tools and techniques to pinpoint and respond to loss on a path

Andy Litzinger Andy.Litzinger at
Tue Jul 16 18:12:32 UTC 2013

> From: Blake Dunlap [mailto:ikiris at]
> While any provider will attempt to fix peer / upstream issues as they can, any
> SLA you would have is between two points on their private network, not
> from point A to point Z that they have no control over across multiple peers
> and the public internet itself.

makes sense- thanks for confirming

> The much more common design is using a single
> provider for each thread between sites. Then at least you have an end-to-
> end SLA in effect, as well as a single entity that is responsible for the entire
> link in question.
> This sounds like you're trying to achieve private link IGP / FRR level site to site
> failover/convergence across the public internet. Perhaps you should rethink
> your goals here or your design?

Kind of- I can actually tolerate the blips, but I want to be able to measure and track
 them in such a way that I know where the loss is occurring.  If a particular path
is reconverging more often than should be reasonably expected I want to be able to
prove it within reason.

We also have a customer who happens to host at DC B with the same connectivity.
Every time there is one of these blips their alerting fires off a thousand messages
and they open a ticket with us.  I'd like to be able to show them some good data
on the path during the blip so we back a discussion along the  lines
of "live with it, or pay to privately connect to us".


> -Blake
> On Mon, Jul 15, 2013 at 4:18 PM, Andy Litzinger
> <Andy.Litzinger at> wrote:
> Hi,
> Does anyone have any recommendations on how to pinpoint and react to
> packet loss across the internet?  preferably in an automated fashion.  For
> detection I'm currently looking at trying smoketrace to run from inside my
> network, but I'd love to be able to run traceroutes from my edge routers
> triggered during periods of loss.  I have Juniper MX80s on one end- which I'm
> hopeful I'll be able to cobble together some combo of RPM and event
> scripting to kick off a traceroute.  We have Cisco4900Ms on the other end and
> maybe the same thing is possible but I'm not so sure.
> I'd love to hear other suggestions and experience for detection and also for
> options on what I might be able to do when loss is detected on a path.
> In my specific situation I control equipment on both ends of the path that I
> care about with details below.
> we are a hosted service company and we currently have two data centers,
> DC A and DC B.  DC A uses juniper MX routers, advertises our own IP space
> and takes full BGP feeds from two providers, ISPs A1 and A2.  At DC B we
> have a smaller installation and instead take redundant drops (and IP space)
> from a single provider, ISP B1, who then peers upstream with two providers,
> B2 and B3
> We have a fairly consistent bi-directional stream of traffic between DC A and
> DC B.  Both of ISP A1 and A2 have good peering with ISP B2 so under normal
> network conditions traffic flows across ISP B1 to B2 and then to either ISP A1
> or A2
> oversimplified ascii pic showing only the normal best paths:
>               -- ISP A1----------------------ISP B2-- DC A--
> |                                                                 |---  ISP B1 ----- DC B
>              -- ISP A2----------------------ISP B2--
> with increasing frequency we've been experiencing packet loss along the
> path from DC A to DC B.  Usually the periods of loss are brief,  30 seconds to a
> minute, but they are total blackouts.
>   I'd like to be able to collect enough relevant data to pinpoint the trouble
> spot as much as possible so I can take it to the ISPs and request a
> solution.  The blackouts are so quick that it's impossible to log in and get a
> trace- hence the desire to automate it.
> I can provide more details off list if helpful- I'm trying not to vilify anyone-
> especially without copious amounts of data points.
> As a side question, what should my expectation be regarding packet loss
> when sending packets from point A to point B across multiple providers
> across the internet?  Is 30 seconds to a minute of blackout between two
> destinations every couple of weeks par for the course?  My directly
> connected ISPs offer me an SLA, but what should I reasonably expect from
> them when one of their upstream peers (or a peer of their peers) has
> issues?  If this turns out to be BGP reconvergence or similar do I have any
> options?
> many thanks,
> -andy

More information about the NANOG mailing list