Ch. 5: Ethernet Switched LANs
What type of copper wiring is used in Ethernet?
4-pair unshielded twisted pair.
What is the core diameter of single mode fiber?
8 or 9 microns
What is the name of its committee for developing LAN standards?
802 committee
Which working group will likely develop security standards to be used by multiple LAN/WAN technology
802.1X and 802.1AE
Which 802 working group creates Ethernet standards?
802.3 working group
What wavelength dominates LANs?
850 nanometers
What three wavelengths are used in optical fiber transmission?
850, 1310, 1550 nanometers
Distinguish between two types of Ethernet transmission link technologies in terms of what they typically connect.
Access links - link that connects hosts to work group switches Trunk links - connects switches to other switches.
What benefit does strong security bring for manageability?
Allows for the firm to use SNMP Set commands to remotely configure switches.
Why does an optical fiber cord have two strands?
Allows the optical fiber to conduct full duplex transmission.
Why has ethernet become the dominant LAN technology?
Because switches and switch forwarding is cheap, efficient and reliable due to hierarchical topography.
100BASE-TX
Category: 5e, 6, 6A Max cord Distance: 100 meters Transmission speed: 100 Mbps
1000BASE-T
Category: 5e, 6, 6A Max cord Distance: 100 meters Transmission speed: 1Gbps
What 802.1X standard does the actual supplicant credentials checking
Central authentication server
What is a state
Conditions in either binary or digital signaling.
What do physical layer standards govern?
Connectors, transmission media, and signaling
Distinguish between two types of Ethernet switches in terms of what they connect.
Core switches - connect other switches to switches. Workgroup switches - connects that connect hosts to the network.
What is the purpose of LLC sub header?
Describes the type of a packet contained in the data field.
What are the steps in converting EUI-48 addresses into hex notation?
Divide 48 bits into 4-bit nibbles. Convert the nibbles into a hexadecimal symbol Put into 6pairs separated by a dash *BA-CC-66-0D-5E-BA
State two installation disciplines that will reduce UTP transmission problems to negligibility?
Do not untwist wires more than 1.25 cm Not going over maximum wire transmission length
What are they called today?
EUI 48 addresses
How many wires are in a UTP cord? How many pairs?
Eight wires, four pairs
What is the purpose of there Frame Check Sequence Field?
Error detection. A field that calculates a 32-bit result and the receiver tries to reassemble this result. If the two are different there is an error in the frame.
How are switches in an Ethernet LAN organized? How many possible paths can there be betWeen two hosts?
Ethernet MAC layer standards require that switches be organized into a hierarchical topography. Otherwise there ow upheld be endless switch loops. There will only be one path between any two hosts.
Why was ethernet created?
For local area network connectivity.
What standards association creates most LAN standards
IEEE standards association
What is the traditional way to solve the problem of single points of failure?
Installing a backup link
Does the signal travel through the optical fiber core, cladding, or both?
It travels through the core, a thin glass string. The cladding is the thin glass cylinder
What are the two components of the Ethernet data field?
LLC sub header Packet
What is the advantage of optical fiber over UDP.
Length.
LANs
Local area networks. Networks that operate on customer premises
Distinguish between the LLC layer and the MAC layer?
Logical Link Control layer - has functionality that all802 standards use to connection the internet and only one standard, 802.2 Media Access Control layer - has functionality specific to each working groups core operation.
What were Ethernet addresses originally called?
MAC addresses.
What is the benefit to having a single possible path?
Makes Ethernet forwarding simple and also inexpensive for implementation.
10GBASE-T, category 6A
Max cord Distance: 100 meters Transmission speed:10Gbps
10GBASE-T, category 6
Max cord Distance: 55 meters Transmission speed: 10Gbps
Which data link layer do networking professionals work with?
Media access layer
What is digital signaling?
More than one bit is sent in a clock cycle because there are more than two states
Is there a maximum length for link aggregation on a network?
No, there is no maximum end-to-end distance between pairs of hosts in an Ethernet network.
How any standards does Ethernet have at the MAC layer?
