Chapter 5 - Ethernet LANs
20a. What information do the two tag fields give?
Answer: First tag field - indicates that the frame is tagged Second tag field - gives the tagged information
3b. What kind of switches connect switches to other switches
Answer: Core Switches
9d. What are the three wavelength windows used in fiber transmission?
Answer: 1. 850 nm 2. 1,310 nm 3. 1,550 nm
5a. Distinguish between binary and digital signaling
Answer: Binary Signaling only has 2 states ( 1 or 0 ) Digital Signaling can have a few alternative states ( 2 to the power of b )
14a. Compare relative cost and distance for multimode and single mode fiber.
Answer: Multimode ( multiple light rays ): shorter distance ; lower cost Single mode ( single light ray ): longer distance ; higher cost
4. What four things do physical layer standards govern
Answer: (1) Connectors (2) Plugs (3) Transmission Media (4) Signaling
5f. Every time you double the number of states how many more bits can you transmit?
Answer: 1 more bit
5c. If you wish to transmit five bits per clock cycle, how many states must the system have?
Answer: 32 2 to the power of 5 which is 2x2x2x2x2 = 32
5d. If you know that a system has 16 states how many bits can it send per clock cycle
Answer: 4 ( 2 to the power of 4 = 16 )
5b. If you wish to transmit 3 bits per clock cycle, how many states must the system have?
Answer: 8 It is 2 to the 3rd power or 2x2x2 = 8
5e. The 802.11 AC Wi-Fi standard uses 256 states. How many bits can it send per clock cycle
Answer: 8 bits ( 2 to the power of 8 = 256 )
6a. How many wires are there in ethernet cable?
Answer: 8 wires
14c. For LAN fiber, what is the dominant signaling wavelength?
Answer: 850 nm
3c. What kind of links connect users to workgroup switches
Answer: Access Links
26b. Where does it tell the victim to send such frames after the attack?
Answer: After the attack it end the frames to the Attacker
25. What type of attack does 802.1AE protect against?
Answer: Attacks on Switches
2f. Why are Ethernet standards formally called 802.3 standards?
Answer: Because They are created by the IEEE 802.3 Working Group
5g. Why is the signal held constant over each clock cycle?
Answer: Because it easier for the "Receiver" to read the signal
9a. How does fiber usually transmit a 1?
Answer: By turning the light signal on Note: when the light signal is turned off it represents a zero
9b. How do fiber chords typically provide full duplex transmission?
Answer: By using 1 fiber strand to transmit in one direction and the other fiber strand to transmit in the other direction ( two way transmission ).
2d. Is the path an Ethernet message takes from the source to destination a physical link, data link or a route?
Answer: Data Link The path that a frame travels through an Ethernet network is a Data Link.
2e. Does Ethernet use EUI-48 addresses or IP addresses?
Answer: EUI-48 addresses Ethernet does not use IP - Internet Protocol
2b. Are Ethernet Messages Packets or Frames?
Answer: Frames A frame is the chunk of data sent over the Ethernet data link.
19a. Are ethernet EUI-48 addresses expressed in hex for humans, devices or both?
Answer: Hex is used for humans ; computers work in binary
6e. What is the benefit of parallel transmission?
Answer: Higher Transmission Speed
17a. How are switches in an ethernet LAN organized?
Answer: In a Hierarchical Topology (topology is the physical organization of switches and transmission links).
6d. How does Ethernet use parallel transmission?
Answer: It transmits on all 4 pairs simultaneously
23a. What is the security benefit of Ethernet VLANs? ( Virtual LANs )
Answer: Keeps network resources separate so that not everybody can see everything Example: marketing department will only see marketing resources not the sales department resources
18a. What is the benefit of having a single possible path through an ethernet network?
Answer: Keeps things simple.
2a. At what layers are Ethernet standards defined?
Answer: Layers 1 and 2 Layer 1 - wires and signals Layer 2 - frames and switches
1. What is a Local Area Network ( LAN)?
Answer: Local area networks are networks that operate on a customers premise. This means all machines on the network are on the premise
18b. Why has Ethernet become the dominant LAN technology?
Answer: Low cost, combined with adequate performance,
14b. Why does multimode fiber dominate LAN installations?
Answer: Lower cost
14d. Why does this wavelength dominate?
Answer: Lowest Cost
10c. What limits transmission distance in a multimode fiber?
Answer: Modal Dispersion ( Light dispersion )
9c. In what units are light wavelengths measured?
Answer: Nanometers (nm)
21c. Are all Ethernet switches manageable?
Answer: No
16a. Do switches know the entire data link between the source and the destination host?
Answer: No.
20b. When is a PAD field added?
Answer: PAD fields are added if the data field is shorter than the expected size
6c. What are the two names for connectors and jacks?
Answer: RJ-45 connectors and RJ-45 jacks
24a. What security threat is 802.1X designed to protect against?
Answer: Security Threats Inside the Company
6f. What propagation problem limits transmission distance in 4-pair UTP?
Answer: Signal dissipation ( In other words the signal gets weaker over distance )
21a. What protocol do companies use to manage their ethernet networks?
Answer: Simple Network Management Protocol (SNMP)
2c. Are Ethernet forwarding devices Switches or Routers?
Answer: Switches A switch connects computers within a single network.
16b. What does a switch know?
Answer: Switches only know what port to use to send their frame back out.
26c. What harm can the attacker do?
Answer: The Attacker can read the messages and pass them on
9e. What is amplitude?
Answer: The Power of a Lightwave
6b. How is each pair organized?
Answer: They are twisted around each other
22a. What reliability problem does Ethernet have?
Answer: They have a single point of failure
24b. When 802.1X is being used, what happens if an attacker plugs his or her host inside a switch?
Answer: They have to "authenticate" ( provide and ID and password )
8. For what purpose were the 2.5G BASE-T and 5G BASE-T standards developed?
Answer: To support faster Wi-Fi access points
26a. Before the attack, where does the ARP cache tell the victim to send a frame carrying a packet to the router?
Answer: To the Router
3d. What kind of links connect switches to other switches
Answer: Trunk Links
3a. What kind of switches connect users to the network
Answer: Workgroup Switches
10a. What is a mode?
Answer: a light ray
28. What is a router?
Answer: a networking device that forwards data packets between two or more networks Note: Switches pass data inside a single network
21b. What are manageable switches?
Answer: a switch that has an SNMP agent.
10b. What is multimode fiber?
Answer: fiber that is designed to carry multiple light rays or modes concurrently
22b. How can some redundant backup links be installed without creating loops?
Answer: using the RSTP ( Rapid Spanning Tree Protocol )
13. Explain the general principle of network design and way you should follow it.
The key general principle of network design is, "Choose the least expensive option that will achieve the required speed."
