50 Fun Facts About Computer Networking

Which short-range wireless technology is named after a tenth-century Danish king who united warring tribes?

Bluetooth borrows the nickname of King Harald, and its logo merges the runes for his initials. Intel's Jim Kardach proposed the name in 1997 because the technology was meant to unite devices too.

Which Hollywood actress co-invented a frequency-hopping radio guidance system for Allied torpedoes in the early 1940s?

Hedy Lamarr devised it with composer George Antheil, but the US Navy rejected the idea as too bulky for a torpedo. Related spread-spectrum principles now run through modern wireless links.

Which kitchen appliance works at roughly 2.45 GHz, the same band as many Wi-Fi networks, and can disrupt them?

A microwave oven leaks a little energy around 2.45 GHz, harmless to people but enough to disrupt Wi-Fi at close range. That band was chosen because it is open for unlicensed use worldwide.

Which birds carry the data in RFC 1149, a 1990 April Fools' networking standard later tested for real in Norway?

Pigeons delivered nine packets across about five kilometres when a Bergen Linux group tried it in 2001. Only four replies came back, the fastest after 50 minutes.

What carries nearly all international Internet traffic, with capacity measured in terabits per second?

Submarine cables win because satellites carry only a very small percentage of international traffic. Sharks have even been recorded biting the lines.

Which device, essential for dial-up Internet access, turns digital data into signals a telephone line can carry?

Modem is short for modulator-demodulator, since it reverses the conversion for incoming signals. In the 1990s tens of millions of Americans went online with one.

Which security system, a term networking adopted in the 1980s, filters traffic entering and leaving a private network?

Firewall first meant a wall that confines a blaze within a row of adjoining buildings. Before dedicated products existed, routers did the filtering.

Which command, written by Mike Muuss in 1983, tests whether a remote computer is reachable and times the reply?

Ping is named after the pulse of sound that sonar sends out, because the tool likewise waits for an echo from the other machine.

Which pioneering US network carried the message 'lo' in 1969 after crashing midway through the word 'login'?

ARPANET's first link ran from UCLA to the Stanford Research Institute, and the full word got through about an hour later.

Which cable design, still used for Ethernet, did Alexander Graham Bell invent in 1881 to cut telephone interference?

Twisted pair keeps both wires the same average distance from a noise source, so interference hits them equally and can be cancelled at the receiver.

Which technology uses encryption and tunnelling to carry an office's internal traffic across the public Internet?

VPN stands for virtual private network, and its split-tunnelling mode lets a laptop reach office systems and ordinary websites at the same time.

Which network architecture, popularised by Napster in 1999, has computers share files directly with one another?

Peer-to-peer contrasts with the client–server model, where central machines supply everything. Many such systems still keep one central server to help users find each other.

Which term for the delay before data arrives, measured in milliseconds, do online gamers experience as 'lag'?

Latency rises with distance, since data sent farther needs more transmission and routing. In online games, lag turns severe once round trips pass about 100 milliseconds.

Which type of network, often built on leased lines, spans cities or countries and counts the Internet as an example?

WAN stands for wide area network, and a router at each end of a leased line typically joins one office's local network to another's.

Which network topology, one of the most common, connects every host to a single central device?

Star wiring means a broken cable cuts off only one host, though the central device becomes a single point of failure for everyone.

Which web protocol uses port 443 by default and has been used more often than its older sibling since 2018?

HTTPS keeps browsing private and proves a page is authentic, while its older sibling sends everything unencrypted on port 80.

Which system, often called the phone book of the Internet, translates names like example.com into numeric IP addresses?

DNS, created by Paul Mockapetris in 1983, replaced a single text file called HOSTS.TXT that mapped every host name to its address.

Which short-range radio technology, limited to a few centimetres, lets a phone make contactless payments with a tap?

NFC needs such close contact that signals are hard to intercept in a crowd, yet the plain standard itself has no protection against eavesdropping.

Which attack floods a victim with traffic from many different sources at once, typically a botnet of hijacked machines?

DDoS stands for distributed denial of service, and a 2021 attack through the Mirai botnet peaked at 17.2 million requests per second.

Which networking giant, founded by two Stanford computer scientists in 1984, has a logo based on the Golden Gate Bridge?

Cisco took its name from San Francisco, which is why its engineers insisted on writing a lower-case 'cisco' in the early years.

Which Internet addressing scheme writes each 128-bit address as eight groups of hexadecimal digits separated by colons?

IPv6 was developed because the older scheme's 32-bit addresses were running out. Its own supply runs to about 340 undecillion.

Which type of address, 48 bits long and usually assigned by the manufacturer, is burned into a network card?

MAC is short for medium access control, and each address typically carries a code that identifies the company that made the hardware.

Which protocol automatically assigns IP addresses to devices joining a network, in four stages nicknamed DORA?

DHCP hands out each address as a lease with a time limit, so the server can reclaim any that are not renewed and give them to other devices.

Which core Internet protocol opens every connection with a three-way handshake of SYN, SYN-ACK and ACK?

TCP guarantees that every byte arrives intact and in order, which costs time, so applications that prize speed over reliability use UDP instead.

Which protocol, first specified in 1971, opens its control channel on port 21 and often accepts 'anonymous' logins?

