4.1 Internet Notes
Internet College Board Assignment
- Computer Networks and Systems
- How Computers Are Connected
- Packets
- The Internet
- Protocols
- Internet and Transport Layers
- Internet Layer
- Application Layer
- Web Servers:
- DNS - Domain Name Service
- Scalibility of the Internet
- Local Area Network (LAN)
- Intranet:
- Autonomous Systems (AS):
- The Internet consists of:
- Encryption
Computer Networks and Systems
- A computing device is a physical artifact that can run a program.
- A computer network is a type of computing system
- A path between two computing devices on a computer network (a sender and a reciever) is a sequence of directly connected computing devices that begins at the sender and ends at the receiver.
- Routing is the process of finding a path from sender to receiver.
- The bandwidth of a computer network is the maximum amount of data that can be sent in a fixed amount of time.
- Bandwidth is usually measured in bits per second.
How Computers Are Connected
- A computing system is a group of computing devices and programs working together for a common purpose.
- A computer network is a group of interconnected computing devices capable of sending or receiving data.
Packets
- A packet is a small amount of data sent over a network. Each packet also includes the source and the destination information.
- The message (file) is broken up into packets and sent in any order. The packets are reassembled by the recipient’s device. (Packet Switching)
The Internet
- The Internet is a computer network consisting of interconnected networks that use standardized, open (nonpropritary) communication protocols.
- Access to the Internet depends on the ability to connact a computing dvice to an internet connected device.
- Routing on the Internet is usually dynamic; it is not specified in advance
- Information is passed through the Internet as a data stream. Data streams contain chunks of data, which are encapsulated in packets
- Packets contain a chunk of data and metadata used for routing the packet between the origin and the destination on the Internet, as well as for data reassembly
- Packets may arrive at the destination in order, our of order, or not at all
- The World Wide Web is a system of linked pages, programs, and files
- The World Wide Web uses the Internet
Protocols
- A protocol is an agreed-upon set of rules that specify the behavior of a system.
- The protocols used in the Internet are open, which allows users to easily connect additional computing devices to the Internet.
- IP, TCP, and UDP are common protocols used on the Internet
- TCP does error checking and error recovery so it is slower
- UDP performs error checking, but it discards erroneous packets
- HTTP is a protocol used by the World Wide Web
Internet and Transport Layers
- Transport Layer - How the packets are sent, and for what
- Reliability - reliable - sender gets a receipt back, resend as needed TCP
- Unreliability - send and forget. UDP
Internet Layer
- IPv4: Example 192.168.24.1 32 bits, separated into 4 “octets” 8 bits long (0-255)
- Separated into 2 parts:
- Network (1-31)
- Device (32-network bits)
- Three targets that can be addressed using IP
- Unicast - A specific device. Internet wide access. TCP is used.
- Multicast - A group of devices. It is specific range of IP addresses. Internet-wide access. UDP is used.
- Broadcast - All devices. LAN-wide. Data stops at the router. UDP is used.
Application Layer
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Key protocols used:
- http. How to ask and receive data from web servers. Normally uses TCP, Port 80 at the transport layer
- https. Like http but with security. Usually uses TCP Port 443
Web Servers:
- Programs running on machines connected to the Internet
- Provides clients web pages - data linked to other pages using URLs (Uniform Resource Locations)
- The World Wide Web (WWW) is this network of linked data and programs, running over the Internet
DNS - Domain Name Service
- Applications that translate a human readable URL (e.g. www.mycompany.com) to an IP address
- DNS holds a database of mapping of names to IPs. Servers running DNS are spread across the internet
- There are large computers serving and managing these name/IP Mappings for each Domain (.com, .net, .gov, etc.)
- You use a DNS server every time you ask for a web page on a browser
Scalibility of the Internet
- The scalability of a system is the capacity for the system to change in size and scale to meet new demands.
- Able to change in size and scale to meet new demands
Local Area Network (LAN)
- Physical Connections, limited by hardware
- 1 to 100s of systems
Intranet:
- LANs connected by Routers within an organization
Autonomous Systems (AS):
- Large intranets linked together under the control and policies of major organizations. Large routers link networks with large telecommunications connections
The Internet consists of:
- Autonomous Systems linked together
- Large Routers linking Ass via special telecom means (Fiber, T3, Satellites)
- Major infrastructures - DNS (.com, .net, etc.), Cyber Operations
- Authentication measures such as:
- Strong passwords
- Multifactor authentication.
- Encryption: the process of encoding data to prevent unauthorized access
- Decryption: the process of decoding the data.
- Two common encryption approaches are:
- Symmetric key encryption involves one key for both encryption and decryption
- Public key encryption pairs a public key for encryption and a private key for decryption.
- The sender does not need the receiver’s private key to encrypt a message, but the receiver’s private key is required to decrypt the message
- Certificate authorities issue digital certificates that validates the ownership of encryption keys used in secure communications and are based on a trust model.