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title: WWDC2003 Session 105
framework: wwdc
role: article
path: wwdc/wwdc2003-105
---

# WWDC2003 Session 105

## Transcript

Kind: captions Language: en good afternoon and welcome to the rendezvous session I'm Craig Keithley I'm apples io technology evangelist and world wide developer relations one of those Iowa technologies is rendezvous and over the past year we've been working very hard to bring rendezvous to as many products as possible I have over a hundred and twenty developers actively working on projects more than 35 or thereabouts-- have shipped there's more on the way if you are at the session earlier this week for open source you saw that open play now has added rotted route support so in the future games that use open play will automatically enable rhonda rooms a big step forward so if you're a game developer and you're here to learn more about rendezvous best recommendation i have for you is go check out open play you're going to get benefits of Oakland played plus the benefits of rendezvous automatically you know as we look over the history of networking communications there are a couple of important stages you know I can think back to the first time I used a dial-up modem dialed into ARPANET from my local university and how exciting that was and then as appletalk came out in the mid 80s and I was able to easily network products this is the next generation it's the way that people should be doing zero configuration networking it's plug and play it's how we want to make devices work so to go into that the this session will detail what Ronnie who is what we've been doing for the past year the new features that are coming in Panther the new API that will be available to you in the future and we want to go over some hints for software developers and hardware developers this will run the range both from software techniques to licensing the logo all of you if you're doing rendezvous development should be licensing the logo it's free it's an easy way for your customers to know that they bought a product that works with rendezvous so without very much further ado let's bring up Stuart Cheshire we will go into all this thank you [Applause] once again just like the last year it's a great turnout I'd like to ask everybody to shuffle in and fill up the seats because there are still people standing in the doorway and people trying to get in so if there any gaps close them up so I'd like to just get a show of hands how many people saw the WWDC presentation last year on rendezvous okay about half that's good so I'm not going to repeat that material this year I'm going to do a quick overview to remind you what it was all about but if you want to see more detail about that pull out your old DVDs from last year and have a look or if you weren't here last year then you know you might be able to find one from a friend and have a look at that so right now I'm just going to quickly skip through to refresh your memory we're going to talk about why we did rendezvous we're going to talk about what we did to solve the problems and we can talk about how we made it all work so let's get on with that quick it we've got a lot to cover so the Y is 20 years ago many people in this room are probably not old enough to remember that but 20 years ago there was huge competition in wide area networking or all these different protocols and devices from one vendor normally wouldn't work with devices from another bender and this was obviously not a good situation and the good news is that in the last 20 years they've all died and the only thing we seriously considered these days is tcp/ip which is great so now let's look at local communications in the similar era 10 to 20 years ago we had all these different connectors on our computer and the good news is those have pretty much died and gone away as well unfortunately we still have all these different ways of connecting to something like a local printer and as time moves forwards the list is getting longer these are not all technologies that Apple ships but they're all local communication technologies that are in the market place that people working on and developing so what did they do to solve this incompatibility problem in the wide area and the answer was they picked one protocol and said everything talks that protocol and yeah there may be some little benefits of another protocol but there's a bigger benefit in having the standard so we should do the same thing for local communications and going even further naps the protocols local communication should be the same one that is already one in wide area communications now when I say that a lot of people react by saying well that's crazy nobody wants to type in subnet masks and IP addresses just to print on their inkjet printer and of course they don't want to the point is to make it so that you don't need to do all of that to make IP work so the answer to solve this problem you all know that's why you're here its rendezvous and the press has been saying marvelous things about rendezvous there were lots and lots of good stories about it one of my favorite headlines is a backstage pass for the future I think that really sums it up Tim O'Reilly very well known and widely respected person in the industry said this about rendezvous it is truly revolutionary it's one of the things that's going to have the largest impact on application design over the next couple of years we're just at the beginning of the second internet revolution and rendezvous is a big part of it you can't get much better than that so here's the quick recap of last year what you need to do to do IP networking well you need an address you need to be able to use names and you need to be able to browse the network to see what's there very simple solutions the point of this is to make it simple when you've got a gigahertz processor and lots of RAM most software problems can be done with enough effort but when you've got a little inkjet printer for fifty dollars with a tiny amount of firmware in a slow process you don't have that luxury so one of our