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UID:pretalx-denog18-EMHXW7@cfp.denog.de
DTSTART;TZID=CET:20261117T133500
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DESCRIPTION:Internet exchanges have presented as shared layer 2 networks fo
 r thirty years. I will show the mechanisms that silently blackhole exchang
 e traffic or forward it to the wrong port: missing or incorrect neighbour 
 entries\, and unknown unicast flooding. In each case BGP stays established
  to the route servers and nothing reports a fault.\n\nA large exchange sta
 ted in writing that it gives no guarantee traffic sent to a peering LAN go
 es to\, and only to\, the port of the network it was meant for\, and that 
 it knows of no exchange that does. I do not know how many members expect t
 hat answer.\n\nThe rest of the industry has spent years dismantling large 
 layer 2 domains in favour of routed ones. Perhaps it is time for internet 
 exchanges to forward at layer 3\, rather than running a layer 2 forwarding
  domain with a route server making routing decisions.\n\nIn many cases thi
 s needs no new hardware. The switches already used to build exchange fabri
 cs forward at layer 2 and at layer 3 at line rate. Route scale is where ca
 reful consideration is needed.\n\nThe shape of a layer 3 internet exchange
  switch is already commonplace: each PNI switch a CDN or ISP operates is a
  routed exchange with several settlement-free peers and one customer on it
 .\n\nRunning at layer 3 gives participants complete isolation between port
 s\, the same model that already applies to every other upstream connection
  that networks buy. RTBH works at the exchange rather than depending on a 
 peer to honour it. Debugging becomes possible from the participant side\, 
 because traceroute shows the exchange hop.
DTSTAMP:20261005T184756Z
LOCATION:Saal A
SUMMARY:Maybe it is time to consider layer 3 internet exchanges - James Ric
 e
URL:https://cfp.denog.de/denog18/talk/EMHXW7/
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