Bandwidth Throttling - Georgia Libraries Tech Center

wartrashyNetworking and Communications

Oct 26, 2013 (3 years and 11 months ago)

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Bandwidth Throttling

Reason for Implementing Bandwidth
Throttling


Limited Available Bandwidth


If left unattended, patron internet traffic can place a strain on
the available bandwidth.


Limiting can stabilize and increase the productivity of both
staff and other library services.



Prioritize Important Programs and Services


At peak usage, patron internet traffic can essentially absorb
all the available bandwidth.


Limiting allows other important programs and services access
to the required bandwidth when they need it no matter the
time or day.


FCPL Data Network Overview


Our Switching Environment


Switches


Cisco 2960 Series Switches


WS
-
C2960
-
48TC
-
L


WS
-
C2960
-
48TT
-
L


WS
-
C2960
-
24TC
-
L


IOS


12.2(44) SE2 LAN BASE CRYPTO


12.2

(
50) SE1 LAN BASE CRYPTO

Where to Begin


Organize your Network


Organizing your switching network allows for a more
seamless implementation of changes.


We have separate switches for, server, staff, and patron computers. If
having multiple switches isn't an option, organize group together the
interfaces on the switches. This will make adjusting these interfaces in
the future easier.


Document your Interfaces


Know which interfaces have servers, workstations and patron
computers.


Know
your switch
u
sernames and passwords.


Backup your Switches


Bandwidth Throttling


Several Different Methods


Most throttling options center around Quality of Service
settings.


Quality of service is the ability to provide different priority to
different applications, users, or data

flows, or to guarantee a
certain level of performance to a data flow.



We Throttle Using Egress Queues


Adjust Shared and Shaped Egress Queue Settings.



Shaped and Shared Mode


Our Cisco switches employ Shaped Round Robin (SRR). SRR is a scheduling
service for specifying the rate at which packets are de
-
queued. With SRR there
are two modes, shaped and shared.


Shaped


Shaped mode is only available on the egress queues. Shaped egress queues reserve a
set of port bandwidth and then send evenly spaced packets as per the reservation.
Shaped SRR is used to shape a queue or set a hard limit on how much bandwidth a
queue can use. When you use shaped SRR, you can shape queues within a port's
overall shaped rate.


Shared


Shared egress queues are also guaranteed a configured share of bandwidth, but do
not reserve the bandwidth. That is, in shared mode, if a higher priority queue is
empty, instead of the servicer waiting for that reserved bandwidth to expire, the
lower priority queue can take the unused bandwidth. Shared SRR is used to get the
maximum efficiency out of a queuing system, because unused time slots can be
reused by queues with excess traffic.


Shaping and sharing is configured per interface. Each interface can be uniquely
configured.


Different ways to Adjust the Egress
Queues


Cisco Network Assistant


Graphic User Interface created by Cisco for managing
network devices



Commands


Accessing the switches through network using telnet or
serial port using hyper terminal


Cisco Network Assistant


Using Cisco Network Assistant


Version


Download


Install


Setup


Connecting



Adjust Egress Queues using Cisco Network Assistant


Where to adjust


How to adjust


What to adjust


Base Settings


Increase


Decrease



Using Cisco Network Assistant


Version


The latest version is 5.6.1


Any version of Cisco Network Assistant (CNA) will allow you to connect to
network devices, but recommend latest version.



Download


Cisco Network Assistant can
be downloaded directly from the Cisco website.


Log in using your Cisco credentials, search for Cisco Network Assistant
within product support, then follow the prompts to download the software.



Install


Initiate the install and follow all default prompts.


The only adjustable option
is the
installation location. Adjust
if
necessary.


Using Cisco Network Assistant
Continued


Setup


Launch Cisco Network Assistant


Under Connect select “Create Community”


Name the Community


Select the best way to discover your devices


Select the devices


Click “OK” to create the community


Enter in the device username and password



Connecting


Select “Connect to:”


If your community name isn’t already within the field, click the drop
down and select it.