overwhelming goals of rendezvous and driving principles is making something that isn't just for Macs and PCs it's for all of the other little devices out there as well and not just the devices that currently do networking but many of the devices that don't do networking at all right now so in that principle of simplicity you need an IP address pick one at random send an ARP request if nobody answers you can use that address just like Apple talk did very simple there's a range of addresses reserved by iono for this purpose and there's an internet draft describing how to do it and you can find that at zero comp torg but what I said is pretty much summing up how you do linked local addressing link local great sync isn't new you've probably seen it before when you see 169 dot 254 in the control panel you say networking is broken and it's understandable why people think that but they think that because on its own a self-assigned address isn't very useful in Jaguar we introduce the rest of the technologies to make it useful and now you can do things with that link local address even if you can't communicate with the global internet and buy books from Amazon or do whatever you want like that it's been around since 1998 in mac and windows it's in OS 10 it's in linux pretty widespread you may know it under the names autonet auto IP and of course ipv6 already has linked local addressing rendezvous works both on v4 and v6 so naming similar principle as before dhcp is great if you have a dhcp server that's great but if you don't make up your own address same thing here DNS is if you have a DNS server there's no reason not to use it but if you just have two computers and you want to exchange the file and you forgot to bring a DNS server with you that shouldn't cripple you so multicast DNS is how you do name lookups when you don't have a dns server same packet format same query syntax just multicast it every device has a little responder just like an apple talk NBP responder and when it sees a request for its name it answers again we want to make this very simple the specifications for that you can find it multicast DNS dot org but again to description i gave is most of what you need to know about it the client has been in since mac OS 9 it's in 10 of course it's in Linux there are several products projects if you go to dot local dot org you'll find several people working on multicast DNS for linux microsoft characteristically vague i can say that at the IETF plenary presentation last summer in Japan they described multicast DNS as a vital technology for ipv6 and said it was under consideration and or underway at Microsoft so you have to take that for what it's worth what this gives us is the ability laser eye to dot local into your web browser and connect to the configuration page of your printer without having to know what address it picture itself so this is a huge step forward over typing dr. desk my dear dresses but of course we're not content to stop there because appletalk did better than that and we want IP to do better than that so we want to raise the bar we want you to be able to find what's on the network without having to know what name to type in now devices we know are going to need link-local addressing any way to work usefully they're going to need local naming to work anyway rather than add a third different body of code to do service discovery the insight we realized is that the multicast dns code also gives you service discovery for free and for the guys making the fifty-dollar inkjet printer that's a big win I'll explain quickly how that works you do a standard DNS query for record type PTR and here the query is semantically saying find me devices on the network that speak the IPP printing protocol because I'm an IPP printing client and that's what I'm looking for you do that query and you get back one or more responses from the devices on the network that implement IPP and we want these names to be user friendly just like Apple talk so these are structured names with three parts and the first part is to use a friendly name that you display in a graphic user interface normal host names in DNS are limited to letter digits and hyphens and they have to be short because you want to type them on a command line but these things you pick in a browser so they can be long they can have spaces they can have upper case lower case punctuation full utf-8 you can put counting character then because you don't have to type them you just click on them and list the names of structure just like the old appletalk name type and zone and here its service name is the first part the second two labels are the service type in other words the protocol name of the service and the remainder is the domain now right now the only domain we support is got local for multicast but this applies exactly the same for wide-area unicast lookups using a conventional DNS server because it's using standard DNS quit which nothing different about the queries here it's just a convention for what you ask for what responses you expect to get back service types important points here a service is identified by the protocol it speaks human beings think in terms of objects like printers but from a software point of view if you've got an IPP client what you're interested in is finding things that speak IPP some of them may be printer some may not there may be printers that don't speak IPP and you can't talk to them it's no benefit finding something you can't talk to so at the network level what you're looking for is the software entities that implement a particular protocol not bits of hardware and that's an important point because many service discovery protocols get that wrong they look for hardware and then having found the hardware you're not quite sure what it does and then you have to go through a whole negotiation phase so having found the names of the services on the network what is it that we found the name of and the answer is in DNS we found the name of that service record and the txt record describing that service so when it's time to print you want to know the IP address and port