Chapter 3

AIMD = Once the threshold in Slow Start is reached, the congestion window size is increased additively (by one segment per RTT) Slow Start = The congestion window size is doubled until congestion is detected Congestion = It is detected when there is packet loss Congestion Window = It is the maximum number of packets that can be sent before receiving an acknowledgement

A seller gradually increases product prices until sales drop, then cuts prices significantly to lure customers back, and then starts increasing slowly again = AIMD A company launches a new product and initially experiences a sudden surge in demand = Slow Start A company realizes that its current marketing strategy is causing customers to lose interest = Congestion A company can only produce a limited number of units per day and cannot meet the high demand = Congestion Window

Multiplicative Decrease = The congestion window size is halved Additive Increase = The congestion window size is increased by a fixed amount Segment = A unit of data in TCP RTT = Round Trip Time, the time it takes for a packet to travel from sender to receiver and back

Transport Layer = Manages process-to-process communication Network Layer = Manages host-to-host communication TCP = Provides reliable connection-oriented communication UDP = Faster and requires fewer resources, but does not provide reliability or security

TCP = Provides reliability, flow control, congestion control, timing, throughput guarantee, and connection setup UDP = Does not provide reliability, flow control, congestion control, timing, throughput guarantee, security, or connection setup SSL = Provides encrypted TCP connection, data integrity, and end-point authentication DTLS = Provides secure UDP connection

Two applications on different computers exchanging data = Transport Layer Your computer sending data to a server, where the focus is on getting the data between devices = Network Layer Process-to-process communication = Transport Layer Host-to-host communication = Network Layer

TCP = Port number 443 instead of 80 UDP = No specific port number mentioned SSL = No specific port number mentioned DTLS = No specific port number mentioned

Transport Layer = Responsible for the ordering of packets Network Layer = Manages host-to-host communication TCP = Provides reliable connection-oriented communication UDP = Faster and requires fewer resources, but does not provide reliability or security

TCP = No specific encryption mentioned UDP = No specific encryption mentioned SSL = Provides encrypted TCP connection DTLS = Provides secure UDP connection

TCP = Less control over what data is sent and when UDP = Finer application-level control over what data is sent and when SSL = No specific control over data transmission mentioned DTLS = No specific control over data transmission mentioned

Multiplexing = Combining multiple data streams into a single stream to be sent over a network Demultiplexing = Separating a single data stream into its original multiple streams upon receipt UDP = No connection establishment, no connection state, small packet header overhead TCP = Richer demultiplexing, ensures data integrity

Multiple apps on your computer listening for incoming data = TCP Resource-Constrained Environments = Stop-and-wait High Error Rate Channels = Stop-and-wait Controlling spacecraft or other sensitive equipment = Stop-and-wait

UDP = Avoids the three-way handshake, does not ensure data integrity TCP = Has 20 bytes of header information for each segment, ensures data integrity Multiplexing = Determines server for packet to be sent Demultiplexing = Determines which client receives packet

UDP Checksum = A basic method to detect errors in the transmitted data in UDP State Machine = Diagrams representing states and transition of a system Stop-and-wait = Sends a package and waits for an acknowledgment before sending the next Pipelining = Sending multiple packets without waiting for the acknowledgment of the previous packets

UDP = Two-tuple (dest addr, dest port) TCP = Four-tuple (source addr, source port, dest addr, dest port) UDP Checksum = 1s complement of the sum of all the 16-bit words in the segment State Machine = Useful for describing the various states a TCP connection goes through

Stop-and-wait = Advantages: Simple, ensures data integrity. Disadvantages: Slow, especially over long distances Pipelining = Advantages: Faster transmission, efficient use of network bandwidth. Disadvantages: Increased complexity, potential for out-of-order packet delivery UDP = Advantages: No connection establishment, no connection state, small packet header overhead. Disadvantages: No data integrity, potential for data loss TCP = Advantages: Richer demultiplexing, ensures data integrity. Disadvantages: Higher overhead, slower than UDP

Multiplexing = Combining multiple signals for transmission Demultiplexing = Directing received data to the correct process UDP Checksum = A computed value based on the contents of the UDP data State Machine = Useful for describing the various states a TCP connection goes through

Pipelining = Allows for multiple packets to be transmitted consecutively without waiting for acknowledgments for each one Go-back-N (GBN) = If a packet is found to be missing or in error, the receiver discards it and all subsequent packets and GBN resends all packets after a lost one Selective Repeat (SR) = SR resends only the specific lost packets, making it more efficient but more complex Sliding Window = A TCP tool that adjusts the rate of transmission based on the receiver's buffer availability

Pipelining = Faster, especially over long distances or high-speed networks Go-back-N (GBN) = Simplifies the receiver's structure Selective Repeat (SR) = More efficient as only the missing or erroneous packets are retransmitted Sliding Window = Ensures the receiver can process data at its own pace

