Disney Transport Layer: Understanding Network Communication

Disney Transport Layer Considerations

The transport layer is the heart of the whole hierarchy of protocols.

Function: To provide efficient, reliable, and economic data transport processes for the application layer, regardless of the physical network or networks.

There are two types of service: connection-oriented and connectionless.

If there is an error in the lower layers, where n can be controlled at higher x, the error is corrected at the transport layer.

• Disorders
• Duplication
• Loss

Causes of errors:

• Cable errors
• Interference
• Inadequate blockade operation

Functions in the Transport Layer

• End-to-end reliable communication
• Error control
• Flow control
• Multiplexing of several connections

Origin and destination communicate through a network. The transport layer specifies how applications communicate.

Elements of Transport Protocol

1. Addresses

When establishing a connection, what will connect the remote process?

Transport addresses should be established.

• Port model in TCP/IP
• AALSAPs in ATM

2. Establishing a Connection

• Client sends a connection request
• Server sends a connection response

3. Releasing a Connection

• Symmetrical connection release: Each connection is released separately.
• Asymmetrical connection release: The connection is released at a given time and can cause data loss.

4. Flow Control and Buffer Release

Ports and Sockets

Port

Each process must communicate with another identified with one or more ports.

Port number 16 is a bit that identifies what protocol level (application program) must give the received segment.

Applications that send a segment host (@ IP) need to identify specific processes (ports) in the system.

Well-Known Ports

1. Assigned to application servers using standard protocols: HTTP server 80.
2. They are assigned by the IANA.
3. They are within the range 0 .. 1023.
4. Enable clients to find servers without configuration information.

Ephemeral Ports

1. Assigned to client applications.
2. Clients do not need well-known ports to initiate communication with servers and send the port number within the segment.
3. The operation provides a host port on each client while the process requires it.
4. Random port range 1024 .. 65535 depending on the operating system.

Sockets

• A socket address is the triplet: (protocol, local address, local process) e.g., (TCP 192.168.5.10, 6003)
• An association or connection is five times that completely specifies the two processes of a connection: (protocol, local address, local process, address Pool, Pool process) e.g., (TCP 192.168.5.10, 6003, 192.168.5.1, 53)
• The average association is also called a connector, socket, or transport address.
• A connection is formed by an origin socket and a destination socket.
• The socket concept was introduced in Berkeley Unix and has become a de facto standard.

Socket Interfaces

The socket interface is distinguished by the different services provided:

• Interface Sockets oriented stream: Connection-oriented reliable service.
• Interface Sockets oriented datagram: Connectionless service.
• Low-level socket interface: Allows direct access to low-level protocols such as IP and ICMP.