ch 14 fcs Flashcards
Network
computer network connects computing devices, called ‘network nodes’, together to enable the exchange of data and access to shared peripherals
Opposite of a network
standalone computer.
use of networks
share data and resources, internet services and to communicate with each other.
Networks models
outline rules and standards about how communications should take place over a network and between networks
2 types of Network models
1 TCP/IP 2.OSI
Data Encapsulation
This process adds extra information (protocol
details) to the data at each layer of the OSI or
TCP/IP model. These added features ensure
secure and reliable data transmission
Data De-encapsulation
encapsulated data is de-encapsulated. This means the added information (headers and trailers) is removed to reveal the original data.
what happens at the application layer
user enters URL The browser sends a DNS query to resolve the domain name into an IP address
The browser prepares an HTTP request to the server.
The HTTP request is handed over to the Transport Layer (Layer 4) via TCP.
what happens at the transport layer
It establishes a TCP connection between the client (browser) and the server using a three-way handshake.
It segments data into smaller chunks, assigns sequence numbers, and adds checksums for error checking.
It ensures reliable delivery by retransmitting lost or corrupted segments.
What is the three-way handshake in TCP?
SYN: The client sends a “synchronize” message to the server.
SYN-ACK: The server replies with a “synchronize-acknowledge” message.
ACK: The client sends an “acknowledge” message to complete the connection.
What information does TCP add to the data segments?
Source port : Identifies the client application.
Destination port (e.g., 80 for HTTP or 443 for HTTPS): Identifies the server application.
Sequence numbers and checksums for error detection and reliable delivery.
What happens at the Network Layer?
The TCP segments are encapsulated into IP packets.
Each packet includes:
Source IP address: The client’s local IP (e.g., 192.168.1.5).
Destination IP address: The server’s IP (e.g., 93.184.216.34).
The IP packet is forwarded to the Data Link Layer (Layer 2) for further processing.
What is DNS, and why is it used?
DNS (Domain Name System) translates human-readable domain names (e.g., www.example.com) into machine-readable IP addresses (e.g., 93.184.216.34).
What is the purpose of the three-way handshake in TCP?
It ensures a reliable connection is established between the client and server before data is transmitted.
What is the difference between a source port and a destination port?
Source port: Identifies the application on the client side (e.g., 12345).
Destination port: Identifies the application on the server side (e.g., 80 for HTTP or 443 for HTTPS).
What happens to the IP packet at the Data Link Layer (Layer 2
The IP packet is encapsulated into an Ethernet frame.
What is the purpose of the Data Link Layer (Layer 2)
It handles the packaging of data into frames and ensures reliable communication within the same local network (LAN).
What is the source MAC address in the Ethernet frame?
It’s the MAC address of the client’s Network Interface Card (NIC)
What is the destination MAC address in the Ethernet frame?
It’s the MAC address of the default gateway/router
What is a MAC address?
A unique identifier assigned to a device’s Network Interface Card (NIC) for communication on a local network.
encapsulation at the Data Link Layer
wrapping the IP packet with a header and trailer to create an Ethernet frame.
What happens at the Physical Layer (Layer 1)
The Ethernet frame is converted into bits and transmitted as electrical signals (via Ethernet cables or Wi-Fi) to the router.
What does the router do when it receives an Ethernet frame?
It takes off the Ethernet header and looks at the IP packet.
What happens if the IP packet is too large for the outgoing network?
The router fragments the packet to fit the Maximum Transmission Unit (MTU).
How does the router determine where to send the IP packet?
It checks the destination IP address and uses its routing table to find the next hop.
What happens after the router determines the next hop?
The packet is forwarded to the next router or the destination server through various hops.
What does the final router in the destination network do?
It creates a new Ethernet frame with the server’s MAC address and sends it to the server’s NIC.
What does the server’s NIC do when it receives the Ethernet frame?
It checks the destination MAC address, confirms it’s for the server, and passes the frame to the Network Layer (Layer 3).
What happens at the server’s IP Layer (Layer 3)
It checks the destination IP address, strips off the IP header, and hands the packet to the Transport Layer (Layer 4).
What does the server’s Transport Layer (Layer 4) do
It reassembles fragmented segments, checks the destination port number , and verifies data integrity using checksums.
What happens if the data at the Transport Layer is incorrect?
The segment is discarded, and the client is asked to resend the data.
What happens at the server’s Application Layer (Layer 7)?
The HTTP request is processed, and the server generates an HTTP response
How does the HTTP response travel back to the client?
It passes down through the server’s layers (Application → Transport → Network → Data Link → Physical) and travels through the network to the client.
What happens when the HTTP response reaches the client’s router?
It is passed up through the client’s layers (Physical → Data Link → Network → Transport → Application).
What is the purpose of the checksum at the Transport Layer?
To verify the integrity of the data and ensure it wasn’t corrupted during transmission.
