[ih] "The First Router" on Jeopardy

[Jack Haverty]

I just ran across a contemporary article on the current use of BGP in 
the operational Internet:

https://krebsonsecurity.com/2021/11/the-internet-is-held-together-with-spit-baling-wire/

Fascinating, to me at least, since I lost track of how BGP was being 
used back in the 80s when we created it as an interim technique. Honest, 
I didn't see this article before I sent my historical offering below.   
Looks like "baling wire" is still in the Internet operators' toolbox, 
after 40 years.

Jack Haverty


On 11/25/21 12:16 PM, Jack Haverty via Internet-history wrote:
> On 11/24/21 5:47 PM, Guy Almes via Internet-history wrote:
>> First, by 1987, when both the ARPAnet and the proto-NSFnet backbone 
>> were both operational, networks that connected to both had to decide 
>> which to use, and that led to interesting routing decisions. Problems 
>> encountered then led, for example, to creation of BGP. 
>
> FYI, for The Historians, I offer a little of the earlier history, all 
> from the 1980-1983 timeframe.
>
> At the ICCB (before it was renamed IAB) meetings, there was a list 
> kept on the whiteboard of "things that need to get figured out". One 
> of the items on that list was "Routing", which included issues like 
> "Type Of Service", "Shortest Path First", and "Policy Routing" -- all 
> part of the "How should routing behave in the future Internet?" 
> topic.  There were two concrete motivators for these issues.
>
> The Internet had started to evolve from its "fuzzy peach" stage, where 
> essentially the ARPANET was the peach surrounded by a fuzzy layer of  
> LANs, into a richer topology where there were actually choices to be 
> made.
>
> First, SATNET had linked the US and Europe for a while, but Bob Kahn 
> initiated the addition of a transatlantic path using the public X.25 
> service.   The interconnect was called a "VAN Gateway" (VAN stood for 
> Value Added Network but I never did understand what that really 
> meant).   The VAN gateway essentially added an interface option to the 
> existing gateways, allowing them to connect to the public X.25 
> networks, and use them as a "circuit" (albeit virtual) between 
> gateways.  In effect, the entire X.25 public network system was made 
> an available component of the Internet; it became just another network 
> that could be used within the overall Internet.
>
> The "dial up" nature of the X.25 service also introduced the 
> possibility of dynamic configuration of the Internet topology -- e.g., 
> adding or deleting circuits between pairs of gateways as a situation 
> warranted, simply by using the dialup infrastructure of the public 
> X.27/X.75 system.  We called that something like "Dynamic Adaptive 
> Topology", but I don't recall ever actually trying to use that 
> capability except on the single US<->EU path in parallel with SATNET.
>
> This "VAN" capability was used to create a topology where there were 
> two ways IP datagrams could cross the Atlantic.   Bringing economics 
> into the picture, the SATNET path was funded by ARPA, to be used only 
> for ARPA-approved projects.   The X.25 path was funded by whoever 
> opened the circuit first (which we, as ARPA contractors, silently 
> engineered to be usually the European side; seemed like the right 
> thing to do).   This issue appeared on the ICCB's to-do list as 
> "Policy Based Routing".
>
> Pending the "real" solution, I don't recall exactly how the gateways 
> back then made the choice of path for each packet; my vague 
> recollection is that it had something to do with destination addresses 
> - i.e., a host might have two distinct IP addresses, one for use via 
> SATNET and the other for use via X.25.   And a single physical net 
> would be assigned two network numbers (no shortage then), one for use 
> via X.25 and the other for use via SATNET. IIRC, that's how the UCL 
> network in London was configured.  The early Internet had to sometimes 
> use patching plaster and baling wire to keep it going as the research 
> sought the right way for the future.
>
> Second, the Wideband Net, a satellite-based network spanning the US, 
> was made part of the Internet topology by gateways between it and the 
> ARPANET.   There were then multiple network paths across the US.   But 
> the gateways' routing metric of "hops" would never cause any datagrams 
> to be sent over the Wideband Net.   Since the Wideband Net was only 
