9.4 The Transmission Control Protocol - internet protocol (TCP IP) Flashcards
What does TCP / IP stand for?
Transmission control protocol / internet protocol.
What is TCP / IP?
A protocol that is used in all parts of the internet to enable different devices to communicate.
What are the 4 layers in the TCP / IP stack?
Application, transport, network, link
What is the role of the application layer in the TCP / IP protocol?
Selects and uses the correct protocol to transmit data. The layer interacts with the user with application software like a web browser.
What is the role of the transport layer in the TCP / IP protocol?
Establishes a virtual path between the sender and the receiver. Splits the transmission into packets. Each packet has a sequence number which identifies a packet’s position in relation to other packets that form part of the same message. They also contain the port number to be used which identifies the protocol in use.
What is the role of the network layer in the TCP / IP protocol?
Provides the correct IP addresses for each packet’s source and destination. Routers work within this layer, using the IP addresses on a packet to send it to its destination.
What is the role of the link layer in the TCP / IP protocol?
Controls physical connections between pieces of hardware in a network. Adds MAC addresses to packets which it receives from the network layer. MAC addresses change with every hop through a network
How does the TCP / IP protocol work at the receiving end?
Once a packet has been received by its recipient it is stripped of its extra information by reversing the TEP / IP stack.
What is the role of the link layer in the receiving end of TCP / IP protocol?
Removes MAC addresses from the packet
What is the role of the network layer in the receiving end of TCP / IP protocol?
Removes IP adresses
What is the role of the transport layer in the receiving end of TCP / IP protocol?
Uses the packet’s port number to determine the correct application to send the packet to. It also uses the packet’s sequence number to ensure that it is in the correct position relative to other packets in the same transmission.
What is the role of the application layer in the receiving end of TCP / IP protocol?
Receives the packets and displays the information to the user accordingly
What is a socket address?
When an IP address is combined with a port number.
What does a socket address do?
Identifies which of the applications on the recipient device a packet should be sent to.
What port(s) does the FTP (file transfer protocol) use?
20 and 21
what port(s) does the SSH (secure shell) use?
22
What port(s) does the HTTP (Hypertext transfer protocol) use?
80
What port(s) does the HTTPS (hypertext transfer protocol secure) use?
443
What port(s) does POP3 (post office protocol 3) use?
110 & 995
what port(s) does SMTP (simple mail transfer protocol) use?
25, 587 & 465
What is the purpose of FTP (file transfer protocol)?
Sending files between devices
Clients can access FTP servers
anonymously or non anonymously
What is the purpose of SSH (secure shell)?
Remote management of computers
Requires a username / password combination
Encrypts information during transmission
How does SSH (secure shell) work?
In order to access a remote computer SSH requires a username / password combination and encrypts information during transmission. SSH clients are pieces of software which can be used to make a TCP connection to a remote port. Once connection is established commands for application level protocols can be sent to the remote computer.
What is the purpose of HTTP (Hypertext transfer protocol)?
Sending web pages in text form from web
how does HTTP (Hypertext transfer protocol) work?
The server waits and listens for requests (most run 24/7)
The client sends an HTTP request for a web page to the server. The server receives the request. The server sends an HTTP response which encapsulates the requested page. The client receives the response and displays the web page in the web browser
What is the purpose of HTTPS (Hypertext transfer protocol secure)?
Performs the same function as HTTP, but encrypts information during transmission
Keeps information sent by clients secure
Helps to prevent information from being tampered with or modified during transmission
What is the purpose of POP3 (Post office protocol 3)?
Retrieving emails from an email server
Checks for and downloads any new messages
How does POP3 (post office protocol 3) work?
Email servers are responsible for receiving and sending emails. POP3 communicates with emails servers to check for and download any new messages
What is the purpose of STMP (simple mail transfer protocol)?
Sending emails
Used between a client and an email server
What are the two parts of which an IP address is split into?
A network identifier and a host identifier.
What are subnets?
Networks divided into smaller networks. Each subnet has a different network identifier.
How can subnet masks be used to identify the network identifier part of the IP address?
convert its IP address and subnet mask to binary
perform a logical AND operation on the two binary numbers
convert the result to decimal
what are the two types of IP addresses?
