TweetFollow Us on Twitter

Multihoming with Homedoor
Volume Number:12
Issue Number:1
Column Tag:Internet Special

Inside HomeDoor

Make one web server act like a network of servers

By Alan B. Oppenheimer

The HomeDoor™ Default Home Page Server is a newly-announced product from Open Door Networks. HomeDoor enables a single Macintosh Web server to serve default home pages for multiple domains. This article describes the inner workings of HomeDoor.

Product Summary

HomeDoor is a Macintosh extension and associated Admin application which enables an Ethernet-based Macintosh to redirect requests for particular default home pages to particular subdirectories on any Web server. For example, HomeDoor can redirect URLs of the form http://www.companyX.com/ to the form http://www.yourwebserver.com/companyX/. HomeDoor supports up to 256 such redirections, allowing you to set up a large number of default home pages on a single MacOS-based Web server. HomeDoor also supports the creation of complete “virtual” domains associated with each of these home pages.

The Web server (or servers) to which HomeDoor redirects requests do not necessarily have to be in the same machine, or even on the same network, as HomeDoor. You configure HomeDoor with a unique IP address for each default home page it is going to serve. You will also generally want to assign a domain name, such as www.companyX.com, to each of these addresses. For each address, you then configure HomeDoor with the URL to redirect that address to. When HomeDoor gets an HTTP request to one of the addresses it’s managing, it redirects that request to the configured URL. HomeDoor can be used to serve default home pages in this manner, and also to serve full “virtual” domains, redirecting not only URLs of the form http://www.companyX.com/, but also URLs of the form http://www.companyX.com/file-or-directory. When redirecting such URLs, HomeDoor preserves the “file-or-directory” part, thus supporting the creation of complete virtual domains.

Multihoming - The Key to HomeDoor

The key architectural component of HomeDoor is multihoming. Multihoming is the ability of a single physical node on a network to have more than one address (or “home”) on that network. Neither MacTCP nor the TCP/IP implementation in Open Transport provides multihoming, although Apple intends multihoming to be a feature of Open Transport 2.0. HomeDoor thus had to implement a simple form of multihoming itself. HomeDoor’s multihoming is limited to those Internet protocols required for HTTP (specifically ARP, IP and TCP), plus a small subset of ICMP so that HomeDoor can respond to pings for its addresses. HomeDoor does not provide a general-purpose implementation of multihoming.

HomeDoor’s multihoming is implemented directly on top of the Macintosh Ethernet driver, below the TCP/IP stack. HomeDoor tells the Ethernet driver to pass it all packets of Ethernet type “ARP” or “IP.” Because of the way the IP protocol suite works, the packets HomeDoor needs to receive are either broadcast (ARP packets), or sent directly to the Macintosh’s Ethernet address (IP packets). This fact is important, because it prevents HomeDoor from needing to have the Ethernet driver listen to every packet sent on the network, which would adversely affect performance.

After being passed an ARP or IP packet from the Ethernet driver, HomeDoor determines if the packet is intended for an address in its address range. If the packet is in range, HomeDoor processes the packet as appropriate, implementing the required parts of ARP, IP, TCP or ICMP. If the packet is not in HomeDoor’s address range, and MacTCP is running, HomeDoor passes the packet to MacTCP. Otherwise HomeDoor discards the packet. By passing packets to MacTCP, HomeDoor can run on the same Macintosh as any MacTCP client or server, and specifically in the same Macintosh as a Web server for which it is serving default home pages. HomeDoor does not, however, require MacTCP to run. HomeDoor also will not currently run at all on a Macintosh which is running Open Transport, due to OT’s radically different driver architecture.

Redirection

As shown below in figure 1, HomeDoor takes advantage of a feature in HTTP known as redirection. A browser wishing to look at a Web page issues an HTTP GET command to the address indicated by the first part of the URL, after obtaining that address from a domain name server (DNS). If the address is being managed by HomeDoor, HomeDoor receives the request and returns an HTTP REDIRECT in response. The REDIRECT contains the actual URL of the associated default home page. The browser receives the REDIRECT and then requests that page directly from the actual server, using the new URL. From then on, the browser talks directly to the Web server if other (relative) links on that server are accessed.

Figure 1. How HomeDoor works

Virtual domains

To be precise, HomeDoor actually does more than simply returning, in the REDIRECT, the URL that has been configured for the address requested. Technically speaking, HomeDoor actually replaces the part of the URL which specifies the Web server itself with the URL to be returned. So a URL of the form http://www.companyX.com/ is returned as http://www.yourwebserver.com/companyX/, but a URL of the form http://www.companyX.com/file-or-directory becomes http://www.yourwebserver.com/companyX/file-or-directory. Since the “file-or-directory” part can in fact be arbitrarily long, a full “virtual” domain can be served by HomeDoor.

