lab terms Flashcards
1
Q
Transport layer
A
This layer has two important functions - distinguishes individual connections at the same device using ports and also controls the speed of data flow (co-called flow control)
2
Q
Does the UDP provide connection-oriented communication?
A
No
3
Q
Which layer performs routing?
A
Network layer
4
Q
Devices that are completely independent from any protocol
A
Hub, repeater
5
Q
Local area network (LAN)
A
‘Local’ refers to the networks of relatively small size, which usually connect end stations together and have connection to Wide area network
6
Q
What are the three main functions of TCP?
A
- Guarantee data delivery in a correct order
- Distinguish individual connections
- Data flow control
7
Q
DHCP(Dynamic host configuration protocol)
A
DHCP is a service for automatic configuration of network interfaces in one segment of local network. DHCP works only for IPv4 addresses (DHCPv6 is used for IPv6)
8
Q
Can the individual layers be changed without change in functionality of neighboring layers?
A
Yes
9
Q
Define the mask
A
A mask is a 4-byte number that binary starts with a sequence of ones which is followed by a sequence of zeros. The size of both sequences is arbitrary. The mask is paired with a specific IP address
10
Q
3 protocols of network layer
A
IPv4, IPv6, IPX-SPX
11
Q
Each network service expects to communicate on a specific…
A
port
12
Q
Are routers able to interconnects networks of a completely different types? If yes, why?
A
Yes, they can, because physical router ports, in contrast with switch and hub, can have different physical and link layers
13
Q
How does TCP distinguish individual connections and services?
A
By using source and destination port, which are represented by a 16-bit numeric value
14
Q
Does TCP guarantee data delivery in a correct order?
A
Yes
15
Q
Switch
A
Switch is a device used for station interconnection in one local network segment. This device basically only forwards data frames between its ports based on the MAC address
16
Q
Physical layer
A
The first layer of ISO/OSI model that takes care of data transfer thriugh physical medium
17
Q
Are there any switches that work on the network layer?
A
Yes, Layer 3 switches
18
Q
Can different LANs use the same private IP addresses ranges?
A
Yes, because LANs use private IP addresses which are unique only within particular LAN
19
Q
How to check that a device can communicate with different networks?
A
The device has its own simple routing table. If everything is OK, the routing table contains both special entries
20
Q
Which architecture does DHCP have?
A
Client-server
21
Q
Name the ways of classifying IPv4 and IPv6
A
Class and classless, for IPv6 it is only classless addressing
22
Q
What happens to the link layer header while routing?
A
It is discarded and replaced by the new one
23
Q
What are the phases of TCP connection?
A
Establishment, data transfer, termination
24
Q
On which layer does the switch work?
A
The Link Layer
25
Pure virtual interfaces lack this layer (loopback)
Physical layer
26
When the switches can drop the packets?
In case of congestion
27
Why repeaters and hubs are slow?
Because their principle allows only one network interface to communicate within the network segment
28
Does NAT change port numbers?
Yes
29
A device connected to a network through a network interface is
a single-port router from a certain point of view. Instead of forwarding data between networks, it only sends and receives data from the network
30
Firewall
By a firewall, we mean a router that, in addition to routing, allows to apply a security policy (such as packet filter or proxy server)
31
Dynamic NAT
We talk about dynamic translation if we translate a range of IP addresses into one IP address
32
At which layer of ISO/OSI model TCP takes place?
On the trasport layer
33
What is defined on second layer of ISO/OSI model?
MAC address
34
What is dynamic routing?
When the routing table can be filled automatically using routing protocols(RIP, OSPF)
35
Is there any difference between manual and automatic IP address from communication point of view?
No, there is no difference (It is just some kind of address assigned to the interface)
36
How to find a MAC address in OS unix?
ifconfig -a
37
Network address translation (NAT)
Network Address Translation (NAT) is a complementary service of router. Basically, it is a packet filter that changes packet headers for network and transport layers based on set rules
38
2 protocols of transport layer
TCP, UDP
39
On which layer of ISO/OSI model does UDP take place?
On the transport layer
40
The hardware part of the interface
For example, the port to which we connect the cable + combined electronics
41
How is the default gateway entry added to the routing table?
