e2 Flashcards
50: (p.38) What is layer 7 of the OSI model?
application
51: (p.38) What layer number is the Application layer of the OSI model?
7
52: (p.38) What is layer 6 of the OSI model?
presentation
53: (p.39) What layer number is the Presentation layer of the OSI model?
6
54: (p.39) At which OSI layer is encryption / decryption?
6 or presentation
55: (p.39) At which OSI layer is data compression?
6 or presentation
56: (p.39) What is layer 5 of the OSI model?
session
57: (p.39) What layer number is the Session layer of the OSI model?
5
58: (p.40) What is layer 4 of the OSI model?
transport
59: (p.40) What layer number is the Transport layer of the OSI model?
4
60: (p.40) What does MTU stand for?
maximum transmission (or transfer) unit
61: (p.40) What is the typical value for MTU (in bytes)?
1500
62: (p.41) At which OSI layer are software ports?
4 or transport
63: (p.41) What does TCP stand for?
transmission control protocol
64: (p.41) Which protocol provides for guaranteed delivery of information?
TCP, or Transmission Control ProtocolTCP, the Transmission Control Protocol, provides guaranteed delivery throughretransmission as needed.
65: (p.41) At which OSI layer is TCP?
4 or transportTCP is suitable for le transmission where accuracy is more important thanavoiding delays.
66: (p.41) Which protocol provides for fast (but not guaranteed) delivery ofinformation?
UDP, or User Datagram ProtocolUDP, the User Datagram Protocol, provides fast delivery but does not guar-antee delivery.
67: (p.42) What does UDP stand for?
user datagram protocolUDP is suitable for live voice, live sound, and live video, where avoidingdelays is more important than absolute accuracy, and dropped data canusually be ignored.
68: (p.42) At which OSI layer is UDP?
4 or transport
69: (p.42) At which OSI layer do we nd segments?
4 or transport
70: (p.42) What is the Protocol Data Unit at OSI layer 4?
segment
71: (p.42) What is layer 3 of the OSI model?
network
72: (p.43) What layer number is the Network layer of the OSI model?
3
73: (p.43) At which OSI layer is the Internet?
3 or network
74: (p.43) At which OSI layer are Wide Area Networks?
3 or network
75: (p.43) What does WAN stand for?
wide area network
76: (p.43) At which OSI layer is IP Addressing?
3 or network
77: (p.43) At which OSI layer is Logical Addressing?
3 or network
78: (p.43) At which OSI layer does a router operate?
3 or network
79: (p.43) At which OSI layer does a gateway operate?
3 or network
80: (p.44) At which OSI layer is Network Address Translation?
3 or network
81: (p.44) At which OSI layer is Port Address Translation?
3 or network
82: (p.44) At which OSI layer do we nd packets?
3 or network
83: (p.44) What is the Protocol Data Unit at OSI layer 3?
packet
84: (p.44) What is layer 2 of the OSI model?
datalink
85: (p.44) What layer number is the Data Link layer of the OSI model?
2
86: (p.45) What does MAC stand for?
media access control
87: (p.45) How does a typical laptop computer discover its own MAC ad-dress?
It already knows it. It is burned in on the network card.
88: (p.45) At which OSI layer is the Local Area Network?
2 or datalink
89: (p.45) At which OSI layer is MAC Addressing?
2 or datalink
90: (p.45) At which OSI layer is Physical Addressing?
2 or datalink
91: (p.45) At which OSI layer is Ethernet?
2 or datalink
92: (p.45) At which OSI layer does a switch operate?
2 or datalink
93: (p.45) At which OSI layer does a bridge operate?
2 or datalink
94: (p.46) What is a multi-port bridge called?
switch
95: (p.46) What is a two-port switch called?
bridge
96: (p.46) At which OSI layer do we nd frames?
2 or datalink
97: (p.46) What is the Protocol Data Unit at OSI layer 2?
frame
98: (p.46) What is layer 1 of the OSI model?
physical
99: (p.46) What layer number is the Physical layer of the OSI model?
1
100: (p.47) At which OSI layer is wireless signal?
1 or physical
101: (p.47) At which OSI layer is coaxial cable?
1 or physical
102: (p.47) At which OSI layer is cat5 cable?
1 or physical
103: (p.47) At which OSI layer is ber-optic cable?
1 or physical
104: (p.47) What is a multi-port repeater called?
hub
105: (p.47) What is a two-port hub called?
repeater
106: (p.47) At which OSI layer does a hub operate?
1 or physical
107: (p.47) At which OSI layer does a signal repeater operate?
1 or physical
108: (p.48) At which OSI layer do we nd bits?
1 or physical
109: (p.48) What is the Protocol Data Unit at OSI layer 1?
bits
110: (p.52) What is a software port?
A port is a number that indicates which computer program should receivethe message.
111: (p.56) What is a hop?
A hop is the moving of a packet from one LAN to another.A hop is the activity performed by a router when it receives a packet on onelocal area network, and passes it across to a dierent local area network,one step closer to its nal destination.
112: (p.57) What does TTL stand for?
time to live
113: (p.57) What is the purpose of TTL?
It reduces the risk of network loops.
114: (p.59) What does having a routable address mean?
Packets can be sent to you across the Internet just using your own IPaddress.
115: (p.60) What are the ve non-routable IP address blocks?
10.x.x.x, 127.x.x.x, 169.254.x.x, 172.16-31.x.x, and 192.168.x.x.
116: (p.60) What does NAT stand for?
network address translation
117: (p.60) What does PAT stand for?
port address translationPAT is another name for Network Address Translation. NAT is the generallyused terminology.
118: (p.61) Explain Man In The Middle?
Man in the middle is (a) a hacking technique. (b) Two computers believethey are talking to each other. (c) Instead they are talking through (byway of) a third computer.
119: (p.63) In NAT, how does the router remember the original sender?
The router keeps a table that matches outside port numbers with insideIP address and port number pairs.
120: (p.63) What is garbage collection?
Reclaiming resources that are no longer in use.
121: (p.64) How long do NAT address pool entries last?
Address pool entries often expire (a) after ten minutes, or (b) when thetable is full the most stale entry expires.
122: (p.64) What is a keep-alive?
A keep-alive is a message that is sent between two computers just to keepthe connection from timing out and being dropped.
123: (p.68) What does DMZ stand for?
demilitarized zonePort forwarding can be set up with triggers, but it’s still tricky.These methods are really a last resort. They work but they are dicult toset up and use.