Segment
On the sending side, the transport layer converts the application-layer messages it receives from a sending application process into transport-layer packets, known as transport-layer segments in Internet terminology. This is done by (possibly) breaking th
User Datagram Protocol (UDP)
Provides an unreliable, connectionless service to the invoking application.
Transmission Control Protocol (TCP)
Provides a reliable, connection-oriented service to the invoking application. The application developer selects between UDP and TCP when creating sockets.
Multiplexing
The job of gathering data chunks at the source host from different sockets, encapsulating each data chunk with header information (that will later be used in demultiplexing) to create segments, and passing the segments to the network layer is...
Demultiplexing
At the receiving end, the transport layer examines these fields to identify the receiving socket and then directs the segment to that socket. This job of delivering the data to the transport-layer segment to the correct socket is...
Transport Layer
The layer is the fourth layer of the OSI reference model. It provides transparent transfer of data between between end systems using the services of the network layer (e.g. IP) below to move PDU's of data between two communicating systems.
Port
Virtual ports are part of TCP/IP networking. These ports allow software applications to share hardware resources without interfering with each other.
Socket
A method for communicating between client and server programs. It is defined as "the endpoint in a connection.
Connection
TCP connection provides a full-duplex service: If there is a TCP connection between Process A on one host and Process B on another host, then application layer data can flow from Process A to Process B at the same time as application layer data flows from
Connection-Oriented
TCP is said to be __________ because before one application process can begin to send data to another, the two processes must first "handshake" with each other--that is, they must send some preliminary segments to each other to establish the parameters of
Nmap
a security scanner used to discover hosts and services on a computer network, thus creating a "map" of the network.
Listening Socket
The servers socket just sits there and waits for a connection.
Datagram Socket
It is a type of connectionless network socket, which is the sending or receiving point for packet delivery services. Each packet sent or received on this socket is individually addressed and routed
Well-Known port numbers
Each port number is a 16-bit number, ranging from 0 to 65535. The port numbers ranging from 0 to 1023 are called well-known-port-numbers.
Connectionless Transport
A data transmission method used in packet switching networks by which each data unit is individually addressed and routed based on information carried in each unit, rather than in the setup information of a prearranged, fixed data channel as in connection
Checksum
It is used to determine whether bits within the UDP segment have been altered as it moved from source to destination.
ACK
The message was received and was not garbled
NACK
The message was received but garbled
Finite State Machine
Definitions of the rdt1.0 sender and receiver are shown in Figure 3.9, page 206. Also, a mathematical model of computation used to design both computer programs and sequential logic circuits.
End-to-End Principal
Application-specific function ought to reside on the end nodes instead of the intermediary nodes. This provides error detection for UDP.
Automatic Repeat Request (APR)
Reliable data transfer protocols based on such retransmission are known as ARQ. It is an error-control method for data transmission that uses ACKs and timeouts to achieve reliable data transmission over an unreliable service.
Timeout
An interruppted signal generated by a program or device that has waited for a certain length of time for some input but has not received it.
Cumulative ACK
The receiver an ACK signifying that the receiver has received all data preceding the acknowledged sequence number. The sender sets the sequence number field to the sequence number of the payload byte in the segments data field, and the receiver sends an A
Stop-and-Wait
The sender sends a message and waits for the receivers response.
Sequence Number
A simple solution to duplicate packets is to add a new field to the data packet and have the sender number its packet by putting a these into this field. Also, a they allows the transport layer functions on the destination host to reassemble segments in t
Maximum Transmission Unit (MTU)
The MTU of a communications protocol of a layer is the size (in bytes) of the largest protocol data unit that the layer can pass onwards.
Maximum Segment Size (MSS)
The ____ is typically set by first determining the length of the largest link-layer frame that can be sent by the local sending host (the so-called MTU), and then setting the ___ to ensure that a TCP segment plus the TCP/IP header length will fit into a s
Window Size
As the protocol operates, this window (figure 3.19 page 220) slides forward over the sequence number space. For this reason, N is often referred to as...
Sliding Window
As the protocol operates, this window (figure 3.19 page 220) slides forward over the sequence number space. For this reason, N is often referred to as the window size and the GBN protocol itself as a sliding-window protocol.
Round Trip Time (RTT)
The time required for a signal pulse or packet to travel from a specific source to a specific destination and back again.
SYN
Synchronize sequence numbers. Only the first packet sent from each end should have this flag set.
FIN
No more data from the sender
TCP Flags
They are controls bits that indicate different connection states or information about how a packet should be handled.
Piggybacking
It is a bi-directional data transmission technique in the network layer. It makes the most of the sent data frames from receiver to emitter, adding the confirmation that the data frame sent by the sender was received successfully.
Path MTU Discovery
It is a standardized technique in computer networking for determining the maximum transmission unit size on the network path between two internet protocol hosts, usually with the goal of avoiding IP fragmentation.
Fast retransmit
In the case that three duplicate ACKs are received, the TCP sender performs this, retransmitting the missing segment before that segment's timer expires.
SYN Flood Attack
In this attack, the attacker(s) send a large number of TCP SYN segments, without completing the third handshake step. With the deluge of SYN segments, the server's connection resources become exhausted as they are allocated (but never used!) for half-open
Slow Start
It is part of the congestion-control strategy. It is used in conjunction with other algorithms to avoid sending more data than the network is capable of transmitting, that is, to avoid causing network congestion.
Exponential Weighted Moving Avg
It is a type of infinite impulse response filter that applies weighting factors which decrease exponentially.
Flow Control
It is thus a speed-matching service--matching the rate at which the sender is sending against the rate at which the receiving application is reading.
TCP State Diagram
TCP protocol running on each host make transitions through various TCP states.
Offered Load
The rate at which the transport layer sends segments into the network will be denoted lamda_in bytes/sec. lamda_in is sometimes referred to as...
Congestion Control
As noted earlier, a TCP sender can also be throttled due to congestion within the IP network; this form of sender control is referred to as...
AMID
The congestion control for TCP. Know for "Sawtooth
Congestion
Different sources compete for resources inside a network.
Congestion Window
One of the factors that determines the number of bytes that can be outstanding at any time. This is not to be confused with TCP window size which is maintained by the receiver.
Three-Way Handshake
Because three segments are sent between two hosts, the connection-establishment procedure is often referred to as a _______. Often referred to as "SYN-SYN-ACK" because there are three messages transmitted by TCP to negotiate and start a TCP session betwee