number where that service can be reached now with DHCP or link local addressing the addresses might not be the same from day to day just like Apple talk so when the user picks the default printer we don't save the IP address because that might be wrong tomorrow what we save is the rendezvous name and then on demand we resolve that for an address by doing this query and the answer we get back is that the sales printing service today can be found on 4631 at my printer dot local it's a postscript printer so it's page description languages post grip and clever thing about DNS is it can give you answers you didn't ask for if it thinks that you're likely to need to know that information to say is you asking another question and in this case the responder said well you didn't ask for the address of printer dot local because you didn't know it's printed on local when you ask the question but you going to want to know that so I'll give you the answer anyway so there you see the address has been put in the packet automatically so one query one response you have the information you need to print on that printer this was launched with great fanfare last year and Jaguar it's in Darwin so it's very easy to get it and runs on any platform you want there are also other independent implementations completely separate from Apple which is which is great just like the others specification is freely available and you can get it from DNS cache SD for dns service discovery toward so that was the recap of where we were last year what's happened since then we ship jaguar and we shipped a few bits of software that we use in rendezvous i chat is an obvious example finding their to apprentice is another obvious example although this time last year there weren't many rendezvous printers on the market that's changed dramatically finding apple share service is another example since then we've done some more updates and we've advertised some more services you will see HTTP when you turn on personal web sharing you'll see it showing up in Safari you might say that too many of them are showing up in Safari it kind of shows how many people have accidentally turned on personal web sharing but don't actually have a web page there that they're intending to share Apple of ships hardware products using rendezvous the obvious candidates are the ones that don't have a screening keyboard so the only way to find them is over the network and you need to be able to do that no matter how Gus did the network is you need to be able to find it if if the airport base station is your DHCP server then you don't have dhcp until you've connected to it to turn on dhcp so the bootstrap problem there software products you've all seen Safari you've all seen iTunes the shake network video transcoding software is another thing that uses on David a lot of products from third parties absolutely amazing to me for a technology to get this much adoption in just one year I can't think of any other new technology that's had such an overnight success and I think that says a lot about the cost-benefit ratio of rendezvous it is so easy to do and the benefit is so immediate and so obvious that there is really no reason not to use rendezvous anywhere that you do networking were you looking for service your advert at you providing a service adding those few extra lights do rendezvous in such an obvious win so printers were the first candidate because Apple tour printers were the mainstay of network printing and those are the first people to jump on board rendezvous got some other little bits of hardware which I'll show you later on tivo's in the home great example you have music and photos on your Mac and you don't want to sit around the computer to watch them you want to sit in the living room and watch them on the TV I talked about TiVo last year as a purely hypothetical example of something I thought would be good and the great news is that they actually did it in less than a year later they're shipping that is a real product customers chaparral raid just like xlr8 another example of a headless device Martian net drive is another great product little box $400 puts in your garage turn it on it's a network file server no screen no keyboard it just shows up on the network you can figure it through safari which shows up automatically using rendezvous and saves it gives you a place to store the data in your house so your computer doesn't have to be turned on all the time lots lots of software products network databases games Hydra is a great example I'll show you that in a minute as well ftp clients and servers lots and lots of software things because it's so easy to do we have rendezvous on other platforms the crocodile rendezvous ftp server for windows advertisers using rendezvous on windows and shows up in the ftp rendezvous menus on all ftp clients on mac and windows swamp wolf has taken the apple darwin code and done some extra work on that to turn it into a system service for windows and i hope to show you that a bit later as well j rendezvous is an implementation of java written information of rendezvous written in pure native java interesting exercise in showing what java can do and the people doing that are running it on cell phones apparently they have cell phones that have a java ranging in them and so everything you write has to be in java i don't know about their product plans but we can only speculate that way that might be going and there's apparently a version in python as well lots of things that people are doing and Linux as always has a lot of open source efforts going on local dog is an interesting resource for the Linux work so time for some demos let's go to number four please alright so let's plug plug in and see what we have on this network so i connect the cable and let's see what okay first thing we have a brother printer here one of the first companies to ship a rendezvous printer let's turn that on okay well that's okay we have links late i'll give that a second so if you're buying a printer now pretty much all the printer vendors have printers with rendezvous built in but if you have an