Specifications

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7.5 Gateway
Ethernet is a local network. This means each device is in direct communication with all other devices.
When a device needs to discover information on the LAN it broadcasts the request to everyone. This is
ideal on a small network but does not scale very well; the network quickly becomes overloaded with
broadcast traffic. The solution to this problem is to interconnect individual LANs with a router. Routers
have the intelligence to interconnect multiple networks. This confines broadcast discovery to a small group.
When a host is unable to connect directly to another host it forwards the packet to the router. The router
determines how best to deliver the packet. It may deliver it directly to the recipient or have to forward it to
another router. Routers exchange route messages among themselves to determine the best route. Each
router segment is called a hop.
One of the parameters each host needs to know is the address of its local router, also called a Gateway.
When a DHCP server is used it sets this address automatically. In our network the Gateway address is the
broadband router.
The name Internet is a contraction of Inter-network. The Internet is a network of networks.
7.6 Name Resolution
Entering long strings of numbers such as 192.168.0.3 is not very convenient. The Domain Name Service
(DNS) allows a name to be used instead of a number. When you enter a Uniform Resource Locator (URL)
into your web browser, such as http://www.yahoo.com, the browser first checks to see if this is a name of a
local device on the LAN. If it is not local the name resolution request is forwarded to a DNS name server.
Your ISP provides the first name server in the chain. If it doesn’t know the address the request is passed to
other DNS servers until the targets IP address is found. Once the system obtains the IP address it uses the
address to connect to the remote host. DNS names are a convenience for humans, computer use IP
addresses to communicate. DNS acts as a giant Internet “White Pages.”
Computers on the LAN use a different name resolution mechanism. Names are broadcast using NetBIOS
over IP. This works well when on small LANs, it eliminates the need to use a local DNS server or other
name resolution technique.
7.6.1 Naming Convention
URL names provide a friendly handle to access a particular site. Domain names are hierarchal, the highest
level is called the top-level domain (TLD) these are the COM, EDU, ORG, MIL and GOV of the world. As
the Internet expanded each country was assigned a unique two letter top level domain. For example the
TLD for the United Kingdom is UK. Within each domain various agencies are responsible for name
registration. This has been the source of much controversy in recent years but need not concern us here.
The role of the agency is to insure each registered domain name is unique within a top-level domain. For
example in our case the “Schmidt.com” domain was already assigned so we picked tschmidt.com.
Sometimes a company adds additional sub domains such as www.tschmidt.com for web access,
mail.tschmidt.com for mail or product.tschmidt.com for product info. The name hierarchy is evaluated
from right to left starting with the TLD.
7.7 Whois
Some times it is useful to look up the owner of a domain. The WHOIS database stores contact information
for each registered domain name.