Networks Flashcards
1
Q
What is a network?
A
A group of 2 or more devices that are able to communicate with each other
2
Q
Name 2 Variations of connections.
A
Connection oriented where there is a open and closed connection e.g. Landline
Connectionless where data is just sent along and we dont know the direction E.g. The postal system. The protocol for connectionless is IP
3
Q
Name all the topologies and at least 1 advantage and disadvantage
A
Bus Dis - There are collisions. If 1 node fails the whole network fails
Bus Adv - Quick and easy to set up
Token ring Adv - * All nodes on the network have a chance of transmitting data
* It has good quality service
* There are no collisions
Token ring Dis - * If one node or cable goes down so does the whole network
* Tokens get lost or corrupted
* Difficult to add and delete nodes to/from the ring]
Hierachical topolgy
Star dis - Central point of failure
Nodes can get Isolated
Star adv - Less traffic
Mesh adv - less traffic
Mesh dis - Expensive
4
Q
Compare the ring and bus topology
A
Ring has no collisions and poor latency.
Bus has collisions but better latency.
5
Q
What does CSMA/CD stand for
A
Carrier Sensor Multi-access collision detection
6
Q
Describe the steps for CSMA/CD ?
A
- The algorithm is listening for transmissions of data(Listening for the voltage). Once it cannot hear any more transmissions then you can then start a transmission
- Then it checks if there are collisions if not then it finishes the transmission
- If there is transmission then it transmits data until the maximum packet time(time to deliver data) is reached in order to alert all other nodes that there has been a collision
- Once alerted there is a random back off algorithm that is run so when nodes start transmitting again no 2 nodes transmit at the same time in order to avoid collisions
7
Q
How do collisions happen ?
A
When 2 devices try to transmit at the same time.
8
Q
Go through access and distribution rules?
A
Access rules follow the CSMA/CD algorithm.
The distribution rules allow traffic to go everywhere but only one packet at a time.
Ethernet devices also follow access and distribution rules
9
Q
What is POE ?
A
Stands for power over ethernet. This is when you use thernet cabling to deliver power to some devices connected to the ethernet like the telephone and WAP.
It is useful when you dont have power outlets
10
Q
What is a gateway used for ?
A
To access another network beyond your own over the internet
11
Q
What is octetcs ?
A
The 4 groupings in the IP address
12
Q
What are the 2 types of IP ?
A
Static IP - IP that doesnt change
Dynamic IP - IP allocated from the main part of the domain
13
Q
How many bits are used for IPv4 and IPv6
A
IPv4 - 32 bits
Ipv6 - 128 bits
14
Q
What is the difference between hardware and software ?
A
Hardware is what physically connects devices in a network.
Software is what enables us to use the hardware for info exchange
15
Q
What does ISO stand for ?
A
International Organisation for Standardisation
16
Q
Why do we need Standardisation ?
A
So we get effective networks that are compatible and can communicate with each other
17
Q
What does NIC stand for?
A
Network Interface Card
18
Q
Describe the 3 way handshake ?
A
- Node wants to communicate with server so we send data over and tries to sync with the server
- Once this sync is acknowledged by the server the sequence number of the packet number is incremented and becomes the acknowledgement number
- Then the node gets a new sequence number
- Then when the node gets sent out there is a new sequence number
The previous sync becomes the acknowledgment number but increments
19
Q
When sending data how do we determine if the location is on the same network or another network?
A
We use the ARP (Address Resolution Protocol )
20
Q
How many bits are used for subnet mask fields ?
A
32 They are used to determine the network and host address
21
Q
Describe the NIC ?
A
NIC allows us to communicate across the network
NIC has MAC address
NIC read all broadcast messages
22
Q
Why go digital ?
A
Most computer data is digital
Higher data rates
It is easier to switch
Better data rates
23
Q
What does interoperable mean ?
A
This means all devices can connect on the network regardless of the operating system.
24
Q
Name some characteristics of the switched ethernet ?
A
. Automatically learns source address
. Forwards selectively to the destination
. Supports many ports per switch
. Supports different rates in each port
25
What is the difference between a switch and a hub ?
The switch operates in store and forward meaning it holds the packet interrogates it and forwards the packet
* Switch checks the header so less time efficient but fewer collsions
* Switch gets a ping return with the IP address
. Switches have a look up table
Hub just takes info in and sends the data straight away. It handles one packet at a time.
