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Apple Releases Rendezvous for Linux, Java, Windows
mblase writes "Apple released yesterday a developers preview of their Rendezvous technology for Windows, Linux, FreeBSD, Solaris and Java. Rendezvous is an open protocol which uses industry standard IP protocols to allow devices to automatically find each other without the need to enter IP addresses or configure DNS servers."
Reader xxdarkxxmatterxx adds a link to a story at Macworld about the release."
If you look at it using a sniffer like ethereal, it's actually multicast DNS, so it will work with either IPv4 or IPv6 as it's a layer-4 thing.
Slashdot still doesnâ(TM)t support Unicode after it was added to the HTML standard in 1997.
For anyone who is interested, Rendezvous is Apple's implementation of of ZeroConf
While Apple's Rendezvous overview gives some decent information, the ZeroConf site provides a lot of good technical resources.
Apple really needed ZeroConf as they transitioned to all-IP networking. Although OS X supports AppleTalk, the AppleTalk protocol has clearly seen it's day and the world is clearly moving to IP-only. Previously, when Macintosh machines were largely communicating via AppleTalk, all of the things that ZeroConf addresses were handled by the AppleTalk protocol suite (service discovery, address allocation, etc), and this ease of use that is signature to the Macintosh is important for Apple to maintain.
That said, Apple releasing this code is pretty significant, as aside from this project, there hasn't been much use of ZeroConf in the wild.
bash-3.00$ uname -a
SunOS panda 5.10 Generic sun4u sparc SUNW,Ultra-2
We've launched this only a few weeks ago: Pocketster. It contains an implementation of Rendezvous for the Pocket PC and it also gives you wireless filesharing capabilities (we have a new version coming out on July 6th). It's free, so give it a try if you want (that is if you have a Pocket PC). Also, you might want to check JmDNS (Java version of Rendezvous) and Howl for a Windows implementation. Razvan
A prime example of Rendevous is two Powerbooks in a cafe, both with Airport wireless. You can set up an Ad Hoc wireless network between these computers, and they will auto configure their IP's and other information so that they can talk to each other. Then open up any Rendevous enabled app and you'll be able to see the other users resources, i.e. bookmarks, printers, music, etc.
So Rendevous is not designed to replace DNS/DHCP, but merely to find a way for network configuration when there is no established network structure. Rendevous also works on networks where DNS and DHCP are available, without any change. This is really the beauty of it, because it can determine what configuration is necessary and do whatever needed to get the computers networked, all transparently!
Rendezvous is based on a few underlying services: Dynamic Configuration of IPv4 Link-Local Addresses, Multicast DNS, and DNS-based Service Discovery.
Dynamic Configuration of IPv4 Link-Local Addresses: In the absence of a DHCP server, the machine is able to configure itself with an IP address in a reserved range such that it doesn't clash with other IP addresses configured by other machines on the same network in a similar manner.
Multicast DNS: Multicast DNS Responder services on each machine respond to multicast queries for their DNS information.
DNS-based Service Discovery: Querying for the existence of services (HTTP, FTP, SSH, etc.) via DNS.
So, in a sense, "everything is a DNS/DHCP/Directory server" but only for the information and services provided by that particular machine.
UDP traffic is pretty lightweight. ZeroConf is basically just some ICMP traffic (when the nodes are assigning themselves addresses) and then DNS. Apple's implementation will aggressively cache query results, and the devices incremementally scale back their announcements.
Another nice feature is that nodes can cache the results of other nodes' queries. Since all of the DNS traffic is mulitcast on the local subnet, every node sees every query and every response. Apple's code expolits this to further reduce the need for duplicate queries. It's a pretty nice setup.
IIRC HP has had rendezvous support in their printers for a while now.
It's not the concept that is a security hole...it was (is) all the buffer overflow/run exploits in Microsoft's UPnP implementation.
No one is using UPNP that I know of.
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Many would disagree. O'Reilly wrote up a good piece about the two technologies a while back. Its a good overview of what they offer and the pros and cons of each.
A quick rundown? Zeroconf (Rendezvous) provides a way to discover services and addresses automatically, without address duplication by multiple devices. UPnP does the same thing. The difference is that UPnP also dictates HOW to talk to devices and services, while Zeroconf forces devices to know how to talk to each other.
Taft
Rendezvous is three things:
- automatic link-local IP addressing for cases where DHCP fails (like APIPA)
- multicast DNS for announcing device names (.local domain)
- service announcements and discovery via DNS-SD
Mac OS X also supported SLP, but Rendezvous / ZeroConf is clearly the more comprehensive technology, as several projects (such as GNOME) are actually moving *over*.
