Out of band, it was shared that this may involve Cisco Ironport, but searching through their public manuals did not help. I tried a GitHub code search but couldn't find any significant HTTP-related usages of port 554 there.
Bug 1687282 Comment 3 Edit History
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Out of band, it was shared that this may involve Cisco Ironport products, but searching through their public manuals did not help. I tried a GitHub code search but couldn't find any significant HTTP-related usages of port 554 there.