. Hub brodcasts data
* Advantage is time efficiency. Disadvantage is increased collision
26
What are the 2 types of virtual circuits ?
Switched virtual circuit (SVC) and Permanenet virtual circuit (PVC)
27
Give some characteristics of value added LANS?
. Unlimited distance
High speed and expensive and complex design
28
Give examples of a switched virtual circuit (SVC)
. Dial up lines
. X.25
. ATM
29
Give an example of a permanent virtual circuit (PVC)
. Frame relay
. Virtual circuits
. ATM
30
What is a virtual LAN?
Software that gives the appearance of a physical connection. E.g a VPN
31
Give some other names for data
Packets or frames or cells
. Packet and frames are of variable length. This means they require software processing which limits the data processing e.g. X.25
32
What data is fixed length?
Cells. They are processed in hardware meaning higher data rates
33
What is an alternative to X.25?
Frame relay
34
What is x.25 ?
X.25 is an ITU-T standard protocol suite for packet-switched data communication in wide area networks
35
Compare x.25 and frame relay
X. 25 is worldwide but frame relay is only in countries with fibre optic infrastructure
X.25 uses virtual circuits to establish connections between devices, which means a dedicated connection is created for data transmission. Frame Relay, on the other hand, uses virtual circuits as well but is more focused on efficient data transmission without error checking.
In summary, X.25 is an older, slower, and more reliable protocol, whereas Frame Relay is a faster and more efficient protocol. X.25 focused on error detection and correction, while Frame Relay prioritized speed and efficiency.
36
What is a protocol?
A protocol is a set of instructions for how devices should communicate in a network
37
What is a packet?
A packet is a unit or package of data sent across a network.
38
Describe the makeup of a packet
Header - This conatins the recipeint and sender address. It also has coding to handle transmission errors. It also contains the time the packet has to live
Payload - The actual data being transported
The trailer - Contains error checking stuff like checksum
39
What does UDP stand for?
User datagram protocol
40
What does TCP/IP stand for?
Transmission Control protocol / Internet Protocol
41
How are packets sent across a network using TCP/IP?
1.) Data is split into packets by the IP part of TCP/IP and is given header info. (The IP part also determines how much data can fit into a single packet)
2. ) Using the header info the routers determine the best path for each packet to be sent along.
3. ) Once the packet has reached its final destination the TCP part reassembles packets and checks their integrity. If any packets are missing or damaged it requests that those packets are resent.
42
Describe UDP?
Works like a connectionless network meaning when it gets data it just sends it regardless of whether you can receive it or not
. It is an alternative to TCP, it has a poorer quality of service but is faster.
43
Compare UDP and TCP
. UDP is connectionless TCP is connection-oriented
. TCP is used for reliable transport UDP is used for unreliable transport
. UDP is also used for broadcasts and real time
44
Describe how data is sent using layers
. If the destination is local the node can communicate directly else use a gateway
. Once the packet is prepared it's passed to the network layer.
. The network access layer transmits the packet to the connection media
45
Describe receiving data using layers
. When the packets received they are checked for corruption and the correct address
. If all is good the network access layer extracts the data and passes it to the correct protocol
46
What is OSI reference model?
Enables better compatibility and interoperability between network technologies
47
What is the acronym for the OSI reference model ?
Please Do Not throw Salami Pizza Away
48
What are the 7 layers of the OSI reference model?
. Physical
. Data link
. Network
. Transport
. Session
. Presentation
. Application
49
Describe the physical layer ?
Deals with the physical characteristics of hardware e.g. Voltage levels, timing of voltage, changes and physical data rates
50
Describe the data link layer ?
Deals with transmission across the media
Can provide reliable transit of data across a physical link by using the MAC address
51
Describe the network layer?
Defines end-to-end delivery of packets and makes use of routers.
52
Describe the transportation layer
Regulates info flow to ensure end-to-end connectivity between host applications is reliable and accurate
Breaks data at the host then reassembles it at the recipient end
Makes use of TCP and UDP
53
Describe the session layer
Defines how to start control and end conversations between applications
It synchronizes dialogue between 2 hosts' presentation layer and manages their exchange
54
Describe the presentation layer?