Completing the illusion

HomeDoor effectively allows a single Macintosh Web server to serve default home pages, and in fact full virtual domains, for up to 256 different domain names. HomeDoor does so in a manner that is almost totally transparent to Web browsers. The only significant exception is that most browsers display a page’s actual URL in their “location” f ield. Thus, for example a browser user would see the URL http://www.yourwebserver.com/companyX/, even though they typed in or accessed the URL http://www.companyX/. Even this minor side-effect, however, can be eliminated by using a DNS to set up an appropriate alias to the actual Web server, and using HomeDoor to redirect to that alias as opposed to to the Web server itself. For instance, instead of redirecting http://www.companyX.com to http://www.yourwebserver.com/companyX/, you could redirect it to http://www2.companyX.com/companyX/, where www2.companyX.com is an alias for www.yourwebserver.com. In this way, not only will the Web browser user see the correct domain name in the “location” field, but it will appear to the user that the domain in question has not one but two complete Web servers associated with it (www.companyX.com and www2.companyX.com).

Subtleties of HomeDoor

The HomeDoor design contains a number of subtleties which might not be immediately apparent. These subtleties are based on the fact that HomeDoor allows you to enter a full URL for each address it is managing. This flexibility allows, for instance, a single HomeDoor server to serve home pages and virtual domains for more than one Web server. And, although HomeDoor runs on a Macintosh, there is no reason that the Web servers themselves need to be Macintoshes. HomeDoor can serve default home pages for any type of Web server whatsoever. HomeDoor can also redirect URL’s to other network services, allowing, for instance, an HTTP URL to be redirected to an FTP server. Finally, with some small modifications, the HomeDoor architecture can be enhanced to provide many additional services. One area for immediate investigation involves having HomeDoor redirect a particular URL to a URL chosen randomly or sequentially from a group of other URLs, enabling HomeDoor to serve as the front end to a Redundant Array of Inexpensive Computers (RAIC).

How To Find Out More

Open Door Networks maintains a complete set of home pages on the HomeDoor product. Not only do these pages include product details, example pages served by HomeDoor and a full copy of the HomeDoor Users’ Guide, but also a downloadable evaluation version of the current release of HomeDoor. The HomeDoor pages are at http://www.opendoor.com/homedoor/. General information on Open Door Networks, one of the first Macintosh-based Internet service providers, is available at http://www.opendoor.com. Specific questions should be addressed to help@opendoor.com.

[For those of you that would like to see a real life example of this technology, we use HomeDoor on one of our servers in the Xplain Corp./MacTech offices. In fact, the www.mactech.com and www.devcentral.com web sites are redirected using HomeDoor. This allows us to have an all Macintosh Internet site without having to resort to Unix. We’re very pleased with this solution.

There are some minor limitations to the way that HomeDoor works (although it does benefit from an all Macintosh user interface). If you want a different solution, Unix does offer the most complete “multi-homing” solution available. And, if you want to stay with the Macintosh (and why wouldn’t you?), then MachTen from Tenon is your answer - it’s a kinder, gentler Unix. :) - Pub. nst]

 
AAPL
$119.00
Apple Inc.
+1.40
MSFT
$47.75
Microsoft Corpora
+0.28
GOOG
$540.37
Google Inc.
-0.71

MacTech Search:
Community Search:

Software Updates via MacUpdate

Skype 7.2.0.412 - Voice-over-internet ph...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more
HoudahSpot 3.9.6 - Advanced file search...
HoudahSpot is a powerful file search tool built upon MacOS X Spotlight. Spotlight unleashed Create detailed queries to locate the exact file you need Narrow down searches. Zero in on files Save... Read more
RapidWeaver 6.0.3 - Create template-base...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
iPhoto Library Manager 4.1.10 - Manage m...
iPhoto Library Manager lets you organize your photos into multiple iPhoto libraries. Separate your high school and college photos from your latest summer vacation pictures. Or keep some photo... Read more
iExplorer 3.5.1.9 - View and transfer al...
iExplorer is an iPhone browser for Mac lets you view the files on your iOS device. By using a drag and drop interface, you can quickly copy files and folders between your Mac and your iPhone or... Read more
MacUpdate Desktop 6.0.3 - Discover and i...
MacUpdate Desktop 6 brings seamless 1-click installs and version updates to your Mac. With a free MacUpdate account and MacUpdate Desktop 6, Mac users can now install almost any Mac app on macupdate.... Read more
SteerMouse 4.2.2 - Powerful third-party...
SteerMouse is an advanced driver for USB and Bluetooth mice. It also supports Apple Mighty Mouse very well. SteerMouse can assign various functions to buttons that Apple's software does not allow,... Read more
iMazing 1.1 - Complete iOS device manage...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
PopChar X 7.0 - Floating window shows av...
PopChar X helps you get the most out of your font collection. With its crystal-clear interface, PopChar X provides a frustration-free way to access any font's special characters. Expanded... Read more
OneNote 15.4 - Free digital notebook fro...
OneNote is your very own digital notebook. With OneNote, you can capture that flash of genius, that moment of inspiration, or that list of errands that's too important to forget. Whether you're at... Read more

