How Does Internet Reach To Home?

Internet is basically a large network of networks. Thorough certain hierarchy of Internet Service Providers (ISPs) Internet reaches to end user. Large communications companies having their own dedicated inter-country or inter-continent submarine cables to form Internet backbones are termed as Tier-1 ISPs, e.g., Verizon, AT&T. Tier-1 ISPs sell Internet access to regional ISPs and regional ISPs in turn sell it to local ISPs. Local ISPs allow end-users to access Internet through various technologies like dial-up, wireless broadband, Digital Subscriber Line (DSL), Cable modem etc. For example, Reliance NetConnect and Tata Photon+ offer wireless Internet broadband, BSNL offers through DSL and dialup Internet. There could be one or more than one ISP in-between end-user and Tier-1 ISP, no strict rules. Regional ISPs often engage in ‘peering’, where multiple ISPs interconnect at Internet Exchange Point, allowing data to route between each network without charging one another, otherwise that data would have passed through upstream ISP, incurring charges from the upstream ISP. In reality, infrastructure is far more complex and covering every aspect is out of scope of this article.

If you are an Internet user in India then it is most likely your overseas Internet communication passes through Mumbai or Chennai, where exactly Submarine cables land in India to let it hook up with Internet. See the map below,

Image Courtesy: Guardian

Why Not Internet Through Satellite?

Before I got to know about Submarine cables, I had a perception that all Internet data routes through satellite but I was quite wrong. Below listed reasons are sufficient to justify the Submarine cable as a choice,

Firstly, Satellite can offer maximum download speed as 1Gbps and maximum upload speed as 10Mbps which is way lower than Submarine cable data transfer speed counted in Terabits per second. Secondly, signal latency is higher in satellite communication compared to ground-based communication. Latency is the delay between the actual moment of a signal’s broadcast and the time received at its destination. In case of satellite, as signal needs to travel around 35,780km to reach to the satellite and back to earth again, it takes around 1,000–1,400 milliseconds latency, substantially higher than ground-based communication latency of 150-200 ms. This could lead to adverse experience in online gaming, remote surgery, VoIP, video conferencing. Thirdly, Satellite communications specifically with higher frequency get severely affected by rain or snow fall.

Threats To Submarine Cables

Submarine cables can be damaged by anchors, earthquakes, undersea avalanches and even shark bites. For example, in February 2008, damage to submarine cable caused disruption to 70% of the nationwide Internet network in Egypt, while India suffered up to 60% disruption.[source] However, widespread cable burial has decreased the cable fault incidences significantly. Cables could be cut by enemy forces in wartime or even worse enemy could eavesdrop on the sensitive communications. For an instance, during the cold war, US navy wrapped a special device without piercing the cable case and recorded majority of the unencrypted important Russian communications passing through it. This continued for around 10 years until Russia learnt about the incident in 1981. In fact, this helped to end the cold war as it gave the US a window directly into the Soviet mind. [Read full story about the Operation Ivy Bells here.] I have found one very interesting video, explaining how alert regarding broken cable is received and how problem gets fixed. Click the below image to play,

Courtesy www.orange.com

Submarine cables based on Fiber optic technology. Image Courtesy: NSW

Cable installation in progress.

A specialty ship, owned by France Telecom, to lay submarine cables.

I hope this article would have provided a detailed information about Internet infrastructure, if so then please don’t forget to share it with your friends.