Week 5 - The Internet Flashcards
Describe what the Internet is?
- Gigantic collection of computers.
* Billions of computers connected to the internet.
What is an ISP?
- Internet service provider.
* BT, Virgin, Sky.
How does a business/ university connect to the internet?
- They have a NIC which is directly connected to a LAN inside the business/uni.
- The LAN is connected to an ISP using high-speed data line/ fibre optic.
How do universities specifically connected to the internet?
• After connecting their NIC to their LAN, the uni is connected to JANET which is a network backbone.
What is JANET for uni’s?
- Joint Academic Network
* Network backbone for academic LAN’s.
Who and when was the internet formed?
- Developed by U.S. Department of Defence in 1969.
* Enabled communication over long distance research centres.
What was the first WAN and what was later introduced?
- ARPAnet was first WAN.
* SMTP later introduced for mail.
What was introduced in the early & late 1980’s after the first WAN?
- TCP & IP
* Domain Name System (DNS)
When did the entre for European Nuclear Research release the first WWW software version?
• 1992
Describe what interoperable means?
- Computers connected to the internet can communicate with each other.
- Due to standardised protocols.
What are 2 properties of the internet?
- Easy to use - available to all users.
* Low cost - Cost shared across all users.
What is the Internet Design Principles?
- How to build a system that can handle communication between 2 computers which may:
- any type of OS
- connected using any type of network.
- be at any physical location.
What are the 5 main principles of the Internet Design Principles? Int Uni Lay Sim End
- Interoperability
- Uniform naming & addressing
- Layering
- Simplicity
- End-to-end protocols
What is interoperability in the Internet Design Principles?
- Independent implementations of internet protocols working together.
- Systems assembled using client & server computers.
- Buyers & sellers not required to update simultaneously.
What is Uniform naming & addressing in the Internet Design Principles?
- Each device connected must have an IPv4 address.
* IPv6 being introduced.
What is Layering in the Internet Design Principles?
- TCP/IP model
* Each layer does a specific role to send data from user-to-user.
What is Simplicity in the Internet Design Principles?
- Hides complexity of levels.
* Applications programmers insulated from complexities of different network devices.
What are End-to-end protocols in the Internet Design Principles?
- Interpretation of data happens on the sending & receiving systems.
- Hides the internal structure of the network.
What does the DNS (Domain Name Server) do?
• Offer a uniform method of translating IP addresses to human-readable names.
What is the TCP/IP model?
- Application (HTML)
- Transport (TCP/UDP)
- Network (IP)
- Link (Ethernet)
Describe the link layer in the TCP/IP model?
- Used to route & transport internet traffic.
* Ethernet, token ring, asynchronous transfer mode.
What is the physical address?
- Media Access Control
* Unique identifier assigned to most network adaptors or NIC’s by the manufacturer.
Describe what hubs are?
- Common connection points for devices in a network (LAN)
* Packet arrives at a hub, it is copied across the LAN.
What are 3 problems with hubs?
- Scalability - bandwidth consumed quickly.
- Latency - Nodes have to wait for moment to transmit to avoid collisions.
- Network failure - Wrong broadcast speeds interfere.
Describe what a switch does?
- Selectively forwards packets between LAN segments.
- Forwards data to intended destination.
- Uses MAC address to forward data.
Describe the network layer of the TCP/IP model?
• Routing & addressing protocols are handled here.
Describe what packets are?
- Chunks of data in a numbered order.
* Get sent along different routes to destination.
What is the IP (Internet Protocol)?
- Routes packets around the Internet.
* Time to live (exceeded max hops)
What does a packet consist of?
- Header - source, destination, error detection.
* Payload - packet data
Name 3 examples of control info for packet transmission?
- Header length - size of header info.
- Time to live.
- Header checksum
Describe the purpose of routers?
- Forwards packets to other routers.
* Each router has a local map of networks based off IP addesses.
Describe the transport layer?
- Maintains flow control of data & provides for error checking.
- TCP used.
- Abstraction of reliable byte stream.
Describe what the TCP is?
• Establishes initial connection & maintains it for length of connection between two nodes.
How does the TCP establish a connection between 2 nodes?
- Sends a request message to destination node containing unique address & port number.
- Receiver returns acceptance message containing unique address & port number.
What happens if the receiver doesn’t respond to the TCP connection message?
• Packets are retransmitted until receiver sends an acceptance message.
What is UDP (User Datagram Protocol)?
- An alternative method to TCP.
- Is time-sensitive & drops packets that are delayed.
- Good for audio & video streaming.
Name 2 disadvantages of UDP?
- Doesn’t use hand-shaking.
- Doesn’t guarantee reliable data transmission.
- Datagrams may disappear or arrive out of order.
- No error checking
Describe the Applications layer of the TCP/IP model?
- Supports applications & end-user processes e.g. WWW, email.
- Has quality of service, user security, authentication.
