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VitalQIP Product Description
built-in mechanisms to communicate network reachability information. Essentially, routers
would state, "I can reach the 192.168.10.0 network in 3 hops," while another may brag, "I can
reach the 192.168.10.0 network in 2 hops!" Typically the route with the fewer hops was
chosen to route packets with a destination address within the 192.168.10.0 network.
As adoption of IP exploded in the early 1990's, available address space became scarcer.
Network administrators had to subdivide, or subnet, IP networks in order to maximize
utilization of their IP space. For example, subnetting provides a mechanism for dividing the
192.168.10.0 network further into a number of subnetworks. This is done by applying a "mask"
which determines the number of bits that define the network portion of the address (IP
addresses are represented as four dotted decimal numbers, but when it comes down to it,
they are 32 bit addresses!). Routers only care about the network to which to send the packet,
so they need to know the network, which requires knowledge of the network mask.
The number of bits in the mask is notated following the network address; e.g.,
192.168.10.0/26 indicates a mask of 26 bits. From our earlier example, one could create four
networks from the 192.168.10.0/24 network as: 192.168.10.0/26; 192.168.10.64/26;
192.168.10.128/26; and 192.168.10.192/26. Now instead of one network with 254 hosts, I
have four networks with 62 hosts each. An administrator could now assign these four
networks to four locations of 62 or fewer hosts for example, instead of using one network
address and using three others for the other three sites. As you can see, a reasonably sound
understanding of binary arithmetic is required for proper subnetting.
Today and in the future, the complexity of subnetting, growing networks and even as far as
the introduction of IPv6 as the next generation numbering plan makes manual use of IP
Addresses impossible. Now a network will be defined as 192.168.10.0.192.168.10.0/ VitalQIP
supports both IPv4 and IPv6 today.
1.3.3
Configuring host name to IP address lookup facilities
In section 1.3.1, we described the use of the hosts.txt file. This worked well when there were
a few universities dabbling with IP back in the 1970's. As a new host joined the Internet, the
word went forth to other "members" to update their hosts.txt files accordingly. A master
copy with all Internet hosts to IP address mappings was published and made available for easy
download. As you can imagine, this didn't scale too well. As the rate of new hosts accessing
the Internet grew, the rate of hosts.txt updates grew and more and more hosts grew out of
synch. The Internet Engineering Task Force (IETF) therefore embarked on a more scalable
solution. They arrived at what we know as the Domain Name System or DNS. DNS provides a
hierarchical delegation structure that is best illustrated by example.
Back when Alcatel-Lucent was founded, the Alcatel-Lucent IT group asked the naming
registrar, such as Network Solutions, for the domain name "Alcatel-Lucent.com." Network
Solutions noted that no one else reserved that name, so replied, "OK, you can have Alcatel-
Lucent.com, and everything 'beneath' it, but just tell me where to send folks looking for
Alcatel-Lucent.com or what's beneath." Essentially, Network Solutions delegated the name to
Alcatel-Lucent's IT group along with the responsibility for further handling delegation beneath
Alcatel-Lucent.com, say qip.Alcatel-Lucent.com. Alcatel-Lucent provided the IP addresses of
at least two DNS servers that knew how to translate Alcatel-Lucent.com, qip.Alcatel-
Copyright © 2011 Alcatel-Lucent Technologies
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