FEEDNET

Forth Estuary Experimental Data Network


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Most of what can be achieved via FEEDNET is courtesy of open source software. The sheer hard work, altruism and inventiveness of all open source authors is gratefully acknowledged here.

 

 

 

VOIP (Voice over IP)

VoIP is a technology that allows telephone calls to be made over computer networks like the Internet or FEEDNET.   VoIP converts analogue voice signals into digital data packets and supports real-time, two-way transmission of conversations using Internet Protocol (IP).  There are many advantages to doing this and it is probably fair to say that every single business telephone system sold today uses VoIP.

Standard VoIP telephones can be connected to a FEEDNET node and they will communicate with other telephones on the network.  All the usual telephone features are available - conferencing, recording of calls, etc etc. Usefully, a telephone can obtain an "outside line" by dialling the 9 prefix. So anyone on a FEEDNET node can call any other telephone in the world. Calls from the public network can be placed to arrive at FEEDNET too.  When you place a call to FEEDNET you are asked to dial the FEEDNET extension that you require after which you are connected to the desired extension. If  a call is not answered, all FEEDNET users have a voicemail box where messages can be left.

The external linking is not available unless specifically turned on for RAYNET official User Service requirements. Failure of localised telephone networks is commonplace during emergencies owing to the large volume of traffic that the public try to place on the system. The breakout from FEEDNET to the PSTN can be further way from the locus of the incident and thus can possibly provide PSTN communications in an environment where the local PSTN is overloaded.

Configuration

A computer server is necessary to operate VOIP. FEEDNET uses a small Linux server running the Asterisk open source PBX software. This software is compatible with industry standard SIP telephones.  Each telephone must be configured with the address of the server, a login name and a password. The login name is usually the extension number of the telephone.

SIP telephones can take the form of wired, permanently installed office telephones, such as from the Cisco 7940 range. These plug into the back of a FEEDNET node. Or they can be a "softphone" which makes use of a headset or handset connected to a computer that is connected to the FEEDNET network, either by means of Wi-Fi, or by direct connection.

Another alternative that is very convenient for RAYNET use is a smartphone - either Apple IOS or Android, running VOIP software such as Zoiper. When in range of a FEEDNET node through a wifi link, such a telephone can place and receive calls normally, even if it doesn't have  SIM in it for the normal public Cellphone service. Obviously, it uses FEEDNET thus does not make use of the cellular frequencies at all.

 

 

Steps to installing and operating a Voip PBX on Mesh

  • Set up  a Linux server accessible over FEEDNET.
  • Install Asterisk
  • Configure the sip.conf file to contain entries for all the extension on the system, some general settings, and the details of any gateways to the PSTN. This is not a trivial item, and you'll need to do a bit of reading.
  • Configure the extensions.conf file to reflect the way that you want calls to be routed and delivered. Likewise, not trivial, some reading is necessary.
  • Configure the voicemail.conf file if you want to use this facility.
  • Record voice prompts if you are going to use them
  • On each telephone, install the server address, the login name and the password. There are lots of other options to choose from but most can be left to default.
  • Ensure that the Node to which you choose to connect the server can forward port 5060 to the Server.
  • Enjoy your new Private Automated Branch Exchange !

Using a Cisco Telephone

Cisco telephones are commonplace in the world of commerce because they are well designed and thoroughly dependable.  Costing hundreds of pounds when first purchased, refurbished models are available for as little as 12 on EBay. Many refurbished items turn out to be totally new in original boxes.

Cisco phones are designed for enterprise networks where an IT department in a far away place is responsible for configuration and management of the telephones.

 Here is how a Cisco telephone boots up when switched on - every time it is switched on. It is only an overview - there are a few details glossed over.

1. It looks for a new IP address from a DHCP server on the network.

2. It looks for the IP address of a TFTP file server from which is can seek configuration files. This is typically served from a DHCP server using dhcp-option 150 which is a Cisco proprietary code. dhcp-option 66 can be used if preferred.

3. Having established a connection, the phone looks for a file on the TFTP server whose filename matches its own MAC address.

4. The file is downloaded and the telephone configures itself to be able to talk to the Asterisk PBX, downloads a logo for the screen,  downloads a corporate telephone directory and some other items.

5. The telephone downloads a separate file containing a dialplan. The dialplan tells the telephone how to behave when numbers on the keypad  are pressed. For example, pressing a 9 will provide dial tone to reassure the caller that an outside line has been selected and is available.  If all extensions are four digits, and begin with a 2, then the dialplan can ensure that once these digits have been dialled an attempt can made without further delay to place the call. Remember that analogue telephones send each digit to the network, one after another as they are dialled and it is the network that trundles along, figuring out where to send the call. In IP telephony, the entire string of digits is sent at once and the PABX immediately decides what to do with it. So the dialplan ensures that the telephone knows at what point to send all of the digits.

6. Once it has all of the configurations needed, the telephone will connected to the Asterisk server and register, thus making itself available on the network.

One can see that whoever manages the centrally located configurion files also can manage the behaviour remotely of each and every telephone on the network. This is ideal for large enterprises and can be quite handy for RAYNET too.


A more detailed description of how to install and configure Asterisk is planned soon.

 

 

 

 

 

 

 

 

 

 

 


 


 

 

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Last updated: 02/26/16.