FTP sends its sign-in as plain text, so usernames and passwords cross the network unencrypted, and each file travels over a separate data connection.

Which protocol, published by Jon Postel in the early 1980s, carries email between mail servers on port 25?

SMTP only sends: mail apps typically submit outgoing messages on port 465 or 587 and rely on other protocols to retrieve the inbox.

Which technique hides many private IP addresses behind a single public one, easing the shortage of IPv4 addresses?

NAT was once nicknamed IP masquerading, because a whole network of devices appears to the outside world as a single machine.

Which device learns the address of each connected machine and forwards data only to the right port, unlike a hub?

A switch gives every port its own collision domain, whereas a hub blindly repeats each packet out of all its other ports.

Which lowest layer of the seven-layer OSI model specifies cables, connectors and the transmission of raw bits?

Physical is layer 1, where the standard fixes details as basic as connector shapes, signal levels and maximum cable lengths.

Which kind of network uses Internet technology but is generally restricted to the employees of one organisation?

An intranet stops at the staff, whereas an extranet also lets in customers, suppliers or other approved outsiders.

Which label is commonly given to the eight-contact modular plug found on the end of Ethernet cables?

RJ45 is strictly a misnomer: the name first meant a telephone wiring standard, and the Ethernet plug is properly called 8P8C.

Which abbreviation refers to the name a Wi-Fi network broadcasts, the one users see in a list of nearby hotspots?

SSID stands for service set identifier, and the name can run to 32 bytes, normally broadcast unencrypted in beacon packets.

Which original Wi-Fi security scheme, introduced in 1997, can be cracked in minutes and was deprecated in 2004?

WEP stands for Wired Equivalent Privacy, a promise it never kept: the FBI once demonstrated breaking into a protected network in three minutes.

Which IPv4 address does the name 'localhost' normally resolve to, letting a computer send traffic to itself?

127.0.0.1 is the standard loopback address, so traffic sent there never touches any real network hardware on its way back.

Which IPv4 setting, written in a form such as 255.255.255.0, marks which part of an IP address is the routing prefix?

Subnet mask digits work as a bitmask: combining them with any address on the network by a bitwise AND leaves just the routing prefix.

Which mode, used by a landline telephone call but not by a walkie-talkie, lets both ends transmit at the same time?

Full duplex is why both callers on a landline can talk over each other, whereas walkie-talkie users must say 'over' to hand the channel across.

Which name is given to the data unit at the OSI model's data link layer, a container that wraps a single packet?

A frame wraps its packet between a link-layer header and a check sequence, and each one is separated from the next by a short gap.

What does the 'A' stand for in ADSL, the broadband technology that runs over copper telephone lines?

Asymmetric lines suit home users, who download far more than they upload, so telephone companies made a virtue of a technical necessity.

Which nonprofit, incorporated in California in 1998, coordinates the Internet's domain names and IP address allocation?

ICANN took over work that one researcher, Jon Postel, had long handled himself, and it was set up in California because he was based there.

Which family of IEEE standards, first released in 1997, underlies the products sold under the Wi-Fi brand?

802.11 versions were once told apart only by letters such as b, g and n, until a friendlier scheme of numbered Wi-Fi generations arrived in 2018.

Which country's national science agency, CSIRO, lodged a key Wi-Fi patent in 1992 after work by its radio astronomers?

Australia's CSIRO later collected hundreds of millions of dollars from technology companies in settlements over the patent.

Which protocol did Tatu Ylönen design in 1995, after a password-sniffing attack, as an encrypted replacement for Telnet?

SSH got port 22 because its Finnish creator asked for the number just below Telnet's 23, and his freeware release quickly caught on.

Which protocol, defined in 1982, broadcasts a request on a local network to learn which hardware owns an IP address?

ARP answers are cached, so a machine that has already looked up a neighbour does not have to broadcast the same question again.

Which routing protocol, first sketched on two napkins in 1989, carries routes between the Internet's autonomous systems?

BGP began as a sketch by three engineers at a 1989 meeting in Austin, Texas, and was then written up on just three sheets of paper.

Which field in an IP packet's header is reduced by one at every router, so that lost packets cannot circulate forever?

Time to live was meant to be counted in seconds, but routers simply knock off one per hop, so the newer version of IP renamed it hop limit.

Which engineer invented the Spanning Tree Protocol at Digital Equipment Corporation and summed it up in a poem?

Radia Perlman called the poem 'Algorhyme' and opened it with the line 'I think that I shall never see a graph more lovely than a tree.'

Whose shortest-path algorithm, conceived in 1956, does the OSPF routing protocol use to work out its routes?

Edsger Dijkstra devised the method while working as a programmer in Amsterdam, and it also drives IS-IS, the other common protocol of this kind.

Which access method made early Ethernet stations stop, send a jam signal and wait a random time after a collision?

CSMA/CD has fallen out of use because modern Ethernet isolates every link, leaving no shared cable on which two signals could collide.

Which addressing method gives scattered servers one shared IP address, with routers steering each user to the nearest?

Anycast was first applied to critical infrastructure in 2001, and every one of the Internet's root name servers now runs as a cluster reached this way.

Which command, written by Van Jacobson in 1987, lists each router a packet passes on its way to a destination?

Traceroute goes by 'tracert' on Windows, and unlike a simple echo test it reports the round-trip time to every hop along the way.