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| technology and architecture of the communications networks used to interconnect communicating devices |
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Local Area Network
Wide Area Network
Personal Area Network
Metro Area Network
Global Area Network |
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| Trends that have driven the architecture and evolution of data communication and networking |
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traffic growth development of new services (cell phone vs landline) advances in technology (smaller/faster) |
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Communications Model
Five Parts |
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Definition
Source
Transmitter
Transmission System
Receiver
Destination |
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Communications Model
Source |
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Definition
generates data to be transmitted
ex. telephones and computers |
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Communications Model
Transmitter |
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Definition
| transforms and encodes info to produce electromagnetic signals that can be transmitted |
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Communications Model
Transmission System |
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Definition
connects source and destination
can be single transmission line or complex network
ex. line or wireless |
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Communications Model
Receiver |
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Definition
| accepts signal from transmission system and converts into a form that can be handeled by the destination device |
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Communications Model
Destination |
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| accepts incoming data from receiver |
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Definition
| Transmission of signals in a reliable and efficient manner |
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| Transmissions System Utilization |
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Definition
| makes efficient use of transmission facilities that are usually shared amoung a number of different devices (more bandwidth) |
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Definition
| used to allocate the total capacity of a transmission media among users |
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| Congestion Control Techniques |
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Definition
| used to ensure that the system is not overloaded by an excesive demand |
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Definition
| device must be able to communicate with the transmission system. depends on use of electromagnetic signals propagated over transmission medium |
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Definition
required after the interface is established
Properties of the signal must be such that the signal is:
capable of being propagated through the transmission system
interpretable at the receiver |
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Definition
| used to coordinate the tranmitter and receiver so that they know when a signal starts to arrive and when it ends |
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| manages the requirements for communication, including using duplex or simplex, amount of data to be sent at one time, data format, and what to do if an error occurs |
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| Error Detection and Correction |
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Definition
| determins if an error happens during transmission and methods to correct the error |
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Definition
| makes sure that the source does not overwhelm the receiver by sending data too fast to be processed |
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Definition
| addressing assures that only the destination system receives the data and the routing determines the route or path that the data will take to get there |
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Definition
needed when an information exchange is interruped due to a fault somewhere else in the system
Objective: to be able to resume activity at the point of interruption or at least resore the state of the systems to the condition before the exchange started |
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Definition
| agreement between the two parties as to the form of the data |
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Definition
| ensures that only the inteded reciever gets the data |
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Definition
| needed to configure the system, monitor status, respond to problems, and plan for future growth |
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Definition
cover large geographical area
usually consists of a number of interconnected switching nodes
usually implemented using circuit switching or packet switching.
new: frame relay and ATM networks |
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Term
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Definition
dedicated communications path is established between two stations through the nodes path is connected sequence of physical links each link a logical channel is dedicated to the connection data generated by the source station are transmitted along the dedicated path as quickly as possible, at each node, incoming data is routed to the appropriate outgoing channel without delay most common exampe: telephone network
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Term
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Definition
Doesn't use a dedicated transmission path data isn't sent in one batch data is sent in a sequence of small chunks each packed is passed through the network from node to node along the path from source to destination path could be different each node receives the packet and transmits it to the next node commonly used for computer communications developed when long-distance transmissions had a high error rate so a lot of overhead is built into the packets to compensate for errors
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Definition
more modern equipment has decreased the error rate in data com takes advantage of high data rates and low error rates original networks had a data rate to the end user of about 64kbps this is designed to have a data rate of up to 2Mbps the key was to strip most of the overhead involved with error control
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Definition
evolution from frame relay frame relay uses variable length packes called frames this uses fixed-length packets, called cells little overhead for error control allows definition of multiple virtual channels with data rates that are dynamically defined at the time the virtual channel is created designed to wrok in the range of 10's and 100's of Mbps and into the Gbps range
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Definition
purpose is to interconnect end systems, called hosts |
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Definition
| hosts are connected to a ___________ |
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Definition
| networks are connected to a __________ |
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Definition
| a host may send data to another host anywhere on the internet. the source host breaks the packed to be sent into a sequence of packets--called IP datagrams or IP packets. Each packet includes a unique numeric address of the destination host--aka an IP address |
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Definition
| computers, sometimes found in a LAN |
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Definition
| Internet Service Provider--hosts are connected to ISP throught a POP (Point of Presence) |
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Definition
Customer Premises Equipment
example: model/DSL box
connection starts with CPE |
