Wednesday, June 27, 2007


yup , I set up a SIP server (SIP proxy) to test VoIP with our IP DSLAM ... no problem so far , VoIP use very little band width. In the beginning I thought it will be very difficult to set up a SIP server , but it was much easier than I expected and the software are available freely from many vendors. Here I will explain how to use :

SIP server : ( SIP server 2.0)
SIP client : (X-lite 3.0)

first : you need three PCs ( or two PCs also is oki ) and a Small Hub to make a small network

*** may be u can use VMware to run Three OS in the same PC so you do not need a network

Step - 1

install the SIP server in Server- Windows XP is the best for this ( get Academic licence - the process is bit long but it works and its free ) ...

Install the SIP server : to an easy and trouble free installation ,

1) make you IP address fixed ( Manually assigned - NO DHCP) - if the IP address is "assigned by DHCP" the server will refuse to start !!
2) MAke sure that you can acess internet through the same IP address.

*** even if u cannot access internet through the same IP you can get this working but ... kind of .... can cause u trouble . . . just follow the instructions on

username : sa
password : sa

add two user account :

* better to user numbers as user accounts - eg : 101 , but you can use names as well , eg : "ruwan" ...

SIP server uses the TCP port 5060 , make suer that network you are in allows this port !!! ( if this is a local environmant and NO filer wall you do not have to worry abt these stuff )

Add the user info :

click "add" - and thats it !!! and another user the same way , may be as user name "104" so that you have two account for VoIP phones , 103 and 104 can call from 103 to 104 abd vice versa ...

step 2 : set up two "sip clients on two PCs" or ...two virtual machines ...

install ....

add new SIP account ( add user ) - "SIP account settings"

Now just type the number of you other SIP client ( may be 104 ) ... :D ....yha u will hear the ring !!! ha ha ha

u can always contact me if u face any issue !!! ah ha ha ...

Friday, June 15, 2007

Active FTP vs Passive FTP

wooooow ... yup ...spend almost a day testing active FTP and passive FTP through a firewall , what was interesting is not the firewall but the "active and passive FTP"

tools :
Fedora core 6 - FTP server
Fedora core 4 - FTP client

I actually tried to use Windows client but could not find the command to disable "passive mode FTP " ...but I found one artical about how to disable passve FTP in internet explorer
suprizingling I found a bug in Fedora Core 4 - when the FTP client send "PORT" command or "Passive" comand etc the pkt sent has a check sum error - in the TCP section !!!

the first problem I faced - how can I initiate an Active FTP session because all FTP clients use passive FTP by default !!! .... after lot of search I figuredout that its not that difficult ,

open linux shell , tupe "ftp" and then type "passive" - then u will see the message "passive mode is off"
shell> ftp
ftp> passive
Passive mode off

then just use get command to download some file !!! u have ur self an ACTIVE FTP connetion !!!
ftp> get test.txt

and use "etheral to capture pkts " ... then u can see for sure that it was an Active FTP session !!!

Saturday, June 2, 2007


I did a small online research on different methods of providing broad band services over ADSL, well … mainly it can be PPPoE , PPPoA or IPoE (actually because one customer asked me this question ) . PPPoE is the most popular and IPoE is the most modern but due to some security lacks and technology immaturity not used in large scale .

PPPoE - the PPPoE client can be in the PC or in the modem , the diagram below is the case when PPPoE client is built in the modem. The user name and password will be set in the modem. For IP DSLAM there is nothing much to do about the PPPoE pkts than pass-through. According to TR-101 the DSLAM should add a tag to identify the ADSL port from which the PPPoE session is initiated.

for testing purposes , you can use a Linux PC and run RP-PPPoE server on Linux(I used FC4) or if you LOVE windows you can use RASPPPoE protocol , this works both as server and the client .

PPPoA - PPPoA client can be the modem or an ATM network card plugged in a PIC slot of the PC , anyway it seems like using PPPoA is not very popular now due to the popularity in Ethernet technology , anyway DSLAMs are suppose to be able to detect what type of connection the modem is requesting automatically , therefore if u set PPPoA in your modem (though the originally it was set to PPPoE ) there is a good possibility that ISP's DSLAM will automatically detect this and allow ur modem to establish a link.

Pure PPPoA environment , when the ISP's network infrastructure is ATM ,

PPPoA in PPPoE environment , the IP DSLAM will convert the PPPoA in to PPPoE ,

IPoE - was the easiest to set up and configure , I used IEEE 802.1x for authentication and DHCP with relay agent and option 82 .