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

Pete Lumbis alumbis at
Wed Jul 17 00:22:51 UTC 2013

IP SLA + EEM on the 4900. You can have the 4900 run pings/latency tests and
then run commands and pipe them to flash when the issue happens.


On Mon, Jul 15, 2013 at 5:18 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

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