WEB AND INTERNET: |COMPLETE STUDY GUIDE WITH
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Route: Answer: datagrams between two network interfaces
Fragment: Answer: datagrams according to physical layer characteristics
Properties of IP Answer: Packet-switched: small packets/datagrams are sent over the networks
Connectionless: does not create an endless connection between a source and destination points
Datagrams are routed independently do not require a connection to be set up Datagrams are not
persisted in the IP layer beyond the first delivery attempt for each router (no re-retry)
unreliable
Transport: Answer: Deliver packets between (back and forth) two processes Reliable delivery
Segment packets Flow control limits the rate at which a sender transfers data
Naming: Ports and Sockets: Answer: a process is identified by a host IP address and a port
number
a socket is a combination of an IP address and a port
Notion of socket is in the TCP (Transmission Control Protocol) specification Assignment of
sockets to services is outside the TCP specification
TCP message: Answer: A TCP Message consists of: header data contents Data is provided by
the Web layer or the Application Layer The full TCP Message (Header + Data) becomes
payload for the IP layer below
TCP header: Answer: Mandatory section consisting of 20 bytes, followed by an optional
section. - A header identifies the source and destination ports of the message. - Sequence
number: number assigned to the first data byte of this segment (all bytes being numbered for
the current session) — ordering. - Acknowledgement Number: 1 + number of the byte so far
acknowledged. - Window size is number of bytes a receiver is ready to receive. Ports are 16
bits longs, and therefore have a value between 0 and 65535
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,Synchronisation (SYN) Answer: used for synchronising sequence number i.e. to tell the other
end which sequence number they should accept.
Acknowledgement (ACK) Answer: used to acknowledge packets which are successfully
received by the host
Finish (FIN) Answer: used to request for connection termination i.e. when there is no more
data from the sender, it requests for connection termination.
Connection-Based Communication Answer: IP is packet switched
Each datagram/fragment routed independently TCP is session-based (TCP connection)
Messages can only be sent once a session has been established between sender and receiver A
TCP connection is NOT a pre-planned route to send message
Maximum segment size: Answer: Application/Web data is segmented into multiple segments,
each with their TCP header 1. MSS, maximum segment size: the largest IP datagram that the
host can handle minus the IP and TCP header sizes 2. Segment size sharing (a.k.a. negotiation)
The MSS value is sent as a TCP header option only in TCP SYN segments Each side of a TCP
connection reports its MSS value to the other side The MSS value can vary between the
forward and reverse directions of a TCP data flow The sending host is required to limit the size
of data in a single TCP segment to a value less than or equal to the MSS reported by the
receiving host
Reliability: Answer: Acknowledgement messages (ACKs) are sent with an acknowledgement
number by the receiver of data to tell the sender that data has been received to the specified
byte
Reliability is achieved by the sender detecting lost data and retransmitting it
Two key mechanisms are used by TCP to identify loss of data
Duplicate acknowledgements
Time-out
Sliding Window: Answer: Flow control: avoid a situation in which the sender sends data too
fast, and the receiver is unable to receive it and process it reliably TCP uses flow control
protocol based on a sliding window mechanism In each TCP segment, the receiver specifies in
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,the receive window field the amount of additional data (in bytes) that it is willing to buffer for
the connection
Encapsolation Answer: A simplified version of the network stack is:
Application layer Example: web, email, chat
Transport layer Example: TCP, UDP
Network layer Example: IP
Link / Physical layer
So the flow is:
Application data → wrapped by Transport → then wrapped by IP → then sent by lower layers
TTL: Answer: TTL (Time To Live) is a field inside the IP packet header.
👉 It is a number that limits how long a packet can stay in the network.
Step 1: Packet starts with a TTL value
When a packet is created, it is given a TTL value, like:
TTL = 64 (very common)
TTL = 128
TTL = 255
Step 2: Each router reduces TTL
Every time the packet passes through a router:
👉 TTL = TTL − 1
Step 3: When TTL reaches 0
If TTL becomes:
TTL=0TTL = 0TTL=0
👉 The router drops (destroys) the pac
TOPOLOGY Answer: What is topology?
Topology means the shape or structure of a network.
It answers questions like:
Which devices are connected?
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, How are they connected?
What path can data take?
Think of it like a map of roads between cities.
MAC: Answer: If your laptop wants to send a frame to your router on the same local network,
it uses the router's MAC address.
So:
IP tells you the larger destination across networks
MAC tells you the next local device on the same link
IPv4: Answer: IPv4 is the older and most familiar Internet addressing system.
An IPv4 address is:
32 bits
usually written as 4 bytes
Example:
192.168.1.5
Each part is from 0 to 255.
What IPv4 does
It gives a logical address to a device on a network, so packets can be routed across multiple
networks.
Unlike MAC:
MAC is local
IPv4 works across the Internet
Problem with IPv4
IPv4 only has a limited number of addresses, because 32 bits is not enough for the whole
modern Internet forever.
That is one reason IPv6 was introduced
IPv6: Answer: What is IPv6?
IPv6 is the newer Internet addressing system.
