Description: This document shows you how to set up the QoS rules in a LANCOM router firewall in order for them to operate with the settings recommended for VoIP connections.
Requirements: Procedure: | Info |
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The firewall settings described here depend on the following:
- The Diff-Serv flag generated by the VoIP application (generally EF)
- Which codec is used, as this determines the guaranteed bandwidth (e.g. G.711, G.729)
- The ports (usually port 5060 for SIP signaling)
In order for the QoS to work properly, it is important that the bandwidth values made available by the provider are specified on the Internet connection, otherwise the mechanism has no reference values! Please note the special notes on using Unify telecommunications systems from Deutsche Telekom in the following instructions! |
1) Firewall rule 1: 1.1) In LANconfig, open the configuration dialog for the LANCOM router and switch to the menu item
Configuration -> Firewall/QoS -> IPv4 rules -> Rules.
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Image Added 1.2) Enter a
name for the firewall rule and
set the priority to 1. 
1.3) The
action must be set to the
action object ACCEPT.
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Image Added 1.4) On the
QoS tab you need to
add a custom QoS action.
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Image Added 1.5) Configure a
guaranteed minimum bandwidth of 1 kbps per session.
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Image Added 1.6) On the
Stations tab set the
Connection source and Connection destination to
all stations.
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Image Added 1.7) On the
Services tab, under
Target services you add a
new service object for the
SIP service.
On the
General tab, give the
new service object a name.
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Image Added 1.8) On the
Services tab, select the option
Custom protocols -> Edit custom protocols... 1.9) In the
Ports field, enter the
ports 5060 and 5061 separated by a comma.
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Image Added 1.10) The new service object is entered in the
List of target services. Finish the configuration of the first firewall rule with
OK.
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Image Added 2) Firewall rule 2: The second firewall rule prioritizes the RTP data. Your IP phones must be set so that the
RTP data is marked with the EF flag.
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This is a presetting for many IP phones. However, just to be on the safe side you should check the configuration of your phones. |
2.1) In the
Firewall objects section, click the button
Action objects and
add a new action object in the dialog that follows.
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Image Removed2.3) Enable the option
for DiffServ-CP and select the flag
EF . Close the dialog with
OK.
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Image Added | Info |
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The Unify telecommunications systems from Deutsche Telekom and also some telecommunications systems from other manufacturers send a dummy RTP packet at the beginning of a phone call, which has a wrong DiffServ tag. As a result, the created firewall rule would not apply if the DiffServ tag "EF" was used. We therefore recommend that when using these PBXs, you create an action object that does not use a DiffServ tag. In addition, later in step 2.12, the firewall rule is restricted to the local IP address of the PBX so that it only applies to packets that are sent to the PBX. 
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2.4) In the
Firewall objects section, click the button
QoS objects and
add a new QoS object in the dialog that follows.
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Image Added 2.5) On the
General tab, give the action a descriptive name. On the
Actions tab, click
Add.
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Image Added 2.6) Add
three QoS conditions. For each of the conditions, enable the option
for DiffServ-CP and set the flag to
EF.
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Note for users of Internet connections with low bandwidth: For Internet connections with low bandwidth (guide value <50 Mbit / s downstream & 10 Mbit / s upstream), it makes sense to also configure fragmentation and PMTU reduction: - Configure a maximum packet size of 576 bytes for the fragmentation of the remaining packets.
- Configure a reduction of the PMTU to 576 bytes.
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2.7) Confirm your configuration with the OK button.
2.8) Navigate to the menu
Configuration -> Firewall/QoS -> IPv4 rules -> Rules and add
another firewall rule.
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Image Added 2.9) On the
General tab, enter a descriptive
name.
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Image Added 2.10) On the
Actions tab,
select the action object you created in step 2.2.
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Image Added 2.11) On the
QoS tab,
select the QoS object you created in step 2.4.
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Image Added 2.12) On the
Stations tab, set the
Connection source and Connection destination to
all stations.
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Image Added | Info |
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When using a Unify PBX from Deutsche Telekom, you must specify the PBX as the connection source so that the rule only takes traffic to the PBX into account. In the example, a firewall object was created and used for the local IP address of the PBX. 
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2.13) On the
Services tab you set the
Protocol/source services and Protocol/target services to
all protocols/source services.
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Image Added | Info |
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When using a Unify PBX from Deutsche Telekom, it makes sense to configure the UDP protocol here. 
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2.14) Complete the configuration of the second firewall rule with
OK and write the configuration back to the LANCOM router.