Rendevous is some what like making each computer a DNS/DHCP/Directory server, however that's not completely accurate.
It's not so much that it's not completely accurate as it is that it's completely wrong.
Rendezvous has nothing to do with DNS, DHCP, or directory services. It's a service discovery framework, and that's all. Here's how it works.
Let's say you've got some program, Foo.app, that has a feature for talking to other instances of Foo.app over the network. Doesn't matter what it is. It could be iTunes music sharing or iChat or distributed compilation or whatever you want.
Without Rendezvous, you'd have to tell your instance of Foo.app where to find other instances. That'd require some kind of setup and some kind of maintenance.
With Rendezvous, your instance of Foo.app sends out a single multicast message when it starts up. That message says that there's an instance of Foo.app available at our IP address. Other instances on the network receive that message and make a note of it. They maintain a list in memory of available services, all automatically, without your intervention.
Does this involve a lot of network traffic? Not really. It requires some, but not much. When an instance of Foo.app starts up, it (1) announces its own presence, and (2) sends out a multicast request for other instances, and the other instances reply. When Foo.app shuts down, it sends out an announcement of its own termination. That's it.
Does this involve terrible security risks? Not really. All Rendezvous does is publish the availability of services that are already running on the network. The responder daemon itself doesn't run with any privileges (on a Mac, it runs as the "nobody" user), and all Rendezvous requests are handled by that one daemon. If something magical happened and somebody was able to get mDNSResponder to run arbitrary code, there would have to be another exploitable security hole somewhere else on the system, because mDNSResponder doesn't have privilege to do anything.
A prime example of Rendevous is two Powerbooks in a cafe, both with Airport wireless. You can set up an Ad Hoc wireless network between these computers, and they will auto configure their IP's and other information so that they can talk to each other.
That's not Rendezvous. That's nothing more than self-assigned IP addresses. When your computer can't find a DHCP server, it self-assigns an address in the 169.254/16 network. Which means any two computers on the same network segment that have self-assigned IPs can talk to each other. This has been around since long before Rendezvous.
So Rendevous is not designed to replace DNS/DHCP, but merely to find a way for network configuration when there is no established network structure.
No, that's overstating it. The sole purpose of Rendezvous is service discovery. That's it. It's independent of network configuration. It works with or without DHCP, DNS, or any other network stuff. As long as you've got an IP address, Rendezvous does its thing.
This is really the beauty of it, because it can determine what configuration is necessary and do whatever needed to get the computers networked, all transparently!
No, no, NO! That's not Rendezvous, that's DHCP. Rendezvous is ONLY for service discovery. Rendezvous doesn't set your IP address or your routing table or your hostname resolution parameters. It doesn't do any of those things. All it does is facilitate service announcement and discovery for your applications.
I write in my journal
grr, use preview carefully!
That's 6 MONTHS versus 2 WEEKS.
Bryan
Comparisons have been done. I'd rather have low traffic and better service separation vs the "use-http-for-everything" strategy
You are focusing on the part that doesn't matter. I suspect that in real life, you'd have a hard time finding any performance difference due to the heavier traffic. It's lost in the noise.
The part that is important is specifying the commands and data to/from devices. We learned this lesson back with SCSI-1. When you leave important things up to each vendor (like the way Rendezvous leaves stuff in unstructured text fields for the vendors to define), you end up having to build into your host software a bunch of vendor-specific knowledge. You end up not being able to just go buy and plug in a printer or scanner or whatever and have it work, because the vendor hasn't released documentation to the Linux developers yet.
Notice how much cleaner everything was with SCSI-2 due to having all the important commands specified in the standard, so that you could have generic disk and tape and other drivers that utilized all the device capabilities.
It seems to me that Rendezvous is making the SCSI-1 mistake, which was understandable for SCSI-1 since they didn't have anything to apply hindsight to. The Rendezvous people should be able to look at SCSI-1, though, and see the importance of complete device specifications.
Microsoft has been in alpha now for a bit with a product called "Windows NCD Technology" (I'm a tester). This is Apple's shot across MS's bow.
From the alpha page, Windows Network Connected Device (NCD) Technology is a comprehensive set of Windows technologies that allow devices on a local network to discover, communicate with, and control each other.
Around the early 90's, Apple developed a prototype operating system called Pink, which they later spun off into a company called Taligent, with the help of IBM and Hewlett Packard. Here is an old article about it and why it was canned. I remember reading something about how former Apple CEO John Scully gave a demonstration to some people of what looked like the Macintosh operating system running on a PC. As I recall it could run on both Mac and PC hardware platforms, and was designed in such a way that programmers could create programs that ran on both platforms through object-oriented programming. I purchased a book on it ages ago in which it was described as an "application system". It was meant to be a true cross-platform operating system.
