Chapter 12 Notes
Allows bit streams to be created and to travel.
Layer 2: The data link
layer is concerned with physical (as opposed to logical) addressing, network
access, error notification, ordered delivery of frames, and flow control.
Packages those data packeges into framesto be converted to bit streamsand makes LAN delivery possible.
Layer 3: The network
layer is a complex layer that provides connectivity and path selection
between two host systems
that may be located on geographically separated networks.
Layer three packes data from
upper layers in packets and makes routing and WAN delivery possible.
devides outgoing messages into segments
reassembles messages at the destination station
re-sends anything not received
messages from incoming segments.
User Datagram Protocol (UDP)-
The connectionless transport protocol in the TCP/IP protocol stack. UDP
is a simple
protocol that exchanges datagrams, without acknowledgments or guaranteed delivery. Error processing and
retransmission must be handled by other protocols.
UDP transports data unreliably between between hosts.
transmit messages (called user datagrams)
provides no software checking for message delivery (unreliable)
does not reassmble incoming messages
uses no acknowledgment
provides no flow control
TCP Segment Fields
source port- number of calling port
destination port- number of called port
sequence number- number used to ensure correct sequencing of arriving data
acknowledgment number- next expected TCP octet
window- number of octets that the sender is willing to accept
Both TCP and UDP use port (or socket) numbers to pass information to the upper layers
Numbers below 255 - for public applications
Numbers from 255-1023 - assigned to companies for marketable applications
Numbers above 1023 - are
TCP hosts establish a connection-oriented session with one another using a three-way handshake
A three-way handshake synchronises the connection on both ends before any user data is sent
Window size determines the
amount of data you can transmit at one time before receiving an acknowledgement