This binding couch together lots of opus , worth picking aside one at a metre :
BonjourBonjourallows serve on a computer or gadget to publicize themselves across a net so that other equipment can discover them . Printers , Web servers , and a host of other communications protocol can be discoverable over a local electronic connection with Bonjour . Bonjour only works only local networks , however ; it ’s blocked by gateway , like an AirPort Extreme Base Station , that link up unlike web , such as your net connexion to your local machines .
Port MappingMost Wi - Fi and broadband routers hold up a protocol call internet Address Translation ( NAT ) . NAT was created in part to deal with a shortage of IP addresses in the current IP system , known as IPv4 . ( IPv6 will reset the shortage , but it ’s only very slowly rolled out over well-nigh a decennary because of how much infrastructure must change . )
NAT prepare use of secret IP address ranges that can be used on local networks . These private ranges — graze bulge with 192.168.0.0 and 10.0.0.0 , for instance — are insure to not be assigned on the public Internet .
A NAT gateway typically works with DHCP ( Dynamic Host Configuration Protocol ) . A DHCP server on the gateway pulls an reference from a secret range , and NAT handles requests that originate from the private range for the all-inclusive - area connection , typically the Internet , for which the request is bandage .
NAT use ports to handle petition ; ports are a fundamental building block of net networking . Where IP addresses uniquely define a computer or host somewhere on the Internet , port limit services at those addresses . guess of apartment building , which have a street number that unambiguously defines their absolute location , and an apartment number , which lets you get hold the manager ’s office or the laundry .
plebeian services like a Web server , Apple Filing Protocol ( AFP ) , and FTP all have fit in - on ports that are used throughout the net for inbound access , like a asking for a Web page . outward-bound requests originate at haphazardly selected port numbers , as they ’re only important for make the association .
For instance , port 80 is used by nonpayment for all WWW servers . If I attempt to load Macworld.com , which has an IP reference of 70.42.185.230 , from my World Wide Web internet browser , my computer first sends the postulation to the gateway , which my information processing system knows is the next footmark to reach the Internet . I might send a postulation for 70.42.185.230 port 80 from my calculator at 192.168.1.100 embrasure 11283 . The NAT gateway experience the postulation , makes a note of the port that I used to send the asking , and open up a link to Macworld ’s World Wide Web server using its own interface . When the connection is open up back to that NAT - cover interface , the NAT gateway devolve the dealings back to my computer on the individual web .
Both NAT - PMP and UPnP grant a program on a computer on a private connection to request a persistent open connection to the outside world . The gateway creates a set interface for this program , and lets the syllabus know which porthole is being used . That allows an outside connection to that port to hand a privately addressed computer reliably .
Wide - Area BonjourBonjour is design to shape on local web , right ? But full - area Bonjour works over , well , wide-cut - surface area electronic connection . It does so by registering info in a DNS ( demesne name organization ) server . DNS server are used to provide the cyberspace glue that link up human - readable arena epithet , like www.macworld.com , with their underlying informatics addresses . They can also store related to information about a domain . Properly equipped DNS server can handle wide - area Bonjour records , and AirPort Extreme Base Stations can interact with these servers to update those records .
inscrutable breathing space for the last piece that ties it all together .
dynamical DNSBecause ISPs often ply IP address that persist only over short period of time — so - called dynamic information science addresses — active DNS ( DDNS ) uprise as a way to allow you to alarm a DNS host that an IP address has changed without manually modifying a DNS track record .
DDNS computer software abound for Mac , Windows , and other political program , and in centre simply supervise your web for an IP computer address changing . When it does it pokes the DNS waiter which update its record . This lets a motionless name map to a dynamic destination .
And it ’s as dewy-eyed as that .
[ Glenn Fleishman is the author ofTake Control of Sharing Files in Leopardand compose daily about wireless networking at his siteWi - Fi Networking News . ]
