: 

PPP 11>list control bod
 
BOD :                                         Disabled
BAP :                                         Disabled
Bandwidth test interval (sec):                15
Add bandwidth percentage:                     90
Drop percentage (links-1):                    70
Max # active links in MP bundle:              2
Time since last Bandwidth check (sec):        19
Currently:                                    
    # active links in MP bundle:              0
    Total MP bandwidth (Bytes/sec):           0
Last Bandwidth Check:                         
    # active links in MP bundle:              0
    Avg Inbound bandwidth util (%):           0
    Avg Outbound bandwidth util (%):          0

control mp
The list control mp command lists the current state of this MP circuit including the number of active links and bandwidth, the configured maximum number of links, and statistics for number of dropped packets. Dropped MP packets are classified into four categories:

M
The packet is dropped because a sequence number has not been received and it is less than the minimum sequence number across all links' last received sequence number.

Timeout
The packet is dropped because a sequence number has not been received during a timeout period.

Q depth
The packet is dropped because the maximum queue depth was exceeded.

Seq order
The packet is dropped because the sequence number received was not expected. This occurs when MP receives delayed packet that it has already declared lost.

If a packet is dropped at the network layer, it can be either an M, Timeout, or Q depth packet. These counters are incremented appropriately when a packet is dropped. 

PPP 11> list control mp
 Current # active links in MP bundle:          0           
 Max # active links in MP bundle:              2           
 Total MP bandwidth (Bytes/sec):               0           
 Dropped Frags (lost packets):                 0           
 Dropped Frags (timeout or receive overflow):  0           
 Dropped Frags (sequence not expected):        0           
                                                           
 PPP 11>

mp
The list mp command lists the statistics for packets which have been sent or received on this MP circuit. The number of bytes displayed is for pre-decompressed packets if compression was negotiated for the multilink PPP bundle. 
PPP 6> list mp
 
MP Statistic                In           Out
------------                --           ---
Bytes (Compressed):         61230        60259

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