Traffic Shaping VoIP

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This scenario shows the configuration of Gibraltar to secure a minimum bandwidth for a internal VoIP telephone system having the IP 192.168.0.40.

The aim of this scenario is to ensure a minimum bandwidth of 1 MBit for the telephone system. The internet connection has a bandwidth of 2 MBit both - up- and download. Because of latency the rest traffic only gets a maximum of 75 % of the total bandwidth. This is a must have if you do not have a provider that supports the QoS based on TOS bits (most providers don't). Furthermore only 95 % of the total bandwidth may be used to ensure a optimal functionality.

shaping_szenario_ipsec

 

System Requirements

A computer with two compatible network interface cards or a Gibraltar Security Gateway.

 

Installation of Gibraltar

 

Please install Gibraltar as described in chapter Installation.

 

System configuration

 

System configuration as described in Scenario 1.

 

Network settings - Network interface cards

 

Network and routing configuration as described in Scenario 2.

 

ATTENTION: By changing the IP address on the network card which you use for access to Gibraltar, the connection is interrupted. Please adapt the IP address on your work station computer as well.

 

Firewall rules

 

Firewall rules as described in Scenario 2.

 

Network - Definitions

 

1.Choose Network in the main menu.
2.Choose Definitions in the sub menu.
3.Choose the index card Host/Net Aliases.
4.Define a host/net alias named "voipHost" with the IP address 192.168.0.40.
5.Save: Confirm your changes with clicking the button Save.

 

The following steps are necessary to be able to manage the total bandwidth:

Definition of the bandwidth of each interface
Classifying the traffic to assign it to the shaping rules
Creating the shaping rules for the regulation

 

Traffic shaping

 

1.Choose Traffic shaping in the main menu.
2.Choose the tab General Settings.
3.Bandwidths: Define the value "2048" for the interface "ext0" for the download and 1024 for the upload.
4.Save: Confirm your changes with clicking the button Save.
5.Choose the tab Classification.
6.Add classification: Click this button for adding a new classification for the source address of the telephone system.
7.Name: Enter a name for the new classification (e.g. "voipSource").
8.Source address: Select the value "voipHost".
9.Destination address: Select the value "ANY".
10.TOS: Select the value "Minimize Delay".
11.Save: Confirm your changes with clicking the button Save.
12.Add classification: Click this button for adding a new classification for the destination address of the telephone system.
13.Name: Enter a name for the new classification (e.g. "voipDest").
14.Source address: Select the value "ANY".
15.Destination address: Select the value "voipHost".
16.TOS: Select the value "Minimize Delay".
17.Save: Confirm your changes with clicking the button Save.
18.Add classification: Click this button for adding a new classification for ICMP. ICMP should be managed by default for error diagnosis.
19.Name: Enter a name for the new classification (e.g. "icmp").
20.Service: Select the value "CUSTOM" from the select box.
21.Protocoll: Select the value "ICMP".
22.Save: Confirm your changes with clicking the button Save.
23.Add classification: Click this button for adding a new classification for the remaining traffic.
24.Name: Enter a name for the new classification (e.g. "rest").
25.Source address, Destination address: Select the value ANY from the select boxes.
26.Save: Confirm your changes with clicking the button Save.

 

ICMP and VoIP traffic will be joined to a group "highPrio". This group should always be observed as a whole to ease troubleshooting.

 

1.Choose the tab Classification Group.
2.Add group: Click this button to add a new classification group.
3.Name: Enter a name for the group (e.g. "highPrio").
4.Add member: Choose the members "voipSource", "voipDest", and "icmp".
5.Save: Confirm your changes with clicking the button Save.

 

Now you must create the shaping rules for the minimum bandwidth:

 

1.Choose the tab Traffic shaping rules.
2.Track: Choose "incoming ext0" to manage incoming traffic to the internal network.
3.Add rule: Click this button to add a new rule.
4.Name: Enter a name for the new rule (e.g. "ruleDownload").
5.Add member: Click this button to add classifications or classification groups.
6.Choose the classification group "highPrio" and set the values "1024" for Min and "2048" for Max.
7.Add member: Click this button to add classifications or classification groups.
8.Choose the classification group "rest" and set the values "800" for Min and "2048" for Max.
9.Save: Confirm your changes with clicking the button Save.
10.Add rule: Click this button to add a new rule.
11.Track: Choose "outgoing ext0" to manage outgoing traffic.
12.Name: Enter a name for the new rule (e.g. "ruleUpload").
13.Add member: Click this button to add classifications or classification groups.
14.Choose the classification group "highPrio" and set the values "512" for Min and "1024" for Max.
15.Add member: Click this button to add classifications or classification groups.
16.Choose the classification group "highPrio" and set the values "450" for Min and "1024" for Max.
17.Save: Confirm your changes with clicking the button Save.

 

Save config

 

1.Save your configuration on an USB-stick or harddisc.

 

The above configuration ensures a minimal bandwidth of 1 MBit for your telephone system. If you notice some troubles during your telephone calls, adapt the values for the "rest" classification down to a lower one. A detailed reporting of your bandwidth management can be seen at Monitoring.