CCNA 1 Module 14

responsible for logical communications between applications running on different hosts; includes TCP and UDP

tracking individual conversations, segmenting data and reassembling segments, adding header information, identifying the applications, conversation multiplexing

responsibility of transport layer to track each set of data flowing between a source and destination

responsibility to divide the application data into appropriately sized blocks; data may be called a segment or datagram

adds information containing binary data organized into several fields to each block of data

transport layer must be able to separate and manage multiple communications with different transport requirement needs; uses port numbers to identify the target application

enables different communications to be interleaved on the same network

specify how to transfer messages between hosts and are responsible for managing reliability requirements

considered a reliable, full-featured transport layer protocol, which ensures that all of the data arrives at the destination; includes additional processing for the hosts and divides data into segments

number and track data segments, acknowledge received data, retransmit any unacknowledged data, sequence data into correct order, send data at an efficient rate that's acceptable by the receiver

simpler transport layer protocol than TCP; provides the basic functions for delivering datagrams between the appropriate applications with very little overhead; connectionless, stateless, best effort

establishes a session, ensures reliable delivery, provides same-order delivery, supports flow control, is stateful so it records which information has been sent and which has been acknowledged

adds 20 bytes when encapsulating the application layer data

source and destination port, sequence number, acknowledgment number, header length, reserved, control bits, window size, checksum, urgent

FTP, SMTP, SSH, HTTP

data is reconstructed in the order it was received, any segments that are lost aren't resent, no session establishment, sending isn't informed about resource availability

source and destination port, length, checksum

live video and multimedia applications, simple request and reply applications, and applications that handle reliability themselves

DHCP, DNS, SNMP, TFTP, VoIP, and video conferencing

the combination of an IP address and a port number; used to identify the server and the service being requested

0-1,023; these ports are reserved for common or popular services and applications

1,024-49,151; these port numbers are assigned by IANA to a requesting entity to use with specific processes or applications; primarily individual applications that a user has chosen to install

49,152-65,535; ephemeral ports; client's operating system usually assigns port numbers dynamically when a connection to a service is initiated

used to verify the active TCP connections which are open and running on a networked host; by default will attempt to resolve IP addresses to domain names and port numbers to well-known apps

option can be used to display IP addresses and port numbers in their numerical form

an active server assigned to a specific port; the transport layer accepts and processes segments addressed to that port

1. SYN: initiating client requests a client-to-server communication session; 2. ACK and SYN: server acks the client-to-server communication session and requests a server-to-client communication session; 3. ACK: initiating client acks the server-to-client communication session

control flag that closes a connection

1. FIN: when client has no more data to send in the stream, it sends a segment with the FIN flag set; 2. ACK: server sends an ACK to acknowledge receipt of the FIN; 3. FIN: server sends a FIN to client to terminate the server-to-client session; 4. ACK: client responds with an ACK

establishes that the destination device is present on the network, verifies that the destination has an active service and is accepting requests, and informs the destination device that the source intends to establish a communication session on that port number

bits in the control bit field; a bit that's set to either on or off

URG, ACK, PSH, RST, SYN, FIN

urgent pointer field significant

acknowledgment flag used in connection establishment and session termination

push function

reset connection when an error or timeout occurs

synchronize sequence numbers used in connection establishment

no more data from the sender and used in session termination

assigned in the header of each packet to make sure all data is received and reassembled in the correct order; represent the first data byte of the TCP segment

during session setup, an ISN is set; represents the starting value of the bytes that are transmitted to the receiving application; number is incremented by the number of bytes that have been transmitted

acknowledgement used by TCP where the ACK number is sent back to the source to indicate the next byte that the receiver expects to receive

receiver can explicitly ask which segments were received including any discontinuous segments so sending host only needs to resend missing data

the amount of data that the destination can receive and process reliably; can adjust the rate of data flow between the source and destination for a given session

determines the number of bytes that can be sent before expecting an ACK; the ACK # is the # of the next expected byte

a destination sends ACKs as it processes bytes received and continual adjustment of the source send window; allows sender to continuously transmit the segments as long as the receiver is acknowledging the previous segments

typically 1,460 bytes of data within each TCP segment; determined by subtracting the IP and TCP headers from the Ethernet max transmission unit which is 1500 by default