What was the "sae-urn" protocol on port 4500?

Port 4500 is a documented home to a couple of standards:^🕗

• 4500 - ipsec-nat-t - IPSec NAT Traversal
• 4500 - sae-urn

IP-Sec NAT traversal is explained in a number of RFCs:

• rfc3947 - Negotiation of NAT-Traversal in the IKE
• rfc3948 - UDP Encapsulation of IPsec ESP Packets
• rfc7296 - Internet Key Exchange Protocol Version 2 (IKEv2)
• rfc8229 - TCP Encapsulation of IKE and IPsec Packets

But what was sae-urn?

It seems to have passed out of all knowledge.

The oldest reference i can find to "sae-urn" comes from the port service mapping of nmap from May 21, 1997:^🕗

sae-urn 4500/tcp # sae-urn sae-urn 4500/udp # sae-urn 

Someone tried asking what sae-urn is^🕗 on a BSD newsgroup in 2002 - but in typical Stackoverflow fashion, people condescendently didn't answer the question:

Googling on that gives this reference.
The rest is an exercise for the reader.

Whatever the sae-urn was, it seems to have been lost to the sands of time.

Does anyone remember what it was?

Know someone who can answer? Share a link to this question via email, Twitter, or Facebook.