Manually
42
How splitting of address space works?
We assign a so-called network address to each segment. This address determines, in addition to the identification, the total range of IP addresses that belong to that segment. The IP address is then divided into two parts: the network address and the interface address in that network
43
What is the difference between router ports and switch/hub ports?
Physical router ports can have, in contrast with switch and hub, different physical and link layers. Routers then are able to interconnect networks of a completelly different types (for example wired and wireless)
44
Can you delete the entries of directly connected networks from the routing table?
Typically, you cannot delete such entry from the routing table by standard means
45
Network card
Physical layer in a network interface that is always implemented by hardware
46
How to prevent private addresses getting outside of their local network?
Network address translation(NAT)
47
Which endpoints define the TCP connection?
Client IP address, client port number, server IP address, server port number
48
How do repeater and hub differ?
1. Hub is multi-port, the repeater is 2-port
2. Hub can divide electrical signal
49
What is a static routing?
When entries in the routing table are manually entered by the administrator
50
Who performs routing?
Routing is performed by a router that contains a routing table
51
Example of purely hardware network interface
Repeaters
52
Ranges of private IP addresses:
10.0.0.0/8
172.16.0.0/12
192.168.0.0/16
53
Can MAC addresses be propagated through the router? Why?
No, they can't. Because during routing the original link layer header is discarded and replaced by the new one
54
Static NAT
This is the translation of one IP address into one IP address
55
Where the broadcast MAC is used?
When we need to send data to all output ports of a switch and it is also used in ARP and DHCP
56
What is routing?
Routing is a packet forwarding mechanism between individual network segments based on a routing table
57
Does the UDP control data flow?
No
58
What can identify incoming connections?
The source port
59
When is the routing being browsed by the router?
When processing each packet
60
Segment of local network
Local networks are divided into segments, each segment is assigned its range of IP addresses which are determined by the network IP address and mask. If we refer to a "network" in the context of addressing, we mean that it is a network defined by network IP address and mask and that it is a single segment of the local network. Connecting devices in each network segment are hubs and switches. Segments are connected with routers
61
Router
Router is a network device, which separates individual network segments. Its basic activity is ensuring communication between network segments
62
When the packet is being sent to the default gateway?
When a matching network in the routing table is not found
63
How to find a MAC address in OS Windows?
By command in terminal ipconfig/all
64
What is routing?
This is a packet forwarding mechanism between individual local network segments based on a routing table
65
How to use mask to get the network address and the rest IP addresses?
The bits in the IP address that correspond to the positions of binary ones in the mask are the network address and the rest of the IP address is the interface address in that network
66
Why do we need the splitting of address space?
If the entire address space were monolithic, it would be a huge burden for network administrators, also if the network was not splitted, broadcast would be delivered to all interfaces throughout the address space (over 4 billion interfaces)
67
How can DNS convert the name address to IP address?
By the other domain name servers or by using its database
68
3 link layer protocols
Ethernet, frame delay, HDLS
69
ARP protocol
ARP (Address Resolution Protocol) finds the binding between IP address and MAC address. The protocol helps to find out what is the MAC address of the interface when we know its IP address. ARP sends a data frame with a message that contains the query: "Who has IP address 10.0.0.2?" and as the destination MAC address broadcast is used, so the frame is delivered to all interfaces in the current segment. The interface that has this IP address responds and thus reveals its MAC address (each data frame has its source and destination MAC address).
70
What is the destination MAC address of the ARP message?
Broadcast MAC address
71
Must the default gateway be marked for routing algorithms?
Yes
72
What will happen if the default gateway is missing?
You will be able to communicate only in the current network segment
73
What is the one common feature of TCP and UDP?
They introduce transport layer addressing
74
Do routers forward broadcast communication?
No
75
Name the devices that work on a physical layer of ISO/OSI model
Repeater, hub
76
By which devices we connect the segments of a local network?
Hubs and switches
77
What type of security policy can we use on the Firewall?
Packet filter or proxy server
78
What serves for identification of network interface and network itself?
IP address
79
Does UDP acknowledge data?
No
80
How many packets does the establishment phase of TCP use?
