Ethernet Overview

Question 1

What is Carrier Sense?

Answer 1

Listens to the segment to see if there are other transmissions. If free, sends the frame. If busy, waits for network to be free.

Question 2

What is multiple access?

Answer 2

Many devices can connect to the network. Therefore, CSMA/CD is a contention access method due to competition from the devices to transmit.

Question 3

What is collision detection?

Answer 3

If two or more stations transmit at the same time, data collides and is destroyed. Jam signals indicate a data collision. When a station detects jam signals, it stops transmitting and retransmits after random time.

Question 4

What device generates a jam signal? How is a jam signal different from other signals?

Answer 4

Data terminal equipment (DTE) that did the transmission emits data jam signal. It is any pattern other than one concluding with a CRC (cyclic redundancy check) as would normally be included.

Question 5

When is a data collision error declared to upper layers?

Answer 5

17th retry, after a wait time has been exponentially increased at the 16th try.

Question 6

What is muxing?

Answer 6

Multiplexing. Multiple data strand combined into one signal over shared medium.

Question 7

How much of a baseband LAN cable’s capacity is used to transmit a single digital signal?

Answer 7

100%

Question 8

What are 4 common types of baseband cables?

Answer 8

• Thicknet
• Thinnet
• UTP
• Fiber optic

Question 9

What is the difference between Thicknet and Thinnet?

Answer 9

Thicknet: 0.4 inch diameter
Thinnet: 0.2 inch diameter; cheaper

Question 10

How many conductors are in UTP and what are they made of? How are they twisted?

Answer 10

8 x 24 gauge copper wires, organized into 4 pairs.

Each pair is twisted at a constant rate, but each pair has different twist lengths.

Question 11

How pure is the glass in fiber optics?

Answer 11

Very pure.

Question 12

Fill in the blanks.

Fast Ethernet is ___ times faster than Ethernet. It is ___________ with regular (___mb/s) Ethernet.

Fast Ethernet is based on the ___ Base-TX/T4/FX standards.

Answer 12

10, backwards-compatible, 10

100

Question 13

How fast does Gigabit Ethernet transmit? The standards for gigabit Ethernet transmission media are: ____ Base-T/LX/SX/CX/XD/LH

Answer 13

1000 Mb/s (1 Gb/s)

Question 14

What is a MIB?

Answer 14

Management Information Base

Question 15

List sine functions that are compatible between all Ethernet types. What does this achieve?

Answer 15

Standard Ethernet frame
MIBs
remote monitoring specification (RMON)
CSMA/CD
common network management tools

User applications can remain the same; speed is increased and NICs and cabling can be improved.

Question 16

10 Gigabit cabling standards are: ___ Base-CX4/SR/LX4/LR/ER/SW/LW/EW.

Answer 16

10G

Question 17

What are 3 significant advances in Ethernet?

Answer 17

Full duplex
Auto-negotiation
10Gbe WAN PHY

Question 18

What is full duplex vs half-duplex?

Answer 18

Half duplex used one wired pair to send/receive, and wired pair to use CSMA/CD. You could either transmit or receive.

Full duplex does not use CSMA/CD, so two stations can simultaneously transmit data, doubling capacity.

Question 19

What is auto negotiation?

Answer 19

Enables devices to negotiate speed and mode (half or full duplex) of an Ethernet link.

Question 20

What is FLP?

Answer 20

Fast Link Pulses, used on fast Ethernet devices between adjacent link stations to negotiate highest service level for that link (part of auto negotiation)

Question 21

What is 10GbE WAN PHY?

Answer 21

10 gigabit Ethernet WAN physical layer bridges Ethernet and SONET/SDH infrastructures

Question 22

Decipher the following:

64o or 1518o

PRE | DA | SA | TYPE | DATA | FCS

Answer 22

64 octets or 1518 octets = bytes = 8 bits

Preamble: for synchronization
Destination Address
Source Address
Ethernet type: protocol type in an Ethernet LAN packet
Data: upper later data (excluding voice)
Frame Check Sequence: math formula to check for transmission errors

Question 23

Is DIX Ethernet frames or IEEE 802.3 Frames?

Answer 23

Ethernet. Digital-Intel-Xerox.

Question 24

Decipher the following:

PRE | SFD | DA | SA | LEN | LLC | DATA | PAD | FCS

What kind of frame?

Answer 24

IEEE 802.3

Preamble (for synchronization)
Start Frame Delimiter: tells that all subsequent info is actual frame
Destination Address
Source Address
Length of LLC field
Logical Link Control: includes end system addressing and error-checking; common standards of data exchange and assembly
Data excluding voice
Padding to meet min size if needed
Frame check sequence: formula to determine transmission errors

Question 25

What are the 3 functional components of CSMA/CD?

Answer 25

Carrier Sense Multiple Access with Collision Detection:

1. Carrier sense
2. Multiple access
3. Collision detection