This document explains the bandwidth reservation and priority queuing features. It includes the following topics:
Bandwidth Reservation System (BRS)
Priority Queuing
Bandwidth Reservation With Priority Queuing
Filtering and Bandwidth Reservation
Configuring Bandwidth Reservation
Bandwidth Reservation Commands
Bandwidth Reservation System (BRS)
BRS allows you to decide which packets the router drops when demand (traffic) exceeds supply (throughput) on a network connection. The router does not use BRS until there are requests for more than 100% of the available line bandwidth.
BRS reserves transmission bandwidth for a network connection by allocating minimum percentages of total connection bandwidth to specified classes of traffic. Figure 1 shows the components of BRS classes.
These reserved percentages are a minimum slice of bandwidth for the network connection. If a network is operating to capacity, the router can only transmit a message if transmitting it does not exceed the bandwidth allocated for the class. When this happens, the router holds the transmission until other bandwidth transmissions have been satisfied. In the case of a light traffic path, a packet stream can use bandwidth exceeding its allowed minimum up to 100% if there is no other traffic. BRS is really a safeguard. In general, a network should not attempt to use more than 100% of its line speed. If it does, you probably need a faster line. The bursty nature of traffic, however, can drive the requested transmission rate to exceed 100% for a short time. In these cases, BRS ensures that the higher priority traffic is delivered and is not discarded. Bandwidth reservation is a feature that runs over interfaces.Note: OpenROUTE Networks recommends that you enable BRS on every PPP interface that you enable for bridging. Bridging cannot run on PPP interfaces if the MRU is less than the maximum Ethernet frame size.
Urgent
High
Normal (the default setting)
Low
CAUTION:
If you set the values for queue length too high, you may seriously degrade the performance of your router.
The priority settings in one bandwidth class do not affect other bandwidth classes. No one bandwidth class has priority over the others. You can only map a network protocol (or several grouped protocols) or filters to a class.
IP tunneling
Rlogin
Telnet
SNMP
IP multicast
MAC Address
BRS Config <NET-2> ASSIGN
Protocol or filter name [IP]? tag15
Class name [DEFAULT]?
Priority <URGENT/HIGH/NORMAL/LOW> [NORMAL]?
Config>network
What is the network number [0]? 2
Circuit Configuration
Circuit Config <NET-2>
Circuit Config <NET-2> brs
Bandwidth Reservation User Configuration
BRS Config <NET-2>
BRS Config <NET-2>enable
Please restart router for this command to take effect.
+network 2
Circuit <NET-2>
Circuit <NET-2>brs
Bandwidth Reservation console
BRS <NET-2>
Not all parameters apply to all router platforms. Press Space twice after you type a command to display the available options for each command for your router. Enter help for information about using the command line interface. [C] means the command is available at the BRS Config <NET-#> prompt. [M] means the command is available at the BRS <NET-#> prompt.
Before using the bandwidth reservation commands, keep the following in mind:
The Class-name parameter is case-sensitive.
To view the current class names, use the list or show command.
add-class
Class name [DEFAULT]? ipx
Percent bandwidth to reserve [10]? 15
|
Class-name
| The name of the bandwidth class. |
|
Percent bandwidth
| The percentage of the bandwidth of the interface to assign to this class |
Assign [C]
Assigns tags, protocols, or filters to a class and assigns a priority within that class.
You can assign up to 64 Tags by entering TAG1 through TAG64 in answer to the Protocol or filter name [IP]? prompt. By assigning a priority to tags, you can prioritize traffic that you tagged using IP filters or MAC filtering. Use the same tag number in the BRS configuration that you used in the IP filter or MAC filter configuration.
The four priority types include:
Urgent
High
Normal (the default priority)
Low
Syntax: assign protocol or tag or filter class-name priority
Example:assign
Protocol or filter name [IP]? tag18
Class name [DEFAULT]?
Priority <URGENT/HIGH/NORMAL/LOW> [NORMAL]?
assign
Protocol or filter name [IP]? ipx
Class name [DEFAULT]?
Priority <URGENT/HIGH/NORMAL/LOW> [NORMAL]?
change test 10
clear
clear-block
You are about to clear BRS configuration information for this interface.
Are you sure you want to do this (Yes or [No]): yes
counters
deassign IP
default-class test normal
del-class ip
disable
exit
enable
last
list
BANDWIDTH RESERVATION listing from SRAM
bandwidth reservation is enabled
interface number 2
maximum queue length 10 minimum queue length 3
total bandwidth allocated 70%
total classes defined (counting one local and one default) 4
class LOCAL has 10% bandwidth allocated
protocols and filters cannot be assigned to this class.
class DEFAULT has 40% bandwidth allocated
the following protocols and filters are assigned:
protocol IP with priority NORMAL
protocol ARP with default priority
protocol IPX with priority NORMAL
protocol AP2 with default priority
protocol ASRT with default priority
filter SNA with priority NORMAL
assigned tags:
default class is DEFAULT with priority NORMAL
CAUTION:
Do not use this command unless it is essential to do so. OpenROUTE Networks recommends the default values for queue length for most users. If you set the values for queue length too high, you may seriously degrade the performance of your router.
Sets the number of packets that the router can queue in each BRS priority queue. Each BRS class has a priority value that you assigned to its protocols, filters, and tags. Each priority queue can hold the number of packets that you specify with this command. This command sets the maximum number of output packets that can be queued in each BRS priority queue. It also sets the maximum number of output packets that can be queued in each BRS priority queue when router input buffers are scarce. Syntax: queue-length maximum-length minimum-length Example:
queue-length
BRS priority queue maximum length [10]?
BRS priority queue minimum length [3]
show
BANDWIDTH RESERVATION currently in RAM
interface number 2
maximum queue length 10 minimum queue length 3
4 current defined classes:
class LOCAL
class DEFAULT
class ipx
class ip
protocol and filter assignments:
Protocol/Filter Class Priority
--------------- ----- --------
IP DEFAULT NORMAL
ARP DEFAULT LOW
IPX DEFAULT NORMAL
AP2 DEFAULT LOW
ASRT DEFAULT LOW
Not all parameters apply to all router platforms. Press Space twice after you type a command to display the available options for each command for your router. Enter help for information about using the command line interface. [C] means the command is available at the BRS Config <NET-#> prompt. [M] means the command is available at the BRS <NET-#> prompt.
Add-circuit-class [C]
Adds a class to the BRS configuration and allocates a designated amount of bandwidth to the Frame Relay circuits assigned to the class.
Syntax: add-circuit-class class-name percent-bandwidth
add-circuit-class
Class name [DEFAULT]? ip
Percent bandwidth to reserve [10]? 25
|
Class-name
| The name of the bandwidth class. |
|
Percent bandwidth
| The percentage of the bandwidth of the Frame Relay circuit to assign to this class |
Assign-circuit [C]
Assigns a Frame Relay circuit (DLCI) to a circuit class.
Syntax: assign-circuit circuit# class-name
assign-circuit
Circuit to assign [16]?
Class name [DEFAULT]?
change-circuit-class
Class name [DEFAULT]? ipx
Percent of bandwidth to reserve for circuit class [30]? 20
circuitCircuit to reserve bandwidth [16]? 16
clear-circuit-class
You are about to clear BRS configuration information for this interface.
Are you sure you want to do this (Yes or [No]): yes
deassign-circuit
Circuit to deassign [16]?
default-circuit class
Class name [DEFAULT]? ipx
del-circuit-class
Class name []? ipx