Tcp/ip

Hello ther can anyone help me?

I believe that UDP and TCP both use packet switching, -yet when TCP is described it sounds exactly like circuit-switching. If they do both use packet-switching why does TCP sound like circuit switching?

what is the relation of connection-oriented and circuit switching as they sound exactly the same.

if any one can explain this to me i'd be very happy!!!!!

 

See if this helps, please click HERE

 

hi thanks for that, but it still just sort of makes tcp sound like circuit switching! do you know if TCP is circuit switching or packet switching
Thanks

 

As Brett would say

Click I think this will answer your question

 

Thanks very much for your help BearNunya,
That confirms that TCP is packet switching. But the main problem is that TCP, when described, is connection-oriented and when you describe connection-oriented it sounds exactly the same as circuit-switching. This is what i dont understand!!!!

i.e. circuit switching requires a connection to be set up end to end before communication begins, when the circuit becomes reserved, all packets follow the path, which means they cant arrive out of order. etc etc

packet switching -doesnt set up a connection and just sends data out over the network.

TCP/IP uses a connection-oriented service; connection-oriented service is described as: source & destination machines establish a connection before any data are transferred. all frames are received in the right order. etc

the last paragraph sounds exactly like circuit-switching to me. If TCP/IP is packet switched why is it described as it is (like circuit-switched)?

 

Lets break out the terms a little.

The OSI model:
http://www.webopedia.com/quick_ref/OSI_Layers.asp

IP; Layer3; A packet switched protocol that rides on top of data link layer
TCP; Layer4; a connection oriented implementation that rides on top of IP
UDP; Layer4; a connectionless (read: traditional ) packet switched protocol, rides on top of IP.

TCP adds a sequence identifier, and specifies methods for retransmissions, ordered reassembly and flow control. This is implemented in such a way that the presentation layer sees the data stream as reliable, distinct, and guaranteed. This is the source of using the commonly accepted terminology of 'connection oriented' to describe tcp.

The terms you are using appears to be in context of layer 1 and layer 2 in the OSI model.. Its a little more complex than that out here on the interweb.

Its all a ruse tho.. but shh, dont tell anybody or the whole house of cards will come crashing down. Your packets are blown in the wind, its a miracle the internet works!

 

With TCP frames are not necessarilly received in the correct order. However as BenMcDonald stated, the frame are provided with an identifier which allows the receiving computer to reassemble the frame into the right order before passing them to the application.

My definitions would be:
Circuit switched - On initiation the pathway is set exclusively for current communication. All packets of information go along that pathway and that pathway only. As there is only one path all packets are received in the order they are sent.

UDP - Packets are sent without a requirement to check for receipt. They are just sent out to the right address, but can take which ever path they find presented to them as the pass over the network.

TCP - Packets are sent at the start of communication to check the recepitant is ready to receive a communication. Those packets are packet switched in that they can take which ever path is presented to them. Once communication is set up a conversation goes on between the two end points along the lines of :

S "I want to send you some packets "
R "Great - use this session 187, send them over "
S "I'm sending you packets 1,2,3,4,5 "
R "I've received packets 2,1,3,4,5; send me the next lot "
S "Here come the next group of packets "
R "I got all but packet 8. Can you send 8 again please? "
S "OK - here comes 8 again "
R "Got that. Send me the next group "
S "Here come the next lot, and this is the last lot "
R "OK, close session "
S "Session closed "

So you can see that a session does represent a virtual connection. However, the path each packet takes will be based on the network structure at the time each packet passes. In effect TCP is exactly the same as UDP except that a nanny system is set up to make sure that all the packets sent out are received by the recipient system. That nanny system is the communication protocol alluded to above.