Dual Homed BGP

Anurag Bhatia me at anuragbhatia.com
Mon Jan 27 12:19:53 UTC 2020


Interesting discussion.

Besides the point about control which many people have made, I would like
to point - it also depends on your geography and peering in that geography.
Cannot generalise but typically in the US and Europe you will find
reasonably good peering across larger operators and hence cases of your
traffic taking really odd path (like going out of country and in forward /
reverse direction) would be low. That may not be the case in certain other
geographies like say Asia or Africa. In my home country India I find
occasional cases of traffic leaking out of the country.

I recently posted this trace taken from an Indian RIPE Atlas probes to a
popular content site with frontend mostly on Akamai:
https://atlas.ripe.net/measurements/23857778/#!probes


Traceroute to www.hotstar.com (104.123.148.87), 48 byte packets

1 172.16.0.1 0.943ms 0.828ms 0.821ms
2 172.16.1.100 0.743ms * 13.019ms
3 103.145.6.4 AS139540 0.684ms 3.548ms 2.972ms
4 103.145.6.3 AS139540 5.035ms 17.172ms 0.664ms
5 59.162.52.161 59.162.52.161.static.vsnl.net.in AS4755 0.92ms 0.845ms
1.218ms
6 115.112.167.241 115.112.167.241.STATIC-Kolkata.vsnl.net.in AS4755 4.522ms
21.518ms 29.118ms
7 172.25.87.174 13.919ms 13.741ms 13.509ms
8 172.31.180.57 53.947ms 93.642ms 58.971ms
9 180.87.36.9 ix-ae-4-2.tcore1.cxr-chennai.as6453.net AS6453 54.4ms
53.752ms 53.721ms
10 180.87.36.41 if-ae-34-2.tcore1.svq-singapore.as6453.net AS6453 85.424ms
85.835ms 86.098ms
11 120.29.215.39 AS6453 86.247ms 85.818ms 86.203ms
12 49.45.4.87 AS64049 84.675ms 84.555ms 84.614ms
13 49.45.4.87 AS64049 83.941ms 83.835ms 84.163ms
14 103.198.140.185 AS64049 85.437ms 85.498ms 85.506ms
15 172.16.23.9 100.334ms 100.817ms 172.25.106.39 100.344ms
16 172.16.2.70 98.977ms 98.835ms 98.795ms
17 172.16.2.41 99.69ms 99.628ms 99.565ms
18 172.16.0.210 102.005ms 102.059ms 101.929ms
19 104.123.148.87 a104-123-148-87.deploy.static.akamaitechnologies.com
AS55836 105.386ms 105.358ms 105.284ms



Ignoring the DNS based mapping and associated challenges of Akamai and
speaking purely from routing. Say if AS139540 had full table it would
simply have picked direct route to AS55836 which is one of it's upstream (
https://bgp.he.net/AS139540#_graph4).

Thus 100ms would be down to probably sub 20ms levels. Whether or not such
issues affect you depends on whether upstreams or upstream's upstream peer
in the region or not. In this case upstream AS4755 & AS55836 are not
exchanging traffic locally. Furthermore their upstream AS6453 and AS64049
are also not exchanging traffic locally either. So if I have to decide, I
will always pick full table in these cases. AS_PATH will help and one can
always tweak for larger known cases.




On Sun, Jan 26, 2020 at 10:11 AM Aaron Gould <aaron1 at gvtc.com> wrote:

> I’m listening to the advice of others and taking it in….
>
>
>
> For my ISP, I’ve had 2 or 3 internet uplinks for about 12 years now for
> 50,000 subs, and have only learned a default route on them.  It’s been good
> up to this point.
>
>
>
> -Aaron
>
>
>
>
>


-- 


Anurag Bhatia
anuragbhatia.com
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