Hardware: SAS (2)

Question 1

What were the details of the earliest networks?

Answer 1

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

Question 2

What is packet switching?

Answer 2

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

Question 3

Describe the internet.

Answer 3

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.

Question 4

What are the details of ethernet cables?

Answer 4

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.

Question 5

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

Answer 5

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.

Question 6

What are computer addresses?

Answer 6

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.

Question 7

How does packet switching works in regards to MAC addresses?

Answer 7

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.

Question 8

What is an IP address?

Answer 8

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.

Question 9

What is an IP address?

Answer 9

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.

Question 10

How does DHCP server work?

Answer 10

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).

Question 11

What are loopback addresses?

Answer 11

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

Question 12

What is the DNS?

Answer 12

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).

Question 13

What are the details of data in relation to networks?

Answer 13

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.

Question 14

How do firewalls work?

Answer 14

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.

Question 15

What is wi-fi?

Answer 15

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

Question 16

What is WAP?

Answer 16

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.

Question 17

Why do we upgrade?

Answer 17

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.

Question 18

What must we consider when upgrading?

Answer 18

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.

Question 19

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

Answer 19

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).

Question 20

What should we be careful of when updating?

Answer 20

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.

Question 21

What must we consider when troubleshooting?

Answer 21

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.

Question 22

What should be in a troubleshooting toolkit?

Answer 22

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.

Question 23

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

Answer 23

‘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?

Question 24

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

Answer 24

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

Question 25

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

Answer 25

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

Question 26

What should you do when troubleshooting hardware?

Answer 26

, 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.