Many applications require DNS in order to work. Among them are Java applets, chat programs and the SOCKS4 protocol. The SOCKS protocol is becoming an increasingly popular choice among programmers when adding proxy support to applications. ICQ, Instant Messager and a number of other applications utilize the SOCKS protocol for proxy support.

The Sambar DNS Server is a partial DNS implementation, the server does not respond to requests for NS-Records (used by other DNS servers) or CNAME-Records (aliases). The server is designed to service UDP requests for host addresses (A-Record requests) and mail servers (MX-Record requests). All other other requests are forwarded (along with unknown A-Record and MX-Record requests) to your ISPs DNS server (these must be configured in the config.ini as the DNS Primary and DNS Secondary). In a future release, the Sambar DNS server will provide caching of proxied A-Record and MX-Record requests to enhance DNS lookup performance.

Hosts File
The hosts file used by the Sambar DNS Server can reside anywhere on the machine. On Windows NT, the default location for the file is %ServerRoot%\System32\Drivers\Etc. On Windows 95, the default location for the file is %ServerRoot%. The Sambar Server assumes the file is in the config directory where the Sambar Server is installed. You may wish to change the DNS configuration to point to the Operating System's hosts file.

The format of the file is the same as the format of the UNIX /etc/hosts file; each line consists of an IP Address in dotted-octet notation (i.e. 209.157.142.114), followed by whitespace and the name(s) of the host (i.e. www.sambar.com www). Note: The canonical name of the host should appear first, followed by any aliases.

Note! If DNS Wildcards is set to true in the config/config.ini file, basic wildcard pattern matching will be used when performing A record lookups against either the hosts or mxhosts files.

MXHosts File
The mxhosts file used by the Sambar DNS Server and mail server. The Sambar Server assumes the file is in the config directory where the Sambar Server is installed (there is no equivalent for the mxhosts file on Windows machines). MX records are used exclusively for mail routing. This service is largely provided by your ISP; the functionality is included in the Sambar Server for testing mail configurations and local distribution of mail (behind a firewall).

The format of the file consists of an mail server hostname (i.e. smtp.sambar.com) followed by whitespace and the name(s) of the mail domains:

smtp.sambar.com sambar.com sambar.net

DNS Overview
A domain name is an addressing construct used for identifying and locating computers on the internet. An example of a domain name is sambar.com. While computers use Internet Protocol (IP) addresses to locate each other, these long numberic addresses are much less convenient to remember than symbolic names (web addresses). Not many users know the IP address for Sambar Technologies, but it is fairly easy to remember www.sambar.com. The Domain Name Server acts like the white pages of a telephone directory. It maintains a list of network names and their corresponding IP addresses. So the entry for www.sambar.com would look something like:

209.157.142.114 www.sambar.com

DNS databases are distributed in a hierarchical manner. The "root" DNS servers maintain the locations of other name servers with are authoritative for their domains. Each network must maintain a DNS server for the IP addresses that can be reached via that network; this task usually falls to your ISP. So a DNS search proceeds from the "root" name servers downward getting progressively closer to the name server that actually knows the name and IP address of the destination in question.

When given www.sambar.com as a destination, your web browser requests the IP address from a Domain Name Server. The DNS daemon looks in its database for the name and returns the IP address, or forwards the request to the appropriate server. Your browser then sends its request to the resolved IP address.

There are usually two name servers for a particular domain. The primary name server is consulted first by the resolver on a host machine in order to obtain DNS information. If the primary does not respond, the resolver will attempt to obtain the information from the secondary. If neither name server responds, you will typically see a The Server does not have a DNS entry error message in your application.

DNS Forwarding
DNS forwarding is useful for a protocol like SOCKS4, where it is necessary to perform name resolution in order to contact internet hosts. If DNS forwarding is enabled, the Sambar Server will forward all DNS requests that can't be resolved locally to the specified DNS server (typically your ISPs) and return the response to the client.

To see if the DNS requests are reaching the Sambar Server, make sure that Trace DNS = true in the config/config.ini file. The next step to make sure DNS requests are being passed through the server is to edit the config/hosts.ini and add the entry: 127.0.0.1 www.yahoo.com. As a result of this entry, the Sambar Server should translate DNS requests for www.yahoo.com to your local machine (localhost). Removing this entry should again result in the DNS lookup request being forwarded to your DNS Primary and/or DNS Secondary server for resolution.

Internet DNS
The Sambar DNS server is NOT appropriate to act as a primary or secondary DNS server for an internet domain. Please do not send mail to Sambar Technologies asking how you can setup www.mysite.com. If you need to ask this question, the answer is always: Contact your ISP.

The Sambar DNS server is designed for intranet use (and internet-proxying) only. For all other DNS needs, you will likely need to run bind.

Configuring DNS Clients
In order to use the DNS Server for your local network, each client machine must be configured to use the Sambar DNS Server:

• Bring up the Network dialog box (Control Panel) and select the TCP/IP protocol line.
• Click the DNS Configuration Tab and then Enable DNS. Under Host, enter the name of your machine.
• Under the Domain, enter the domain name used on the Sambar Server machine.
• In the DNS Server Search Order box, enter the IP address of the Sambar Server machine.
• Click OK to complete the configuration changes.

To verify your Sambar DNS Server is properly configured, you can use the ping utility. Open an MS-DOS Command window and use ping with the name of a machine configured in the Sambar Server hosts file setup with the DNS Server. You should see the DNS request being made to the Sambar Server (via the GUI) and responded to.

DNS Primary/Secondary
The config/config.ini contains entries for a DNS Primary and DNS Secondary server where unresolved DNS requests are forwarded to. In general, these should be set to the primary and secondary DNS servers configured for the host. By default, if blank these are set to:

DNS Primary = 207.217.126.81
DNS Secondary = 207.217.77.82


• Close proximity to a DNS server is important to quick and efficient operation of the mail server. In particular, MX record resolution may time out if the DNS servers specified are slow to respond due to inherent performance or geographic reasons.
• The default servers are owned and operated by Earthlink. If you are not an Earthlink customer, your access to these servers could be terminated at any point resulting in an inibility to delivery mail and potential failure of additional Web services.