7. Data Communication Tasks Routing Delivery Error Feedback Network MGT Flow Control Signal Distortion Bit Error Network MGT Error Detection & Correction Nature and Timing of Signal Security Exchange Management Signal Begins & Ends Messsage Formatting Synchronization Repeater/Amplifier; Propagation; Interoperable Recovery Signal Generation Router / Server / Media Control / Protocol Routing Interfacing Multiplexing Capacity Congestion Control Addressing Data System Utilization
27. Categories of Twisted Pairs Cabling System Specs describe cable Material, type of Connectors, and Junction blocks to Conform to a category 100 Mbps 20 Mbps 16 Mbps 4 Mbps Less than 1 Mbps Maximum data rate Usual application Category 100 Mbps TPDDI 155 Mbps asynchronous transfer mode (certify 100 Mhz signal) CAT 5 Used in 16Mbps Token Ring Otherwise not used much CAT 4 Voice and data on 10BASE-T Ethernet (certify 16Mhz signal) CAT 3 Mainly used in the IBM Cabling System for token ring networks CAT 2 analog voice (plain old telephone service) Integrated Services Digital Network Basic Rate Interface in ISDN Doorbell wiring CAT 1
60. ISO/OSI Reference Model (2) How to transmit signal; coding Hardware means of sending and receiving data on a carrier Two party communication: Ethernet Routing and Forwarding Address: IP End-to-end control & error checking (ensure complete data transfer): TCP Establish/manage connection ASCII Text, Sound (syntax layer) File Transfer, Email, Remote Login
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65. Associated TCP/IP Protocols & Services SLIP (Serial Line Internet Protocol) and PPP (Point to Point Protocol) encapsulate the IP packets so that they can be sent over a dial up phone connection to an access provider’s modem. SLIP/ PPP Provides meaningful names like achilles.mycorp.com for computers to replace numerical addresses like 123.45.67.89. Stands for the Domain Name System. DNS Used to remotely manage network devices. Stands for the Simple Network Management Protocol. SNMP A remote terminal emulation protocol that enables clients to log on to remote hosts on the network. Telnet This protocol, the core of the World Wide Web, facilitates retrieval and transfer of hypertext (mixed media) documents. Stands for the HyperText Transfer protocol HTTP
Notes de l'éditeur
This is intended to be a very general overview of the concepts in computer networking and communication.
Potential topics: TCP/IP and the Internet TCP and UDP Gateway and Routing Protocols Telnet and FTP TCP/IP Configuration TCP/IP and Networks Domain Name Service Network File System
Transmitter: modem Transmission system: public telephone network Receiver: modem Destination: server
Transmitter: modem Transmission system: public telephone network Receiver: modem Destination: server
Network - A group of computers connected together in a way that allows information to be exchanged between the computers. Node - Anything that is connected to the network. While a node is typically a computer, it can also be something like a printer or CD-ROM tower. Segment - Any portion of a network that is separated, by a switch, bridge or router, from other parts of the network. Backbone - The main cabling of a network that all of the segments connect to. Typically, the backbone is capable of carrying more information than the individual segments. For example, each segment may have a transfer rate of 10 Mbps (megabits per second: 1 million bits a second), while the backbone may operate at 100 Mbps. Topology - The way that each node is physically connected to the network.
Backbone example: E.g. each segment may have a transfer rate of 10Mbps (megabits per second or 1 million bits a second) while the backbone may operate at 100Mbps
Similar to a bus network, rings have nodes daisy chained, but the end of the network in a ring topology comes back around to the first node, creating a complete circuit. Each node takes a turn sending and receiving information through the use of a token. The token along with any data is sent from the first node to the second node which extracts the data addressed to it and adds any data it wishes to send. Then second node passes the token and data to the third node, etc. until ti comes back around to the first node again. Only the node with the token is allowed to send data . All other nodes must wait for the token to come to them.
A hub does not perform any type of filtering or routing of the data. A hub is a junction that joins all the different nodes together.
A hub does not perform any type of filtering or routing of the data. A hub is a junction that joins all the different nodes together.
Baud – don’t use; a single state change can involve more than a single bit of data
we will talk about network cables next
CAT 5 is currently under consideration to be incorporated into the Gigabit Ethernet specification for short distance wiring. While longer connections using Gigabit Ethernet use optical fiber, the goal is to leverage the CAT 5 twisted-pair wiring most organizations already have in place for connections out to the desktop.
Use of optical fibers over ; Optical fiber (or "fiber optic") refers to the medium and the technology associated with the transmission of information as light pulses along a glass or plastic wire or fiber. Optical fiber carries much more information than conventional copper wire and is in general not subject to electromagnetic interference and the need to retransmit signals. Most telephone company long-distance lines are now of optical fiber. Transmission on optical fiber wire requires repeater at distance intervals. The glass fiber requires more protection within an outer cable than copper. For these reasons and because the installation of any new wiring is labor-intensive, few communities yet have optical fiber wires or cables from the phone company's branch office to local customers (known as local loop). single mode fiber fiber is used for longer distances; multimode fiber fiber is used for shorter distances.
