Teledyne HPAC-2005, Operation Manual

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3 RU SSPA Chassis Operations Manual 205356 REV T 127
However, the new party-based security system in SNMPv2, viewed by many as overly
complex, was not widely accepted.
The format of the trap message was also changed in SNMPv2. To avoid these compat-
ibility issues, the trap mechanism was not implemented in the Teledyne Paradise Data-
com SSPA MIB.
SNMP V3
Although SNMPv3 makes no changes to the protocol aside from the addition of crypto-
graphic security, it looks much different due to new textual conventions, concepts, and
terminology. SNMPv3 primarily added security and remote configuration enhance-
ments to SNMP.
Many embedded controllers and microprocessors that are used in electronic compo-
nents such as amplifier modules do not have support for SNMP V2 or V3. This is due
to the extensive memory resources required by the computation intensive cryptograph-
ic security of SNMP V3.
For this reason V3 has not gained widespread support amongst embedded MCU
platform manufacturers. Existing port implementations are limited to very powerful
ARM5 or above cores, running under full-scale OS systems (Linux, Android, etc.). At
large, these configurations require external bulk RAM/FLASH to operate. This require-
ment ultimately affects the minimum device startup time (tens of seconds, due to the
large boot BIOS) and working temperature range (mostly indoor).
As noted in Cisco’s release notes about SNMP V3:
SNMP notifications can be sent as traps or inform requests. Traps are
unreliable because the receiver does not send acknowledgments when this
device receives traps. The sender cannot determine if the traps were
received. However, an SNMP entity that receives an inform request
acknowledges the message with an SNMP response protocol data unit
(PDU). If the sender never receives the response, the inform request can be
sent again. Therefore, informs are more likely to reach their intended
destination.
However, informs consume more resources in the agent and in the network.
Unlike a trap, which is discarded as soon as it is sent, an inform request
must be held in memory until a response is received, or the request times
out. Traps are sent only once, while an inform can be retried several times.
The retries increase traffic and contribute to a higher overhead on the
network.
(http://www.cisco.com/c/en/us/support/docs/ip/simple-network-management
-protocol-snmp/13506-snmp-traps.html, last visited on 22 January 2015.)