Ensures that the application layer of one system sent out is readable by the application layer of another system
55
Describe the application layer
Provides network services to the users applications
It synchronizes and establishes agreement on procedures for error recovery and control of data integrity
56
Describe layered protocol envelopes
Protocol info is used as an envelope at each layer.
Protocol is added and removed at each layer
57
What things should you consider when choosing cabling media?
. Bandwidth
. Electrical interference
. Cable length
. Cost
. Environment
58
Name some wireless approaches?
. Satellite communication
. Radar
. Cellular communication
. GPS
. Wi-Fi
. Bluetooth
. Radio Frequency Identification (RFID)
59
Name some wired approaches.
. Twisted pair cabling
. Coaxial cabling
. Fibre optic cabling
60
Give some info on unshielded twisted pair?
. Least expensive
. Can go up to 100m
. Cat 6 is the latest form of unshielded twisted pair
. Token ring makes use of this
61
Describe cat 6 cabling
. Has 2 forms UTP and ScTP
. ScTP has layer of foil to improve interference
. Makes use of PoE
62
Give some info on coaxial cables
. Low noise(low bit error rate)
. The shielding may include multiple layer of foil
63
Give some info on fibre optic cables
. High rates of data
. Has 2 unidirectional links 1 in each direction
. Good noise immunity, high security, lightweight and small
. Approximately the same cost as good quality ethernet.
64
Describe how fibre optic cables work
. Converts electrical signals to light and back
. Media converters are required between different media types to convert light back to electrical signals
65
What is modulation?
Modulation converts a digital signal to analog signal
66
What is demodulation?
. Converts a signal from analog back to digital
67
What does ATM stand for ?
asynchronous Transfer Mode
68
Is ATM connection-oriented or connectionless?
Connectionless but it tries to emulate connection oriented
69
Is ATM a protocol if so where does it operate?
ATM is a data - link layer protocol and is primarily used in WANs
70
What is another form of cell relay?
ATM
71
Give some info on ATM
* Large frames are segmented into cell size pieces for transmission. The cell-size is 48 octets
. There are 53 octetcs in total
. There is an unpredictable amount of time between the arrivals of these individual “cells"
* It has the channel number
* Header Error check
* Type (control or data)
Cell loss priority
72
How does atm WORK?
. ATM follows a layered architecture
. The AAL segments up the cell. . It adds padding if the data doesn’t meet the fixed size
. These cells are relayed (switched) across the network
. The cells are reassembled at the destination
73
Give some info on AAL
It stands for ATM Adaption Layer.
. AAL goes from AAL1- AAL5 . 5 for each different usage of ATM:
- AAL1 Voice and video (constant bit rate)
-AAL 2Compressed Voice and Video (variable bit rate)
-AAL3 & 4 General user data
-AAL 5 TCP/IP
NOTE 3 & 4 are sometimes called unspecified bit rate
74
Give some uses of atm
. Supporting voice, compressed video, and data
. A major feature of ATM is its built-in quality of service (QoS)
. It resides in the high-speed core portion of the network
75
Give some advantages and disadvantages of ATM
Advantage :
* Meets international and Industry Standard
. Operates over most current high-speed WAN circuits
. Cost competitive within the high speed core network
. Supporting voice, compressed video, and data
. Directly supports quality of service (QoS) for multimedia transmission needs
Disadvantage :
* Complex operation and configuration (provisioning)
* Somewhat inefficient (the “cell tax” 10% overheads) we cant have oversized packets
Not currently cost competitive at the “edges” of the network
76
What does TLS stand for ?
Transparent LAN Services
77
Give some info on TLS
* TLS is a carrier bridge betwwen your gepgraphically seperated LAN
* It makes the all appear in 1 big LAN
. Decreasing subscriber WAN management Burdens
* These are often ATM Circuits
* A good example of the heavy reliance on ATM by carriers
* Ethernet access to carrier’s ATM net
* Called “Metro Ethernet” “Ethernet Transport” etc
Available in all Ethernet data rates
* In TLS You don’t have to deal with the WAN
You don’t have provision for frame relay, ATM, leased lines, etc
78
What does voip stand for?
Voice over Internet Protocol. It refers to making phone calls that are made through the internet, rather than through a regular landline or a mobilenetwork
79
Give some disadvantages to voip.