old one laying around that doesn't have rendezvous this is a great little product from seh intercon network print server this little box here implements a print server so i plug it into the parallel port on this old printer here this is just an obsolete printer i found lying around in the chorus at apple that's the reason you notice obsolete is because it doesn't have rendezvous but there's hope for it because we have this so this is the brother took a minute just a power on and just like that without knowing what address it picked for itself we're now connected to its status page and we can do the toner levels and view all of its configuration information so easy one-click connection I plugged in the intercom print server and it shows up as well and that's it when I was bringing all this equipment and setting it up the conference organizers were saying you're mad you can't do this just like this is not the keynote you don't have two hours to set up you know you've got 15 minutes between sessions I said it's ok guys its rendezvous just I don't need to set it up so we'll we'll see whether they were right this is something i love have to tell you about this people work in data centers probably familiar with all the equipment in the 19-inch racks that's got serial ports onyx for configuration and set up and we don't have serial ports on our computers anymore so you end up meeting one of these USB to serial adapter as well this is like that except this is an Ethernet to serial adapter and you just take this and plug this into the serial port on whatever device you want to configure and it advertises telnet service so now you don't have to run Cyril wires all over your data center it's just on the networks like anything else and you can telnet to it and I forget the price of these I think these are about fifty dollars these are even cheaper than USB to serial adapters and this does Ethernet so this is a cool site player if you go to site player com sorry I think I think sites left is the place to look all right good yep site SI te pla ye are in fact why don't i plug it in and then we'll see so plug it in light is on okay this thing has 16 k a flash memory and in that 16 cade the guys implemented TCP IP UDP our dhcp client dns client rendezvous web server telnet server okay and a knob and of that 16 k9k of it is the HTML text of the web pages so it's got 7k for code and this is not even assembly code this is C absolutely incredible so there we go site player click it and Safari should open a window and just like that we connected to it have access to its configuration page so well rendezvous is all about enabling IP so in as much as you can run IP over USB which you can do with various products that I think emulate ethernet over USB then rendezvous just works transparently like any other IP device but if you've got a device that doesn't speak IP then it's kind of operating in a different world things things like this intercom print server are the kind of gateway from the IP world to that world so I was going to bring some equipment with me but unfortunately most of the things these days that use serial ports kind of 50 19-inch racks and are a bit bulky but this is one thing I found at home this is a little voice over IP product it's got ethernet on it but you have to connect the serial port with a terminal to configure it so this is a great thing for connecting to the site player maybe we'll get time to look at that more later I think maps for this round of demos let let's go back to the slides please [Applause] alright so what new features do we have to offer you in Panther Jack you had ipv6 supporting the colonel but rendezvous didn't use it the good news now is that rendezvous is using it it sends its queries over v4 and v6 annual advertise services that are running on v4 and v6 so when you resolve you can now expect be getting v6 arcaders back as well as v4 and you should pay attention to that in your code generation was always before we have subtype browsing for more selective queries that's described in the draft we have a lot of performance improvements both in terms of CPU performance and in terms of smarter algorithms to make use the network more efficiently these are things that we all had planned on the road map but didn't make it into Jaguar we have a cool feature that gives you faster pershing of stale cache data which has been very widely requested I'll talk a bit more about that network administrator's last year at the feedback forum asked us for a way to enumerate all services on the network now for a software vendor finding everything on the network isn't very useful if you can't communicate with it it's only useful to find things that you know how to communicate with but for an administration put points of view finding everything on the network is useful so we we had to work out a way to do that there was elegant and efficient and we did do that so that's now in Panther we have a bunch of new client applications using rendezvous services and we have some slight improvements for the api's that reflect feedback we got from developers over the last year one of the trade-offs in any network protocol including rendezvous is if you're going to present a list of resources on the network you have a trade-off between the timeliness of that data and the accuracy of it and how quickly you pull the network and if you're willing to pull the network once a second you can have very up-to-date data but of course that would be bad so we try to make rendezvous very efficient on the network and very frugal with its use of packets and that means it will cache data typically for up to two hours and what that means is that if you shut down your Mac gracefully it sends a goodbye packet and it disappears from Oprah's browser list but if you just yank the cable ethernet cable out of the printer it doesn't get a chance to send a goodbye packet and people see these stale entries showing up in the browser list and that's frustrating because they see the printer they tried to print they get an error they go back to the list it's still there they try again they