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SNMP Message (PDU) Encoding

SNMP not only describes its data structures in terms of ASN.1, it also uses to define its message format (ie, its PDUs, or "packets"):
SNMP-Message ::= SEQUENCE {
    version INTEGER { version-1 (0)},
    community OCTET STRING,
    data ANY
}
The data field of the SNMP message contains the SNMP PDU. For example, an SNMP get-request PDU is defined as follows:
GetRequest-PDU ::= [0] IMPLICIT SEQUENCE {
    request-id RequestID,
        -- 4 byte integer to match requests and responses
    error-status ErrorStatus,
    error-index  ErrorIndex,
        -- both single byte integers, = 0 in requests, error status in responses
    variable-bindings VarBindList
        -- list of desired object identifiers as name/value pairs
SNMP (normally) uses the low-overhead, connectionless UDP protocol for transmission of requests and responses.
 
Lecture 23: Network Management #3 Copyright © 2004 P.Scott, La Trobe University Bendigo.



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