Multimode has a larger core than single mode optical fiber
Starband.com DirectDuo DirectPC
In wireless LAN (WLAN) technology, 802.11 refers to a family of specifications developed by a working group of the Institute of Electrical and Electronics Engineers ( IEEE ). There are three specifications in the family: 802.11, 802.11a, and 802.11b. All three of the above mentioned specifications use CSMA/CD carrier sense multiple access with collision detection ( CSMA/CD )as the path sharing protocol. If a source station has a data packet to send, the station checks the system to see if the path medium is busy. If the medium is not busy, the packet is sent; if the medium is busy, the station waits until the first moment that the medium becomes clear. Testing is done repeatedly by the source via a short test message called RTS (ready to send). The data packet is not transmitted until the destination station returns a confirmation message called CTS (clear to send). If two stations send at exactly the same time, CSMA/CD prevents the loss of data that might otherwise occur and provides a system for retrying. The 802.11 and 802.11b specifications apply to wireless Ethernet LANs, and operate at frequencies in the 2.4-GHz region of the radio spectrum. Data speeds are generally 1 Mbps or 2 Mbps for 802.11, and 5.5 Mbps or 11 Mbps for 802.11b, although speeds up to about 20 Mbps are realizable with 802.11b. The 802.11b standard is backward compatible with 802.11. The modulation used in 802.11 has historically been phase-shift keying ( PSK ). The modulation method selected for 802.11b is known as CCK (complementary code keying), which allows higher data speeds and is less susceptible to multipath-propagation interference. The 802.11a specification applies to wireless ATM systems and operates at radio frequencies between 5 GHz and 6 GHz. A modulation scheme known as OFDM (orthogonal frequency-division multiplexing) makes possible data speeds as high as 54 Mbps, but most commonly, communications takes place at 6 Mbps, 12 Mbps, or 24 Mbps.
Nowadays you see hubs with switches; but basically the hub is the place where data comes together while the switch determines how and where data is forwarded from the place where data comes together.
bridge In telecommunication networks, a bridge is a product that connects a local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or token ring). You can envision a bridge as being a device that decides whether a message from you to someone else is going to the local area network in your building or to someone on the local area network in the building across the street. A bridge examines each message on a LAN, "passing" those known to be within the same LAN, and forwarding those known to be on the other interconnected LAN (or LANs). In bridging networks, computer or node addresses have no specific relationship to location. For this reason, messages are sent out to every address on the network and accepted only by the intended destination node. Bridges learn which addresses are on which network and develop a learning table so that subsequent messages can be forwarded to the right network. Bridging networks are generally always interconnected local area networks since broadcasting every message to all possible destinations would flood a larger network with unnecessary traffic. For this reason, router networks such as the Internet use a scheme that assigns addresses to nodes so that a message or packet can be forwarded only in one general direction rather than forwarded in all directions. A bridge works at the data-link (physical network) level of a network, copying a data frame from one network to the next network along the communications path. A bridge is sometimes combined with a router in a product called a brouter.
The range for WAN transmission will vary: 56 Kb/s to 1.544 Mb/s
Communication path established between two
What is the third generation speed for ISDN?
http://www.informit.com/newsletter.asp?link=320 The 802.3 standards put down in writing what happens at the very basest level of network communication: that which actually travels through the wires and hardware.
Structure of protocols architecture: file transfer module contains all logic for file transfer applications (transmitting passwords, file commands, and file records). Need is to transmit the files and commands reliably. Some sorts of reliability are relevant to a variety of applications (e.g. e-mail, document transfer) Met by separate communication service modules that can be used by a variety of applications. Communication service modules assumes two computer systems are active and ready for data transfer, and keeps track of data being exchanged to assure delivery. A structured set of modules are used that implements the communication functions.
It is use to guide product implementors so that their products will consistently work with other products.
OSI divides telecommunication into seven layers. The layers are in two groups. The upper four layers are used whenever a message passes from or to a user. The lowest three layers (Up to network layer) are used when any message passes through the host computer. Message intended for this computer pass to the upper layers. Message destined for some other host are not passed up to the upper layers but are forwarded to another host. Physical layer: Bit stream through network at electrical/mechanical level
There are several higher layer application protocols that use TCP/IP to get to the internet. They include World Wide Web’s Hypertext Transfer Protocol; File Transfer Protocol (FTP); Telnet (Telnet) [ allow you to logion to remote computers], Simple Mail Transfer Protocol (SMTP) These and other protocols are often packaged together as a suite. TCP keep track of the individual packets that a message is divided into for efficient routing through the internet
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