get another error very frustrating so what we do now is we don't continue you pull the networks because that would be bad but when you try to print or use a service and fail then internally the code kind of ask itself a question it says well why were they trying to use that service well maybe it's because it's in the browser list and if it didn't respond that maybe it shouldn't be in the browser list so the time to live on that cache entry shortened from two hours down to a few seconds the Machine sends a couple of queries and if it doesn't get an answer then it's flush from the cache Nick disappears and that produces a dramatic difference in user perception they see the stale printer they try to print it doesn't work they go back to the list and it's not there anymore somebody must have just turn the printer off now that's not actually what happened it was actually turned off half an hour ago but the important thing this is very important from a sort of human factors point of view is that the person has a consistent mental model for what happened and then they're not frustrated because at least it makes sense them what going even beyond that when the other machines on the network see you do a couple of queries and not get any answer then they also conclude that that data must be still and delete it from their caches as well so only one person has to try to access the stale printer and equably gets the benefit of having it disappear so big improvement in user experience there without any extra packets on the wire which is great [Applause] one of the future plans i said this only works right now we've got local with local multicast but we are planning i'm not announcing any dates or timetable here but we are planning to do this globally using unicast dns queries and dns dynamic update so where that in mind when writing your code don't assume that the domain will always be dot local okay so back to number four please so one of my earliest memories of computing when I was very young was the big teletype machines that printed out on rolls of paper at 110 bored and that was how everybody connected to the UNIX and mainframe was was over these serial connections and the DNA of that kind of lives on in OS 10 and terminal may actually be the oldest DNA in that sense that that's in OS 10 this is emulating a roll of paper on a teletype and there are lots of things using rendezvous in panther but I thought going all the way back to the start would be interesting so can something as ancient as this benefit from rendezvous and this is pretty neat command shift k and we've got a little server list and right there is telnet connection to this site player box let's put it into character mode and let's plug it into this piece of prehistoric hardware I was talking about getting this demo set up with the hardest demo of everything I did and if you remember using Cyril puts this stack of gender changes in DC and DPA and CTS are tsx on X off-board rates and you know you type stuff and nothing happens and you know is it turned on what's good but I finally found a combination that works let's power this guy on and see what happens all right so you know we can set its IP address we can reboot it we can let it do its thing and this could be something over the other side of the data center and you just tell net to it and in fact all the serial ports on your data center just show up these things here all right thank you back to the slides so what new api's do we have the good news is their modest improvements they are not things that are can require you to gut your code and change it NS net services is unchanged CF net services is unchanged we've made some minor updates to the low-level dns service discovery api's but the old calls are still supported so your current applications will continue to work and just to remind you of the architecture at the coop on top of the colonel at the lowest level is the mbms responder demon that implements the protocol the dns service discovery API is communicate with that demon to communicate what services you want to register and what things you want to browse for led on top of that is the core foundation CF net service and then on top of that is the co co NS net service and depending on whether you're writing a Coco application or a row of VFD command line tool influences which of those api's you would want to use it's really personal preference but at the low level the new dns service register call offers a few improvements some people need to advertise services on a specific interface on multi-home machines this is not common but if you want to do that you can now specify an interface when you pass empty string for the name to register the system will use the default name for you but you don't know what that name is that's kind of the point of passing empty string is it saves you needing to know what it is but if you're writing an application where you want to filter yourself out of the list of results you get back knowing what name the machine picked for you is useful so we've added that we've raised the limit on text record size the guidance for txt records remains the same they're intended to be a few bites of ancillary information but we did have some applications that legitimately needed a little bit more and the txt record was when we thought about it the correct way to solve that applications problems so we've raised that limit a little bit we don't want to raise it above 1,400 because we want these things to fit in single Ethernet packets things get much less efficient when you have to fragment the IP packets txt record can contain arbitrary binary data that was almost true in the past except ascii one was used as a delimiter now it's just an opaque blob of data rates passed as a pointer to data and length so you can pass through binary data now and we've added a new facility which came as a request from the printing industry for what we call placeholder names or flagship names and the idea there is if you have a printer that offers IPP printing and you call it sales and you have another printer but also offers printing but