rDNS can be populated with a great deal of useful information, if you are trying to diagnose an asymmetric routing issue between two internet service providers. Particularly if both of them have had the forethought to give reasonable, understandable, hierarchical names to their globally distributed POPs. Other things like "ae" that show up in a traceroute can be indications of an 802.3ad aggregated link, which juniper calls an Aggregated Ethernet. Same as interface abbreviations for Cisco and juniper you will find like "hu", "te", "xe", etc.

One example: say you have a $200/mo dedicated server customer, as an ISP, you're giving them a /29 of public IP space. That /29 exists as a vlan subinterface of one of your juniper routers and is trunked across the datacenter through various switches to the server. Let's say it's vlan 2659. Somewhere in the public rDNS for the default gateway IP of that /29, you would have the string "vl2659”.