- A computer network is a set of computers sharing resources
- Communications are commonly established using cables or radio waves
- Network nodes are identified by a network address (ex: IP address)
- That can be accompanied by a more memorable hostname
- The Internet is a global system of interconnected computer networks, with:
- Local scopes, with private network addresses (ex: LANs, RFC 1918)
- A global scope, with public networks addresses managed by the IANA
- Made accessible by ISPs
- ISO: International Organization for Standardization
- FCC: Federal Communications Commission
- 1985: made ISM radio bands license free (enabling Wi-Fi, LoRa, ...)
- IEEE: Institute of Electrical and Electronics Engineers
- The IEEE 802 defines standards for LAN, PAN, MAN, notably:
- IEEE 802.1: Higher Layer LAN Protocols Working Group
- IEEE 802.3: Ethernet (wired)
- IEEE 802.11: Wireless LAN (WLAN) & Mesh (Wi-Fi certification)
- The IEEE Registration Authority manages globally unique variables:
- MAC addresses and OUIs (Organizationally Unique Identifiers)
- EtherType values
- Individual Address Blocks (IAB)
- Unique Registration Numbers (URN)
- Manufacturer IDs
- Standard Group MAC Addresses
- The IEEE 802 defines standards for LAN, PAN, MAN, notably:
- ICANN: Internet Corporation for Assigned Names and Numbers
- The IANA (Internet Assigned Numbers Authority) manages:
- Data in the DNS root nameservers (partly DNSSEC keys, ...)
- Globally unique variables:
- Transport layer services port numbers
- ASNs (Autonomous System Numbers)
- Public IP addresses, handled by RIRs (Regional Internet Registries)
- The IANA (Internet Assigned Numbers Authority) manages:
- src: wikipedia
- Collisions: will occur when devices both:
- Can only handle one operation at any given time
- Are queried operations while another is in progress
- Collision domain: link in which collisions can happen, resolved with:
- Duplex system: two connected parties can bilaterally communicate
- Half: a device can either send or receive at any given time
- Full: a device can both send and receive at the same time
- Flooding: received data is forwarded through all but the receiving port
- Routing: process of selecting network traffic paths
- Delivery schemes can be defined by messages source to target nodes:
- Networking hardware can be grouped by roles, locations
- Core devices interconnect other devices:
- Hubs: half duplex, flood all received frames, almost unused today
- Switches:
- Provide connectivity to hosts within the same LAN
- Maintain a FIB (Forwarding Information Base)
- Maps MAC addresses to physical ports
- Aka:
- A CAM table (Content Addressable Memory)
- A MAC address table (Media Access Control)
- Routers:
- Originally called gateways
- Provide connectivity between LANs (Local Area Networks)
- Can be used to send data over the Internet
- Maintain a routing table
- Wireless Access Points: half duplex
- Border devices generally sit between networks:
- Firewalls
- Permit or deny inbound or outbound traffic by setting rules
- Can be hardware (network fw) or software (host based fw)
- Firewalls
- Hosts, End Systems, Data Terminal Equipment (DTE)
- Network Interface Controller (NIC): can connect a computer
- Modem (MOdulator DEModulator)
- Converts data to a format adapted to transmission mediums:
- DSL (Digital Subscriber Line): over telephone lines
- CATV (CAble TV): over CATV lines
- Takes advantage of existing lines
- Can be separate devices, or integrated into home routers
- Converts data to a format adapted to transmission mediums:
- 1950s: the SAGE computer network is built for the US military
- Coordinates radar sites to produce wide airspace imagery
- Uses the Bell 101 modem, 1st commercial modem (AT&T, release: 1958)
- Transmit over telephone lines at 110 bits/s
- 1960s
- Development of the concept of packet switching for computer networking
- 1969: the ARPANET goes online:
- A packet switching network between labs and universities
- 1970s
- 1973: The CYCLADES allows internetworking (connecting
$n$ networks) - 1974: RFC 675 contains the 1st: use of the term Internet and TCP specs
- 1973: The CYCLADES allows internetworking (connecting
- 1980s: RFC 799: Internet Name Domains
- 1983-01-01: ARPANET adopts TCP/IP, becoming a subnet of the Internet
- 1989: 1st Internet public access offered by ISPs in the US and Aus
- 1991: The World Wide Web (www.) introduction helps global adoption
