Archive for February, 2010

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Creating copy of Virtual Box instance

Sunday, February 28th, 2010

I had faced  problems in creating a same copy  of the VB system .
I tried to do by creating a copy of the hard disk and adding it to the environment. This will not work since the copied will has the same hard disk identification of  the source .
I was able to solve this issue using the command “VBoxManage clonevdi ”
you need to give the full path  for the files eg

VBoxManage clonevdi  /home/itsupport/.VirtualBox/HardDisks/PBX1.vdi /home/itsupport/.VirtualBox/HardDisks/PBX2.vdi

, otherwise it will throw an error

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Blocking downloading of files using SQUID

Wednesday, February 24th, 2010

Blocking downloading of files using SQUID

We can use ACL to block the download
Step 1
add following lines in to the ACL  ection
acl blockfiles urlpath_regex “/etc/squid/blocks.files.acl”

and to display cusotm error message when users try to download
add

# Deny all blocked extension
deny_info ERR_BLOCKED_FILES blockfiles
http_access deny blockfiles

Step 2
After editing and closing the file . Create custom error message file called “ERR_BLOCKED_FILES” in /etc/squid/error/ directory or /usr/share/squid/errors/English directory.

<HTML>
<HEAD>
<TITLE>ERROR: Blocked file content</TITLE>
</HEAD>
<BODY>
<H1>File is blocked due to new IT policy</H1>
<p>Downloading files causes network trafic</p>

Step 3
nano /etc/squid/blocks.files.acl
add the follwing text

\.[Ee][Xx][Ee]$
\.[Aa][Vv][Ii]$
\.[Mm][Pp][Gg]$
\.[Mm][Pp][Ee][Gg]$
\.[Mm][Pp]3$

A restart of squid will do the trick



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Understanding Digium Cards naming scheme

Wednesday, February 24th, 2010

Naming method looks like

  • “CCC X S O E/B “
  • CCC = is the interface type ,
  • TDM => PCI
  • AEX => PCI Express

It is read as

  • X => X is the no of port , it can be 4,8,24
  • S => S is the no of extensions or FXS lines
  • O => is the no of trunk lines
  • E/B can be either E which means hardwre echo cancellation module
  • B => Only Base module

My selected card is TDM-808EF
ie PCI card, with 8 port , 8 FXO , with echo cancellation

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Projects which I would like to try

Tuesday, February 23rd, 2010
  1. try “gtkwhiteboard”  or   port “WiiWhite board” to Linux
  2. Configure LIRC (Linux Infra Red Remote Control)
  3. Configure anyRemote
  4. boxeeTV

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Portal Notes

Sunday, February 21st, 2010

We have
1> IAS server
2> Infra server , which has database server

(more…)

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Books I like to Buy /Own

Thursday, February 18th, 2010
  • Cambridge English for Job-hunting

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List of GPL based IP-Based PBX systems

Thursday, February 18th, 2010

I have come across three GPL based IP-Based PBX systems
They are

  • 1> Asterisk
  • 2> Call Weaver
  • 3> FreeSwith
  • 4> Yate

There are GUI for the above Telephone Systems they are

For Asterisk

  • FreePBX => http://www.freepbx.org/
  • Trixbox => http://trixbox.org/
  • Elastix    => http://www.elastix.org/
  • Askozia   => http://www.askozia.com/
  • Briker      => http://www.briker.org/
  • EasyAsterisk => http://www.easyasterisk.org/

For FreeSwitch

  • http://www.fusionpbx.com

For Yate
I have not come across any work , If any one know about it please do let me know

For CallWeaver

I have not come across any work , If any one know about it please do let me know

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What I understood about SS7

Wednesday, February 17th, 2010

SS7 is an example of CCS (Common Channel Signalling ) Protocol

  • It is not a single protocol
  • It is a suite of Protocol
  • It is not an access protocol
  • It is a net work protocol
  • It is point to multipoint

ISUP(ISDN user part) and TUP (Telephone User Part)  are in the call control layer

There is MTP (Message transyer layer ) which has three layers:-MTP1 , MTP2 , MTP3

Here in MTP1 (OSI -Physical layer ) has E1,T1

My opinion
So we have E1 , T1 links available in MTP1 layer , is this enough for the PBX . ie If we take the E1 link from MTP1 to the foneBRIDGE , it should work.

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Etisalat :- ISDN Basic Rate Interface (BRI)

Wednesday, February 17th, 2010

ISDN Basic Rate Interface (BRI)

ISDN BRI offers either 64Kbps or 128Kbps data transfer rates. Calling Line Identification Presentation (CLIP) is offered as standard.

Basic Rate Interface (BRI) can support two dial-up services at the same time. One line could be used for data access and the other for voice calls, for example. A maximum of 8 multi-subscriber numbers can be associated with a Basic Rate ISDN line.

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Etisalat :- Primary Rate Access (PRI)

Wednesday, February 17th, 2010

A 2Mbps pipe from the exchange to your business provides thirty channels, each at speeds of 64Kbps. They can be used for voice and data dial-up services.
With ISDN PRI, almost all modern voice and data communication systems from PBXs, mainframe and distributed systems through to your company LAN/WAN can be connected to your ISDN service.
The use of routers, multiplexers, ISDN controllers and video/audio conferencing units is also supported.

Additionally, Digital Telephone Switches can use our Direct Inward Dialling (DID) facility over PRI. DID offers a single interface for up to 30 concurrent calls, as well as for up to two hundred free DID extensions.

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