NEC SL1100/SL2100 SIP Trunk Requirements

NEC SL1100/SL2100 SIP Trunk Requirements

  • NEC SL1100/SL2100 SIP Trunk Requirements

1. Introduction

The purpose of this document is to define the firewall and general router configuration necessary to implement Voice over Internet Protocol (VoIP) communications using a NEC SL1100/2100 PBX across a local area network.

Disclaimer:
The information contained within in this document is updated regularly to keep abreast of current trends. Best 4 Business Communications cannot accept responsibility for costs you may incur should it be necessary to update your network as a result of changes to this information.

2. IP Addresses

Two static IP Addresses required outside scope of DHCP. These must be assigned by the network administrator responsible for the site. These addresses are referred to as IP Address A and IP Address B throughout this guide.
  1. IP Address A - used for SIP
  2. IP Address B - used for Voice Media
If the installation is to use IP handsets, then a sufficient quantity of DHCP addresses should also be available. A separate article is available describing bespoke DHCP Options that automate the installation of NEC IP Phones.

3. NAT Forwards 

Mandatory Forwards

Port Number
Destination
Purpose
TCP/UDP 5060
IP Address A
SIP
UDP 10020 - 10277
IP Address B
Voice Media
TCP 8000
IP Address A
Admin
TCP 35300 - 35301
IP Address A
Web Admin

Optional Forwards 


The following NAT forwards are only required if 3rd Party SIP extensions or Proprietary NEC IP Phones are to be used from a remote location and a secure VPN is not practical. Please contact B4BC Support if you are uncertain if these ports are required or not.

Port Number
Destination
Purpose
UDP 5080 - 5081
IP Address A
NEC Propriety IP Phone
UDP 5070
IP Address A
3rd Party SIP Phone


4. Firewall Rules

Ingress and egress traffic from the following IP Addresses must be permitted.

Inbound Rules (Mandatory)

Source IP Address
Destination IP Address
Source Port
Destination Port
Purpose
93.95.124.0/24
IP Address A
TCP/UDP 5060
TCP/UDP 5060
SIP
93.95.124.0/24
IP Address B
UDP 10000 - 60000
UDP 10020 - 10277
Voice Media
146.101.248.192/26
IP Address A
TCP/UDP 5060
TCP/UDP 5060
SIP
146.101.248.192/26
IP Address B
UDP 10000 - 60000
UDP 10020 - 10277
Voice Media
46.102.218.74
IP Address A
Any
TCP 8000
Admin
46.102.218.74
IP Address A
Any
TCP 35300 - 35301
Admin

Outbound Rules (Mandatory)

Source IP Address
Destination IP Address
Source Port
Destination Port
Purpose
IP Address A
93.95.124.0/24
TCP/UDP 5060
TCP/UDP 5060
SIP
IP Address B
93.95.124.0/24
UDP 10020 - 10277
UDP 10000 - 60000
Voice Media
IP Address A
146.101.248.192/26
TCP/UDP 5060
TCP/UDP 5060
SIP
IP Address B
146.101.248.192/26
UDP 10020 - 10277
UDP 10000 - 60000
Voice Media
IP Address A
8.8.8.8 + 8.8.4.4
UDP 53
UDP 53
DNS
IP Address A
216.239.35.0
UDP 123
UDP 123
NTP
IP Address A
142.0.176.0/20
Any
TCP 587
SMTP

Optional Inbound Rules (Only required if implementing IP Extensions over NAT)

Source IP
Destination IP Address
Source Port
Destination Port
Purpose
Any UK
IP Address A
Any
UDP 5070
3rd Party SIP
Any UK
IP Address A
Any
UDP 5080 + 5081
NEC Proprietary SIP

5. ICMP

Please set your firewall to permit ICMP packets from 93.95.124.0/24 and 146.101.248.192/26. These are purely intended to monitor the health of the SIP Trunk.

6. SIP ALG

SIP ALG must be disabled on all routers. SIP Application Layer Gateway (ALG) is common in many routers and in many cases enabled by default. Its primary use is to modify VoIP packets to aid NAT traversal. Active SIP ALG has been known to cause a mixture of problems by adjusting or terminating VoIP packets incorrectly, manifesting in a range of intermittent issues such as one way audio, dropped calls, problems transferring calls and handsets dropping registration.

B4BC will be unable to accept any faults or investigate any issues with its VoIP service if SIP ALG is enabled. For instructions on disabling this feature please refer to the specific router user guide.

7. UDP NAT Session Timeout

B4BC configures its VoIP user agents to register every 180 seconds with the ITSP. This is an outbound initiated connection utilising the UDP protocol. The purpose of the registration is to inform the ITSP how to route calls to the respective user agent.

Many routers default settings will terminate idle UDP sessions after a very short time (typically less then 30 seconds).

The effect of this is that following SIP registration, inbound calls will only be successful for the first few seconds after registration, and inbound calls presented outside the default UDP session time will invariably fail until the user agent re-registers. To prevent this scenario, it is vitally important that the edge router’s UDP NAT session timer is set to a value of at least 180 seconds . Please refer to your vendor’s documentation for instruction.

8. Quality of Service

Quality of service (QOS) refers to the ability of your router to prioritise voice traffic (VoIP) differently from regular internet traffic leaving your network. VoIP uses a real time protocol which means that if information is lost or delayed it will result in a noticeable drop in call quality or a complete loss of it. Symptoms of network congestion include garbled speech and dropped calls.

A VoIP call consists of two basic components, signalling and RTP (the actual conversation). B4BC uses the G711 codec to encode RTP which requires 87 kbps per call. SIP itself uses up to 65.5 kbps per call.

To this end, sufficient bandwidth should be reserved to satisfy the quantity of voice channels and/or remote extensions connected to the network.

9. Virtual LAN

If you require VLANs to be used, we will need to know which physical port/s to connect to in the case of port based VLANs.

In the event that an IEEE802.1Q tagged VLAN is to be used, we will need to know the required VLAN tag values. It is possible to use DHCP to steer most current models of NEC IP  phones to the correct VLAN.

Installations on VLANs do require prior planning, and often require cooperation between ourselves and the network administrator/s. If a installation on a VLAN is required, please make us aware of this as soon as possible.



















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