What is in this article?:
Best effort
Networks are “best effort,” meaning packets may get to their destination, or they may not. No assumptions are made that the network absolutely will deliver any particular packet. This may seem like a crazy assumption. After all, the whole point of the system was to get absolutely critical information transferred from one place to another, possibly during a nuclear attack. But, freeing designers from the constraint of having to guarantee that the network was responsible for ensuring messages made it from one place to another actually allowed a number of creative solutions to the problem, many of which are employed with professional video today.
If a packet is lost, there are many options: The receiver could request retransmission, the receiver could mask the error without actually having the original data, or the receiver could reconstruct the missing information from additional error correction data sent separately. All of these options are solutions to resolving the fact that a packet did not arrive. The key, remember, is that they work without having to somehow ensure that the network remains viable 100 percent of the time.
Autonomous and decentralized
Another key assumption is the network does not have any centralized control system or centralized routing function. Designers wanted to ensure that, even in the case of a successful nuclear attack, the remaining portions of the network could continue to operate. Packets make their way from source to destination without a “router control system,” a different approach from what we are familiar with in the video router environment.
Not only are network operations autonomous, but they are decentralized as well. For example, the Domain Name System (DNS) is a distributed database that helps computers find each other. Without it, we would not be able to use domain names such as Google.com. Instead, we would have to rely on IP addresses such as 98.223.42.21. Remember also that having a central database would violate the “smoking hole” assumption. Instead, DNS works by having tens of thousands, perhaps millions, of DNS servers available. An entry is created in one database, but this entry is then replicated across the entire Internet as different users look up the same destination entry.
