Podcast
Questions and Answers
Why does the transport layer focus on logical connections rather than establishing a physical path?
Why does the transport layer focus on logical connections rather than establishing a physical path?
- To optimize the use of physical cables and reduce hardware costs.
- To ensure compatibility with different types of physical media.
- To provide reliable end-to-end communication between processes on different hosts, independent of the underlying physical network. (correct)
- To reduce the complexity of routing algorithms in the network layer.
How does the transport layer's end-to-end service contribute to reliable data transfer?
How does the transport layer's end-to-end service contribute to reliable data transfer?
- By establishing a dedicated physical connection between the source and destination.
- By providing reliability, error detection, retransmission, and flow control between the source and destination processes. (correct)
- By optimizing the routing path to avoid congested network segments.
- By encrypting data to prevent interception by intermediate nodes.
Which of the following elements is NOT typically found in a transport layer segment header?
Which of the following elements is NOT typically found in a transport layer segment header?
- Physical address of the destination (correct)
- Destination port number
- Sequence number
- Source port number
What is the primary purpose of segmenting data at the transport layer?
What is the primary purpose of segmenting data at the transport layer?
How does a receiver utilize sequence numbers in the context of transport layer reassembly?
How does a receiver utilize sequence numbers in the context of transport layer reassembly?
In the context of network communication, how do port numbers and IP addresses work together to deliver data to the correct application on a destination computer?
In the context of network communication, how do port numbers and IP addresses work together to deliver data to the correct application on a destination computer?
What is the primary goal of flow control mechanisms, such as the Sliding Window Protocol, in TCP?
What is the primary goal of flow control mechanisms, such as the Sliding Window Protocol, in TCP?
How does a receiver use a checksum to detect errors in received data?
How does a receiver use a checksum to detect errors in received data?
What does the term '3L/R' represent in the context of network transmission?
What does the term '3L/R' represent in the context of network transmission?
In the formula (3L/R) / (RTT + L/R) used for evaluating network pipeline efficiency, why is the denominator RTT + L/R instead of RTT + 3L/R?
In the formula (3L/R) / (RTT + L/R) used for evaluating network pipeline efficiency, why is the denominator RTT + L/R instead of RTT + 3L/R?
What is the key characteristic of the Go-Back-N ARQ protocol in handling transmission errors?
What is the key characteristic of the Go-Back-N ARQ protocol in handling transmission errors?
In the Go-Back-N protocol, why is ACK 1 sent when packet 3 is discarded due to an error?
In the Go-Back-N protocol, why is ACK 1 sent when packet 3 is discarded due to an error?
In the context of sliding window protocols, why do the sender's and receiver's windows appear different?
In the context of sliding window protocols, why do the sender's and receiver's windows appear different?
What is the key difference between RDT 2.1 and RDT 2.2 in handling errors and packet management?
What is the key difference between RDT 2.1 and RDT 2.2 in handling errors and packet management?
In the three-way handshake process for establishing a TCP connection, what is the correct sequence and purpose of each step?
In the three-way handshake process for establishing a TCP connection, what is the correct sequence and purpose of each step?
Flashcards
Transport Layer
Transport Layer
End-to-end communication between processes, ensuring reliable data transfer through logical connections, without establishing a physical path.
End-to-End Service
End-to-End Service
Ensures communication between source and destination processes, providing reliability, error detection, and flow control.
Segmenting Data
Segmenting Data
Breaks application data into smaller pieces, assigns sequence numbers for reassembly, and adds header information.
Reassembly Process
Reassembly Process
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IP Address
IP Address
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Port Number
Port Number
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Flow Control
Flow Control
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Checksum Error Detection
Checksum Error Detection
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3L/R
3L/R
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Go-Back-N
Go-Back-N
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RDT 2.0
RDT 2.0
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RDT 2.1
RDT 2.1
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RDT 2.2
RDT 2.2
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RDT 3.0
RDT 3.0
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Three-Way Handshake
Three-Way Handshake
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Study Notes
Transport Layer Basics
- The transport layer manages end-to-end communication between processes on different hosts through logical connections.
- It provides reliable data transfer between end systems, offering features such as error detection, retransmission, and flow control.
Segment Structure
- A transport layer segment includes a header and a payload.
- The header contains source and destination port numbers, sequence number, acknowledgment number, flags, and error-checking information.
- The payload contains the actual data being transported from the application layer.
Segmenting and Reassembly
- The transport layer divides application data into segments and assigns each segment a sequence number.
- At the destination, the receiver uses sequence numbers to reconstruct the original message, reordering segments if necessary.
- Lost or corrupted packets are handled via retransmission mechanisms, such as those used by TCP.
IP Addresses and Port Numbers
- An IP address identifies the destination computer similar to a street address.
- A port number directs data to a specific application on that computer, like an apartment number.
Flow Control
- Flow control prevents a fast sender from overwhelming a slow receiver.
- TCP utilizes the Sliding Window Protocol to efficiently manage data flow.
Checksum for Error Detection
- The sender calculates the checksum by adding all data bits and taking the complement.
- The receiver validates data by adding the received bits (including the checksum) and checking if the sum is all 1s; if not, an error occurred.
Formula Explanation
- 3L/R represents the time to send three packets of size L over a link with bandwidth R.
- (3L/R) / (RTT + L/R) assesses pipeline efficiency by comparing the amount of data sent to the total delay, with the denominator including round-trip time and one packet transmission time.
Go-Back-N Protocol
- Go-Back-N is an ARQ protocol that allows a sender to transmit multiple frames before requiring an acknowledgment.
- In case of an error, all subsequent frames are retransmitted.
- Acknowledgments are sent in order, and if a packet is lost, subsequent packets are not acknowledged until the missing packet is successfully retransmitted.
- The sender’s sliding window advances as new packets are sent, while the receiver’s window moves only when it receives in-order packets, with the window reflecting data sequences.
RDT Protocols
- RDT 2.0 uses ACK/NACK to handle errors.
- RDT 2.1 introduces sequence numbers to manage duplicate packets.
- RDT 2.2 eliminates NACKs, relying solely on ACKs with sequence numbers.
- RDT 3.0 employs timeouts and retransmissions to address packet loss.
Three-Way Handshake
- SYN (Client → Server): Client sends a SYN message (e.g., SYN=1, seq=100).
- SYN-ACK (Server → Client): Server responds with SYN + ACK (e.g., SYN=1, ACK=101, seq=300).
- ACK (Client → Server): Client sends final ACK (e.g., ACK=301, seq=101).
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