We have seen earlier about the different
types of peering. We have mandatory
multilateral peering known as MMLP
where each participant is forced to
appear with every other participant as
part of the membership this is no
history of success and the practice is
strongly discouraged.
There may be a couple of instances
worldwide where MMLP works
out of the hundreds of
exchange points in operation today.
Multilateral peering known as MLP is where each
participant peers with other
participants usually via our art server
we'll have a look at what a route server
is soon bilateral peering is where
participants at appearing with each
other according to their own
requirements and business relationships
this is the most common situation at
internet exchange parts today operators
have three types of peering policies
there is open peering for an ISP public
States that they will appear with all
parties who approach them for peering
and this is commonly found at exchange
points for ISPs participate via our art
server selective peering is where an ISP
Spearing policy depends on the nature of
the operator who requests peering with
them at exchange points operators will
not peer with the right server but will
only appear bilaterally and finally
there's restrictive peering where an ISP
decides who is peering partners are and
is generally not approachable to
creating peering opportunities the
peering database documents ISPs peering
policies and contact information and the
URL is shown on the screen all operators
of autonomous systems are encouraged to
register in the peering database all
operators who are considering peering or
are appearing must be in the peering
database to enhance the peering
opportunity also participation in the
peering fora is strongly encouraged
there's a global peering forum which is
used by the mid and larger ISPs but
they're also regional peering fora for
example in all the major continents
Europe Middle East Asia Caribbean Latin
America Africa and so on and in fact
many countries now have their own
peering fora taking place alongside or
part of the various network operations
groups let's have a look at some of the
routing setup the operators need to
consider at exchange points the ISP
border routers at the exchange point
must not be configured with a default
route
or carry the fool internet routing table
carrying the default or the full table
means that this router and the ISP
network is open to abuse by non peer
exchange point members the correct
configuration is only to carry the
rights offered to IXP peers on the IXP
peering rata do note that some ISPs
offer transit across ix5 breaks they do
so at their own risk I would not
recommend this at all it's easier and
better to provide that transit service
with a separate private network
interconnect or P&I even in the same
facility as the exchange point is
located much better doing that than
offering the transit across the exchange
point fabric the ISP border routers of
the exchange point should not be
configured to carry the exchange point
line within the internal BGP we have
seen in the initial part of these
presentations about the next hop self
ibgp concept it's important that this is
used and this means we don't need to
carry the exchange point land around
within our network keeping the exchange
point line address block in the IGP
however ensures that trace routes across
the exchange point do not break and this
may be useful for troubleshooting
purposes also it's really important that
the service provider does not generate
the aggregates on their exchange point
peering router
if the connection from the backbone to
the exchange point peering router goes
down normal BGP failover will then be
successful if they generate the
aggregate on the peering router and the
link from the peering router to the rest
of the backbone goes down the peering
router has no way of knowing that that
link is broken and will carry on
announcing the ISPs aggregate to the
exchange point members while outbound
traffic will proceed just fine from the
member to the others via the members
upstream transit provider the return
traffic best path will be to the peering
router that's just been disconnected
from the backbone
thereby cutting off the member from all
the others across the exchange point.
© Produced by Philip Smith and the Network Startup Resource Center, through the University of Oregon.
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