it's using PDL data stream protocol instead each services its own namespace and most of the time this is good you can have a file server called sales department in a printer call sales department and that's not a conflict because they're different things but having two printers call sales department is confusing so the printer guy said when we register a printer name called sales department we want to know that no one else is using that name not just for IPP printing but for any kind of printing and the solution to that problem is that for each family of protocols like printing one protocol is picked as kind of the flagship protocol of the fleet and even if you don't implement that protocol you register a service a fake service with the port number of zero for the flagship protocol so a printer that only speaks IPP would also register an LPR printing service with no port number it won't show up in any browser lists when people are browsing for LPR printers but if another printer tries to register that name it will get a name conflict and will be told you can't have that name because that's in use so this allows protocols to be grouped into families that kind of are conceptually common functionality even though they're a different protocol browsing again if you want to pick a specific interface you can and the result the replies that come back indicate which interface the reply was found on and when you have two services with the same name one on Ethernet one on airport knowing which one you're talking about is useful it doesn't happen very often but when it does happen they solves that problem and the resolve call similarly will take an interface ID which is what you got from the browser's call right now the resolve call always gives you the IP address and the port number and the txt record and normally that's what you want to connect to a service but certain specialized applications want to monitor for changes in information continuously ichat is the best example of this because I chat uses the txt record to encode your status about busy idle away and because of that all the ichat clients leave their resolves active because they want to keep getting callbacks when that information changes but they don't need to be constantly querying for IP address and port number they only want to know about the txt record so the new call lets you be more selective and consequently more gentle on the network by only asking for what you really care about txt record limit as I said has been raised in this call as well and you can fetch crew binary data in this court and we've made a number of efficiency improvement so that when things like ichat do leave their queries active on the network it generates a lot for your packets some specialized calls if you want to make a proxy responder which is advertising services on their behalf so you've got old network printers that don't have rendezvous and you want to run a proxy that advertises on their behalf the register record call lets you register a whole bunch of Records more efficiently and lets you do specialized DNS records it lets you reg to any arbitrary DNS record whereas the previous calls are focused around the standard DNS service discovery conventions DNS servers query lets you query an arbitrary record and the reconfirm record is one of the triggers for the mechanism of torque map before for the fast fast cash expiration if you get an IP address back from dinner service discovery and when you try to open a TCP connection it doesn't work you can call this routine to give a hint to MDS responders that that data it gave you may not be good anymore and it should go back and check on the network obviously use that cautiously because if you had a bug that could do bad things for the network so in the last year we've had a lot of software developers use run boo and we've found some common themes emerging as things we had to help them with so I'm going to talk about some of those today so obvious advice use rendezvous and put the logo on the box if you're a software developer it's very similar to using the QuickTime logo if you use rendezvous on OS 10 you can use the logo and that's the message to your customers that you have a quality product that's easy to use people were confused initially about naming and unfortunately it is just a little bit confusing there are two kinds of name there are short names that you type on the command line you want them to be short and easy to type and don't have funny characters in the more punctuation and that's good for command-line interfaces but when your browser seng there's no reason to be restricted to that so in Jaguar there are two names in the sharing control panels does the computer name and there was the thing that was labeled the rendezvous name and it is the rendezvous name in the sense that it's your link local host name for command line use but a lot of people took that to mean that rendezvous names have to be lowercase letters digits and hyphens just like host names that's not the case and when you register service most of the time use empty string and the system will just use the default computer name for you and if there's a name conflict on the network it will add a number two on the end and re-register so it'll handle all of that for you if the user changes the name in the sharing panel then it will update the name of your service automatically so for most applications using empty string is what you want if you want to specify a different name that's fine as well itunes is an example of that in iTunes you can give a name to your music library which may not relate to the name of your computer because it's really naming the music it's not naming the piece of hardware where the music is living so pick which is appropriate for your application very important the service types are how you identify what service a client is looking for and if different people use the same service type then this is going to cause conflicts that's not good clients are going to browse and find things that don't actually make sense good example of this is web dev is a file sharing