"Insightful" my ass. "Delusional" would be the better adjective. Releasing an OS for Intel would never happen not because Jobs was paid off but because Apple is now, and always has been, a hardware company. A company that makes ~4 billion a year in hardware revenues is not going to abandon that in favor of the few hundred million they make in software.
Apple was "paid off" but the payoff was to drop a lawsuit not to drop development of "rhapsody for Intel" and/or "rhapsody for Windows" which had already been abandoned.
ZeroConf means a visiting professor walks into a lab at a university and can automatically print. There's zero configuration.
It means an iTunes user can broadcast their library on the network and another iTunes user can pick it up with no problem. There's zero configuration.
It means I can open iChat, not go onto AOL's network, and see my coworkers down the hallway with zero configuration.
It means I can share a workgroup document we are editing in SubEthaEdit and easily invite coworkers on the LAN. There's zero configuration
And now it means that non-Mac users can start getting in on a lot of the same stuff.
- Allocate addresses without a DHCP server.
- Translate between names and IP addresses without a DNS server.
- Find services, like printers, without a directory server.
- Allocate IP Multicast addresses without a MADCAP server.
You are quite accurately describing point 3 whereas the parent was describing points 1,2 and 4. But ALL FOUR are rendezvous/zeroconf.Running a PowerBook with the lid closed is officially supported by Apple, and is mentioned in the instruction manual which is included with the machine. As long as the machine detects an external display and a USB keyboard plugged in, it will run perfectly in lid-closed mode.
I know this is different to closing the lid and then stuffing it into a backpack to use as an overgrown iPod, but the point is that lid-closed operation is not a 'banned' operation because of heat issues. It is very much supported for certain applications.
From what I remember this technology either came from Apple or was given a major helping hand. I beleive that the head of the ZeroConf working group is an Apple employee.
Go out and get sailing!
- This is not Appletalk. IT is new.
- This is open
- The *key* feature is the mDNS system.
- Yes, it does automatic IP allocation if there is no DHCP server.. so does Windows (though apple is much faster at it for some reason).
- mDNS is not to be confused with "The global DNS system" that you use to lookup Address records, etc, though it can do that. mDNS is DNS adapted to multicast, for service and host discovery. HOw?
- Instead of querying a DNS server, you query a multicast group (the link-local group in this case) and say "Who has a webserver?" or "who has ssh?" or "hey FOO, what is your IP?" or.. more importantly "Who is a real internet DNS server?" or "Who has an internet gateway?". "Who else is running itunes?".
- a machine joining the network will broadcast once, to send out that it has joined, and what services it has, also via mDNS... so anyone listening can update their caches, etc. The opposite happens when it leaves.
This does not create an extra burden of traffic. Previous to this, most protocols that need to find something in the network do so by rather rude broadcasts.. and usually generate quite a bit of unnecessary traffic.
YES, having a set infrastructure, DNS servers, DHCP, etc, and using DHCP to hardcode everything else, avoiding the need for local network discovery is more efficient. The point is, this works very well WITHOUT any infrastructure.. like 10 guys sitting in a conference room with wireless cards and no servers... or 3 guys on the bus. etc.
NO, rendezvous does not grant ACCESS to your computer.. it merely discovers advertised services... much like an X browser can find a bunch of remote X desktops, or windows TS can find all the terminal servers in the network, or the "network neighborhood" list is populated in windows. It's just a more elegant, scaleable approach.
- mDNS is *not* dns... it is mDNS but if you understand DNS you will understand mDNS. They chose to not make a new protocol, and instead adapt an existing one... which makes it much easier to learn and work with.
One feature I occasionally use is concurrent editing of a document via Rendezvous.
You appear to be mistaken concerning the role that Rendezvous plays in an app like SEE. According to the SEE FAQ, the network protocol used to implement concurrent editing is BEEP.
What Rendezvous is used for is to automatically find other instances of SEE on the local LAN. That's not required for concurrent editing, and in fact SEE allows you to manually specify host names and/or addresses if you need to connect to a machine that Rendezvous can't find automatically.
With this release, the SubEthaEdit team might produce a port to Windows soon
Don't hold your breath. According to that same FAQ, SEE is Cocoa. Unless Apple decides to resurrect Yellow Box, aka OpenStep for Windows, Cocoa apps aren't easily portable to Windows.
BEEP is an open standard though, so you might be able to find a Windows editor that speaks that protocol and works with SEE.
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