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FIT9137 Introduction to computer architecture and networks - S1 2022 > Week 5 > Flashcards

Week 5 Flashcards

1
Q

What are the three components of CSMA/CD Media Access Control (MAC) protocols?

A

CS
MA
CD

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2
Q

What is the difference between shared ethernet and switched ethernet?

A

Shared ethernet has all hosts connected to the SAME bus and COMPETE for bandwidth

Switched ethernet has one or more direct, point-to-point connections between hosts/network segments.

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3
Q

What is the media access control mechanism of IEEE 802.11 wireless network, CSMA/CA?

A

CSMA works by checking that channels are clear before sending packets across a network.

This ensures there are no collisions of data.

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4
Q

What is LAN?

A

Local Access Network

A network of computers that are directly connected to each other.

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5
Q

What is WLAN?

A

Wireless local access network

A network of computers that are directly connected to each other.

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6
Q

What are properties of (W)LAN?

A
  • limited area
  • circuits owned by the org
  • can be operated without obtaining license
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7
Q

Difference between a forwarding table and routing table?

A
  • Forwarding table use MAC address; routing table uses IP address
  • Routing table connects different subnets
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8
Q

What are the types of switches?

A
  • Cut through
  • Store and forward switching
  • Fragment free switching
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9
Q

What is the ethernet frame structure?

A 
Preabmle
Destination Address
Source Address
Type/Length
Data
FCS
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10
Q

Characteristics of cut through switching?

A
  • transmit as soon as destination address has been read

- low latency, but may transmit frames that have errors

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11
Q

Characteristics of Store and forward switching?

A

switch waits until entire frame is received, performs error control, then transmits

higher latency, but less capacity wasted with errors

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12
Q

Characteristics of fragment free switching?

A
  • reads first 64 bytes (contains header)
  • if OK, begin transmitting
  • compromise between the other two approaches
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13
Q

Characteristics of fragment free switching?

A
  • reads first 64 bytes (contains header)
  • if OK, begin transmitting
  • compromise between the other two approaches
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14
Q

What is throughougput?

A

The total amount of user data transmitted in a given period of time

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15
Q

What are bottlenecks?

A

A point in the network where congestion happens.

This is where the network or device cannot handle the demands of the network

Often resutls in dropped packets

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16
Q

How to find bottlenecks?

A

Check sever utilization
if high (>60%): server is bottleneck
if low (<40%): the circuit is the bottleneck
if moderate: both

17
Q

Improving server performance?

A 
Software improvements
• fine tune network and NOS parameters, e.g.
• memory used for disk cache
• available buffer space
• number of simultaneously open files
Hardware improvements
• add second server (load balancing)
• upgrade server's CPU and/or memory
• add more hard disks
• add second NIC to existing server
18
Q

Improving disk performance?

A

Important!
• disks are the slowest components in a server
• many server tasks require disk access

RAID
• Redundant Array of Inexpensive Disks
• links several hard drives together
• can improve performance (read/write from/to several drives
simultaneously)
• can improve reliability (duplicate files across drives, when a
drive fails, another one still contains the files)

19
Q

Improving circuit capacity?

A

Option 1: upgrade to better standard
• e.g. from 100BASE-T to 1000BASE-T
• requires new NICs and new switches, often new cables
• some switches provide e.g. 16 1000BASE-T ports plus 2 10GbE
ports: only upgrade path to the server

Option 2: segment the network
• add second NIC to server
• increase number of parallel paths to the server

20
Q

How to segment a network?

A
  • Add a second NIC
  • Split into two LANs
  • Add rounter to connect LANs
21
Q

How to reduce network demand?

A

Move files to clients
• e.g. heavily used software packages

Install disk caching software on clients
• can store often used files locally
• reduces need to access file server

Spread out tasks to off-peak time
• let automated tasks such as backups run e.g. at night

22
Q

What is CS?

A

CS = carrier sense

23
Q

What is MA?

A

Multiple access =

24
Q

Why CSMA/CD for wired?

A

Access point can detect which devices are talking and points to ONE device to talk at once. Then the next and so on.

25
Q

What is CD?

A

Collision detection =

26
Q

Why CSMA/CA for wireless?

A

Hidden node problem!

Collisions MUST be avoided

FIT9137 Introduction to computer architecture and networks - S1 2022 (9 decks)

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