These are variations of the TTL flash developed by Canon. They are available on some Canon camera bodies and dedicated flash units. The differences can be summarized as follows: TTL measures light reflected off the film plane during flash exposure. Once enough light has reached the film for proper exposure, the flash pulse is cut short. A-TTL uses a pre-flash and a light sensor on the flash unit to evaluate the proper illumination needed.

Add domain (subdomain) in section hosts, remember ip for this subdomain, register this domain (subdomain) on your DNS servers (sub.domain.com , www.sub.domain.com ).

If you have source for BIND, you can modify it as indicated in the diff below. It causes the global variable _dns_ttl_ to be set with the TTL of the most recent lookup. Then, when you compile Squid, the configure script will look for the _dns_ttl_ symbol in libresolv.a. If found, dnsserver will return the TTL value for every lookup. diff -ru bind-4.9.4-orig/res/gethnamaddr.c bind-4.9.4/res/gethnamaddr.c --- bind-4.9.4-orig/res/gethnamaddr.c Mon Aug 5 02:31:35 1996 +++ bind-4.9.4/res/gethnamaddr.

The TTL tells a DNS server how long it is allowed to cache a DNS record. Caching is a standard feature in the DNS. When one DNS server queries another DNS server for a record, it is allowed to store the answer in its local memory cache for the number of seconds specified by the TTL value. Only after the TTL has expired will the caching server repeat the query to get a fresh copy of the DNS record from the authoritative server.

A Subdomain is the Internet address (URL) of a website that is located in a subdirectory of a registered domain. For example, this newsletter is a subdomain of USASTAR.COM. (www.usastar.com/newsletter). Websites established as subdomains do not need to register and pay fees associated with InterNIC (see the InterNIC explanation above). Internet domain names have become a vital part of corporate identity.