3
81
This layer ensures that there is no collision on the shared medium
Link layer
82
ISO-OSI model
This model developed in 80s divide the processing of network communication into several layers
83
Which phase of the TCP connection uses the 3-way handshake?
Establishment
84
Domain name system(DNS)
Domain Name System is a network service, which, using its database or thriugh the communication with other domain name servers, can convert a name address to IP address. For example, fit.cvut.cz → 147.32.232.248
85
How to recognize the directly connected network entry?
By an IP address of direction, which is 0.0.0.0
86
What information does DHCP server provide to a client?
Assigned IP address and mask, IP address of default gateway(most commonly IP of the router, where DHCP is running), IP address of DNS server
87
The MAC address is the hardware part of each..
Network interface
88
Link layer
The second layer of ISO/OSI model that is responsible for data transfer between two or more devices, typically in one LAN segment
89
CAM table
CAM table for each port creates a list of MAC addresses that access the switch via this port
90
On which ISO?OSI layer the IP address is defined?
On the network layer
91
Do routers accept the broadcast communications?
Yes
92
How and when the direcly connected network entries are added to the routing table?
These entries are added to the table automatically by the operating system each time an IP address is set for any network interface
93
WHAT IS AN IDENTIFIER IN TCP?)))))))))))))))))))))))))))))))))))
PORTS)))))))))))))))))))))))))))))))
94
How to distinguish different connections?
Using ports
95
What entries does the routing table have?
IP address and mask of the destination network, direction to this network(represented by the IP address of the neighboring router or in case of point-to-point connection the output network interface) and path quality
96
Example of pure software network interface
Virtual network adapter in combination with a network tunnel; or loopback
97
What address we use to communicate within one local network?
MAC address
98
How does assigning of IP address happen?
Network interface, which is connected to the network without configuration knows only its MAC address. Using MAC broadcast it sends discover message, which means a search for the presence of DHCP server. If server responds, client sends a request for IP address. Server sneds a message with assigned IP address and a period of validity for that address. After this time, DHCP client should ask for a new one (but it is not his obligation).
99
Tell me about bytes of MAC address
The first three bytes is unique for each manufacturer and can be uniquely identified in each MAC address. The second three bytes is unique to each network interface manufactured by one manufacturer. Altogether, both parts form a unique worldwide address, so collisions caused by address matching cannot happen under standard local networking conditions
100
What is a default gateway?
The default gateway is the IP address of the router that is on the way to the Internet or the larger network
101
How does TCP guarantee data delivery in the correct order?
By server-client communication, when the client establishes a connection with the server using the three-way handshake method and each sent packet is confirmed by the packet receiver
102
Which process is responsible for link layer header change?
Routing
103
How does data transfering in link layer works?
Layer adds its header and checksum to the communication data from the network layer
104
What does NAT change?
IP address and port numbers
105
Which layer performs logical addressing?
Network layer
106
Connection(TCP)
An error-free point-to-point channel that delivers messages or bytes in the order in which they were sent
107
Which purposes does the UDP have?
Only one - to distinguish connections and services using numeric ports
108
Network interface
The network interface is a hardware or software element that allows the operating system to communicate over the network
109
Are all layers of ISO/OSI model implemented on each device?
Not always
110
User Datagram Protocol (UDP)
UDP is the sister protocol of TCP on the transport layer of the ISO-OSI model
111
IP address
Internet Protocol address or network address has length of 4 bytes (IPv4) or 16 (IPv6) and is defined at the network layer of ISO-OSI model. It serves for identification of individual network interface and network itself. IP address is used for the communication between individual network interfaces and whole networks. IP address are entered manually, in case of network interface DHCP (IPv4) or autoconfiguration (IPv6) service can be used. IP address is in most cases paired with network mask
112
How is data flow control made by TCP?
By the sliding window communication scheme
113
How the default gateway can be recognized in a routing table?
By the IP address of the source network, which is 0.0.0.0
114
On which layer does the router operate?
Mainly on the third (network) layer of ISO-OSI model, but mostly can also handle protocols of the upper layers
115
Is there any difference between manual and automatic IP address from administration point of view?
Yes, the automatically assigned addresses may change , DHCP client periodically requests an IP address. In a network with DHCP service, we can work with manually configured IP addresses, it is just necessary to enter the correct configuration consistent with the configuration assigned by the DHCP server
116
How many and what types of NAT do we have?