Latest Forum Discussions

See All

Raby (Games)
Raby 1.0.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.3 (iTunes) Description: ***WARNING - Raby runs on: iPhone 5, iPhone 5C, iPhone 5S, iPhone 6, iPhone 6 Plus, iPad Mini Retina, iPad Mini 3, iPad 4, iPad Air,... | Read more »
Oddworld: Stranger's Wrath (Games)
Oddworld: Stranger's Wrath 1.0 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0 (iTunes) Description: ** PLEASE NOTE: Oddworld Stranger's Wrath requires at least an iPhone 4S, iPad 2, iPad Mini or iPod Touch 5th gen... | Read more »
Bounce On Back (Games)
Bounce On Back 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »
Dwelp (Games)
Dwelp 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: === 50% off for a limited time, to celebrate release === Dwelp is an elegant little puzzler with a brand new game mechanic. To complete a... | Read more »
Make Way for Fat Chicken, from the Maker...
Make Way for Fat Chicken, from the Makers of Scrap Squad Posted by Jessica Fisher on November 26th, 2014 [ permalink ] Relevant Games has announced they will be releasing their reverse tower defense game, | Read more »
Tripnary Review
Tripnary Review By Jennifer Allen on November 26th, 2014 Our Rating: :: TRAVEL BUCKET LISTiPhone App - Designed for the iPhone, compatible with the iPad Want to create a travel bucket list? Tripnary is a fun way to do exactly that... | Read more »
Ossian Studios’ RPG, The Shadow Sun, is...
Ossian Studios’ RPG, The Shadow Sun, is Now Available for $4.99 Posted by Jessica Fisher on November 26th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Mmmm, Tasty – Having the Angry Birds for...
The very first Angry Birds debuted on iOS back in 2009. When you sit back and tally up the number of Angry Birds games out there and the impact they’ve had on pop culture as a whole, you just need to ask yourself: “How would the birds taste... | Read more »
Rescue Quest Review
Rescue Quest Review By Jennifer Allen on November 26th, 2014 Our Rating: :: PATH BASED MATCH-3Universal App - Designed for iPhone and iPad Guide a wizard to safety by matching gems. Rescue Quest might not be an entirely original... | Read more »
You Can Play the Final Chapter of Lone W...
You Can Play the Final Chapter of Lone Wolf: Dawn Over V’taag Right Now Posted by Jessica Fisher on November 26th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »

Price Scanner via MacPrices.net

Black Friday: $300 off 15-inch Retina MacBook...
 B&H Photo has the new 2014 15″ Retina MacBook Pros on sale for $300 off MSRP as part of their Black Friday sale. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina... Read more
2014 1.4GHz Mac mini on sale for $449, save $...
 B&H Photo has the new 1.4GHz Mac mini on sale for $449.99 including free shipping plus NY tax only. Their price is $50 off MSRP, and it’s the lowest price available for this new model. Adorama... Read more
Early Black Friday pricing on 27-inch 5K iMac...
 B&H Photo continues to offer Black Friday sale prices on the 27″ 3.5GHz 5K iMac, in stock today and on sale for $2299 including free shipping plus NY sales tax only. Their price is $200 off MSRP... Read more
Early Black Friday sale prices on iPad Air 2,...
 MacMall is discounting iPad Air 2s by up to $75 off MSRP as part of their Black Friday sale. Shipping is free: - 16GB iPad Air WiFi: $459 $40 off - 64GB iPad Air WiFi: $559 $40 off - 128GB iPad Air... Read more
Early Black Friday MacBook Air sale prices, $...
 MacMall has posted early Black Friday MacBook Air sale prices. Save $101 on all models for a limited time: - 11″ 1.4GHz/128GB MacBook Air: $798 - 11″ 1.4GHz/256GB MacBook Air: $998 - 13″ 1.4GHz/... Read more
Why iPhone 6 Tablet/Laptop Cannibalization Is...
247wallst.com blogger Douglas A. McIntyre noted last week that according to research posted on the Applovin blog site the iPhone 6 is outselling the iPhone 6 Plus by a wide margin . Hardly a surprise... Read more
Worldwide Tablet Growth Expected to Slow to 7...
The global tablet market is expected to record massive deceleration in 2014 with year-over-year growth slowing to 7.2%, down from 52.5% in 2013, according to a new forecast from International Data... Read more
Touchscreen Glove Company Announces New Produ...
Surrey, United Kingdom based TouchAbility specializes in design and manufacture of a wide variety of products compatible with touchscreen devices including smartphones, tablets and computers. Their... Read more
OtterBox Alpha Glass Screen Protectors for iP...
To complement the bigger, sharper displays on the latest Apple devices, OtterBox has introduced Alpha Glass screen protectors to the iPhone 6 and iPhone 6 Plus. The fortified glass screen protectors... Read more
Early Black Friday Mac Pro sale, 6-Core 3.5GH...
 B&H Photo has the 6-Core 3.5GHz Mac Pro on sale today for $3499 including free shipping plus NY sales tax. Their price is $500 off MSRP, and it’s the lowest price available for this model from... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.