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Understanding BGP graphs
I am wondering what BGP graphs on HE show exactly?.
What is the relation between those ASNs.
Why the arrows not stopping at certain Tier 1 Providers.
I think its showing the paths it can take to those ASN. The bold one is the most used one. Correct me if wrong .
Why should the graph stop at Tier 1 Providers? Most of the ASNs in the world use some Tier 1 as upstream, direct or indirect.
I got that part. Im confused about those arrows.
Yeah. So it should end at a Tier 1 ISP at right ? like ASN24608 ->ASN6939 (HE)
But some routes are going beyond Tier 1 ISP, ASN24608 ->AS3320 (Deutsche Telekom)->AS3257(Tinet Spa)
So what's the difference between those two routes.
HE is not Tier 1 (at least for IPv4).
If AS3320 (Deutsche Telekom) is an upstream provider of AS24608, it's their job to announce all AS24608 prefixes to all peers/downstreams.
So where these arrows supposed to stop. In some graphs there are arrows/routes from Upstream provider to Tier 1 ISP to another Tier 1 ISP. But in some others it stops at first Tier 1 ISP.
It depends how they peer. And keep in mind, this graph is from the view of Hurricane Electric. It may be incomplete.
The data is from routeviews (and so HE claims) meaning the paths are done in normal IX/DC points.
HE goes out of their way to cut the path and have it start at the first Teir 1 (or what ever defined list they have of transit providers) as the start of their path
For example (hypothetical path original path)
Destination ASN <- DC Upstream <- NTT <- HE <- Telia <- DC ASN <- Origin ASN
will become post processing in HE
Destination ASN <- DC Upstream <- NTT <- HE <- Telia
while if we have
Destination ASN <- DC Upstream <- HE <- Origin ASN
Destination ASN <- DC Upstream <- HE
and for extra bonuses:
Destination ASN <- Origin ASN
Will not even show up on the graph at all and instead will show up as a direct peer in the peer tabs
Okay. It makes sense now.