protocol that runs over HTTP which is a reasonable design decision but it's a private design decision for the protocol if you have a webdav server don't advertise it as underscore HTTP because even though it is using HTTP it's not something that a user necessarily expect to see in their web browser and connect to and see something that's human meaningful now you may have a web interface your server as well in which case you advertise that but underscore HTTP means something a human being would like to look at in their web browser web dev as a file sharing protocol should be advertiser's underscore web dev and the fact that it's led on top of HTTP is just an implementation detail and if you think about this everything runs on top of TCP and everything runs on top of IP but that doesn't mean all protocols are the same the fact that they share a common trend a foundation doesn't mean that they're semantically of the same protocol you don't have to pay to read for a protocol name you just fill in the form if you want to play around and experiment all legal service names are 14 characters or less so make a longer name when you know you won't conflict with a real product some developers have concerns that by registering their service they give away the product they're working on so that's fine to work with some kind of temporary placeholder name but when you ship do the eye on a form and get a legal service name because that way you own it and you can take action if other people come and trample on your service name and mess up your product just like using empty string for name when you extra service or when you browse the services use empty string for domain empty string means do the default do the right thing that the system has been configured to do and right now that means local but in future that will mean different things and if you pass local we'll assume you meant you only want local so unless that's really what you mean pass empty string another common error partly because the sample code we gave our kind of illustrating how to do resolves and people assume that you had to do it that way you don't need to resolve everything you find that very hard on the network you only need to resolve when you're ready to actually use as a service and the related point is don't store an IP address and port number the preference file because it might be wrong don't even sort of host name store the service name look it up on demand don't assume ipv4 anymore every Jaguar and Panther system runs ipv6 and when you browse you will find ipv6 addresses so you should either use them or you should very least be aware of them and handle them properly in your code don't don't crash or bail out just because you get a sockaddr that's not AF inet when you do a result remember to cancel it afterwards because as long as that result is active like ichat it's constantly querying the network saying has the data change has the data changed and you do this enough it can be a big burden on the network so after you've established your TCP connection you can cancel the result now remember that our resolve can and usually will return more than one results if you've got multi-homing if you've got v6 you may have link local addresses and global addresses and v4 addresses and the resolved call will give you all of those you don't know which if any of those addresses are reachable to you so if you really want to write a robust application you have to try connecting to each of those and see which one works but having succeeded it's time to kill the result because you don't need it anymore common error in the applications that were resolving everything they found which is bad in the first place when they got a removed message for service going away they would do is stop resolve on that object and that doesn't work when you have a NS net service object and you start to resolve on it you have to stop the resolve on that object not a different object that happens to contain the same service name and that was an easy mistake to make but when you every resolve you start you've got to keep your own data structures in memory your own list of resolves so that you can actually get to those objects and cancel them when they're finished don't overload rendezvous I know it's great and if we loves it but you can take things too far I track is an example of good use rendezvous day they need to communicate information to all the pairs on the network and the choice was use their own multicast protocol or use rendezvous and we looked at the design and we said well you know what there's no point you inventing your own thing rendezvous is there put the data in the txt record leave a resolve active that is the right thing to do and it's the most efficient on the network but before you make that decision look at it and make an informed decision about whether that's really the right way to do it general pieces like this is not really rendezvous but it's good advice black network design now that normal products are doing that's working this gets more important any periodic polling on the network is bad and in your lab it might seem fine but you put a satirist machines doing that and the suddenly things add up very very fast 100 Megan Gigabit Ethernet can carry a lot of traffic but Airport is much slower and multicast or broadcast over Airport is even slower than that Airport slows down from 54 megabits to one megabit to send a broadcast packet so even a small number of broadcasts are disproportionately expensive on an airport be very careful with that also the history of IP has assumed well-known port numbers and that is less and less true especially now with fast user switching you can't assume your application will get deported expect because a milk another copy or application might already be running so past zero when you bind you'll get a random port and the good news is rendezvous advertises your pork you don't need to exports anymore when you're using rendezvous final sanity check when the product is done and it works and everything seems to be good have a look at the wire have a look at the packets on