Midterm Flashcards
(73 cards)
1
Q
What is a two-node point-to-point topology and its attributes?
A
Two nodes, connected with a link.
- Simple topology
- Can serve as a building block for other topologies
- Also used in WAN point to point connections
2
Q
What is a linear topology and its drawbacks?
A
- Multiple point-to-point connections in a linear fashion.
- Drawbacks:
- Data transfer between nodes may need to go through other nodes
- Poor fault tolerance
- Link bandwidth may not be well utilized
3
Q
What is a bus topology? What is a problem and a solution
A
- Linear topology, but all nodes share a common link
- Better utilization, However:
- Transmission may collide
- Solution: Medium access control (CSMA/CD)
4
Q
What are traditional/classical Ethernets (topology) based on?
A
Bus topology
5
Q
What is a ring topology?
A
- Multiple nodes share a single link connected as a ring
- Orderly transmission without collision by token passing mechanism
- Special bit pattern circulating around the ring
- Only a node that ‘captures’ the token can send a message
6
Q
What is the token in a token ring topology?
A
A special bit pattern that allows a node to send a packet.
7
Q
What is a dual ring topology ( FDDI Network)?
A
Two opposing token ring topologies.
8
Q
What is a star topology?
A
- Multiple nodes connected to a central hub
- Hub is like a collapsed bus - serves the same function –> data broadcast to all nodes.
- Has better fault tolerance than the bus topology
9
Q
What type of topology is the CS building? Why?
A
A star topology.
10
Q
What is a mesh topology?
A
- Multiple point-to-point links connected in an arbitrary topology
- Can be a full mesh (all nodes connected) or partial mesh (some links not present)
11
Q
What is used for simple length extension?
A
repeater/hub
12
Q
What is used for length extension and filtering
A
switch/bridge
13
Q
What is used for extension + filtering and Interconnection of two topologies
A
Router
14
Q
What is used for the interconnection of two different protocols (e.g. tcp/ip to DECNet)?
A
gateway
15
Q
What is the main difference between a router and gateway?
A
- A gateway is for two different protocols and router is for different topologies.
16
Q
How does the traceroute utility work?
A
ICMP protocol, TTL set to 1 and increments the value.
17
Q
How does circuit switching works?
A
- A dedicated physical circuit or path is established between the source and destination.
- The circuit or path remains in place for the duration of the communication.
18
Q
What are the advantages of circuit switching?
A
- Dedicated path
- Bandwidth guarantee for the entire duration
19
Q
What are the drawbacks of circuit switching?
A
- Bandwidth cannot be shared
- Unused bandwidth is essentially wasted
- Message cannot be rerouted (faults or congestion)
20
Q
How does message switching work?
A
- Each message is stored and forwarded from node to node
- No dedicated path or circuit is established
- Receiver need not be aware/ready to accept the communication
21
Q
What are the advantages of message switching?
A
- No dedicated path –> better bandwidth utilization
- Paths can be shared –> unused bandwidth != to wasted bandwidth
- Messages can be rerouted
22
Q
What are the drawbacks of message switching?
A
- Long messages can be an issue (exceed buffer)
- Link failure is network expensive (lose a whole message during transmission)
23
Q
What is datagram packet switching?
A
- True packet switching
- Each packet is an independant independent entity - may be routed along different paths.
24
Q
What are the advantages of datagram packet switching?
A
- No dedicated path
- No long messages
25
What are the disadvantages of datagram packet switching?
* Time overhead
* Space overhead
26
What is virtual packet switching?
* Hybrid of circuit switching and packet switching
* A route is established and all packets follow the same route.
* A route is a not a dedicated path
27
What are the advantages virtual packet switching?
* No dedicated path
* Reduce time overhead
* Reduce space overhead
28
What are the drawbacks virtual packet switching?
* Extra cost in routers to maintain tables
* In the case of a fault, the whole connection needs to be reestablish
29
What is the port number of FTP?
20 and 21
30
What is the port number of SSH?
22
31
What is the port number of HTTP?
80
32
What is the port number of telnet?
23
33
What is bandwidth?
* The capacity of a link, or the amount of data that can be carried by a link per sec
* bits/sec
* Depends on link technology
34
What is delay?
* Time is taken for a message entity (a packet) to travel from source to destination
* Nodal delay (node-to-node)
35
What is the nodal delay formula?
processing delay + queueing delay + propogation delay + transmission delay
36
What is Tproc (processing delay) and formula?
* Time to examine a packet header
* Depends on hardware
37
What is transmission delay and the formula?
* Time to push the packet onto to the link
* Depends on the bandwidth of the link
* L/B (L length of the packet in bits, bandwidth in bits/sec)
38
Formula for Propagation delay (Tprop)
Distance/speed
39
What is the formula of traffic intensity?
