In the section we're going to talk about BGP basics and applications running protocols are basically
divided into IGMP and Egypt as you know as it can be understood from the name I keep these are the protocols
used in the internal network and AGP is a general name for the Pericles to use.
But when it works in other net.
In other words between different autonomic systems to get the protocol BGP is also an AGP DGP is very
different from IGP routing protocols as the working mechanism I use criteria called metric to reach
at Target that from one point to another.
For example Ripp uses the metric hop count or SPF and Elijah first try to find the first line and preferred
that but by taking a loop to the bandwidth delay or something like that unlike BGP it's the polis seabeds
running protocol that allows you to control traffic flow using many different features.
The main purpose of BGP is to perform routing between different autonomous systems without the loop
as you can see in our figure we have two systems.
And if you want to share the route between these two it on ARM systems we can use BGP many different
permissions can be used for BGP path selection but if none of these per milliards are configured BGP
behaves like RIP and decide on the number of hops past the hope count means a number in terminology
of BJP.
So let's say the ich ISP has different autonomous number as four and as five let's say that
HQ wants to reach to branch and if I don't configure any BGP attribute the thing I'm going to just look
is the last number that I am passing.
So the rote will be in that direction because I'm just passing I asked the to and oh I'm sure I speak
4 and 5 let's say and they're going to be 23.
I'm just passing I asked before an ISP Phife I'm passing through space.
But any year I'm passing Three-Eyes space so distraught will be perfect.
All right let's take a look to the tables that we are using in BGP we have BGP table neighbored table
and periodic table neighbored table consists of all BGP call for your neighbors.
And please keep in mind that guys neighbors are configured manually on BGP BGP table contains all BGP
routes.
And this table can be very very large sometimes and running table contains the best paths for the destination
networks as happened on the other protocols.
And lastly we are going to focus on the BGP message types the first messages open after the neighbor
who rather is recognized it wants to initiate the neighborhood by sending their rather open message
with this message.
The two rather start the BGP appearing and the second message type is keeping alive to peers periodically
send this message to each other.
Keep alive message is sound.
Air is six the second and with this message the BJP neighborhood remains active and we update my search
running informations sent between two neighbored to peer others and network information is contained
in this update in our search and we have lastly a notification message and this is a message sent by
Pyrenean growlers when there is a problem with the not for cations message.
The neighborhood builder pier is and.