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Extension protocols and network applications 75
Figure 4.11: MIB tree structure
• The group Interfaces is responsible for network adapters. This updates how many packets
and bytes are sent and received through the network, how many are discarded, how
many broadcasts there are and how long is the current execution-queue.
• The group IP is responsible for IP traffic to and from the node. This has several counters
on which are updated the number of packets which are discarded for various reasons.
Statistics are also available about the fragmentation and setting the datagrams back
again. All these items are very important for the management of the routers.
• The group ICMP relates to IP error messages. There is a counter for every ICMP message
in which the number of each type observed are updated.
• The TCP group registers the actual number of opened connections, sent and received
segments and various statistics about errors.
• The UDP group counts the number of sent and received UDP datagrams and also updates
the number of received datagrams which were returned to sender due to an
unknown port or for another reason.
• The last group is intended for the collection of statistics about the functioning of SNMP
itself: the number of messages which were sent, the type of messages, etc.