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]

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Chromium 45.0.2454.85 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 45.0.2454.85: Note: Does not contain the "... Read more
OmniFocus 2.2.5 - GTD task manager with...
OmniFocus helps you manage your tasks the way that you want, freeing you to focus your attention on the things that matter to you most. Capturing tasks and ideas is always a keyboard shortcut away in... Read more
iFFmpeg 5.7.1 - Convert multimedia files...
iFFmpeg is a graphical front-end for FFmpeg, a command-line tool used to convert multimedia files between formats. The command line instructions can be very hard to master/understand, so iFFmpeg does... Read more
VOX 2.6 - Music player that supports man...
VOX is a beautiful music player that supports many filetypes. The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all... Read more
Box Sync 4.0.6567 - Online synchronizati...
Box Sync gives you a hard-drive in the Cloud for online storage. Note: You must first sign up to use Box. What if the files you need are on your laptop -- but you're on the road with your iPhone? No... Read more
Carbon Copy Cloner 4.1.4 - Easy-to-use b...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more
OmniGraffle Pro 6.3.1 - Create diagrams,...
OmniGraffle Pro helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use... Read more
Monosnap 3.1.2 - Versatile screenshot ut...
Monosnap lets you capture screenshots, share files, and record video and .gifs! Capture: Capture full screen, just part of the screen, or a selected window Make your crop area pixel perfect with... Read more
Alfred 2.7.2 - Quick launcher for apps a...
Alfred is an award-winning productivity application for OS X. Alfred saves you time when you search for files online or on your Mac. Be more productive with hotkeys, keywords, and file actions at... Read more
Microsoft Remote Desktop 8.0.19 - Connec...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more

We're Sorry to Report that Moonrise...
Moonrise is a very promising-looking, Pokemon-esque monster collecting and battling game that we were really looking forward to reviewing, but unfortunately it looks like that's never going to happen. [Read more] | Read more »
The Latest Update for The Sims FreePlay...
Commerce has gotten a little more active with the newest update for The Sims FreePlay, making Sunset Mall more of a hangout than ever before. [Read more] | Read more »
This Week at 148Apps: August 24-28, 2015
The Apps of August With 148Apps How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you're looking for. The ones we love become Editor’s Choice, standing out... | Read more »
NASCAR in Real Racing 3? Sure, Why Not?
I have to give Firemonkeys credit - it's very cool of them to add NASCAR to Real Racing 3 via an update rather than making a separate game for it. But that's a different discussion for another time; for now let's sit back and enjoy driving in... | Read more »
The nuyu is an Inexpensive Activity Moni...
Today, Health o Meter nuyu has announced a series of health and fitness-related products, including the aforementioned activity monitor along with a wireless scale. All at a decent pricepoint, no less. [Read more] | Read more »
The Makers of Overkill are Trying Someth...
Craneballs, the studio responsible for the Overkill series, is taking a little break from all that violence (a little break) to bring us Cube Worm - a 3D take on one of the most classic PC/calculator games in existence. [Read more] | Read more »
The Sandbox Welcomes Cutethulu in its La...
Another month, another update to Pixowl's The Sandbox. This time players can say hello to "Cutethulu" - an adorable little rendition of perhaps the most well known (and infamous) of the Elder Gods. [Read more] | Read more »
ReBoard: Revolutionary Keyboard (Utilit...
ReBoard: Revolutionary Keyboard 1.0 Device: iOS Universal Category: Utilities Price: $1.99, Version: 1.0 (iTunes) Description: Do everything within the keyboard without switching apps! If you are in WhatsApp, how do you schedule a... | Read more »
Tiny Empire (Games)
Tiny Empire 1.1.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.1.3 (iTunes) Description: Launch cannonballs and blow tiny orcs into thousands of pieces in this intuitive fantasy-themed puzzle shooter! Embark on an... | Read more »
Astropad Mini (Productivity)
Astropad Mini 1.0 Device: iOS iPhone Category: Productivity Price: $4.99, Version: 1.0 (iTunes) Description: *** 50% off introductory price! ​*** Get the high-end experience of a Wacom tablet at a fraction of the price with Astropad... | Read more »

Price Scanner via MacPrices.net

eFileCabinet Announces SMB Document Managemen...
Electronic document management (EDM) eFileCabinet, Inc., a hosted solutions provider for small to medium businesses, has announced that its SecureDrawer and eFileCabinet Online services will be... Read more
WaterField Designs Unveils American-Made, All...
San Francisco’s WaterField Designs today unveiled their all-leather Cozmo 2.0 — an elegant attach laptop bag with carefully-designed features to suit any business environment. The Cozmo 2.0 is... Read more
Apple’s 2015 Back to School promotion: Free B...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more
128GB MacBook Airs on sale for $100 off MSRP,...
B&H Photo has 11″ & 13″ MacBook Airs with 128GB SSDs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air: $799.99, $100 off MSRP... Read more
13-inch 2.5GHz MacBook Pro (refurbished) avai...
The Apple Store has Apple Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.... Read more
27-inch 3.2GHz iMac on sale for $1679, save $...
B&H Photo has the 27″ 3.2GHz iMac on sale for $1679.99 including free shipping plus NY sales tax only. Their price is $120 off MSRP. Read more
Apple and Cisco Partner to Deliver Fast-Lane...
Apple and Cisco have announced a partnership to create a “fast lane” for iOS business users by optimizing Cisco networks for iOS devices and apps. The alliance integrates iPhone with Cisco enterprise... Read more
Apple offering refurbished 2015 13-inch Retin...
The Apple Store is offering Apple Certified Refurbished 2015 13″ Retina MacBook Pros for up to $270 (15%) off the cost of new models. An Apple one-year warranty is included with each model, and... Read more
Apple refurbished 2015 MacBook Airs available...
The Apple Store has Apple Certified Refurbished 2015 11″ and 13″ MacBook Airs (the latest models), available for up to $180 off the cost of new models. An Apple one-year warranty is included with... Read more
21-inch iMacs on sale for up to $120 off MSRP
B&H Photo has 21″ iMacs on sale for up to $120 off MSRP including free shipping plus NY sales tax only: - 21″ 1.4GHz iMac: $999.99 $100 off - 21″ 2.7GHz iMac: $1199.99 $100 off - 21″ 2.9GHz iMac... Read more

Jobs Board

*Apple* Desktop Analyst - KDS Staffing (Unit...
…field and consistent professional recruiting achievement. Job Description: Title: Apple Desktop AnalystPosition Type: Full-time PermanentLocation: White Plains, NYHot Read more
Simply Mac- *Apple* Specialist- Store Manag...
Simply Mac is the largest premier retailer for Apple products and solutions. We're looking for dedicated individuals with a passion to simplify and enhance the Read more
*Apple* Evangelist - JAMF Software (United S...
The Apple Evangelist is responsible for building and cultivating strategic relationships with Apple 's small and mid-market business development field teams. This 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* Desktop Analyst - KDS Staffing (Unit...
…field and consistent professional recruiting achievement. Job Description: Title: Apple Desktop AnalystPosition Type: Full-time PermanentLocation: White Plains, NYHot Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.