. if the network goes down the phones go down as a result voip is declining
. Traffic
. Quality of connection can be risky because of delay
. Wireless devices can become out of range of an ethernet connection
80
What does SIP stand for ?
Session Initiation Protocol
81
Give some info on SIP
. A signaling protocol in the application layer for real time sessions
. provides a single infrastructure for voice,video and instant messaging
. * It has 5 group categories
User location - real time local discovery
User availability - is the user available to communicate
User capability - choice of media and coding scheme
Session set up – establishing the session
Session management – transferring sessions; modifying parameters,
. Its similar to HTTP
82
List the tiers in the hierarchy of ISPs
* Tier1: International ISPs
* Tier 2: National ISPs
* Tier 3: Regional ISPs
* Tier 4: Local ISPs
83
What does NAP stand for?
Network Access Points(
84
What does IXP stand for ?
Internet Exchange Points
85
Describe how NAP and IXP work together
They interconnect ISPs to exchange traffic
They exchange routing info using BGP-4 a gateway protocol
* Selective private peering with direct inter - ISP links
* NAPs are layer 2 switches
Typically using ATM switching
With support for ISO - provided routers
* NAPs are interconnected by high-speed backbones
86
Name the 7 router capabilities
* Access routers – Edges of the internet
* Enterprise routers – Organisation network
* Core routers – Handling Heavy Data flow
* Routers may also have Layer 2 switching capabilities
* May have hardware or software routing capabilities
* Routers may be table top or chassis based
. Multiple plug-in router modules
87
Name the 4 modern router capabilities
. Embedded routers
* Wireless Access Point
* A small (e.g. 4-port) wired switch
* Firewall (hardware device)
88
What does MPLS stand for ?
Multi-Protocol Label Switching
89
How does MPLS work?
. The MPLS philosophy is switch to the center and route to the edge
. A merger of Layer 3 (e.g. IP) routing protocols and Layer 2 switching.
. Intended for use in the core portion of Intranets/Internet
. Useful for carriers, ISPs and enterprise WAN networks
. Layer 3 is “multi-protocol” since the switching is done at Layer 2
90
Give some benefits of MPLS
. allows many variations (options) including qos
. Traffic engineering capabilities
. MPLS-based VPNs with simpler provisioning
. Improved performance (switching instead of routing at each hop)
. Scalability
. Highlights benefits of connection oriented
91
What is Quality of Service(Qos)
* QoS usually refers to providing support for time-sensitive delivery such as voice and/or compressed video
92
Name 3 efforts that have been made for QOS
. Various forms of IP switching
. Differentiation services (using the IP TOS byte)
. Multiprotocol label Switching (MPLS)
93
What are the 3 key elements of security?
* Security Attack - Any action that compromises the security of information.
* Security Mechanism - A mechanism that is designed to detect, prevent, or recover from a security attack (e.g. antivirus software).
. Security Service - A service that enhances the security of data processing systems and information transfers. A security service makes use of one or more security mechanisms.
94
What are the 3 security goals
Confidentiality,integrity and authenticity
95
What does authenticity mean?
Knowing who created or sent the data
96
What are the 2 forms of security attack
. Interruption - When the source of information is stopped from being sent to the destination. Most of the time you dont know what happened unless you tracked the data
. Modification - The third party gets information and sends false information from the source to the destination. As a result, the integrity is questionable. A solution to this is encryption
97
What are cable taps?
* Cable Taps is tapping into physical cables to extract transmission. This is where fibre optic is better because once you break the glass you break the signal
98
Name and explain the 2 types of security threats
* Passive attacks - eavesdropping on, or monitoring (listening) of transmissions. The goal of the attacker is to obtain the information that is being transmitted (i.e. interception)
. Active attacks - Attempts to cause harm to the victims computer or server typically through system faults or brute force attack e.g. Denial of Service
99
Name the 3 Security Services
* Non - repudiation (the order is final) - The assurance that someone cannot deny something
* Access control (prevent misuse of resources) -Levels of access & Read or write access
* Availability (permanence, non-erasure)
100
Name the 5 methods of defence
. Encyption
* Software Controls - access limitations in a data base, operating system protect each user from other users
* Hardware Controls
Smartcard access to data,
Biometrics, finger prints, iris scans
* Policies and procedures
E.g. frequent changes of passwords
* Physical Controls
Controlled access
101
How do we reduce vunreblities ?
