[ih] "The First Router" on Jeopardy

[Tony Li]

> On Nov 23, 2021, at 10:17 AM, Jack Haverty via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> On 11/23/21 9:51 AM, Steve Crocker via Internet-history wrote:
>> I wouldn’t expect  TCP packets to be routed differently from UDP packets.
> 
> But we *did* expect packets to be routed differently, even though they were all IP packets.
> 
> That was our purpose in putting the Type-Of-Service and Time-To-Live fields in the IP header.  Some packets required more reliable delivery but time didn't matter.  A good example is during transfer of a large file by FTP.  Other packets required fast delivery, since if they arrived too late they weren't useful.  Packet voice is an example.
> 
> By setting the TTL and TOS fields appropriately, a host computer could advise the IP backbone of routers of what kind of behavior was appropriate for that packet.  A packet which is part of a large file transfer might be routed over a satellite link, since time wasn't critical.   That role was envisioned for the "Wideband Net". However, a packet which is part of a conversational voice stream might be routed over only terrestrial nets to minimize delay, and if a router along the way determined that it would take too long to get to a destination (TTL would run down), that router could simply discard it.
> 
> This would require a lot of mechanism in the routers, including multiple, overlapping, and competing routing algorithms, one for each Type Of Service.   At the time (1980ish) the router hardware didn't have the capability, and we hadn't figured out how to implement such functionality anyway.   But The Plan was to have an Internet which would support multiple types of service over the available mix of networks, and route packets quite differently even when they were all IP.
> 
> Then the Internet went commercial in the mid 80s, and it seems that The Plan was lost.
> 
> AFAIK, such capabilities never got implemented in IP, although something similar must have been done when "multi-protocol routers" appeared in the late 80s.  They could simultaneously run several overlapping "internets" of different protocols.   When I was involved in operating Oracle's corporate intranet in the early 90s, we had IP, Netware, Appletalk, OSI, and probably a few others, all running simultaneously.   I don't recommend it; it was a nightmare to operate.


The Plan was not lost. 

TOS routing was implemented and fielded by a few vendors. At the time, the market wasn’t ready and it was ignored.

Then the crush to integrate with telephony via ATM became the drive and we responded with IntServ. It lost, but ATM then collapsed under its own weight. IntServ went on to beget DiffServ, which is still in use, but is more about queue management than routing algorithms.

More complex routing came to the fore in the mid-90’s with RSVP-TE, which is more about routing different traffic types with different constraints than with different algorithms. That has evolved over time and is currently causing a backlash with Segment Routing (and Flex Algo). The jury is still out on whether Segment Routing will flourish.

So, The Plan morphed somewhat, but is still widely in use.  Different traffic paths for different applications is still possible, but TE is more widely used for traffic placement.

Tony