It uses:
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100% ACCURATE QUESTIONS & ANSWERS | ACE EVERY
TEST | GUARANTEED EXCELLENCE.
Route: Answer: datagrams between two network interfaces
Fragment: Answer: datagrams according to physical layer characteristics
Properties of IP Answer: Packet-switched: small packets/datagrams are sent over the networks
Connectionless: does not create an endless connection between a source and destination points
Datagrams are routed independently do not require a connection to be set up Datagrams are not
persisted in the IP layer beyond the first delivery attempt for each router (no re-retry)
unreliable
Transport: Answer: Deliver packets between (back and forth) two processes Reliable delivery
Segment packets Flow control limits the rate at which a sender transfers data
Naming: Ports and Sockets: Answer: a process is identified by a host IP address and a port
number
a socket is a combination of an IP address and a port
Notion of socket is in the TCP (Transmission Control Protocol) specification Assignment of
sockets to services is outside the TCP specification
TCP message: Answer: A TCP Message consists of: header data contents Data is provided by
the Web layer or the Application Layer The full TCP Message (Header + Data) becomes
payload for the IP layer below
TCP header: Answer: Mandatory section consisting of 20 bytes, followed by an optional
section. - A header identifies the source and destination ports of the message. - Sequence
number: number assigned to the first data byte of this segment (all bytes being numbered for
the current session) — ordering. - Acknowledgement Number: 1 + number of the byte so far
acknowledged. - Window size is number of bytes a receiver is ready to receive. Ports are 16
bits longs, and therefore have a value between 0 and 65535
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,Synchronisation (SYN) Answer: used for synchronising sequence number i.e. to tell the other
end which sequence number they should accept.
Acknowledgement (ACK) Answer: used to acknowledge packets which are successfully
received by the host
Finish (FIN) Answer: used to request for connection termination i.e. when there is no more
data from the sender, it requests for connection termination.
Connection-Based Communication Answer: IP is packet switched
Each datagram/fragment routed independently TCP is session-based (TCP connection)
Messages can only be sent once a session has been established between sender and receiver A
TCP connection is NOT a pre-planned route to send message
Maximum segment size: Answer: Application/Web data is segmented into multiple segments,
each with their TCP header 1. MSS, maximum segment size: the largest IP datagram that the
host can handle minus the IP and TCP header sizes 2. Segment size sharing (a.k.a. negotiation)
The MSS value is sent as a TCP header option only in TCP SYN segments Each side of a TCP
connection reports its MSS value to the other side The MSS value can vary between the
forward and reverse directions of a TCP data flow The sending host is required to limit the size
of data in a single TCP segment to a value less than or equal to the MSS reported by the
receiving host
Reliability: Answer: Acknowledgement messages (ACKs) are sent with an acknowledgement
number by the receiver of data to tell the sender that data has been received to the specified
byte
Reliability is achieved by the sender detecting lost data and retransmitting it
Two key mechanisms are used by TCP to identify loss of data
Duplicate acknowledgements
Time-out
Sliding Window: Answer: Flow control: avoid a situation in which the sender sends data too
fast, and the receiver is unable to receive it and process it reliably TCP uses flow control
protocol based on a sliding window mechanism In each TCP segment, the receiver specifies in
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2
,the receive window field the amount of additional data (in bytes) that it is willing to buffer for
the connection
Encapsolation Answer: A simplified version of the network stack is:
Application layer Example: web, email, chat
Transport layer Example: TCP, UDP
Network layer Example: IP
Link / Physical layer
So the flow is:
Application data → wrapped by Transport → then wrapped by IP → then sent by lower layers
TTL: Answer: TTL (Time To Live) is a field inside the IP packet header.
👉 It is a number that limits how long a packet can stay in the network.
Step 1: Packet starts with a TTL value
When a packet is created, it is given a TTL value, like:
TTL = 64 (very common)
TTL = 128
TTL = 255
Step 2: Each router reduces TTL
Every time the packet passes through a router:
👉 TTL = TTL − 1
Step 3: When TTL reaches 0
If TTL becomes:
TTL=0TTL = 0TTL=0
👉 The router drops (destroys) the pac
TOPOLOGY Answer: What is topology?
Topology means the shape or structure of a network.
It answers questions like:
Which devices are connected?
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3
, How are they connected?
What path can data take?
Think of it like a map of roads between cities.
MAC: Answer: If your laptop wants to send a frame to your router on the same local network,
it uses the router's MAC address.
So:
IP tells you the larger destination across networks
MAC tells you the next local device on the same link
IPv4: Answer: IPv4 is the older and most familiar Internet addressing system.
An IPv4 address is:
32 bits
usually written as 4 bytes
Example:
192.168.1.5
Each part is from 0 to 255.
What IPv4 does
It gives a logical address to a device on a network, so packets can be routed across multiple
networks.
Unlike MAC:
MAC is local
IPv4 works across the Internet
Problem with IPv4
IPv4 only has a limited number of addresses, because 32 bits is not enough for the whole
modern Internet forever.
That is one reason IPv6 was introduced
IPv6: Answer: What is IPv6?
IPv6 is the newer Internet addressing system.
It uses:
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