Click “OK” to connect to your community.


Adjust Egress Queues using
Cisco
Network Assistant


Where to Adjust


Select Configure | Quality of Service | Queues.



How to Adjust


Adjust Single Interface


Select the single interface and click “Configure”.


This displays the “Configure
QoS

Queues for Interfaces” window.


Make adjustments to the egress queues of a single interface within this
window.


Adjust Multiple Interfaces


Select multiple ports using control or shift click and then click
“Configure”.


This displays the “Configure
QoS

Queues for Interfaces” window.


Make adjustments to the egress queues of multiple interfaces within this
window.


Adjust Egress Queues using Cisco
Network Assistant Continued


Base Settings


Make sure that you document your base settings so that you can revert
back to them if needed.


In addition to base setting documentation, be certain that you
document which interfaces you have adjusted.



Queue ID

Shared
Weights

Shaped

Weights

1

25

25

2

25

0

3

25

0

4

25

0

Default Settings

Adjust Egress Queues using Cisco
Network Assistant Continued


What to Adjust


Adjust the values within the “Shaped” and “Shared” fields assigned to
Queues 1
-
4.


Be cautious when adjusting these queues. Verify which interfaces you are
adjusting.


We worked with Cisco to develop these settings, and they work well for our
environment. These may not be ideal for your infrastructure, but can be
adjusted to best fit your needs.

Queue
ID

Shared
Weights

Shaped

Weights

1

25

25

2

25

0

3

25

0

4

25

0

Queue
ID

Shared
Weights

Shaped

Weights

1

10

10

2

10

0

3

60

0

4

20

350

Default Settings

Adjusted Settings for 300k/s

Adjust Egress Queues using Cisco
Network Assistant Continued


Increasing and Decreasing Bandwidth


If you increase the Queue ID 4 under the “Shaped Weight” field, it will
decrease the bandwidth. If you decrease the Queue ID 4 under the “Shaped
Weight” field, it will increase the bandwidth.


“5” equals roughly 10k/s.


We started with a 350 in Queue ID 4 under the “Shaped Weight” field.
Example #1 shows it increased to 355, which will decrease the bandwidth.
Example #2 shows a decrease to 345, which will increase the bandwidth.

Queue
ID

Shared
Weights

Shaped

Weights

1

10

10

2

10

0

3

60

0

4

20

355

Queue
ID

Shared
Weights

Shaped

Weights

1

10

10

2

10

0

3

60

0

4

20

345

Example #1

Example #2

Cisco Network Assistant

Video Demonstration


Video Demonstration


Setting up a community


Adding a switch to the community


Adjusting the shared and shaped weights on a single
interface


Saving the changes to the switch



Suggested Implementation and
Limitations


Start Out Slow


Start with an unused interface or a backup switch. Adjust the settings and
test them before performing a bulk implementation.


Double
-
Check Interfaces Before Applying Settings


If you have several workstations that use one interface through a standalone
hub or switch, all of those workstations must share the bandwidth that you
allocate to that interface.


Know the Limitations


These settings will throttle not only outbound internet traffic, but all
network traffic. File transfers , Windows update downloads, and other
common LAN tasks will also be affected. Keep that in mind when you are
implementing this solution.

Testing and Monitoring


Testing


Several free programs

are available that can be installed on workstations to
test your bandwidth speeds.


Using a web based solution, like speedtest.net or cnet.com, offers a less
intrusive way to gauge your throttled settings and provide you with a real
-
time analysis when increasing or decreasing those settings.


Monitoring


A library’s network is constantly changing and evolving. Settings you
implement today may not be ideal for the network weeks, months, or years
from now.


Set up basic throttling and adjust the settings for how it works best with
your programs and services.


The GPLS
InterMapper

is a great resource to view your network utilization
and make throttling adjustments based upon that data.


Questions?

Contact Derek Williams at
williamsd@forsythpl.org