2 types. Dynamic NAT and static NAT
117
How does the direction network represented in case of point-to-point connection?
It is represented by output network interface
118
Give the example of dynamic NAT
The typical situation in which it is used is where multiple LAN interfaces need to access the Internet. In this case, they must appear on the Internet under the address with which the router is connected to the Internet
119
Network layer
Serves for communication between segments of local network
120
MAC address
Media Access Control address or link address is 6 bytes sequence number, which is unique for each network interface. Serves for communication in one segment of local network
121
MAC broadcast
The broadcast MAC address is used for delivering a frame to all interfaces in the current segment, it sends data to all output ports. The address consists of binary ones
122
Transmission Control Protocol(TCP)
TCP provides connection-oriented communication on the transport layer of the ISO-OSI model
123
This layer is implemented on all physical network devices
Physical layer
124
What is the difference between public and private IP addresses?
Public are used within the Internet, private in local networks
125
What can we use to connect LAN and WAN?
Network address translation(NAT)
126
What is the destination of MAC address of ARP request and why?
In an ARP request, the destination MAC address is set to the broadcast address FF:FF:FF:FF:FF:FF. Since the ARP requester does not know the MAC address of the target device, it uses the broadcast address to ensure that all devices on the local network receive the request
127
When is ARP protocol called or when the record is added to ARP table?
ARP protocol is called when a device needs to find the MAC address corresponding to an IP table, joins a network or a devise changes its IP or MAC address. The record is added to ARP table when the ARP reply is received
128
How many messages have DHCP client and server to exchange for first IP address assignment?
Discover, offer, request, ACK
129
What are the destination MAC addresses of all messages?(DHCP)
Discover: broadcast, offer:client MAC address, request:broadcast, ACK: client MAC address
130
What are the IP addresses of all messages?
DHCP Discover:
Source IP: 0.0.0.0
Destination IP: 255.255.255.255 (broadcast)
DHCP Offer:
Source IP: Server's IP address
Destination IP: 255.255.255.255 (broadcast) or the client's MAC address
DHCP Request:
Source IP: 0.0.0.0
Destination IP: 255.255.255.255 (broadcast)
DHCP ACK:
Source IP: Server's IP address
Destination IP: Client's assigned IP address
131
What information contains DHCP offer message?
Offered IP Address
Subnet Mask
Default Gateway
Router (Gateway) Addresses
DHCP Server Identifier
DNS Server Addresses
132
Are default gateway and DNS required for communication in local network segment?
No, the default gateway and DNS server addresses are not required for communication within a local network segment
133
In which situation we will need default gateway and DNS?
Default Gateway: Required for routing traffic to networks outside the local subnet, such as accessing the internet or communicating with devices on different subnets
DNS Server: Required for translating domain names to IP addresses
134
Does user before communication starts need to know MAC addresses of other interfaces connected to the same segment?
No, the user or the device does not need to know the MAC addresses of other interfaces connected to the same network segment before communication starts. The Address Resolution Protocol (ARP) handles the discovery of MAC addresses dynamically.
135
Does user before communication starts need to know IP addresses of other interfaces connected to the same segment?
No, the user does not need to know the IP addresses of other devices connected to the same network segment before communication starts. However, the device initiating communication typically needs the IP address of the target device to establish communication
136
Why do we need to specify an output interface when using the ping utility?
When using the ping utility, specifying an output interface might be necessary in certain situations to ensure that the ICMP Echo Request packets are sent through the correct network interface
137
Does the user need to know the IPv6 addresses of the other interfaces before starting communication in the LAN segment?
The user generally needs to know the IPv6 address of the target device to initiate communication
138
Does the user need to manually configure IPv6 addresses to communicate in the LAN segment?
Manual configuration of IPv6 addresses is not necessary due to SLAAC and DHCPv6, which allow devices to automatically configure their own IPv6 addresses
139
How does NAT distinguish particular connections?
By ports
140
How can help hardware acceleration of NAT?
Hardware acceleration of NAT (Network Address Translation) can significantly improve network performance and efficiency
141
Will another NAT set in front or behind existing NAT solve shortage of possible open connections?
No