* We need to protect our hardware and software
. Users need to be trusted.
102
Name the security policies based on Organisational requirements
* Prevent/Detect Security Violations
* Disaster Recovery
* Security Risk Policy
* Legal Requirements-Data Protection
103
Name some vunerabilities/problems in security
* Remote attacks - attacks from outside the building
* Software developed with back doors - Can be done by design or by mistake
* Insecure Configuration
* Internal attacks - knowing exactly where to destroy a system
* Access Control - Giving someone who should not have access the wrong access
* Attaching personal devices to work networks
104
Name some security management methods
* Control and Distribution - Control what people can see or download basically controlling data
* Event Logging - When you do anything to a system it logs whos done it and what the change was
* Monitoring - Similar to event logging but also looks at how long software is running and perhaps seeing if they create vulnerabilities
. Parameter Management
105
Name some security mechnisms
* Encryption/Decryption
* Message Authentication
* Password Policy
* Digital Signatures
* Access Control
106
What does SSL stand for ?
Secure Sockets Layer
107
What is SSL ?
It means that your connection to a website is secure and encrypted e.g. https
108
What are the 2 types of encryption ?
symmetric (private)
asymmetric publickey
109
Name some encyption standards
AES Advanced Encryption Standard
DES Data Encryption Standard
Triple
110
Give some benefits of VPNs in security
. Encapsulation is in routable IP packets
* An outsider might intercept packets, but cannot, read them or modify them without detection
111
Give some info on user radius protocol
. provides Authentication, Authorization checking and accounting
. Uses Point-to-Point Protocol (PPP)
. Operates on port 1812
. Commonly used to facilitate roaming
. Can provide customizable login prompts
112
How do we prevent unaithorised internet access
User firewalls. There are different types:
.router based firewall
. host based firewall
. router filtering is also another solution
113
Name some goals for network management
* Help Desk
* Network support technicians
* Network systems management
○ Monitors the network
○ Providing the ability to diagnose and control the network
* Runs on a simple workstation (PC)
114
What are the 3 distinct needs in TCP/IP network management?
○ A protocol to write/read critical network management data
○ Event reports
○ Database of specific parameters
115
What does SNMP stand for?
Simple Network Management Protocol
116
Describe the steps in SNMP?
○ Read the value of the individual parameters (SNMP Get)
○ Read sequences of table entries (SNMP Get_Next)
○ Write into parameter values (SNMP Set)
○ Receive unsolicited event reports (SNMP Trap)
117
What does RMON stand for?
Remote monitor
118
How is RMON implemented?
○ Independent probe devices(software) attached to each LAN segment
○ Can be integrated into networking devices
119
What are the 2 forms of RMON ?
○ RMON 1 monitors OSI layers 1 and 2 which has Collision statistics and error statistics
. RMON 2 includes monitoring of higher levels
120
Give some benefits of RMON
* Can be cost effective
* Help control traffic throughput by monitoring the host and applications and seeing what causes the most traffic
* Increases the effectiveness of network management personnel
* Identifies where the problems are for trouble shooting.
121
What are the 5 areas of network management that OSI identifies
○ Configuration
○ Fault management
○ Performance management
○ Accounting management
○ Security management
122
What does Configuration management include
○ Configure Switch and routers to filter out certain types of traffic
○ Multi protocol routers can be configured to run selected protocols
○ Configuration of bit rate, parity etc
* Address and name assignments to network devices
* Hardware/software updates to Switches, routers
Software license control etc
123
What does fault management do and name some tools/techniques?
. Fault managemnet identifies and isolates faults
Tools/techniques:
○ Bit-Error Rate Test (BERT)
○ Time Domain Reflectometer (TDR)
. Optical TDR (OTDR)
* Protocol analyzer (for data links and LANs)
124
How do we isolate faults
We can isolate via router configurations and switches
125
Give some info on performance management
○ Buffer size adjustments
○ Setting timer values
* Establishing a baseline
* Concerned with statistical data
○ Round trip delays
○ Throughput
* May require prioritization of certain traffic
○ Including other QoS capabilities
* Tuning of performance (eliminating bottlenecks)
○ Access to servers resources e.g. disk storage
○ Parts of the network that are nearing overload
126
Give some info on accounting management
* Can be the billing for network usage
○ Number of connections made
○ Duration of each connection
○ Number of e-mail messages sent and received
○ Number of packets sent and received
○ Systems that are accessed across the network
○ Internet usage.
