Mapping Signalling Transport, over TDM vs ATM vs IP

AAL5       ATM Adaptation Layer 5
ATM        Asynchronous Transfer Mode
CAP        CAMEL Application Part
INAP       Intelligent Network Application Part
IP         Internet Protocol
M2PA       MTP Level 2 Peer-to-Peer Adaptation Layer
M2UA       MTP Level 2 User Adaptation Layer
M3UA       Message Transfer Part 3 - User Adaptation Layer
MAP        Mobile Application Part
MTP        Messge Transfer Part (SS7)
MTP3b      MTP Level 3 with broadband enhancements
PDH        Plesiochronous Digital Hierarchy
SCCP       Signaling Connection Control Part
SCTP       Stream Control Transmission Protocol
SDH        Synchronous Digital Hierarchy
SONET      Synchronous Optical Networking
SSCF-NNI   Service Specific Coordination Function - Network Node Interface
SSCOP      Service Specific Connection Oriented Protocol
SUA        Signalling Connection Control Part User Adaptation Layer
TCAP       Transaction Capability Application Part

Mapping the SS7 Protocol Stack with the TCP/IP Model and OSI Model

Ok, now that I have your attention, what is SACK?

SACK stands for Selective Acknowledgment. It is a type of SCTP packet.

What is SCTP? SCTP is a reliable transport protocol which runs on top of an unreliable connectionless packet service, such as IP. SCTP/IP is used in the implementation of SS7 over IP (SIGTRAN)

SACK is an acknowledgment packet sent by a recipient node to sender node to acknowledge the receipt of DATA chunks. SACK is also used to inform the sender node of any missing chunks.

If there are IP network reliability issues, and the sender node does not receive the SACKs, the data window size will be reduced by the sender node. This data window size is refering to the Advertised Receiver Window Credit (a_rwnd) parameters.

So if you find that I have not replied to your email recently, that's because I'm learning to apply SACK :)

The Wireshark display filter allows you to narrow your view on the amount of information contained in the snoop capture. Here are some basic display filter expressions to be aware of.

Source IP

ip.src==192.168.1.1
ip.src==192.168.1.0/24
!(ip.src==192.168.1.1)

Destination IP

ip.dst==192.168.2.1
ip.dst==192.168.2.0/24
!(ip.dst==192.168.2.1)

Ports

tcp.port==1812
sctp.port==2905
!(udp.port==53)

Protocols

ospf
sccp
stp

Combining expressions

ip.addr==192.168.1.1 or ip.addr==192.168.2.1
ip.addr==192.168.1.1 and udp.port==162

Others

frame contains "text-string"

We want to set up a sniffer to monitor the data traffic between several ports. Here we are assuming that the switch you are using is a Cisco IOS switch (e.g. Cisco Catalyst 3750).

Cisco uses the term SPAN (Switched Port Analyzer) port, to refer to ports that are involved in port mirroring or port monitoring.

Source SPAN port refers to the switch port of the server or node which you are interested in monitoring the data traffic.

In this example, Server A is connected to GigabitEthernet1/0/16 and Server B is connected to GigabitEthernet1/0/17. We want to monitor the data packets flowing between Server A and Server B.

Destination SPAN port refers to the switch port where you will be connecting the sniffer or network analyzer.

In this example, the sniffer is connected to GigabitEthernet1/0/28.

With the above information, we are now ready to configure the switch.

The commands are as follows:
For source SPAN ports GigabitEthernet1/0/16 and GigabitEthernet1/0/17

c3750(config)# monitor session 1 source interface GigabitEthernet1/0/16
c3750(config)# monitor session 1 source interface GigabitEthernet1/0/17

For destination SPAN port GigabitEthernet1/0/28

c3750(config)# monitor session 1 destination interface GigabitEthernet1/0/28 encapsulation

Putting it all together:

c3750# configure terminal
c3750(config)# monitor session 1 source interface GigabitEthernet1/0/16
c3750(config)# monitor session 1 source interface GigabitEthernet1/0/17
c3750(config)# monitor session 1 destination interface GigabitEthernet1/0/28 encapsulation
c3750(config)# end
c3750# show monitor session 1
c3750# write

Output of show monitor session 1:

c3750# show monitor session 1
Session 1
---------
Type : Local Session
Source Ports :
Both : Gi1/0/16,Gi1/0/17
Destination Ports : Gi1/0/28
Encapsulation : Native
Ingress : Disabled

To remove SPAN configuration:

c3750# configure terminal
c3750(config)# no monitor session 1
c3750(config)# end
c3750# write

It does get a little annoying when this happens:

You sit down and psyche yourself up to concentrate on an online training video. You click on the video (created using Flash), it plays for a short couple of seconds, pauses to load more content, plays, pauses, plays, pauses ... (and this goes on forever).