One.
What is the advantage of single mode fiber over multimode fiber?
Only the mode that travel directly through can propagate through it thus there is no modal dispersion. Quite a bit more expensive
What is the core diameter of multimode fiber?
Optical fiber that permits multiple modes to travel through it.
At what layers do single networks require standards?
Physical and data link layer
What is POE?
Power over ethernet.
What maximum standard power does POE plus standard specify?
Provides up to 25 watts of power over the UTP access link. Sufficient for VoIP phones surveillance cameras and access points.
What standard allows for backup links for redundancy in Ethernet networks?
RSTP - rapid spanning tree protocol.
RSTP
Rapid Spanning Tree Protocol - in order to increase reliability bad links are connected to Ethernet switches in case of failure. In order to avoid loops created by multiple switches with the same path, RSTP detects and breaks loops.
What are modes?
Rays of light that are at the correct angle to enter the core of optical fiber.
What type of connectors and jacks does 4-pair UTP use? What are they also called?
Rj-45 connectors which plug into RJ-45 jacks. Ethernet
What communication protocol is used between manageable switches?
SNMP - simple network manageable protocol which allows the manager to contact the individual managed switches to trouble shot problems. Saves lots of labor costs
What is terminal cross talk interference?
Signal interference, usually from un twisting the UTP pair wires too far during connectorization, that degrades the signal and it becomes unreadable.
Port-Based Access Control /802.1x
Standard that gives users access to a network by requiring them to prove their identity before switch will allow any further traffic. Switch is the authenticator, peer is the supplicant.
In 802.1X, what device is the authenticatior?
Switch
What are the the four benefits to having a central authentication server instead of an individual authenticators?
Switch cost, consistency, reduced management cost, rapid changes
Do switches know the entire data link between the source host and the destination host?
Switches do no know the entire path of a frame
Why are routers expensive for the traffic volume they handle?
The additional work a router has to do to identify and forward frames to the appropriate location because there are many paths it could potentially take.
Wavelength
The distance between successive wave heights, troughs, starts, stops and so forth.
Why can signals travel very far through optical fiber?
The light never enters the cladding but rather bounces immediately back into the core and therefore is never lost. There is very low attenuation as signal travels.
What happens if the receiver detects and error in the frame?
The receiver simply discards the frame
What must a sender do to send bits of a frame over a transmission medium?
The sender must've convert the message bits of 1's and 0's into physical signals
What is modal dispersion?
The two rays of light (modes) traveling through the fiber arrive at the destination point at different times. One mode travel directly through the fiber, the other bounces at angles off the cladding exiting and entering the fiber.
What is a single point of failure .
There is a single path between switched hosts in a switched hierarchy, this causes a single point of failure in connection if the parent or chid host fails.
Why do core switches need ore processing power than workgroup switches?
They carry the frames of a many conversations over the network.
What threat does 802.1X address? And how?
Thwarts ability for hackers to simply plug into a network by requiring user to prove identity to the authenticator switch.
Why's binary transmission error resistant?
Transmission is fairly error resistant to transmission impairments caused by signal attenuation. A signal can attenuate by 50% and the receiver can still correctly record the signal . The more states that exist, the smaller propagation effect may cause an 11 to be misrepresented as a 10
What is optical fiber?
Transmission medium that sends data using light.
What is parallel transmission?
Transmitting voltage signals over more than one pair of wires. This enables faster transmission speeds.
What serial transmission?
Transmitting voltage signals over single pair of wire
What is binary signaling?
Two state transmission processing which 1's and 0's are represented by light or voltage level.
How many priorities can ethernet switches implement?
Up to 8: 000 - 111
What is link aggregation?
Using two UTP or optical fibers to connect two switches to extend the range of a network. Also called "bonding".
Of what wire characteristic is category a measure of?
Wire quality.
Can ethernet switches implement priority?
Yes.
What is the ability to transmit in both directions simultaneously called?
full duplex transmission
What information does a switch know?
they know only the information provided in the switching table. (What port to send the frame too)