DQ Mode (Packeteer)

Packeteer DQ Mode

How do I use DQ Mode?

First, you must enable DQ Mode. Do this with the command

sys set testShapingModes 1

Then, to enter DQ mode, use the command:

set shaping dq

To exit DQ mode, use

set shaping off

The steps to setting up a DQ environment are:

1. Set the DQ Mode Global or per Connection
2. Set the DQ Speed Link speed being simulated
3. Set the Latency Latency to be introduced for each packet
4. Set the Loss Rate Percentage of dropped packets to be simulated
5. Switch to DQ Operation. Turn it on with set shaping dq

Example

The following example is the normal procedure for enabling DQ mode, setting a link speed (in this case, T1), and setting a latency (in this case 15ms one-way, +/- 2ms)

PacketShaper# sys set testshapingmodes 1

PacketShaper# set shaping dq
Changing packet shaping from on to dq. Note that this will
put the PacketShaper into delay queue mode, which is a lab test
mode which should be used only with additional instruction.

Please confirm if you really want to proceed (YES): y

PacketShaper# dq mode global

Changing mode to global

PacketShaper# dq speed 1544000

PacketShaper# dq latency ?

usage: latency <base> [var_within_conn][var_among_conns]

PacketShaper# dq latency 15 2 2

Latency base 15 variable 2 variable between conns 2
PacketShaper#

Remember that the latency is one way, so a ping, which measures round trip time, would show about 30ms in this example.

DQ Loss may also be set, but modern communication links have almost no loss today. Most loss that is seen on a private network is typically attributable to Router Queuing drops, a problem which is normally alleviated by the deployment of PacketShapers and TCP Rate Control.

 

What are the individual commands?

dq mode

usage: mode ["global" | "conn"]

Global mode causes the settings to apply to the link as a whole. Connection mode causes the settings to be applied to each connection separately.

dq speed

usage: speed <bps>

Sets the speed of the link being simulated, in bits per second. In global mode, this is the speed of the line. In connection mode, this is the speed of each separate connection.

dq loss

Sets the loss rate for the simulation.

usage: loss [pkts dropped per thousand] [congestive rate]

where:

[pkts dropped per thousand] base rate of packet loss
[congestive rate] chance of a drop if the previous packet was dropped

Example:

dq loss 40 100

would set a base chance of 40‰ that a packet is dropped with a 100‰ chance of loss if the previous packet was dropped.

dq latency

Sets the link latency to be simulated

usage: latency <base> [var_within_conn][var_among_conns]

where:

<base> base latency in milliseconds
[var_within_conn] packet-to-packet variation, in milliseconds
[var_among_conns] modifier for each connection, in milliseconds

Example:

dq latency 200 20 50

in global mode, sets a latency between 180 and 220 ms for each packet. in connection mode, picks a random base latency between 150 and 250 ms for each flow and then modifies that + or – 20 ms for each packet within the flow.

What are some good values to use for latency?

If you are trying to simulate a specific network, you may use values gathered from ping or (better) from the RTT measurement of the PacketShaper’s Response Time statistics. Don’t forget to divide Round Trip Time (RTT) by two to get link latency.

Some common values:

T1

100 Miles 5-15 ms

56k

100 Miles 15-45 ms

64k

Transoceanic 250 ms

128k

Satellite 375 ms

128k

ISDN 10-30 ms

28.8

Modem 75 - 150 ms

Links

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