Page 123 - DMGT505_MANAGEMENT_INFORMATION_SYSTEM

Management Information Systems

Notes UDP Checksum: It gives an option of integrity checking.
At this point, it is important to understand the layering concept along with the need for headers.
The relationship between the IP and UDP has been depicted in Figure 6.18.

There are a number of good reasons for choosing UDP as a data transport service. When the
amount of data being transmitted is small, UDP is considered the most efficient choice for a
transport layer protocol because of the overhead for establishing connections and ensuring
reliable delivery may be greater than the work of retransmitting the entire data. Applications
for a query-response model also works excellent for using UDP. The response is used as a
positive acknowledgment to the query. When a response is not received within a certain time
period, the application initiates another query.
Some examples of the usage of UDP are Remote file server (RFS), name translation (DNS), intra-
domain routing (RIP), network management (SNMP), multimedia applications and telephony.

Figure 6.18: Relationship between the IP and UDP

IRP

Routing refers to the process of selecting the shortest and most reliable path intelligently over
which to send data to its ultimate destination. IP routing protocol makes the distinction between
hosts and gateways. A host is the end system to which data is ultimately delivered. An IP
gateway, on the other hand, is the router that accomplishes the act of routing data between two
networks. A router can be a specialized device supporting multiple interfaces, with connected to
a different network or a computer multiple interfaces (commonly called a multihomed host)
with routing services running in that computer.

By OSI norms and standards, a gateway is not only a router but also a connectivity device that
provides translation services between two completely hybrid networks.

Example: A gateway (not a router) is needed to connect a TCP/IP network to an AppleTalk
network.
It is important to know that both hosts and IP routers (gateway) perform routing functions and
therefore, compatible implementations of the IP protocol are necessary at both ends. In other
words, datagrams are submitted either to a host that shares the same physical network with the
originating host or to a default gateway for further routing across the network. As such, IP on a
host is responsible for routing packets that originate on this host only, fulfilling local needs for
routing. A gateway, on the other hand, is responsible for routing all traffic regardless of its
originator (as long as the TTL field is valid).

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