IPv4 and IPv6
Why was IPv6 introduced?
IPv6 addresses use 128 bits which allows for far more unique permutations than
IPv4 addresses
What is the differences between routable and non routable addresses?
Routable (public) IP addresses are globally unique whereas millions of devices can have the same non-routable IP address, provided they are not on the same network.
Why is Dynamic host configuration protocol (DHCP) used?
The number of available private IP addresses within a private network is limited
DHCP is used to assign IP addresses to devices as they join a network
How does dynamic host configuration protocol (DHCP) work?
DHCP uses a pool of available IP addresses to allocate IP addresses. IP addresses are allocated for the duration of a device’s session. Once a device leaves the network, the IP address that the device was using is returned to the pool for reallocation
What problem does the network address translation (NAT) get around?
If a device on the network sent a packet to the server, the server couldn’t respond to the computer directly because the computer’s IP address is non-routable - not globally unique.
Explain the functionality of network address translation (NAT)?
When a device on the private network needs to
communicate with a device on the Internet , it sends packets through the router,
which makes a record of the packet, replaces the private IP address of the computer with its own routable IP
address. When a response is received, it is sent to the router’s public IP address , which then forwards the response to the correct private IP address by using the record it made
when sending the packet
Why is NAT used?
Routers have two network interface cards, one for their private network and one for
the Internet. Routers have two IP addresses, a private address and a public address
When a computer on the private network communicates with a device on the Internet, the device couldn’t respond to the computer directly because the computer’s IP address is not globally unique, NAT gets around this problem.
When is port forwarding used?
When a client needs to communicate with a server that is connected to a private network.
How does port forwarding work?
The client sends packets to the public IP address of the router belonging to the server’s private network. The packets sent by the client contain the port number of the application running on the server that the client wishes to access. The private network’s router then forwards the packets to the server using NAT.
What is the client server model?
A network model, where clients send request messages to servers which reply to the clients with response messages. These messages may contain requested information, a confirmation that a requested action has been completed or a message explaining why the request action hasn’t been completed.
What is the web socket protocol?
An example of an API which operates in the application layer of the TCP / IP stack. The protocol can be used to provide a constant stream of information between to devices.
When is the web socket protocol used and why?
Because it allows for fast transmission of data by reducing the size of packet headers it is used in video streaming, online games and instant messaging.
What does CRUD stand for?
Create, retrieve, update, delete.
What is the SQL equivalent of each word in the CRUD acronym?
Create - INSERT
Retrive - SELECT
Update - UPDATE
DELETE - DELETE
What does REST stand for?
Representational state transfer?
What is REST?
A design methodology for online database applications that are queried with a web browser. It enables CRUD to be mapped to database functions (AQL)
What request methods does REST use and what is the SQL equivalent?
REST uses the HTTP request method.
Post - INSERT
GET - SELECT
PUT - UPDATE
DELETE - DELETE
How do databases deliver responses to queries?
Using JSON or XML.
what are the differences between JSON and XML?
JSON is more compact, easier to read, easier to create and faster for computers to process than XML. XML is sometimes seen to be more flexible than JSON.
How do thin-client networks work?
the majority of the network’s processing power belongs to servers which provide services and resources including storage and processing.
What are the advantages of thin-client networks?
Easy to add new clients to the network.
Clients themselves are inexpensive machines.
they also allow for greater centralised control of the network as software updates and security can be managed from the server.
What are the disadvantages of thin-client networks?
Require a powerful server which is expensive and requires expertise to set up and maintain.
how do thick-client networks work?
The clients are powerful enough to provide their own processing power and storage. This independence eliminates the requirement from a server, although it it possible for thick-client networks can make use of a server.
What are the disadvantages of a thick-client network?
More expensive to set up as it requires more powerful clients.
They are harder to maintain because there is no facility to issue updates and manage security from a central server.
What are the advantages of a thick-client networks?
They are cheaper in the long-run as no need for maintenance of an expensive server.
Less experience needed to maintain the server.
Less likelihood of data collisions
