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Win a PC for example is connecting to a web server on the internet.

Traffic will be sent from a source IP address to a destination IP address.

So the source IP address in this transmission will be from the host 10 1 1 1 to the server 10 1 to 1.

Traffic will be routed from the PC to the server and when the traffic arrives at the server the server

needs a way to differentiate which application to send the traffic to the well-known port numbers are

used for various common day applications like HTP.

So this server will be running a web server application like ISIS or Petchey which serves up the web

pages for the web browser using Apache as an example.

The Apache server will be listening to traffic on port 80 which is the well-known port number for HTP.

Your browser will automatically open up a connection to the servers IP address on that port number.

If the defaults a used when their traffic arrives at the transport layer TZP will send that traffic

to port 80.

The port number the Apache server is listening on and the Apache server at the application layer will

process the data received.

The pc will use a random source port number in a specific range that range is dependent on the operating

system and whether the Ayana standards are followed.

But essentially a random port number is used as a source and a well-known port number is used as the

destination.

In this conversation when the reply from the server is sent back to the PC.

Note that the source address will be the servers IP address and the port number will be port 80 the

destination IP address will be the PC's IP address and the port number the PC selected as the source

port number.

So no return traffic has the IP addresses reversed and the port numbers are reversed.

The PCs web browser.

Let's say for instance Internet Explorer will be listening on those ports 60000 and when the traffic

arrives at the PCs transport layer.

In this case TZP TZP will push that traffic to port 60000.

The port number that Internet Explorer is expecting to receive the traffic on that's port numbers bind.

Les afford to lay A7 allowing applications to communicate.

Now they are some well-known port numbers that you need to remember well-known port numbers are in the

range less than or equal to 1023.

So for example HTP uses port 80 and TZP as its transport layer protocol.

If the control which is used for the server and find negotiation uses port 21 using TZP data which is

used for the actual transmission of data and if ATP uses port 20 and TZP telnet used for management

uses port 23 and uses TZP DNS is an interesting case because it uses both TZP and UDP and uses port

53 DNS primarily uses UDP on port 53 to serve requests.

In other words when a host needs a resolution for say Cisco Racan that will usually be port 53 TZP is

used when the response data exceeds 512 bytes or for tasks such as zone transfers zone transfers are

used for replication of databases containing DNS data across a set of DNS servers

TFT users UDP port 69 and SMP uses UDP port 161 once again to see a list of court numbers go to Google

and type on a port numbers and as you can see here the internet assign numbers authority or on a number

list is available for viewing as you can see here the well-known port numbers on the range 0 to 1023

I have that because of the number of applications that don't use is the second range known as the registered

ports in the range 1024 3 to 49 1 5 1 which are generally used for proprietary applications.

Dynamic or private port numbers on the range 4 9 1 5 2 3 to sixty five thousand five hundred thirty

five.

As you can see the full port ranges from 0 to 6 5 5 3 5 to search for a well-known application I'm just

going to use the key sequence control F and then type in for example Telenet.

And as you can see here telnet uses port 23.

Now both TZP and UDP could be used for telnet but in most implementations TZP is used.

I could search for another protocol like let's say TFT P And as you can see here TFT P uses port 69.

Once again TZP or UDP could be used but in real world applications UDP is used.

I could search for example for HTP.

And as you can see here notice port 80 there are many applications here some of which you may never

have used or seen.

There's another example.

BP and its derivative DHP use port 67 and 68.

I could scroll down the list and show you many many port numbers as an example of the way.

And here's an example of some of the port numbers used by Bloomberg.

Now according to the owner there are three ranges of port numbers.

Well-known port numbers are less than or equal to 1023 registered port numbers on this range 1024 2

4 9 1 5 1 and dynamically assigned port numbers which should be used by hosts when initiating sessions

for instance well-known import numbers on the range 4 9 1 5 2 2 6 5 5 3 5.

However Venda implementations do not necessarily follow that recommendation.

Ephemeral port numbers are short lived Portes used for the client side of a connection.

So when your PC initiate a session to a web server and ephemeral code will be used they are temporary

and only last for the duration of the session.

As I've shown you the honor suggests the range for 9 1 5 2 to sixty five thousand five hundred thirty

five.

However BSD uses this range 1024 through 4 9 9 9 Linux or Linux users.

Ports 3 2 7 6 8 2 61000 windows through to server 2003 use the range 1000 and twenty five to five thousand

Windows Vista and 7 use the actual eye on a range and Free BSD users on a range since version 4.6.

So just be aware the source port number is used by hosts will very based on the Venda implementation

and which ephemeral port numbers that vendor has decided to use.

So in this example this host which may be running Windows Vista is using a source port of 60000 when

connecting to this Apache server on well-known port 80.