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Questions and Answers
Which transport layer protocol is known for its low overhead and lack of reliability?
Which transport layer protocol is known for its low overhead and lack of reliability?
- TCP
- UDP (correct)
- HTTP
- FTP
What does UDP lack in comparison to TCP?
What does UDP lack in comparison to TCP?
- Connection-oriented communication
- Reliability features like retransmission and flow control (correct)
- Ability to establish sessions before communication
- High data throughput
How does UDP handle datagrams that arrive out of order?
How does UDP handle datagrams that arrive out of order?
- It discards them
- It doesn't care about the order (correct)
- It reorders them automatically
- It requests retransmission
Which protocol requires sessions to be established before communication takes place?
Which protocol requires sessions to be established before communication takes place?
What must be implemented externally if reliability is required when using UDP?
What must be implemented externally if reliability is required when using UDP?
What is a key characteristic of UDP regarding data sending?
What is a key characteristic of UDP regarding data sending?
Which range of port numbers do well-known ports belong to?
Which range of port numbers do well-known ports belong to?
What is another name for dynamic or private ports (49152 to 65535)?
What is another name for dynamic or private ports (49152 to 65535)?
When initiating a connection, what type of ports are usually assigned to client applications?
When initiating a connection, what type of ports are usually assigned to client applications?
Which network utility can be used to verify active TCP connections on a networked host?
Which network utility can be used to verify active TCP connections on a networked host?
What information does the netstat command provide about connections?
What information does the netstat command provide about connections?
Which type of programs might connect using dynamic or private ports (49152 to 65535)?
Which type of programs might connect using dynamic or private ports (49152 to 65535)?
What is required before data can be exchanged in a TCP communication?
What is required before data can be exchanged in a TCP communication?
Why is it important for each host to be prepared for communication?
Why is it important for each host to be prepared for communication?
In TCP, what function does the three-way handshake serve?
In TCP, what function does the three-way handshake serve?
What happens after data exchange is completed in a TCP communication?
What happens after data exchange is completed in a TCP communication?
Can an individual server host two services on the same port number within the same transport layer?
Can an individual server host two services on the same port number within the same transport layer?
What does the connection and session mechanism enable in TCP?
What does the connection and session mechanism enable in TCP?
What does the source port number represent in a communication?
What does the source port number represent in a communication?
How are port numbers assigned for server processes?
How are port numbers assigned for server processes?
What is a socket in networking terminology?
What is a socket in networking terminology?
Who assigns port numbers according to the text?
Who assigns port numbers according to the text?
What is the function of the destination port number in a communication?
What is the function of the destination port number in a communication?
How do clients choose port numbers for each conversation?
How do clients choose port numbers for each conversation?
What is the main function of the transport layer?
What is the main function of the transport layer?
What is the purpose of segmenting data in the transport layer?
What is the purpose of segmenting data in the transport layer?
Why are source and destination port numbers important in UDP and TCP packets?
Why are source and destination port numbers important in UDP and TCP packets?
Which transport layer protocol does not pass data to the network until it knows the destination is ready?
Which transport layer protocol does not pass data to the network until it knows the destination is ready?
What mechanisms does TCP use to achieve reliability in data transmission?
What mechanisms does TCP use to achieve reliability in data transmission?
How does the reliability of TCP impact network overhead?
How does the reliability of TCP impact network overhead?
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Study Notes
Transport Layer
- Enables the management of lost data and flow control
UDP: Communicating with Low Overhead
- A simple protocol providing basic transport layer functions
- Has lower overhead than TCP due to lack of connection-oriented and sophisticated retransmission, sequencing, and flow control mechanisms
- Reliability needs to be implemented elsewhere if required
UDP: Datagram Reassembly
- Connectionless, with no session establishment before communication
- Transaction-based, sending data without establishing a session
- Many applications using UDP send small amounts of data fitting in one segment
- UDP does not care about datagram order
UDP Server Processes and Requests
- Different types of port numbers:
- Well-known ports (0-1023)
- Registered ports (1024-49151)
- Dynamic or private ports (49152-65535)
- Dynamic or private ports are usually assigned dynamically to client applications when initiating a connection
Using Both TCP and UDP
- netstat command:
- Verifies active TCP connections on a networked host
- Lists protocol, local address and port number, destination address and port number, and connection state
- Used to examine open connections on a host when performance appears compromised
TCP Connection Establishment and Termination
- A connection is established before data exchange
- Sessions are closed and connection terminated after communication is completed
- Connection and session mechanisms enable TCP's reliability function
TCP Three-Way Handshake
- Establishes the presence of the destination device on the network
- Verifies the destination device has an active service and is accepting requests on the destination port number
- Informs the destination device that the source client intends to establish a communication session on that port number
Identifying Conversations
- Port numbers:
- Source port number: number for a communication associated with the originating application on the local host
- Destination port number: number for a communication associated with the destination application on the remote host
- Socket: combination of the transport layer port number and the network layer IP address assigned to the host
- Example: 192.168.1.20:80
Summary
- Transport layer provides data network needs by:
- Tracking individual communications between applications on source and destination hosts
- Segmenting data and managing each piece
- Reassembling segments into streams of application data
- Identifying different applications
- Performing flow control between end users
- Enabling error recovery
- Initiating a session
- UDP and TCP are common transport layer protocols
- UDP datagrams and TCP segments have headers prefixed to the data that include a source port number and destination port number
- TCP does not pass data to the network until it knows that the destination is ready to receive it
- TCP uses mechanisms of the three-way handshake, timers, acknowledgments, and dynamic windowing to achieve reliable features
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