Introduction to Large Scale Networks

Study Notes

A WAN (Wide Area Network) is a computer network that connects computers that can be far apart, generally with coverage exceeding 100 km.
WANs are used to connect multiple LANs (Local Area Networks) and are commonly found in larger geographical areas.
A WAN operates similarly to a LAN but on a larger scale.
Common protocols used for WANs include TCP/IP (Transmission Control Protocol/Internet Protocol), utilizing routers, switches, firewalls, and modems.
Core components of a WAN: Hosts, Clients, Bridges, Servers, Routers, Link media (e.g. fiber optic, copper wire), Applications, Protocols, Hardware, and Software.

1940: George Stibitz invented the teletype, enabling the sending and receiving of typed messages.
1964: IBM implemented SABRE, a reservation system and online transaction processing system that connected 2,000 terminals in 65 cities to a pair of IBM 7090 computers, delivering flight data in less than three seconds.
1980s: ARPANET (Advanced Research Projects Agency Network) emerges as the first wide-area packet-switched network with distributed control. This was significant in the development of the internet.
2000s: ADSL (Asymmetric Digital Subscriber Line) was launched in the UK – a technology that offered faster internet speeds over regular phone lines.
2011: Fiber-optic broadband and new DOCSIS standards enabled significantly increased broadband speed (reaching 100 Mbps). This demanded improved routers to handle the increased speed.
2014: The new Wi-Fi standard, 802.11ac, was released, offering considerably faster speeds (over 2 Gbps) compared to the previous 802.11n standard, and enhanced signal coverage.

An ATM is a switching technique employed by telecommunication networks that encodes data into small, fixed-size cells, utilizing asynchronous time-division multiplexing.
An ATM is different from Ethernet or internet, which use variable packet sizes.

ABR (Available Bit Rate): Guarantees a minimum capacity but allows for data bursts to higher capacities when network traffic is low.
CBR (Constant Bit Rate): Specifies a fixed bit rate for a steady data stream, similar to a leased line.
UBR (Unspecified Bit Rate): Doesn't guarantee throughput and is suitable for applications like file transfers that can tolerate delays.
VBR (Variable Bit Rate): Offers a specified throughput but data isn't sent evenly, making it a popular choice for voice and video conferencing.

ATM designers faced challenges in balancing the requirements of three intended uses: voice, video, and data, as each has its own set of requirements.
For instance, voice and video demand low delay and low jitter (variation in delay) to ensure smooth audio and video delivery without gaps or delays.
Video requires a significantly higher data rate than audio.

ATM's capability to provide high bandwidth and low delay made it ideal for high-speed, multimedia applications.
ATM networks relied on cell switches to manage the flow of data cells.
ATM switches could connect to each other, creating a larger network capable of handling a vast amount of data.

The complexity of ATM networks and the cost of deployment were obstacles to its wider adoption.
As Ethernet technology and internet protocols matured, offering comparable performance at lower costs, ATM's adoption declined.