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Flashcards in Hardware: SAS (2) Deck (26)
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1

What were the details of the earliest networks?

Earliest networks were circuit switching, connection routed + dedicated circuit opened for connection duration e.g. public service telephone network (PSTN).

2

What is packet switching?

More efficient way to use links for multiple connections, break down comms into small packets + send through network, each using cheapest/most efficient route. Reassemble message at end. E.g. Internet

3

Describe the internet.

Uses standardised protocols for data transmission (TCP/IP), routing (BGP), fault tolerance + naming (DNS). Uses standardised uniform resource identifier (URI). Present data via HTTP using HTML. Network card/NIC/ethernet card, 10baseT, 100baseT, 1000baseT, gigabit ethernet card. Some motherboards have LAN chips.

4

What are the details of ethernet cables?

To prevent attenuation + electromagnetic crosstalk, ethernet cables manufactured as twisted pairs. Originally, shielded (STP), now unshielded (UTP). Cat 1 = standard telephone cabling, Cat 5 = up to 100Mbps, Cat 5e = 1GBps, Cat 6 = Up to 10GBps.

5

What are the pros/cons of bus + star networks?

Old bus networks were prone to error (any fault stopped everything), lots of collisions, eminently hackable/eavesdroppable + cabling nightmare. Star network has individual point-to-point links, central hub (box/switch), link issues affect 1 device + centralised cabling.

6

What are computer addresses?

Most comps have 2 addresses: Ethernet/MAC +IP. MAC used on local network frame only (switch). IP used to identify comp & find out where it is, used beyond local network frame.

7

How does packet switching works in regards to MAC addresses?

Switches know which MAC addresses on which ports. Packet comes in for IP X, ask which has IP X, system S responds + packet passed. Switch now remembers MAC address of S (in ARP table). Open to man-in-the-middle attacks but standard to stay.

8

What is an IP address?

Internet Protocol address traditionally IPv4, 32-bit, represented by dotted quad. IPv6 has 128-bit nums as 8 sets of 4 hex digits & sets of 0’s omitted.

9

What is an IP address?

Internet Protocol address traditionally IPv4, 32-bit, represented by dotted quad. IPv6 has 128-bit nums as 8 sets of 4 hex digits + sets of 0’s omitted.
Some reserved to avoid conflict with real-world IP ranges. In IPv4, these private addresses are 192.168, 172. & 10.

10

How does DHCP server work?

Local IP addresses assignment manually/automatically, automatically assigned from Dynamic host configuration protocol server. Static/dynamic (subject to change per session/connection).
Once system assigned IP address, provided for certain time (DHCP lease). After that, re-request, may change. Multiple DHCP servers can cause chaos. IP address e.g. 192.168.0.1, netmask e.g. 255.255.255.0 (is it local?) + gateway e.g. 192.169.0.254 (non-local traffic).

11

What are loopback addresses?

Private, loopback interface loops back to same machine. 127.0.0.1 – 127.255.255.255.254. 127.0.0.1 most common.

12

What is the DNS?

Hierarchical distributed naming system. Starts with root servers, then each step has more info in turn.
Layers: physical (cables/sockets/electricity), data link (MAC/switches), addressing machines (IP), finding machines (netmasks/gateways/routers), naming machines (DNS).

13

What are the details of data in relation to networks?

Transmission control protocol (TCP), User datagram protocol (UDP) & Internet control message protocol (ICMP/ping). For TCP + UDP, connect to remote system on specified (decimal) port. Common ports: HTTP 80, HTTPS 443, SMTP 25 & SSH 22.

14

How do firewalls work?

On servers, run services, listen for connections on given ports. Now have servers behind firewalls & manage what comes through + from where.
Home firewall routers/network address translation (NAT) routers: Turn internal network address into packet that can be returned, many machines share 1 acc internet address.

15

What is wi-fi?

Wireless Fidelity standard is IEEE 802.11, uses service set identifier (SSID) to identify network.

16

What is WAP?

To connect device, connect to configured wireless access point (WAP), most home/SoHo routers have WAP built-in. In enterprise settings, have range of WAPs throughout building, all using same/multiple SSIDs. Passcode not sufficient for enterprise, so various authentication protocols exist to use existing network authentication.

17

Why do we upgrade?

Improves perf/capability (new requirements + more space), new feature, repair faulty system. Typical upgrades incl. increasing RAM, add/replace storage, removable drives, ext interfaces (USB3), sound card, graphics card, CPU & MB, displays, printer, scanner, keyboard, mouse + VR headset.

18

What must we consider when upgrading?

Consider whether it fits (connection type, num spare connectors, case space), whether it works (OS drivers, power, ext interfaces, MB tech compatible), gains (improvement, address bottleneck) + whether it’s cost effective.

19

What should we consider once we've decided to upgrade?

Can we trial it? For large organisations, small num machines to trial upgrade + monitor or return component/managed upgrade agreement. On smaller scale, many retailers take returns if careful + has compatibility ambiguity. If works, is it an improvement, file papers (receipts/shipping notes) + update corporate config management DB (CMDB).

20

What should we be careful of when updating?

Ensure equip off, disconnected from mains + have anti-static wrist strap, careful w/ cases, keep track of screws, wear PPE. Backup all, doc as you go (photos/vids/logs), upgrade 1 thing, check it works, repeat, don’t throw away part.

21

What must we consider when troubleshooting?

Consider its priority, how many affected, available workaround. Is user ‘technically challenged’, try again? Did it work last time, what normally happens, error message, what diff, many faults are user generated. Turn it off + on, disconnect diff things. Identify problem (symptoms, expected op), identify hypothesis, test hypothesis, devise solution, implement solution + test functionality.

22

What should be in a troubleshooting toolkit?

Screwdriver (multi-driver), tools w/ odd ends, pliers, grips, screw-catchers, drill, hammer, varied screws, bolts + spacers, USB sticks/optical drives w/UBCD + other utilities, IDE/SATA to USB adapter, cleaning products (screens, keyboards, discs, compressed air), multimeter + paper/pen/cam.

23

What might you do if the user said they had a blank monitor?

‘What do you mean by blank?’ (no display, blank window, colour). Waggle mouse/hit keys, power light/switch (turned on?), plugged in, plugged into comp, comp switched on, power cut?

24

What might you do if the user said the printer wasn't printing?

‘What is error message?’, print to right printer, plugged in, turned on, detected by OS, ever work/when last work, offline in driver/printer?

25

What might you do if the user said there was a funny noise coming from the computer?

‘What type of noise’ (hum), when (startup, shutdown, insert CD, continous), when start, what moving parts (fans, drives), environment (dirty/dusty, hot).

26

What should you do when troubleshooting hardware?

, reconnect & check wires (firm connections + fraying), replace (swap working parts), clean contacts (no dust). If driver issues, install manufacturer-provided driver (not windows default), did update break it? Remove poss. conflicting devices (expansion cards). Use common sense + simplest answer, record & GOOGLE.