* **L**ength of packet
* the **a**verage arrival of packets (packets per sec)
* **B**andwidth
* La/B
40
What are the five layers of the TCP/IP stack (top to bottom)
* Application
* Transport
* Network
* Data link
* Physical
41
Describe the application layer of the TCP/IP stack and example services.
* Allows the user to access the network
* Services:
* FTP
* Mail services
* Directory services
* Network management
* Remote access
* Data compression
* Encryption
42
Describe the transport layer of the TCP/IP stack.
End to end transfer between hosts
* Segmentation and reassembly
* Connection control
* Flow control
* Error control
43
Describe the network layer of the TCP/IP stack.
* Concerned with delivery across multiple networks
* Path determination and routing are the main functions
* Uses logical addressing (e.g. IP addresses)
44
Describe the data link layer of the TCP/IP stack.
* Medium access control
* Techniques to regulate access to a link
* Error detection and control
* Frame reliability
* Flow control
* Regulates flow of frames
* Uses physical addressing
* Addressing on a network (e.g. MAC address)
45
Describe the physical layer of the TCP/IP stack.
Interface to the link
* Bits to signal conversion and vice versa
* Defines bit representation and data rates
* Defines characteristics of the device and the link
46
What are examples of application layer protocols?
* HTTP
* FTP
* TFTP
* SNMP
* NFS
* Telnet
* SSH
* DNS
* BGP
47
What are examples of transport layer protocols?
* TCP
* UDP
48
What are examples of network layer protocols?
* IP
* ICMP
* IGMP
* ARP
* RARP
* RIP
* RGIP
* EIGRP
* OSPF
49
What are examples of data link layer protocols?
* IEEE 802.3, 802.5, 802.11
* SLIP
* PPP
* FR
* AIM
50
What are examples of physical layer protocols?
* IEEE 802.3, 802.5, 802.11
* SLIP
* PPP
* FR
* AIM
51
What are the all encapsulated elements of a frame (left to right)?
* source MAC
* next node
* source IP
* destination IP
* Source port number (over 49,152 to 65,535)
* Destination port
* Data
52
What are the elements of a TCP header?
* Port numbers
* Sequence numbers
* ACK numbers
* Header length
* Flags
* Window size
* Checksum
* Urgent pointer
* Options
53
What is the size of every 'row' in the TCP header?
32 bits
54
What is contained in the IP header?
* IP version
* Header length
* Type of service
* Total length
* Fragment ID
* TTL
* Protocol
* Source and destination address
* Options
55
What is a twisted pair cable?
Two insulated copper conductors twisted together in pairs
56
What is the purpose of 'twisting' twisted pair cables?
* Reduces electromagnetic interference from external sources such as crosswalk between neighbouring pairs
* Reduces radiation emitted from the pairs.
57
What is the quality determinant of a twisted pair capable?
* The number of twists/inch
58
What is a coaxial cable?
A shielded copper wire
59
What is the skin effect? How do you prevent it?
* Power dissipation on the outer surface can cause signal attenuation (a phenomenon known as "skin effect".
* Shield the cable
60
What is a fiber optic cable? Structure? How does **blank** travel through an optical cable?
* A cable that transmits signals in the form of light beam
* Structure:
* Outer jacket of Teflon or PVC
* Kevlar fiber for protection
* Plastic coating to cushion the fiber
* Central optical cable made of glass/plastic material
61
How do wireless transmissions work? What is the unit of measurement?
* Transmission of signals as electromagnetic waves in free space
* Frequency in Hertz (Hz)
62
What frequency encompasses most wireless frequencies (wireless and LAN)?
800 KHz - 5GHz range
63
What type of link has digital data and digital transmission?
Ethernet
64
What type of link has digital data and analog transmission?
WiFi and Dialup
65
What type of link has analog data and analog transmission?
Telephone
66
What type of link has analogue data and digital transmission?
VoIP and Digital Telephony
67
Describe the components of the cable specification: X BASE/BROAD Y
* X bandwidth in Mbps
* Baseband digital
* Broadband analog
* Y is the distance in 100m or type
68
What is 100 BASE 5?
* 100 Mbps
* Digital
* 500 meters
69
What is 10 BASE 2?
* 10 Mbps
* Analog
* (2 x 100m) 200m
70
What is the type TX?
UTP or twisted pair
71
What is the type FX?
Fiber
72
1000 BASE TX?
* 1000 Mbps
* Baseband (digital)
* Twisted pair or UTP
73
1000 BASE FX?
* 1000 Mbps
* Digital (baseband)
* Fiber
