Important Memorisation

Question 1

What is the IP protocol number for TCP?

Answer 1

6

Question 2

What is the IP protocol number for ICMP?

Answer 2

1

Question 3

What problem does IPv4 face?

Answer 3

Address exhaustion

Question 4

What service does TCP give applications?

Answer 4

Reliable ordered byte stream

Question 5

How many packets make up the TCP three‑way handshake?

Answer 5

3

Question 6

In TCP, sequence numbers count what?

Answer 6

Bytes

Question 7

Which TCP option enlarges the receive window?

Answer 7

Window scaling

Question 8

Which phase starts TCP congestion control?

Answer 8

Slow start

Question 9

What is the minimum TCP header size?

Answer 9

20 bytes

Question 10

What is the size of the UDP header?

Answer 10

8 bytes

Question 11

Does UDP guarantee delivery?

Answer 11

No

Question 12

Give one application class that prefers UDP.

Answer 12

Voice or video

Question 13

Which two extra fields does RTP add?

Answer 13

Timestamp and sequence number

Question 14

Why does RTP include a timestamp?

Answer 14

To replay media at the right time

Question 15

What kind of database is DNS?

Answer 15

Distributed hierarchical key‑value store

Question 16

Which DNS record delegates a sub‑zone?

Answer 16

NS record

Question 17

Which DNS record holds zone parameters?

Answer 17

SOA record

Question 18

Which DNS flag shows an authoritative answer?

Answer 18

AA

Question 19

What is the classic DNS message size limit without EDNS?

Answer 19

512 bytes

Question 20

What famous attack poisons DNS caches?

Answer 20

Kaminsky attack

Question 21

Which DNS field sets how long data may be cached?

Answer 21

TTL

Question 22

What is a glue record?

Answer 22

IP address of a delegated nameserver

Question 23

What model does HTTP use?

Answer 23

Request–response

Question 24

Which HTTP method fetches only headers?

Answer 24

HEAD

Question 25

Which header gives HTTP body length?

Answer 25

Content‑Length

Question 26

If Content‑Length is missing, how is message end signalled?

Answer 26

TCP connection close

Question 27

Which HTTP method is common for uploads?

Answer 27

POST

Question 28

What device breaks a collision domain?

Answer 28

Switch (or bridge)

Question 29

Which domain only a router divides?

Answer 29

Broadcast domain

Question 30

What access method did early Ethernet use?

Answer 30

CSMA/CD

Question 31

What is the max segment length for 10BASE5 coax?

Answer 31

500 metres

Question 32

Why limit Ethernet cable length?

Answer 32

To detect collisions before frame ends

Question 33

What standard defines VLAN tags?

Answer 33

802.1Q

Question 34

Do VLANs provide security?

Answer 34

No

Question 35

What main problem does NAT solve?

Answer 35

IPv4 address shortage

Question 36

What mapping does a NAT table hold?

Answer 36

Internal IP/port to external IP/port

Question 37

Typical idle TCP NAT timeout?

Answer 37

≈60 minutes

Question 38

Typical idle UDP NAT timeout?

Answer 38

≈10 seconds

Question 39

Which Internet principle does NAT break?

Answer 39

End‑to‑end principle

Question 40

Which tech coined QoS terms like CBR and VBR?

Answer 40

ATM

Question 41

How large is an ATM cell?

Answer 41

53 bytes

Question 42

What does MPLS forward packets by?

Answer 42

Labels

Question 43

Why shape traffic at a network edge?

Answer 43

To keep flow within agreed rate

Question 44

How many bits are in an IPv4 address?

Answer 44

32

Question 45

How many bits are in an IPv6 address?

Answer 45

128

Question 46

What protocol carries ping and traceroute messages?

Answer 46

ICMP

Question 47

Which ICMP type does ping use?

Answer 47

Echo request/reply

Question 48

Which ICMP message does traceroute rely on?

Answer 48

Time Exceeded

Question 49

Does ICMP carry user data?

Answer 49

No

Question 50

What field advertises flow control in TCP?

Answer 50

Receive window size

Question 51

Which IP header field says what protocol the payload is?

Answer 51

8‑bit Protocol field

Question 52

What DNS flag turns a query into a response?

Answer 52

QR

Question 53

Which DNS flag asks the server to recurse?

Answer 53

RD

Question 54

Which DNS flag shows the server did recurse?

Answer 54

RA

Question 55

Which DNS record carries arbitrary text like SPF?

Answer 55

TXT record

Question 56

Which TCP option lets the sender recover multiple losses at once?

Answer 56

SACK (Selective Acknowledgement)

Question 57

What event triggers TCP Fast Retransmit?

Answer 57

Receiving three duplicate ACKs

Question 58

Which TCP option stamps packets for precise RTT measurement?

Answer 58

Timestamp option

Question 59

Which ICMP message enables Path‑MTU Discovery?

Answer 59

Destination Unreachable – Fragmentation Needed

Question 60

What algorithm does OSPF use for shortest‑path calculation?

Answer 60

Dijkstra’s algorithm

Question 61

Why is RTP useful for multiple media streams?

Answer 61

Because it handles each stream separately with timestamps and SSRCs (streamIDs), allowing synchronised delivery of audio, video, and more in real time.