> interconnected by gateways to ARPANET nodes, any route that used the 
> Wideband Net would necessarily be 2 hops longer than a direct path 
> across the ARPANET.   The routing mechanisms would never make such a 
> choice.    This issue was captured on the ICCB's list as "Expressway 
> Routing", a reference to the need for car drivers to make a decision 
> to head toward the nearest freeway entrance, rather than taking a 
> direct route toward their destination, in order to get to their 
> destination faster.
>
> I don't recall how people experimented with the Wideband Net, i.e., 
> how they got datagrams to actually flow over it.   Perhaps that was a 
> use of the "Source Routing" mechanisms in the IP headers.   Maybe 
> someone else remembers....
>
> We didn't know how to best address these situations, but of course 
> there were a lot of ideas.  In addition, the existing Internet lacked 
> some basic mechanisms that seemed to be necessary.  In particular, the 
> use of "hops" to determine which path was the shortest was woefully 
> inadequate.   A "hop" through a Satellite net might be expected to 
> take much longer than a hop through a terrestrial net, simply due to 
> Physics.   But a hop through the ARPANET traversing many IMPs, when 
> the net was congested, might actually take longer than a satellite 
> transit.  A time-based metric was not feasible in the gateways without 
> some means of accurately measuring time, at a precision of 
> milliseconds, in the routers scattered across the continents.
>
> Dave Mills was on the ICCB, and he took on this quest with unbridled 
> energy and determination.   NTP was the result - an impressive piece 
> of engineering.   Using NTP, computers (e.g., routers, gateways, 
> hosts, servers, whatever you call them) can maintain highly 
> synchronized clocks, and measure actual transit times of IP datagrams 
> for use in calculating "shortest path". Everyone can thank Dave and 
> his crew that your computers know what time it is today.
>
> The Time mechanisms would be helpful, but much more was needed to 
> handle "Policy Based" and "Expressway" routing situations.  Lots of 
> people had ideas and wanted them put into the "core gateways" that BBN 
> operated.   But doing that kind of experimentation and also keeping 
> the Internet core reliably running 24x7 was a struggle.
>
> I was also on the ICCB at the time, and I recruited Dr. Eric Rosen 
> back at BBN to help think about it.   He and I had numerous day-long 
> sessions with a whiteboard.  The result was EGP - the Exterior Gateway 
> Protocol.   If you read Eric's now ancient RFC defining EGP, you'll 
> see that it was not intended as a routing protocol.   Rather it was 
> more of a "firewall" mechanism that would allow the Internet to be 
> carved up into pieces, each of which was implemented and operated at 
> arm's length from the others but could interoperate to present a 
> single Internet to the end users.
>
> The intent was that such a mechanism would make it possible for some 
> collection of gateways (e.g., the "core gateways" of the Internet at 
> that time) to be operated as a reliable service, while also enabling 
> lots of other collections of gateways to be used as guinea pigs for 
> all sorts of experiments to try out various ideas that had come up.   
> Each such collection was called an "Autonomous System" of gateways 
> using some particular technical mechanisms and under some single 
> operator's control.   EGP was a mechanism to permit reliable 
> operational services to coexist in the Internet with research and 
> experimentation.
>
> When the ideas had been tried, and the traditional "rough consensus" 
> emerged to identify the best system design, the new algorithms, 
> mechanisms, protocols, and anything else needed, would be instantiated 
> in a new Autonomous System, which would then grow as the new system 
> was deployed - much as the ARPANET has served as the nursery for the 
> fledgling Internet, with all IMPs disappearing over time as they were 
> replaced by routers directly connected with wires.
>
> That's where my direct involvement in the "research" stopped, as I 
> went more into deploying and operating network stuff, from about 
> mid-1983 on.   Perhaps someone else can fill in more gaps in the History.
>
> Enjoy,
> Jack Haverty
>
>
>
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