[ih] The story of BGP?

Guy Almes galmes at tamu.edu
Mon Feb 11 10:01:10 PST 2013

   Your points make sense to me.
   I'll stick with my "regrettable" word, if only in two limited senses:
<> the degree to which the elegant "full AS path" metric combined with 
the "local decision" idea resulted in the current highly complex and 
somewhat fragile inter-AS routing structure was probably greater than we 
imagined back in 1989,
<> it's just a reminder that both the engineering technology of BGP 
itself *and* the highly dynamic nature of the operational and business 
dynamics of the 1989-ish Internet combined in interesting ways.

   I will *not* contradict that, to the degree that this messiness 
bought us the wonderful scalability of the Internet, this 
messiness/complexity was worth it.
	-- Guy

On 2/11/13 11:38 AM, Tony Li wrote:
> Hi Guy,
>> And, of course, key disadvantages:
>> <> elevating local inter-AS routing decisions, which inevitably mixed technical, operational, and business aspects to being non-local / community / political decisions.
>>   Instead, of course, we have very messy BGP configurations.
>>   These stemmed, in part, from the early BGP implementations using the full AS path *length* as the de-facto "metric".
>>   That was implementable, but obviously resulted in weak selections of inter-AS routes.  The patches to BGP to ameliorate this weakness are perhaps both regrettable and inevitable.
> I'll agree with the inevitable portion.  As we found when working on IDPR, the need for interesting peering policies in a newly commercialized Internet was paramount.  Unlike the benign dictatorship of DARPA or the more cooperative but still segregationist NSFnet, the wild and wooly commercial Internet had many ISPs who were mutually hostile.  Sometimes openly so, but more frequently under the table.
> The ability to craft policy that optimized for local routing at the expense of one's neighbors (i.e., hot potato routing) was one expression of this.
> So, this was indeed an inevitable outcome of commercialization.  However, I'm not sure that it was all that regrettable.  The result is far more expressive than a centralized (and politicized) routing authority or even link-state protocol could have ever supported.  As such, it has proven to be extremely flexible and allowed the Internet to grow freely.
> If BGP complexity is the price of freedom, it's well worth paying.
> Regards,
> Tony

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