Port 196: DNSIX Session Management — Where Military Networks Remembered Everything

Port 196 is a well-known port officially assigned to dn6-smm-red (DNSIX Session Management Module Audit Redirection). It's a ghost from the Cold War era of network security—a protocol designed to ensure that classified military networks never forgot what happened on them.

What DNSIX Was

DNSIX stands for "Department of Defense Intelligence Information System Network Security for Information Exchange." In plain language: a set of security requirements for Defense Intelligence Agency networks in the 1990s.¹

The protocol had one job: make sure every security-relevant action on classified networks generated an audit record. Port 196 specifically handled session management audit redirection—routing audit messages about who logged in, who logged out, who accessed what, and when.²

How It Worked

Port 196 was part of a family of DNSIX ports:

• Port 195: Network Level Module Audit (dn6-nlm-aud)
• Port 196: Session Management Module Audit Redirection (dn6-smm-red)

The protocol used DMDP (DNSIX Message Delivery Protocol) to send audit messages to collection centers. Network equipment—particularly Cisco routers—would generate audit messages and transmit them to specified hosts for centralized security monitoring.³

The "redirection" part meant that audit messages could be sent to primary and secondary collection centers, with authorization mechanisms controlling where audit trails ended up.

The History

Port 196 was assigned in RFC 1700 (October 1994) with Lawrence Lebahn (email: DIA3@PAXRV-NES.NAVY.MIL) listed as the contact person.⁴ The Navy email address tells you everything: this was military infrastructure, designed for classified networks where accountability wasn't optional.

This was the era when the Department of Defense was learning that networks needed memory. That you couldn't secure what you couldn't audit. That transparency—even in secret systems—was the foundation of trust.

Why This Port Matters

Port 196 represents an important principle that outlived the protocol: auditability is a feature, not an afterthought.

Every modern security protocol—every SIEM system, every audit log, every "who accessed this file" record—inherits from the idea that DNSIX embodied: systems should remember what happens on them.

The protocol itself is obsolete. You won't find DNSIX running on modern networks. But the principle—that secure systems must be auditable, that actions must leave traces, that accountability is baked into the network layer—that's everywhere now.

Current Status

Port 196 is officially assigned but rarely seen in practice. The DNSIX protocol was specific to 1990s-era Department of Defense networks and has been superseded by modern security and audit frameworks.

Some security sources note that port 196 has occasionally been used by malware for command-and-control communications, as obsolete assigned ports sometimes attract malicious attention precisely because they're not actively monitored.⁵

Checking What's Listening

To see if anything is listening on port 196 on your system:

# On Linux/Mac:
sudo lsof -i :196
sudo netstat -tulpn | grep :196

# On Windows:
netstat -ano | findstr :196

If you find something listening on port 196, it's worth investigating—it's almost certainly not DNSIX.

Related Ports

• Port 195: DNSIX Network Level Module Audit
• Port 161/162: SNMP (the modern standard for network device monitoring)
• Port 514: Syslog (common for centralized logging)

The Truthline

Port 196 carried audit messages from classified military networks—a protocol designed to ensure that in secure government systems, nothing disappeared without a trace. The protocol is gone, but the principle survived: security without auditability is just obscurity.