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a little something about BGP Mike Gaertner, Sabay Digital
ah?
Ê what is the internet
Ê who controls it?
Ê what problem does BGP solve
Ê how to get free internet (yes that’s a lie, but stay to learn the truth)
Ê BGP at Sabay practical stuff
what is the internet, really?
Ê a collection of 52059 autonomous systems (AS) on Oct 15 2015
Ê each network has a number of IP address, group into prefix
Ê 575,609 prefix are visible in the global routing table
Ê no government regulations
who is in charge?
how?
Ê if you have IP address space from APNIC they will assign you a AS number for free J
Ê AS numbers used on the internet to identify each of the 52000 participating networks
Ê anyone can get a IP address range from APNIC if they can demonstrate the need it
Ê the need arises if you connect to more then 1 ISP and you have infrastructure that will use 50% of the allocation within 1 year
BGP
Ê DNS is the address book of the internet
Ê BGP is the mapping software of the internet
Ê it glues together 52,000 networks and remembers at its core where to find over 570,000 prefixes / destination networks
Ê BGP in it’s most simple form connects 2 network
Ê it is established between 2 AS numbers and it exchanges information about prefixes own by each AS and installs a route for each prefix (mostly)
what is a prefix?
118.67.200.0/21 118.67.200.0/24 118.67.201.0/24 118.67.202.0/24 118.67.203.0/24 118.67.204.0/24 118.67.205.0/24 118.67.206.0/24 118.67.207.0/24
118.67.200.0/23 118.67.202.0/23 118.67.204.0/23 118.67.206.0/23
118.67.200.0/22 118.67.204.0/22
if you wonder how 52,000 networks can have 570,000 prefixes, that’s how! pollution is the right word
in the beginning
Ê BGP was designed during a break at a IETF meeting in January 1989 in Texas, Austin
Ê 3 napkins where used to “invent” the core concepts
Ê by October 1989 at the IETF meeting in Hawaii version BGP-‐v2 was introduced
Ê 1991 BGP-‐v3 was being used at a peer-‐by-‐peer bases, Cisco adding support for BGP
Ê 1993 most networks had implemented BGP-‐3, facing out EGP
Ê 1994 BGP-‐v4 universal adoption at tier 1 carriers
BGP get connected
Ê so you have your IP space, got your ASN and now?
Ê get connected
Ê transit, you buy access to the internet from a transit provider
Ê peer direct with friendly networks
Ê or peer at a free peering exchange like CNX
Cambodia -‐ transit
Peers at CNX
you can reach every internet user in Cambodia via CNX peers for free
BGP @ Sabay – our peering
7712 CORE
TCT
CNX SI
7712 DC
204/23 PPPoE 201/24 Backup 200/24 Content 202/24 Games
MKN
BGP @ Sabay -‐ our routing policy
Ê we want to deliver content as cheap as possible and as fast as possible to users in Cambodia
Ê we want to give out customers a smooth internet access experience
Ê remember: Ê routes you import decided your outgoing traffic routes
Ê what you export decides how traffic gets to you
• TCT • 0.0.0.0/0.0.0.0
• CNX • everything < /24 • highest local preference
• MKN • everything < /24 • second highest local preference
• SI • nothing
BGP @ Sabay -‐ import policy
7712
TCT
CNX
SI
MKN
default only?
7712
TCT SI
HK SIN
EU US
NY DC
You are only in charge of selecting the first hop a packet may travel to it destination!
BGP @ Sabay – export policy
7712
TCT
CNX+ MKN
SI
118.67.200.0/21 118.67.200.0/24 (content) 118.67.202.0/24 (game)
remember what you export controls how traffic comes to you!
the net
+1
BGP export – puts you in control
7712
TCT
MKN
118.67.200.0
/21
118.67.200.0/21
If we only announce 118.67.200.0/21 then ISP X can choose which way he want to send traffic to us.
ISP X
BGP export – puts you in control
7712
TCT
MKN
ISP X
118.67.200.0
/21
118.67.200.0/21 118.67.200.0/24 118.67.200.0/24
but if announce important parts of our network only via the free peering, then we can ensure traffic for our content will be delivered via our free link.
BGP communities
7712 TCT
GGC
118.67.200.0/21 118.67.200.4/23 -‐ 7712:5555
very simple, community means a extra bit of information per prefix.
the net
118.67.200.0
/21