Pipelining = More complex error handling Go-back-N (GBN) = Potential inefficiency as valid packets received after a missing packet are discarded and need to be resent Selective Repeat (SR) = More complex than GBN since the receiver has to maintain a buffer and keep track of all packets Congestion Control = Prevents network performance degradation

Pipelining = Streaming a video, where data is continuously sent to keep the video playing smoothly Go-back-N (GBN) = Watching a video online and experiencing a brief lag. The service might use GBN, so it starts rebuffering from the point of interruption Selective Repeat (SR) = Streaming a movie, where a minor glitch in transmission doesn't force a rebuffer of several minutes of content but only the few seconds affected Congestion Control = Think of a highway. If too many cars (packets) enter simultaneously, it leads to traffic jams

Flow Control = Mechanism to ensure that a sender doesn't overwhelm a receiver with too much data Congestion Control = Mechanism to prevent too much data from being injected into the network, causing network congestion Slow Start = An algorithm that starts by sending a few segments and doubles the number in every round-trip time (RTT) until a threshold is reached or packet loss occurs Round-Trip Time (RTT) = The time it takes for a packet to travel from the sender to the receiver and back

Go-back-N (GBN) = $N+1$ sequence numbers, where $N$ is the window size Selective Repeat (SR) = Needs $2n$ sequence numbers Pipelining = No specific sequence number requirement Sliding Window = No specific sequence number requirement

Pipelining = Often comes with mechanisms for flow control, which allow for adjusting the rate of packet transmission based on network conditions Go-back-N (GBN) = Only send cumulative ack, always send ACK for correctly received packet with highest in-order seq number Selective Repeat (SR) = Individually acks all correctly received packets, packets out of order: buffer, in-order: deliver if outside window range, ignore Congestion Control = Uses algorithms like Slow Start, Congestion Avoidance, Fast Retransmit, and Fast Recovery to adjust the rate of data sent based on network conditions

Pipelining allows for multiple packets to be transmitted consecutively without waiting for acknowledgments for each one, increasing throughput and utilizing bandwidth more efficiently.

Pipelining introduces more complex error handling, as valid packets received after a missing packet are discarded and need to be resent.

GBN simplifies the receiver's structure.

GBN can potentially be inefficient as valid packets received after a missing packet are discarded and need to be resent.

SR is more efficient as only the missing or erroneous packets are retransmitted.

SR is more complex than GBN since the receiver has to maintain a buffer and keep track of all packets.

GBN requires N+1 sequence numbers, where N is the window size.

Communication between processes refers to process-to-process communication within the same or different hosts, while communication between hosts refers to communication from one host to another, regardless of the specific processes involved.

The transport layer manages process-to-process communication.

TCP provides reliability, flow control, congestion control, handshake (connection-oriented) and secure TCP port number 443 instead of 80. It also provides encrypted TCP connection, data integrity, and end-point authentication.

UDP does not provide reliability, flow control, congestion control, timing, throughput guarantee, security, or connection setup. It is faster and requires fewer resources.

Transport layers are responsible for the ordering of packets.

It is preferable to use UDP over TCP when there is a need for finer application-level control over what data is sent and when.

No, the internet does not provide reliability, timeliness, or packet delivery in order.

The purpose of AIMD is to allow TCP to estimate the network's capacity without congesting it.

A seller gradually increases product prices until sales drop, then cuts prices significantly to lure customers back, and then starts increasing slowly again.

AIMD increases the congestion window size additively, by one segment per Round Trip Time (RTT).

When congestion is detected, the congestion window size is cut in half.

The advantage of AIMD is that it allows TCP to estimate the network's capacity without congesting it.

A seller gradually increases product prices until sales drop, then cuts prices significantly to lure customers back, and then starts increasing slowly again.

TCP estimates the network's capacity by increasing the congestion window size additively until congestion is detected.

When congestion is detected in TCP, the congestion window size is cut in half.

The purpose of AIMD is to allow TCP to estimate the network's capacity without congesting it.

Real-time apps often require a minimum sending rate, do not want to overly delay segment transmission, and can tolerate some data loss. TCP protocol introduces additional overhead for reliability and data integrity, which may not be necessary for these types of applications.

UDP avoids the three-way handshake required by TCP, which eliminates the start-up delay to establish a connection.

UDP does not maintain a connection state and does not ensure data integrity like TCP does. Hence, a server can devote more resources to handling active clients when the application runs over UDP.

UDP has 8 bytes of header information, whereas TCP has 20 bytes for each segment.

The two forms of multiplexing commonly used in the transport layer are Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM).

Demultiplexing in the transport layer involves directing received data to the correct process or socket. It separates a single data stream into its original multiple streams upon receipt.

The UDP checksum provides a basic method to detect errors in transmitted data. The sender calculates the sum of all the 16-bit words in the segment, wraps around any overflow, and stores the 1s complement of the sum in the checksum field. The receiver adds all the 16-bit words in the received segment, wraps around any overflow, and checks if the sum equals 0xFFFF. If it does not, there is a data transfer error.