The Internet (Week 11) Flashcards
What is the Internet?
The Internet is a “network of networks”
A loose, unstructured, ad hoc, chaotic collection of networks, all connected to each other => interconnected networks
These subnetworks might be large, small, corporate, government, private, educational, etc. networks
Each network can have its own network rules and protocols or different types of hardware
To be part of the Internet, individual networks just must support Internet Protocols on top of existing communication mechanisms
What are Communication Protocols?
A large set of protocols define how the Internet works
A communication protocol is a set of rules and conventions that allow two or more parties to exchange information, e.g.
* Who can initiate the communication?
* What is the format for exchanging messages?
* What happens in case of an error (error recovery)?
* Many protocols are agreed to be technical standards
This is similar to social protocols that define how a valid interaction between multiple parties should look like, e.g., etiquette or code of behaviour
How did the internet start?
ARPANET
* Advanced Research Project Agency (Part of US Department of Defence )
* Originally, 4 university sites in the US were connected
October 29th , 1969 – 1st message sent 550 kms
* UCLA to Stanford University.
* System crashed after the letters l and o
Roughly exponential growth of number of hosts (participating computers) in 1980s and 90s
What does it mean that the Internet is a Reliable and Robust Web?
One of the original design purposes: robustness
* Make sure the network would continue to function even if major subnets fail or were destroyed
No dedicated point to point route between any two nodes
If a node/link is down (inactive) – another path is used to communicate
This property of the network is now a major challenge for some governments as it is hard to control
What is a Backbone Network?
A backbone network may be defined by the principal data routes between large, strategically interconnected computer networks and core routers on the Internet.
What is CANARIE?
CANARIE: Canadian National Research & Education Internet Backbone
CANARIE is one of the Internet Backbones in
Canada. Bandwidth on many links: 100 Gbps
What is the BCNET Advanced Network?
BC ́s part of CANARIE
connects 180+ higher education and research sites across British Columbia (including Camosun College)
9,900+ km of network connections
The weathermap shows the current traffic load (only accessible inside BCNET)
https://www.bc.net/advanced-network/traffic-map
What is Internet Routing?
We can monitor the route between network nodes with the program traceroute
Example route from a Camosun computer to the webserver of the University of Ontario Institute of Technology (www.uoit.ca) in 13 “hops”
Data is passed along from node to node until it reaches the destination
What is an Internet Service Provider (ISP)?
Internet Service Providers offer internet access for commercial or private users, e.g. Telus, Shaw, Bell, Rogers, JUCE, Lightspeed, etc.
ISPs typically operate their own networks
* Some ISPs maintain their own regional, national or even global networks
* They connect their networks (and thus their customers) via Internet Exchange Points (IXPs) to other networks
Internet Protocol Version 4 (IPv4) and IP Addresses
Any data is sent bundled in Internet Protocol (IP) packets
Every “node” of the network must have a unique ID: an IP address
An IP address (version 4, IPv4) is a 32 bit number
* 4,294,967,296 unique addresses
* Usually noted as 4 decimal numbers (8 bits each) divided by dots
* 0.0.0.0 to 255.255.255.255
Internet Protocol Version 6 (IPv6)
Next version of the internet protocol IPv6 is here (we’ve run out of available IPv4 addresses):
* Each address is a 128 bit number
Noted as 8 blocks of 4-digit hex numbers divided by colons, e.g.
http://[2607:f8b0:400a:804::200e]
What is Domain Name Service (DNS)?
Humans are not good at remembering long numbers like IP addresses
=> Domain Name System provides names that translate to IP addresses
DNS uses an hierarchical naming scheme
Example hierarchy including online.camosun.ca:
How does Domain Name Service (DNS) work?
DNS translates names into IP addresses (and the other way round)
Since 2009, DNS supports “Unicode” names, e.g. http://монголулс.icom.museum
Your computer knows at least one Domain Name Server, which it asks to translate unknown names (usually a second one is set up as backup)
ipconfig /all (Windows) and ifconfig (Mac) shows the DNS servers your computer uses
You can ask for a particular translation with nslookup [hostname] (same on Windows & Mac)
* You might be able to configure which DNS you use
How is a DNS query resolved, e.g. for www.camosun.ca?
If your computer asks for a host name unknown to your DNS server, the request is passed down the line.
- Ask one of the root domain servers for info about .ca
* One out of a set of 13 highly redundant servers (those make DNS very failsafe) - Ask the domain name server for TLD .ca for camosun.ca
- Ask the sub-domain name server for www.camosun.ca
Domain name servers keep track of recent translations to improve speed => another example of caching to improve performance
What are Top Level Domains (TLD) and who are they restricted to?
The well-known .com, .org and .net domains are open to anyone anywhere – no geographical or national limitation
* Attention: anyone can register a .com-subdomain for a couple of dollars. You may not know who you are dealing with (may be registered anonymously)
New top level domains can still be added: e.g. .biz, .museum, .web, .stockholm, .paris, are some of the “younger” TLDs, see
* e.g. https://start.stockholm/, http://hotels.berlin
* TLDs are managed by the Internet Corporation for Assigned Names and Numbers
Some top level domains are restricted to certain groups of people, e.g. .ca-domains only for Canadian citizens, Canadian companies, etc.