You grumble about the speed of the broadband to anyone who is unlucky enough to be within hearing distance from you. Then you resigned yourself to the predicament you are in. Give up watching and never came back to finish up the training video again.

With this little tip that I'm going to share with you, you will be able to save that training video offline and watch it in your leisure time. No more frustrations!

First, you need to get the Orbit Downloader software. Download here and install it.

Second, run the program. In the Menu bar, choose Tools -> Grab++ . A "Grab++" dialog window will pop-up. We will refer to this window again in step four.


Third, go to your favorite internet browser and load the url of the training video. (e.g. http://www.becomeablogger.com/video-1.html). When you can see the "play" button on the video, click on it.

Fourth, at the Grab++ window, you will see that it has grabbed the filename of the video. Look for those with the flv extention (FLV are known as Flash Video Files). Click on the "Download.." button in the Grab++ window and you will be prompted to the location to save the downloaded video file. Choose the appropriate storage location, then click on the "OK" button.

Fifth, you will see the progress of the file being downloaded. When the download is complete, go to the directory and double-click on the newly downloaded file. If you have the right player program, the FLV file will play immediately from your local disk.

Examples of compatible player programs are:
- Media Player Classic
- VideoLAN VLC media player

Customer: "You want me to back up my hard drive? How do I put it in reverse gear?"
IT support: "... ..." (speechless)

Nope, this is not a post about driving, though if someone really asks me the question above, this person needs to stand 10 meters away from my computer!

Knowing how to back up your important data files, documents, and photographs, etc is essential. I would recommend to try out the SyncBack Freeware software for this purpose. It has 2 main features, Backup and Synchronisation. After installing the software, you will need to create a profile.

The fine tuning of the backup/synchronisation profile can be done in the Profile Setup dialog screen (as seen below). You can use the default settings for a start and customise it to your preference as you go along. When you are satisfied with your configuration, highlight on your newly created profile and click on the "Run" button. A log report will be generated at the end of the backup process. This software also allows you to perform the backup manually or configure the backup to run at a scheduled timing.


I have used this software to back up my data, as well as program and system settings from my computer to my portable hard disk. Works well for me. If you are not sure which directory to backup, you could choose to backup the entire local hard disk. For me, the Source directory is set to "C:\Users\<login-name>\".

I would also recommend that you remove temporary and cached files before performing the backup. You can read more about the software which I use to perform the cleanup here.

So, cleanup then backup, piece of cake...

To learn more about SyncBack Freeware, click here.
If you need a backup software with more advanced features, you can explore SyncBackSE and SyncBackPro.

I'm been getting this annoying error after I switched back to my Pocket PC PDA. Before this I was using an Apple iPhone. I survived for 2 whole months and decided to give it up. I might blog about my painful experiences with iPhone next time, but for now, back to the error message.

This error only happens when I'm connecting to my laptop to perform an ActiveSync. Did a search and found the resolution here:

On the PDA, go to Settings -> Connections -> Network Cards

Tap on Remote-NDIS Host.

Instead of using the default "Use server-assigned IP address", choose "Use specific IP address".
Set the following:
IP Address: 169.254.2.1
Subnet mask: 255.255.255.0
Default gateway:

Performed the ActiveSync again. The error is gone.

If you find that your computer is running out of disk space or crawling like a snail whenever it starts up or launches a program, then you can try the software Crap Cleaner.

This is what it can do:
1. Help you to remove temporary and cached files which are stored by browsers and some utilities application
2. Empty your waste basket (not the physical one, the computer recycle-bin ;) )
3. Help you clean up your pet's poop (ok, I was only kidding about this one).

For those of you who are a little more savvy and not paranoid about system crashes, Crap Cleaner does a good job in cleaning up the obsoletes in your computer registry.

Best thing about this software? It's free and hugely popular!

If you like the software and would like to support the developers, don't forget to donate!
Click on the icon below to go to the web site.