Networking Flashcards
Where is the HTTP protocol used?
Worldwide Web
What is the SMTP protocol used for?
Sending/receiving emails
What is the FTP protocol used for?
File transfers over a network
What is the SMB protocol used for?
Shared folder access over a network
What are port numbers used for?
Since applications do not have direct access to network hardware, the OS will help service the network requests. The OS will assign each application a random port number, so that data packets can be passed back to the correct application.
What does 127.0.0.1 refer to?
loopback network interface/localhost
What is the name of the packet forwarding model used by the TCP and UDP protocols?
Unicasting, whereby data is forwarded from server to server, until it reaches its destination.
What is packet forwarding?
It is the process where data is sent from computer to computer until it reaches its destination.
How does unicast packet forwarding work?
Each computer on the network is connected to a gateway. When an application needs to send data to a destination (IP address), the computer checks all other computers connected to it to see if the destination is listed there. If not, the data is forwarded to the computer’s gateway. At the gateway, the process is repeated. If the destination is not in the list of computers in the gateway, the data is forwarded to the next gateway and checked again until the destination is found and the packet is sent to the destination.
What happens when the DNS client encounters a domain name as the destination in a request?
- DNS client initiates a DNS lookup request, which is sent to the DNS server.
- DNS server checks its own DNS records for the domain name. If DNS record is found, DNS server returns response with the requested IP address. Otherwise, it forwards the request to the next DNS server.
- DNS lookup requests which are unable to find a match in a DNS server finally end up being forwarded to the root name server (part of a network containing other root name servers), which then returns a list of the authoritative name servers for the appropriate top-level domain
- This lookup request can then be forwarded to the appropriate top-level domain (TLD) server which contains the record.
What is the DNS cache?
It is a location where the computer stores the IP addresses returned for the domains. This is done so that next time a DNS lookup is requested, the computer checks in the DNS cache first, to minimize requests to the DNS server.
The DNS cache may need to be flushed if it gets outdated.
What do top level domains (TLDs) refer to?
Suffixes such as .gov, .edu and .com.
What is a protocol?
It is a set of rules for data transmission agreed upon by both the sender and receiver.
What is a protocol suite?
It is a collection of related protocols that are designed to work together.
What is the IP protocol?
It forms the Internet layer of the TCP/IP model.
What are 3 properties of computers in a Local Area Network (LAN)?
The computers in a LAN are usually in close proximity to each other
Computers which are a part of the same LAN can share files with each other over the network and utilitse the same hardware, such as printers and scanners
Computers in a LAN are typically connected using cables or wireless signals
What is a network operating system?
The network operating system provides the set of instructions which all computers on the LAN must follow
What is a server and client?
A server is a computer that provides services on a network
A client is a computer that requests services on a network
How is data transferred in a circuit-switched network?
A route from source to destination is reserved.
Data follows the same route to its destination
The returning data follows the same route back to the source
How is data transferred in a packet-switched network?
The data to be sent is broken up into packets
Packet headers determine the destination and method of transmission
Each packet may go by a different route to its destination
How is a circuit-switched network more advantageous than packet-switched network? (2 reasons)
Dedicated path for transmission, with guaranteed bandwidth
Information is sent in a continuous stream; there is no need for intermediate nodes to store and retransmit information or sequence information stored in the information.
Thus, there is low overhead required for transmission + less chance for data corruption.
How is a packet-switched network advantageous to a circuit-switched network?
Only the sender needs to be ready before transmission begins
If any segment of the network is disrupted, data packets can be routed around the disruption through other segments of the network
Different packets can travel in different routes, enabling greater utilisation of the network, more efficient, saves bandwidth and avoids congestion.
How is data communicated in a client-server model?
A client initiates the communication by sending a request to the server
The server sends data in a response back to the client
How is data communicated in a peer-to-peer model?
All computers may initiate communication by sending a request, or responding to a request.
There is no central server which contains all information
When should a peer-to-peer model be used over a client-server model? (2 reasons)
The existence of a server is not guaranteed, not feasible, or too expensive
Centralisation of data is not a key required feature
How is client-server model advantageous against peer-to-peer model? (4 reasons)
Server can control the access rights to files and programs
If one client fails, the server and other clients are not affected
Resources can be updated faster
It is easier to perform a backup of the resources on the server
What port numbers are well-known and used by system processes that provide widely used types of network services?
0 to 1023
What port numbers are dynamic/ephemeral ports and may be used for any purpose (usually temporary)?
49152 to 65535
What does the OS do during network requests?
The OS assigns each application a random (internal) port number during network requests, so that data packets can be passed back to the correct application.
What port numbers are registered ports and are assigned by the Internet Assigned Numbers Authority (IANA) by request?
1024 to 49151
Split the following URL address to its syntax.
https://docs.google.com/document/d/screwcomputingtheory/edit
Template: protocol://hostname:port/path
protocol: HTTPS
hostname: docs.google.com
port: 443 (not specified here, https follows 443 by default)
path: /document/d/screwcomputingtheory/edit
Explain the purpose of layering in TCP/IP model.
Enables programmers to specialize in a particular layer of the model.
Allows for standardized interfaces to be produced by networking vendors
Describe the function of Application Layer.
Consists of applications/programs and processes that use the network
Describe the function of Transport layer.
establish connection between applications of the sender and the receiver
Describe the function of Internet layer.
finds the best route to deliver data package
Describe the function of Link layer.
Transform data package to electrical signals or radio waves and transmits them to physical devices
