Ethernet concepts exam

What OSI physical layer term describes physical medium for microwave transmissions (transfer)?

Air

Bus

All end systems are chained to each other and terminated (close) in some form on each end. Infrastructure devices such as switches are not required to interconnect end devices e.g., Legacy Ethernet network

Which statement is true about CSMA/CD (carrier sense multiple access/collision avoidance) access method that is used in Ethernet?

All network devices must listen before transmitting

What is contained in trailer of frame?

FCS field (error detection)

Physical topology

Identifies physical connections and how end devices and intermediary devices (i.e, routers, switches, and wireless access points) are interconnected (all connected) Include specific (clearly identified) device location such as room number and location on equipment rack Usually point-to-point or star

Fiber optic

Long haul (distance) networks 10 Mb/s - 100 Gb/s High skills required, immunity to electrical hazards and safety

Two functions performed at LLC (Logical Link Control) sublayer of OSI data link layer?

Puts information in frame that identifies which network layer protocol is being used for frame Enables IPv4 and IPv6 to unitize (use) same network interface and media

What three items are contained in Ethernet header and trailer?

Source MAC address Destination MAC address Error check sequence

Which frame forwarding method receives entire frame and perform CRC check to detect errors before forwarding frame?

Store and forward switching

What action will occur if switch receives frame and has source MAC address in MAC table?

Switch refreshes timer on that entry.

What is the function of CRC (cyclic redundancy check) value that is found in FCS (frame check sequence) field of frame?

To verify integrity (consistency) of received frame

What are two jobs that frame might be dropped?

Too small (runt<64 bytes) Too large (jumbo >1518 bytes) FCS revealed errors

Physical data's role in transmitting data on the network?

Translate data into signals representing bits

Upside and downsize of fiber optic cable

Unaffected by EMI by RFI Faster Longer distances More expensive than copper cables Difficult to install

What are two actions performed by Cisco switch?

Using source MAC addresses of frames to build and maintain MAC address table Utilizing (use) MAC address table to forward frames via destination MAC address

Which statement describes characteristic of frame header fields of data link layer?

Vary (differ) depending (rely) on protocols

In addition to cable length, what three factors could interfere with communication carried over UTP cables?

electromagnetic interference Crosstalk Legal modulation technique

Which switching method has lowest level of latency (delay)?

fast-forward

Which media communication type does not require media arbitration (talks) in data link layer?

full-duplex

What makes fiber preferable (appropriate) to copper cabling for interconnecting buildings?

greater distances per cable run and bandwidth potential limited susceptibility (openess) to EMI/RFI (electromagnetic disturbance/Remote file inclusion

Copper cables

horizontal (straight) cabling structure desktop PCs in enterprise office Most common type of cabling Inexpensive, easy to install, and has low resistance to electrical current, distance, safety, immunity to electrical hazards and EMI and RFI and skills required 10Mb/s - 10Gb/s

Which two fields or features does Ethernet examine to determine if received frame is passed to data link layer or discarded by NIC?

minimum frame size Frame check sequence

A network team is comparing physical WAN topologies for connecting remote sites to a headquarters building. Which topology provides high availability and connects some, but not all, remote sites?

partial (limit) mesh

What is the purpose of FCS field in frame?

to determine if errors occurred in transmission and reception

Two functions performed at MAC sublayer of OSI data link layer?

Allow multiple devices to communicate over shared medium Responsible for sending and receiving data on physical medium

Three factors that influence throughput

Amount of traffic currently crossing network Type of traffic crossing network Latency created by number of network devices that data crosses

Auto-MDIX

Automatic configuration of interface for straight-through or crossover Ethernet cable connection

Full duplex

Both devices can simultaneously (at same time) transmit and receive on shared media. Data link layer assumes that media is available for transmission for both nodes at any time Ethernet switches operate by default Allows sending and receiving of data to happen simultaneously.

Which two devices commonly affect wireless networks?

Cordless phones microphone

Which two statements describe features (parts) or functions (purpose) of logical link control sublayer in Ethernet standards?

Data link layer uses LLC to communicate with upper layers of protocol suite. Logical link control is implemented (added) in software.

What are two jobs done by data link layer?

Encapsulates (close) layer 3 packets into layer 2 frames Translate (move) frames onto network media

Which statement describes extended star topology?

End devices connect to central intermediate (scattered) device, which in turn connects to other central (center) intermediate devices.

Ring

End systems are connected to their respective neighbor. Does not need to be terminated, unlike in bus topology e.g., Legacy Fiber Distributed Data Interface (FDDI) and Token Ring networks

A network administrator is connecting two modern switches using straight-through cable. Switches are new and have never been configured. Which three statements are correct about the final result of connection?

Link between switches will work as full-duplex. Auto-MDIX feature will configure interfaces eliminating need for crossover cable. Link between switches will work at fastest speed that is supported by both switches.

Which two statements describe services provided by data link layer?

Manages access of frames to network media. Packages various Layer 3 PDUs into frame format that is compatible (well-matched) with network interface.

Goodput

Measure of usable data transferred over given period of time Throughput minus traffic overhead for establishing sessions, acknowledgments, encapsulation, and retransmitted bits Lower than throughput, which is generally lower than bandwidth

What are three ways that media access control is used in networking?

Media access control provides placement of data frames onto media. Data link layer protocols define rules for access to different media. Ethernet utilizes CSMA/CD.

UTP (Unshielded Twisted Pair)

Most common networking media Terminated with RJ-45 connectors Consists of four pairs of color-coded copper wires that have been twisted together and then encased flexible plastic sheath that protects from minor physical damage in LANs Twisting of wires help protect against signal interference from other wires Outer jacket protects copper wires from physical damage Twisted-pairs protect signal from interference Color-coded plastic insulation electrically isolates wires from each other and identifies each pair

STP (shielded twisted pair)

Provides better noise protection Significantly more expensive and difficult to install Uses RJ-45 connector Combines techniques of shielding to counter EMI and RFI, and wire twisting to counter crosstalk Terminated with special shielded STP data connectors to gain full benefit of shielding Uses four pairs of wires, each wrapped in foil shield, which are then wrapped in overall metallic braid or foil Outer jacket Braided or foil shield Twisted pairs

Which two functions are performed at MAC (message authentication code) sublayer of OSI data link layer?

Provides synchronization (two objects operating at same time) between source and target nodes. Integrates (form) various physical technologies.