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. An end to end connection between the sender and the receiver. The layer then 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. Also contained in each packet is 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 (media access control) addresses are assigned to every device that can connect to a network by their manufacturer and are unique to that device. The MAC addresses change with ever hop through a network.
How does the TCP / IP protocol work at the receiving end?
Once a packet has been received by its intended recipient it is stropped of its extra information by reversing the TCP / IP stack. Firstly the link layer removes MAC addresses from the packet. Next the network layer removes the IP addresses before the transport layer uses the packet’s port number to determine the correct application to send the packet to. The transport layer also uses the packet’s sequence number to ensure that it is in the correct portion relative to other packets in the same transmission. Finally the application layer receives the packet 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?
A socket address 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. FTP client software can run on devices, allowing them to connect to FTP servers which send files requested by the client. Clients can access FTP servers anonymously or non-anonymously by logging in with a username and password.
What is the purpose of SSH (secure shell)?
to allow remote management of computers, allowing computers to be accessed and controlled remotely.
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)?
Web servers hold web pages in text form which they can deliver to clients using this protocol.
how does HTTP (Hypertext transfer protocol) work?
Application software on the client receives these text files and renders them as web pages.
What is the purpose of HTTPS (Hypertext transfer protocol secure)?
Web servers hold web pages in text form which they can deliver to clients using this protocol, but then encrypts information during transmission. It keeps information being sent by clients secure and prevents information from being tampered with or modified during transmission.
What is the purpose of POP3 (Post office protocol 3)?
Used for retrieving emails from an email server.
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)?
Used for sending emails. SMTP is used between 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’s the difference between a host and network identifier?
Each of the computers in a network she’s the same network identifier but has its own host identifier.
What are subnets?
Networks divided into smaller networks. Each subnet has a different network identifier.
What is a subnet mask?
Used to determine the network identifier part of an IP address.
How does subnet masking work?
Convert the IP address of the device to binary. Then convert the subnet mask to binary perform a logical AND operation on the 2 then convert it back to deanery to get your network identifier.
what does increasing the bits assigned to a network identifier of an IP address do?
Increases the amount of different subnets a network can have.
what does increasing the bits assigned to a host identifier do?
Increases the amount of devices that can be connected to each subnet simultaneously.
what are the two types of IP addresses?
IPv4 and IPv6
Describe the structure of IPv4 addresses?
Dotted quad numbers, they consist of four parts that are separated by dots. Each of the four parts are assigned one byte allowing for numbers from 0 to 255 to be represented.
How many unique IP addresses can IPv4 allow and why was IPv6 created?
Allows for 256^4 unique IP address. They are now in short supply. As there is a rapid increase of the number of devices on the internet that require a routable IP address a new version of IP address had to be created (IPv6)
Describe the structure of IPv6?
Formed pf eight blocks separated by colons. Each block contains four hexadecimal characters. It uses 128 bits instead of 32 allowing for far more unique permutations.
What is the need for routable and non-routable IP addresses?
If every device that is connected to a network had its own IIP address there wouldn’t be enough IP addresses to go around. So each home or business that requires internet access has a small number of public IP 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.
What is the role of global authorities in assigning IP addresses?
To ensure that the same routable IP address is never issued twice
Why is Dynamic host configuration protocol (DHCP) used?
The number of private IP addresses within a private network is limited. Assigning each device on a network its own private IP address would not be sensible as that device may leave and never join again resulting in a wasted IP address to prevent therefore this protocol is used to prevent wasted IP addresses.
How does dynamic host configuration protocol (DHCP) work?
It assigns IP addresses to devices as they join a network. It uses a pool of available IP addresses to allocate IP addresses to new devices for the duration of their session. Once a device leaves the network the IP address that the device was using is returned to the pool for allocation to a new device.
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 before replacing 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
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 an API (application programming interface)?
A name given to a set of protocols relating to how different applications communicate with each other. They define how interaction between the applications should be carried out, allowing applications to make use of other applications.
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.
the connection created by the web socket protocol is full-duplex what does this mean?
Data can be transmitted in both directions at the same time.
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 do the four commands of CRUD do?
They are commands that can be used to query online databases. Each of the commands has an SQL equivalent.
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.
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
What are the steps in order for a client to connect to a database?
- Client-server request made by the client to the web browser
- Web browser responds with the requested web page (which is delivered as a text file).
- This text file contains JavaScript which loads an API. The APO uses REST to enable the database server to be queried by the client with the use of HTTP request methods.
- The client sends HTTP requests to the database server
- The database server responds to the client’s request using either JSON or XML.
- The client’s browser processes the JSON or XML and displays the response to the user.
What does XML stand for?
Extensible markup language
What does JSON stand for?
JavaScript object notation.
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.
What are the 2 ways to configure a network?
thin-client or thick-client
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
