4. Networking and the internet Flashcards
network scopes:
- PAN: personal area network (wireless headset, mouse, etc.)
- LAN: Local area network (one location)
- MAN: (metropolitan network)
- WAN: wide area network (several locations; possibly world wide)
network topologies:
det är hur man koppla ihop dem olika nätvärker.
- Bus: all machines are connected to a common communication line (a bus) (Ethernet) if one computer sends something it goes through the line and any connected computer can see/read it.
- Star: all other machines are connected to one central machine, called access point (WiFi) all communication goes through the access point and no one can see/read.
Network devices
- Hub: connects machines into a network (Bus topology)
- Access point: connects machines into a network (star topology)
- Switch (a smart hub): connects several busses (or machines) into a network; only sends necessary traffic between the busses. (good when you have a lot of PCs)
- Router: connects several networks into an internet (network of networks) can connect busses to stars. — Each router maintains a forwarding table describing to where messages should be send depending on their destination addresses.
An internet
network of networks. Connected by routers and can translate between different standards
Inter-process communication
Client/server: clients request server services, and servers serve client requests. 8Webbservers) it has to be able to serve many clients
Peer-to-peer(P2P): the peers provide service to and retrieve service from each other. (file sharing: music and films) it has to have a central register point. t.ex.: Pirate Bay. Skype
Distributed systems
- Distributed system: consists of software units that execute on several different computers. (have some or full control)
- Cloud computing: huge pools of shared computers can be allocated for use by clients as needed: Nvidia game cloud. (don’t have full control)
Internet architecture
- Started in the 1960s by research project of DARPA.
- Internet today is a commercial undertaking that links a worldwide combination of LANs and WANs involving millions of PCs.
- ISPs (Internet Service Providers): maintains the internet. (telecom)
- End systems/hosts: devices that individual users connect to Internet via some ISP.
- Hot spot: are where wireless Internet access is provided.
Internet addressing
- IP address: a unique identifying address to a computer on Internet (Internet protocol)
- ICANN (Internet Corporation for Assigned Names and Numbers) Gives IP addresses to ISPs.
- IPv4: 32 bits, usually written dotted decimal notation, t.ex. 10.200.45.5. | 8 bits can represent 255. and can have 8 billions addresses and they are out of stock now.
- IPv6: addresses are 128 bits, usually written in 8 groups of 4 hexadecimal digits, each group separated by (:) and some zeros omitted. t.ex. fe80::59c3:f315:b868:1b1f. (ipconfig)
Internet domains
- Domains: internet addresses by mnemonic names, t.ex. ilearn2.dsv.su.se, overseen by ICANN.
- Top level domains: country codes: .se and .com, .gov, .org, .net
- Domain name system (DNS): converts domain to IP addresses.
- DNS server (name server): provides address translation.
- DNS lookup: the process of using DNS to perform a translation.
Internet apps
- file transfer using FTP (file transfer protocol) one of the earliest.
- Remote computer access using SSH (secure shell protocol) PC connection to another PC.
- World Wide Web using HTTP (hypertext transfer protocol) websites.
- Email using SMTP (simple mail transfer protocol) and MIME (multipurpose internet mail extensions)
VoIP: voice over IP. - Multimedia streaming: real-time audio and video.
World Wide Web:
- Came in the start of the 1990s. Tim Berner Lee.
- Hyper text: documents linked by hyperlinks. texts and links to other texts/documents.
- HTML (hypertext markup language): to create documents.
- Browser (web clients): presents documents (and/or other materials) to a user.
- Webserver: provides access to documents (and/or other materials)
- URL (uniform resource locater): identifies a document (or other material) (today often called URI - uniform resource identifier)
- HTTP (hyper text transfer protocol: protocol for transferring documents (and other materials)
- client-side and server-side activities.
Internet software layers
- Application: constructs messages with addresses. prepare and receives messages
- Transport: chops messages into packets. it takes packets and sort them and makes them smaller. its not really transport.
- Network: handles routing through Internet. (Where to send the packets)
- Link: handles actual transmission of packets.
TCP/IP protocol suite
- Transport layer:
— Transmission control protocol (TCP) (reliable), can ask for the rest of packet. t.ex. messages and important data.
— User datagram protocol (UDP) (efficient) t.ex. Voice messages and realtime video. - Network layer:
— Internet protocol version 4 (IPv4)
— Internet protocol version 6 (IPv6)
Secutiry
Attacks:
- malware (viruses: infects your PC and can send it further, worms, Trojan horses: It pretends to be another program, spyware: spy on your device, phishing software: tries to make you give them information)
- denial of service (DoS): a server gets ask too many asks and get crashed.
- spam: via mail,
Protection:
- antivirus software: goes through PC and scan for viruses through specific bit patterns
- firewalls: dont allow any PC to connect or programs or data traffic.
- spam filters: like Gmail spam filter
- proxy servers: made up IP address to not let others see which is mine.
Encryption
An important part of Internet.
- HTTPS: secure version of HTTP using SSL(secure sockets layer) puts a layer over HTTP.
- Public key encryption: _encrypt by public key and decrypt by private key, or encrypt by private key (digital signature) and decrypt by public key.
- Certificate: package of name (identity) and public key.
- Certificate authorities: guarantee certificates authenticity.
