Internet week review

	TZO review: King of the Domain Name by Steve Antonoff

•	Tzolkin's domain name services quickly redirect Web traffic to changed IP addresses

•	It's an axiom of e-commerce: Before customers can buy from you, they have to reach your server by way of a domain name system. Two services from Tzolkin Corp. can help take them there.

•	Most small and midsize companies would prefer not having to choose between using their ISP's DNS and running one of their own. Either option will leave them at the mercy of the ISP for their IP address space. And in the event of a change in IP addresses, it could take several days for the IP information to filter through the Internet.These problems, coupled with dynamic IP address assignment for companies that use DSL or some other connectivity alternative, explain the need for a provider of dynamic DNS.

•	Tzolkin offers two low-cost dynamic DNS services that can help customers access a company's Web site even if the ISP is having trouble with the site's IP address. Tzolkin's basic service, TZO Dynamic DNS (DDNS), provides an address "buffer" between customers and the corporate server, letting commerce-hungry users visit the Web site regardless of changes in the company's IP address.

•	The TZO AutoFailover service, which Tzolkin added recently, begins with the same general functionality as DDNS, but differs in that it lets two or more servers operate as alternative destinations. Using AutoFailover, a company can steer customers to its Web site even if the main server goes offline.

•	Regular Checkups DDNS, in its basic mode, accommodates changes in a Web server's IP address that occur at random times, as in the case of DSL and other dynamic IP address systems. With DDNS, a new IP location can be put into use within two minutes, as opposed to the 24 hours or more that might otherwise be needed. Few customers ever notice the change in address.DDNS accomplishes its task by running a 664-KB application on your Windows NT/2000 server or on a Windows 95/98/ME machine. This small application notifies Tzolkin whenever an IP address change occurs.The Tzolkin server updates its address tables, and future queries return the new address. Since the cache interval is small, most requests have to be refreshed within a few minutes, resulting in only a short disruption.

•	Distributed Backup Consider a scenario in which a midsize company has two Web sites at separate locations--say, one in the United States and the other in the United Kingdom. These sites have the same information but provide primary access to users on the appropriate continent. Should a failed server or Internet disruption bring down one of those sites, an entire continent might be left unconnected, with thwarted customers receiving a "failure" message from their browser.

•	AutoFailover can avert this problem. When AutoFailover is engaged, both servers are listed with the service. A small page is inserted into each site--it needn't be accessible from the home page or have any links to it, but the service must know the page name. At time intervals of one minute to 30 minutes, depending on what the owner of the corporate servers specified, two of the Tzolkin servers will request the predefined page from the corporate Web sites.The two sites request the same page from both corporate servers. When a site fails to access the page, a notice is sent to the central Tzolkin system. If both sites fail, the central system replaces the IP address of the down server with the IP address of the functional server.

•	You can choose when the IP address will be changed back--for instance, when the down system comes back up or when the second system goes down. You can also direct AutoFailover to send notification to one or more e-mail addresses when a server goes down or comes back up. This includes pager notification via e-mail, if your pager supports such capability.A series of Web pages are used to control and configure the AutoFailover service. The first shows all of the options that Tzolkin offers its account holders.

•	The option of interest here is the "AutoFailover--Manage Enterprise" button. Selecting this option brings up a second page, which shows the AutoFailover settings for the account. From this page, you can get to the Notifications options. From the Notifications page, you can designate the e-mail addresses to be notified when a server's status changes.One of the interesting parts of AutoFailover is that Tzolkin keeps track of some uptime statistics for both the primary and secondary sites.AutoFailover supports multiple protocols: HTTP, HTTPS, ping, SMTP and Telnet. For HTTP/HTTPS, you specify a page to query. For the others, you specify a domain or IP address.DDNS and AutoFailover are available for both Windows and Linux.

•	The basic TZO DDNS service costs $24.95 per year ($39.95 if you buy two years at a time). Pricing for the AutoFailover service is considerably more, but still reasonable for what it does: $1,000 per year for the first protocol and $850 per year for each additional protocol. For a business that depends on customers finding its Web site but can't afford to spend "whatever it takes" to provide commerce site redundancy, an investment in DDNS or AutoFailover is well worth making.

•	Steve Antonoff is chief technologist at TesCom-USA, an IT testing organization. He can be reached at santonoff@bigfoot.com