Question

"TCP connection is logical, therefore TCP can be connection oriented protocol"

Wha is meaning of logical connection? Can u discuss brief above two lines?

Comments

I was thinking about some reality :p

Is there any electromagnetic field established ? So, that each tcp packet goes end to end  through this field like pipeline??

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if it exists it will be at physical layer ?

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no physical layer it cannot exists

I donot think so, it will be in transport layer

Either it present in switching network or internet

But I think internet is better preferred option for it

Answer 1

A connection-oriented protocol requires that hosts establish a logical connection with each other before communication can take place. This connection is sometimes called a "virtual circuit", although the actual data flow uses a packet-switching network. A connection-oriented exchange includes three phases:

1. Start the connection.
2. Transfer data.
3. End the connection.

Reference--https://www.ibm.com/support/knowledgecenter/en/SSB27U_6.4.0/com.ibm.zvm.v640.kiml0/asotrans.htm

Comments

although the actual data flow uses a packet-switching network

This is because even though at Transport layer TCP is connection oriented protocol so it should follow circuit switching but TCP segment is encapsulated in IP Datagram which is well-known connectionless packet switching network. So when the packet reaches at the router as the router is level 3 (Upto Network Layer) Device it checks details which are present only at the network layer header and not check those which are at Transport layer.

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circuit switch and packet switch provides wired connection

which is physical connection too

not only logical connection

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No, wired connection is needed only in the case of Circuit switching not in case of Packet switching.

Actually In virtual circuits which is a part of Packet Switching..at every switch some buffers are reserved for the datagrams .Therefore we called it as connection oriented. But but but it should be marked that by being connection oriented, it doesnt mean that it needs any physical connection like wire. I hope u understood.

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TCP is connection oriented in the sense that there's a connection establishment, between the two ends where they may negotiate different things like congestion-control mechanism, reserving the buffers, bandwidth, processors etc.
The transport layer protocols' general purpose is to provide process-to-process delivery meaning that it doesn't know anything about routes; how your packets reach the end system is beyond their scope, they're only concerned with how packets are being transmitted between the two end PROCESSES.

IP, on the other hand, the Network layer protocol for the Internet, is concerned with data-delivery between host to host  yet it's connection-less, it maintains no connection so each packet is handled independently of the other packets if you're using datagram service.
Leaving your system, each router will choose the path that it sees fit for EACH packet, and this path may change depending on availability/congestion.
Not to confuse you though, most connection-oriented services at the network-layer and below mean that the connection, when established, also establishes a virtual-path that all 'packets' must follow like in virtual circuits...

Answer 2

TCP requires some buffers to be reserved at reciever side for its seq no., ack no. adv window. Thatswhy it is called connection oriented. By connection oriented ,we simply means that some buffers need to be reserved at reciever side.

But in UDP, we does not need anything.it is 1 request/1 reply. Infact it is like when we ask time to any stranger, we don't ask his details or his name, we are just interesting in knowing what the time is.