Network Management Information Code
What it is
Purpose of a 0800 network-management message — commonly 001 sign-on, 002 sign-off, 301 echo test; key-exchange and cutover codes vary by network.
Network management (0800/0810) messages are the heartbeat of an ISO 8583 link. DE 70 says why the message was sent: 001 sign-on, 002 sign-off and 301 echo test are near-universal; key change (a new working MAC/PIN key) is 101 on some hosts and 161/162 on others, and cutover is commonly 201. Hosts answer with 0810 and DE 39 = 00. Check the code table of the interface you connect to.
Example values
001Sign-on request.301Echo test (keep-alive).Specification reference
Defined in ISO 8583:1987 (base). Card networks publish their own dialect tables (Visa BASE I / V.I.P., Mastercard CIS) that refine formats, lengths, and — for private-use elements — the entire layout. Always confirm against the interface specification you implement.