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Definition
| physically attached to the 'local loop' or 'last mile' infrastructure between the provider's installation and the site where the host is at |
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Definition
Central Office
place where the phone companies terminate customer lines and locate switching equipment to interconnect those lines with other networks |
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Definition
| Customer Premises Equipment--telecommnications equipment located on the customer's premises |
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Definition
| Network Access Point--major Internet interconnections points that tie all ISP's togehter |
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Definition
| Point of Presence--site with collection of telecommunications equipment, usually an ISP or telephone company site |
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Definition
Layered structure of hardware and software that supports the exchange of data between systems and supports distributed applications (email, ftp) at each layer there is one or more common protocols implemented. Each protocol provides a set of rules for the exchange of data between systems. most common is TCP/IP protocol suite another is the seven layer OSI model Communication is achieved by having the corresponding (aka peer) layers in two systems communicate by using a set of rules known as the protocol
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Definition
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| concerns the format of the data blocks |
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Definition
| includes control information for coordination and error handling |
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| includes speed matching and sequencing |
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| TCP/IP Layers Internet Model |
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Definition
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Term
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Definition
physical interface between data transmission device and the transmission medium/network
ex. NIC
Cabling
Electrical signals
converned with specifying the characteristics of the transmission medium, the nature of the signals, the data rate and other related characteristics |
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Term
TCP/IP
Network Access Layer |
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Definition
concerned with the exchange of data between an end system and the network that it is connected to
sending computer must provide address of the destination computer to network so that it can route the data
sending computer may also set certain parameters like priority. specific software used at this layer depends on teh type of network used
concerned with access to and routing data across a network for two end systems attached to the same network |
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Definition
allows data to travel across multiple interconnected networks when the source and destination computers are not on the same network
uses the IP at this layer to provide routing functions across the multiple networks
IP implemented in end systems and the routers |
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Definition
contains the logic needed to support the various user applications
FTP, email, etc--each requires a different application and a seperate module to handle it |
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Definition
| a processor that connects two networks and whose primary function is to relay data from one network to another on its route from the source to the destination end system |
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Definition
aka host-to-host layer
ensures that all the data arrives at the destination and that the data arrives in the same order as it was sent
provides reliability |
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Definition
two levels
each host ona subnetwork must have a unique global internet address--this allows the data to be delivered to the proper host
each process within a host must have an address that is unique within the host--this allows the host0to-host protocol (TCP) to deliver data--these addresses are known as ports |
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Definition
Protocol Data Unit
contains data and routing instructions (overhead)
sending process generates a block of data and passes to TCP. TCP then breaks it into smaller blocks and appends control info to each block (TCP header) the combonation is TCP segment.
header info includes: destination port, sequence number, and checksum
this segment is then sent to IP, which adds it's own header forming an IP datagram
then sent to the network access layer, which adds it's own information--destination subnetwork address and the facilities request (priority etc) |
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Definition
| each layer adds its own information to the packet |
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Term
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Definition
| Transport Control Protocol |
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Term
| Transport Control Protocol |
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Definition
transport layer protocol for most applications running as part of the TCP/IP architecture
provides a reliable connection for the transfer of data between applications |
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Term
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Definition
made up of minimum of 20 octets--160 bits
source port and destination port identifies the applications at the source and destination systems.
sequence number, acknowledgement number, and window fields are used for flow control and error control
checksum is a 16 bit frame check sequence used to detect errors |
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Definition
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Definition
| does not guarantee delivery, sequence preservation, or protection against duplication |
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OSI Model
Highest to lowest |
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Definition
Application
Presentation
session
transport
network
data link
physical |
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Definition
| Provides access to the OSI environment |
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Definition
| provides independence to the application processes from differences in data syntax |
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Definition
| provides the control structure for communications between applications; establishes, manages, and terminates connections between applications |
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Definition
| provides reliable transparent transfer of data between end points; provides end-to-end recovery and flow control |
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Definition
| provides upper layers with independence from the data transmission and switching technologies used to connect systems. Responsible for establishing, maintaining, and terminating connections |
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Definition
| Provides for the reliable transfer of info across the physical link. sends blocks with the necessary synchronization, error control, and flow control |
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Definition
| concerned with transmission of unstructured bit stream over physical medium. deals with the mechanical, electrical, functional, and procedural characteristics to access the physical medium. |
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Definition
adjusts to changes in delay and throughput and still meet the needs of its applications
example: email, file downloads |
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Definition
does not adapt easily, if at all, to changes in delay and throughput across the net.
example: voice or video applications |
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