the wire with a network sniffer like ether ill or Easter peak or TCP dump newer versions of them already understand multicast DNS if you've got an older version it's very easy to add multicast DNS support because it's standard DNS packet format you just need to tell the packet sniffer that port 53 53 is DNS packets and here's an example how to do it with ether peek you just open the decoder file find the DNS line 35 hex is 50 30 duplicate that line and put in 14 e 9 which is 53 53 in hex you don't need to write that down because you can find out on a multicast DNS website have a look at the packets on the wire and see if there's anything that you might be able to improve it's very easy to have an application we're sitting in front of the computer everything is working fine but on the wire it's sending a hundred packets per second and you say ok there's more to correctness than just does the right thing appear on the screen so hardware developers similar kind of advice put random in your products pass the conformist test and put the logo on the product the conformance test is Apple's assurance and your assurance and the customers assurance that products with the rendezvous logo do in fact work well and do give the experience that people are expecting so putting rondalee in the product is more than just another checklist item on the list of features it really is about does the products work better is it easy to use can you just plug it in like this and have it work and too often people overlook that one of my friends got some product recently some home base station thing and it said on the box that had upnp and after he spent three hours getting it set up he went through the menus and there was a check box that said enable upnp which is off by default so they just missed the point of like they put all that code in the product and then missed the point of why they put it there so we aren't people to make mistakes like that don't skip link-local addressing something we've heard from some developers is well you give us the multicast dns code on the darwin site so that's great but you don't give us links loads addressing so we can't do that it's too hard and the reason we don't have the sample code there is because there really isn't any sample code to give because the algorithm is send an ARP packet listen for now reply and if you get one pick a different random number and the way you send and receive art packets is so platform specific that it would be different in every platform it's not a standard API the way socket is because it's generally down at the kernel level and that means that the only remaining sample code we have left to give you is a random number generator which would kind of be insulting your intelligence so it really is very very simple and it is a vital part of rendezvous because everything you're seeing up on the stage here is using the enclosed addressing right that's how I can just plug it in and have it work and I didn't bring a DHCP server and that's an important part of making network products that cannot fail and that's part of rendezvous it's the when you plug it in it will work no excuses no well well you didn't have the right subnet mask in your dhcp client ID was none of that nonsense right you plug it in it works and for that to be the case you can't be relying on things like DHCP and other infrastructure on the network DHCP is great definitely put a DHCP client in but don't make it your only way of configuring if you're ever in doubt about how fast the things would respond or things like that think about USB you saw when I plugged in these devices here they all showed up within a few seconds there are some vendors who came to us with a thing that would tried DHCP 45 minutes before it gave up and we had to say look nobody wants to wait five minutes struggling you know not sure why their printer isn't showing up because about 30 seconds in you know they're taking a screwdriver to it and changing dip switch settings and fiddling with and thinking the ethernet cables bad and and doing more damage so USB is active within a few seconds and rendezvous network devices should be as well another common thing with network devices when you change your configuration setting you have to power cycle them to make them work don't do that all Ethernet hardware pretty much these days gives you link change detection so when you detect the cable is connected configure a link-local address and advertise your services on that interface just like plugging the USB cable you don't have to parasites or print when you plug in the USB cable and you shouldn't have to Paris like it when you plug in the ethernet cable the easiest way to get at the multicast DNS and bnsf discovery into your product is just to take our code it's about 75 k which is not big in today's world of bloated multi megabyte applications if you're if you're doing something truly tiny then contact us and we can work with you because as I say we've got some developers doing really tiny implementations they cut a lot of corners to do that but talk to us and we can set you up with something that's appropriate but the most full-featured fully tested code is the same code that's in Panther you know that's being run on millions of machines so that is really the codes that you have the most confidence in okay so some other interesting sessions you might want to go to the first one is already over but you'll have it on your DVD so you can review that if you want we have got networking sessions and networking feedback tomorrow and Friday Craig is our develop relations guy if you have any questions contact him for the specifications zeroconf that org multicast dns at all Dino's st dot org all have those drafts they've just been updated last week so they're they're up to date with all the latest stuff in Panther we have apple developer information we also have the apple rendezvous mailing list which is a great place to ask questions so that's often a good place to ask your first question instead of going straight to quake with a question many times asking on the list will get you an answer