○ Server usage (connect time and disk storage)
○ Traffic that needs access to expensive WAN circuits
○ Data storage
* Disc storage space
127
Describe data abstraction
It converts between character sets when implemented
128
Give some anti spam measures
* Only accept mail destined for that mail server
* Only send mail out from mail server when client is in a certain IP range, or he authenticates.
* Open relays
* Real-time blackhole lists (RBL)
129
How do we get our mail?
* If we want to send an email
* First we need to find the IP adress of the mail server
* Mail delivered by SMTP is stored on server.
* Server allows us to access it via POP3.
130
What does the internet society aim to do
* Aims to oversee the standardization of protocols to promote interoperability
* Coordinates Internet ,Design, Engineering and Management
131
What are the 3 main sections of the internet society
* Internet Architecture Board (IAB)-Defines architecture of the internet
* Internet Engineering Task Force (IETF)- Receives Architecture definitions from IAB and Protocol engineering development
* Internet Engineering steering Group (IESG)- Technical management of the IEFT & Defines the Internet Standard
132
What is the criteria (Internet Society)
* Be stable and clear
* Be technically competent
* Have multiple, independent and interoperable implementations with substantial operational experience
* Gain significant public support
* Be useful within the internet domain
133
What does RFC stand for?
Request for comments
134
Describe the steps for a standard to be approved
○ Draft version is developed
○ Made available for consultation
○ The IESG gives final approval
○ Published as a Request for Comments (RFC)
. If the draft hasn’t progressed to RFC within 6 months it is withdrawn
135
Describe progression(Internet Society)
* To gain Standard status there must be at least TWO independent and interoperable implementations.
* If the implementations have been rigorously tested
* Internet standard is assigned along with
○ STD(standard) number
○ RFC number
136
What does ISO stand for?
International Standards Organisation
137
What does the ISO do?
Aim to promote standardisation and related activities to facilitate international exchange of goods and services.
138
Who does the ISO collaborate with?
International Electronic Commission (IEC)
139
Name and describe the 6 steps in the development process
1.) Proposal Stage - New proposal assigned to technical can and working group
2. Preparatory Stage - Groups prepare drafts. Once satisfied it is passed to the commitee for consensus
3.) Committee stage - ○ Registered at ISO central Secretariat
○ Distributed for balloting and comment
○ Once censuses is achieved it becomes a Draft International Standard (DIS)
4.) Enquiry Stage - DIS is given to ISO members where it is given a 5 month time limit for approval. If its approved it becomes a final draft international standard else its returned to the working group
5.) Approval Stage - ○ Redistributed for final acceptance
○ 2 months time limit
6.) Final Stage - Once agreed its an international standard
140
What does ITU stand for
Telecommunications Standardization Sector - its a UN specialized agency
141
Have a look at grouping and broadband
...
142
Describe process(Internet Society)
* Working in 4 year cycles
* Meetings of a world telecommunication standardization conference
* Work program for next cycle established
* Study groups created and abolished
* Process decided submitted questions (results in more groups)
There is an accelerated procedure (1988) allowing recommendations to be approved when they are ready
143
What does IEEE stand for?
Institute of Electrical and Electronic Engineers
144
Describe Initiating the project
* Driven by sponsors input to a collaborative group
A Project Authorisation Request (PAR) is produced
145
Describe a working group
* PAR approved
* Works to create and write standards
Anyone can be included in the group
146
What is ballot?
Asking members of an organisation to vote secretly on
147
Who approves the final standard
IEEE
148
How long are standards valid for?
* Standards are valid for 5 years
* After which they can be:
* Reaffirmed
* Revised
* Withdrawn
149
Frame relay circuits may be configured to have a committed information rate and _____________ information rate.
Excess
150
In frame relay, if the user sends faster than the committed information rate within the excess information rate, the network will:
Mark the data as being “Eligible for Discard”
