Snmp Configuration; Using Snmp - Intermec 700 Series User Manual

SECTION 4

SNMP Configuration

Simple Network Management Protocol (SNMP) was developed in the late 1980s
to provide a general-purpose internetworking management protocol. Its primary
goal was to be simple so nothing would stand in the way of its ubiquitous deploy-
ment. To this end, it has been very successful as it is currently deployed in al-
most every major internetworking product on the market. However, like many
achieved goals, the primary strength can also become a weakness.
The Focus was "Simple"
An extreme example of simplicity versus power can be realized by comparing
SNMP against the Common Management Information Protocol (CMIP), the ISO
entry to the standard management protocol world. CMIP has a very rich set of
primitives and a core set of data elements. However, to implement CMIP, a sub-
set of the protocol must be selected. Then, to achieve interoperability, this subset
must be agreed upon with other implementors. As SNMP was specified com-
pletely and with no options, one implemented what was there and interoperabil-
ity was assured.
Returning to simplicity, SNMP was built simply for a number of reasons other
than time to market: robustness in the face of network failure, low overhead in
the devices running the protocol; and ease of debugging the protocol itself (the
last thing you want to debug is the management protocol that is supposed to be
helping you debug your network). Thus, the SNMP limited itself to the User
Datagram Protocol (UDP). This gave the implementor the ability and
responsibility to manage lost packets and perform any necessary
retransmissions. As network debugging in the face of changing routes will
certainly mean losing packets, retaining this control from the transport service
(layer 4) was considered essential. Since a network management protocol will
run continuously, it is mandatory that it consume as minimal a network resource
as possible. UDP allows the necessary control over packet transmissions, packet
size and content (packetization). It is a natural choice.

Using SNMP

SNMP has three control primitives that initiate data flow from the requester
(get, get-next, and set). There are two control primitives the responder uses to
reply. One is used in response to the requester's direct query (get-response) and
the other is an asynchronous response to obtain the requester's attention (trap).
All five of these primitives are carried by UDP and are thus limited in size by the
amount of data that can fit into a single UDP packet. The relatively small
message size was a goal of the design but for some reasonable set of network
management functions, it imposes a limitation.
Often in network management, it is necessary to obtain bulk information
without knowing at first what is in that bulk. In one case, there is a set of
problems having to do with packets not going where they are supposed to, due to
device misconfiguration that prevents proper protocol operation where one needs
to view the entire set of data.
700 Series Color Mobile Computer User's Manual
Network Support
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