Specifications

Niagara Release 2.3
Revised: May 22, 2002 Niagara Networking & Connectivity Guide
Chapter 1 Understanding Networking and IP Addressing
Networking using IP
1–28
When a host tries to contact a particular name (for example, trying to browse
www.bbc.co.uk), it first looks in the local HOSTS file, and upon finding no entry,
checks with its name server. The name server either returns the information if it
knows it, or contacts a root name server, which passes it the address of one of the
name servers responsible for the .uk domain. Then that server returns the address of
a second-level server handling co.uk, which returns the address of the bbc.co.uk
server, which finally returns the IP address for the host named “www”. The browser
uses the IP address to fetch the data to open the page.
WINS WINS is Microsoft’s Windows-only name resolution protocol used by Windows
machines prior to Windows 2000. Like DNS, WINS is also implemented with a
series of servers that maintain databases of host names to IP addresses. However,
setting up WINS is easier than setting up a DNS because WINS actually receives
most address records automatically. Administrators name hosts and set one or more
WINS server as part of the machine configuration. When a host boots it tells the
WINS server its name and current IP address. However, the name that is registered
is not in the DNS format of host.domain.xxx, but is in a proprietary format.
WINS is typically used within a company to provide host name resolution of
company-specific Windows hosts. It is often teamed with DNS to provide external
resolvability.
A pre-Windows 2000 Microsoft host that needs to do a name lookup first looks it up
on a WINS server, and if a match is not returned, then the DNS server is checked.
For information on troubleshooting DNS problems on Windows hosts, see the
“nslookup” section on page 2-23.
DDNS Dynamic DNS (DDNS) is an Internet standard that specifies an automatic method for
updating DNS records. This frees the administrator from the time-consuming process
of manually updating DNS entries. The server that receives the update must be
DDNS compliant.
Microsoft has chosen to replace WINS with DDNS in Windows 2000 computers.
With DDNS, the host name that registers on the DDNS server is the FQDN.
In addition, some Internet companies offer a DDNS service for Internet hosts that
receive a dynamic IP address from their ISPs. For more information about this topic,
see the “Configuring DDNS on the JACE-4/5” section on page 5-22.
Name lookup from the host follows the rules for DNS.
Proxy Servers and Firewalls
This section discusses these devices and their typical use in IP networks today.
Proxy Server Proxy servers are usually implemented to provide connection sharing. With
connection sharing, an organization can acquire a smaller pool of legitimate IP
addresses based on the number of expected simultaneous connections to the Internet
rather than the total number of hosts. For example, if an organization has 500 hosts,