Lecture 23: Network Management #3

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

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