Page 965 - Unleashing the potenti al of the Internet of Things

Unleashing the potential of the Internet of Things 7

8.2 Application level gateway database

The sensor network gateway should maintain an ALG database. It is constructed with the
information listed below for every SNMP message from the SNMP manager in order to perform
protocol and OID translation between the SNMP and the sensor network management protocol.
– Request ID sequence number (generated by ALG)

– IP header (from SNMP message)
– UDP header (from SNMP message)
– Common SNMP header (from SNMP message)
– Get/set header (from SNMP message)
– Variable binding list (from SNMP message)

The sequence number shall be used as a primary key in this ALG database.

8.3 Translation from an SNMP to a sensor network management protocol message
Figure 4 shows the operational procedure of the sensor network gateway when it receives an SNMP
message from an SNMP manager.

UDP
IP header header SNMP message
SNMP common
header SNMP PDU
VarBindList
First VarBind
... Source Destination ... ... Request ID ... Name Value Name Value ...
IP address IP address

ALG database
Keys Contents
Sequence
number
Source Destination ... Sequence ... ...
sensor ID sensor ID number Name Value
Header VarBindList
Sensor network management protocol message
H.641(12)_F04

Figure 4 – Translation from an SNMP message to a sensor network
management protocol message

When the sensor network gateway receives an SNMP message from an SNMP manager, it
generates a sequence number to be used as the request ID in the sensor network management
protocol message and records this sequence number and the whole message into an ALG database.
Then it creates a sensor network management protocol message. It copies the sequence number in
the ALG database into the sequence number field of the sensor network management protocol
message. It copies the value of the first VarBind into the destination sensor ID field of the sensor
network management protocol message. Then it copies the VarBindList except for the first one into
the sensor network management protocol message. When it copies object identifiers in the
VarBindList, base OID should be removed (see clause 9 and Appendix I).

Rec. ITU-T Y.4701/H.641 (02/2012) 951