1.1 Explain concepts related to the Open Systems Interconnection (OSI) reference model.

Question 1

What is Transport Control Protocol (TCP)?

Answer 1

A connection-oriented protocol good for File Transfer, Email, Web Page request. Uses a three-way handshake each time (SYN, SYN ACK, & ACK)

Question 2

What is User Datagram Protocol (UDP)

Answer 2

A connection-less protocol with no guarantee of delivery; has speed advantage; good for audio/video streamming.

Question 3

What is a Maximum Transmission Unit (MTU)?

Answer 3

This protocol determines the largest frame a particular technology can handle.

Question 4

What is an MTU mismatch?

Answer 4

When packets are too large for a particular technology like Ethernet, which uses 1500-byte frames, they are fragmented.

Question 5

What is a Path MTU Discovery (PMTU)?

Answer 5

A setting that sets a “Do NOT fragment (DF) flag” to the IP packet; it determines the best MTU setting automatically.

Question 6

What is an MTU Black Hole?

Answer 6

Since PMTU runs under ICMP, if ICMP is being blocked, PMTU will not work. This can be remedied by turning off IMP blocking in the firewall.

Question 7

What is OSI Layer 1?

Answer 7

PDNTSPA; transmits logical bits (1s and 0s); Devices include NICs, repeaters, concentrators.

Question 8

What is OSI Layer 2?

Answer 8

PDNTSPA; this is the MAC layer where physical addressing, error detection, and reliable data transfer; devices include ATM, switches, and bridges; protocols include PPP and ARP.

Question 9

What is Link-Layer Control (LLC)?

Answer 9

Happens at Layer 2, governs sequence number and acknowledgements.

Question 10

What is Media Access Control (MAC)?

Answer 10

Happens at Layer 2, governs data transfer and collision handling.

Question 11

What is OSI Layer 3?

Answer 11

PDNTSPA; this is where the logical addressing, route selection, Fragmentation and re-assembly happens; devices include bridges and routers; protocols used include IP, ICMP, IPSec.

Question 12

What is OSI Layer 4?

Answer 12

PDNTSPA; End-to-end connections, flow control and reliability happen at this layer; protocols include TCP and/or UDP.

Question 13

What is OSI Layer 5?

Answer 13

PDNTSPA; this is where inter-host or inter-application communication happens; protocols include RTCP, PPTP, and RPC.

Question 14

What is OSI Layer 6?

Answer 14

PDNTSPA; this is where compatiable syntax, data formats, and data encryption happens at; character encoding happens here with ASCII, UNICODE, or EBCDIC.

Question 15

Wha tis OSI Layer 7?

Answer 15

PDNTSPA; this is where network processes and data is passing to the finished product; protocols include DNS, FTP, SSH.