Chapter 5 Wired Ethernet Lans.docx

9 Pages

Information Studies
Course Code
IST 233
David Molta

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Chapter 5 Wired Ethernet Lans - Ethernet is the way that wired LANs work today, wires not radio - LANs customer premises - -WANs operate outside of customer premises, connect different sites within an organization or transmit data between organizations - -must use transmission carrier-governmental rights of ways to lay wires in public locations or wireless radio signals –LANs bring 100mbps to 1gbps of unshared capacity to each desktop, wans speeds range from 1 mb to 50 mb, shared by multiple users - WANs transmission is expensive, - Standard for wired LANs is Ethernet - Switches that connect hosts to the network are called workgroup switches - Switches that connect switches to other switches are core switches - To connect all of these there is a transmission link, UTP copper wire and optical fiber, one carries electrical signals the other carries light signals through very thin glass tubes - Transmission links that connect hosts to workgroup switches are called access links transmission links that connect switches to ther switches are trunk links Switches Hosts to networks- workgroup switches- access links __ switches to switches- core switches- trunk links are the transmission lines - Fiber is more expensive then UTP - Switches in the network core must carry the frames of many conversations they they must have high processing speeds wich is more $$ - -workgroup only carry the conversation from hosts they serve directly, low costs - MAN metor polittan area network type of WAN limited to a large city and its surrounding communities, shorter distances, lower prices per bit transmittd, man peeds are highter but less then LAN speeds - 802 committee is done in working groups, creates Ethernet standards, Ethernet and 802.3 interchangable - Task groups- create standards then moves on to the working grpu which decicdes the work - After the working group ratifies a new standard it passes through the 802 committee and the IEEE standards association then American national standards institute then ISO - Physical Layer and Data Link Layer- Ethernet networks are single switches networks. - Hardware- network interface card NIC –circuitry - Physical layer- govern connectors and transmission media and signaling. - Bits and signals- signals will (propagate) travel down the transmission link to the device at the other end of the physical links 1s and 0s - binary signaling has two conditions, 0 high voltage,1 low voltage - digital signaling there are few possible states 2,4,8 - digital is more $$$ - Binary is a type of digital, not all digital is binary - Error resistance: digital transmission is accurate and resistance to impairments - Clock cycles- when a device transmits it holds the signal constant for a brief period of time - UTP – 4 pair unshielded twisted pair wiring - Rj45 connectior - 4 pairs of wires permits faster transmission speed - Serial transmission- Transmitting over single pair of wires - Parallel transmission- more then one pair carrying transmission bits - UTP propagation effects - As signals go through a UTP cord it attenuates or gets weaker, if it attenuates too much it won’t be readable at the destination end - Signal to noise ratio is high - Interference- utp wires are long antennas if there are air conditioners or nearby devices that generate electromagnetic energy, they will pick it up and signal can be lost - Twisting the wires give them more resistance - Crosstalk interference- where the wires are untwisted for termination in an rj45jack - Cable quality is determined by its category number - Limiting factor is lan fiber distance is modal dispersion light from sequential light pluses will overlap making the signal too unreadable - Higher quality lan fiber has higher modal bandwidth-measure of how well fiber deals with modal dispersion MHz-km, signaling seed of 1 gbps - Quality in UTP is expressed as a category number, quality in LAN fiber is expressed as modal bandwidth - Core diameter also affects cored maximum propagation distance- smaller diameter allows signals to travel farther. Larger allows modes to enter at higher angles - Wavelength and amplitude- page 191 - Multimode fiber- light modes can enter at various angles - Single mode fiber- - Absorptive attenuation- 192 - Bonding or link aggregation- using two or more trunk lines to connect single pairs of switches - Inexpensive compared to purchasing new faster switches - Ethernet Physical Layer Standards and Network Designs- the 100 meter Ethernet limit for utp and the longer distance limits for fibers apply to physical links between pairs of devices not end to end data links between hosts across multiple networks - The Ethernet frame and data link layer - Ethernet media access control frame- Ethernet frame - Preamble field and start of the frame diameter field synchronize the receivers clock to the senders clock - There is no minimum length for the data field, but if ther data field is less then 46 octets long, then a PAD field must be adde d to bring the total length of the data and pad field to 46 octets - Frame Check Sequence Field- permits error detection - - Question 1 0.6 out of 0.6 points What type of switch connects users to the network? Answer Selected Answer: None of the  above Correct Answer:    None of the above - Question 2 0.6 out of 0.6 points Ethernet receivers detect errors by using the value in the ________ field. Answer Selected Answer: Correct Answer:    frame check sequence - Question 3 0.6 out of 0.6 points When the light energies of two pulses arrive at overlapping times, this is ________. Answer Selected Answer:    modal  dispersion Correct Answer:    modal dispersion - Question 4 0.6 out of 0.6 points The minimum length of an Ethernet data field is ________. Answer Selected Answer: Correct Answer:    There is no minimum length for the Ethernet data field. - Question 5 0 out of 0.6 points In the UTP wiring used in LANs, how 
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