[ih] TTL [was Exterior Gateway Protocol]

[Brian E Carpenter]

So, here's another history question:

On 05-Sep-20 05:11, Tony Li via Internet-history wrote:
...
> Topology.
> 
> Strictly speaking, AS-level routing is not necessary. You can do everything with other protocols and leaking/redistribution except that:
> 
> - No protocol other than BGP can support Internet (or service provider) route scale.
> 
> - Leaking/redistribution has no loop prevention mechanism.

I was taught many years ago that the TTL field (renamed Hop Limit in IPv6) was intended only as a last resort method of loop prevention.

a) Is that accurate?
b) Has it ever saved the Internet?

(It does have one slightly bizarre use today: check that it's still 255 to detect forwarded link-local packets, and there's also RFC5082.)

    Brian