Routing Methods Described

Preface:

Within this paper I'll explain a variety of routing methods and provide some
fundamental particulars featuring about the subject. This paper by no means should be thought about
a resource of full detail about the listed methods. For detailed
details about routing methods I recommend considering the Request
Comments (RFC) for your protocol, goggling them, or possibly going to different
vendor's websites for example 'cisco', Juniper, or Bay systems. Most vendors' web
sites have detailed explanations about all of the Methods there tools
support features. Before you understand routing protocol you'll have to
possess a fundamental understanding or IP systems, Variable Length Subnet Masks (VLSM),
Network Topologies (bus, star, Hub, etc..), and also the OSI model. If you're not
acquainted with any of these subjects you might want to educate yourself and find out about
them before getting into routing methods. Routing methods are why is the
internet work by moving traffic from network to network. Without having routing
methods the web couldn't work because systems would certainly be separate
LANs without any link with others LANs. The web in fundamental terms is simply a
large amount of LANs wired together to create a huge WAN.

Protocol types:

Distance Vector: distance vector routing is a kind of
routing protocol that finds out routes on interconnected systems. The Length
Vector routing formula may be the in line with the Bellman-Ford formula. Good examples of
distance-vector routing methods include RIP (Routing Information Protocol),
Cisco's IGRP (Internet Gateway Routing Protocol) try Google to determine all of the
different methods within the Distance Vector family. Distance Vector methods are
appropriate for more compact systems as most of the methods within this family aren't
scalable in lager complex systems because they are limited. The primary limit to
Distance Vector Methods can there be manner in which requires each router simply
inform its neighbors of their routing table. This routing table update with other
people is bandwidth intensive to lager systems.

RIP (Routing Information Protocol):

Routing Information Protocol (RIP) is among the first methods for use in
networking and it is considered a distance vector routing protocol. RIP uses
broadcast User Datagram Protocol (UDP) data packets to switch routing
information. You will find two versions RIP V1 &lifier V2. RIP Version 1 may be the original
version and it has many restrictions. The metric that RIP uses to rate the need for
different routes is hop count. The hop count metric functions by setting static
routes having a worth of and all sorts of other hubs values are positioned by the amount of
hops (as much as 15) the data must travel though to get at an finish point. RIP
Version 5 supports plain text and MD5 authentication, route summarization,
classless inter-domain routing (CIDR), variable-length subnet masks (VLSMs),
Multicast support. Some suppliers support other non-standard features for RIP but
be cautious as numerous vendor centric features aren't compatible inside a mixed vendor
network.

IGRP (Inter Gateway Routing Protocol):

Interior Gateway Routing Protocol (IGRP) is really a distance vector routing protocol
that is a proprietary and introduced by 'cisco'. It's utilized by hubs to switch
routing data inside an autonomous system (AS). IGRP supports multiple metrics
for routes, including bandwidth, load, delay and MTU. This enhances reliability
over RIP because IGRP uses advanced metrics to check two routes right into a
combined route. The 2 routes together are combined right into a single metric, using
an equation which may be modified via command line. The utmost hop count of IGRP
is 255 that is a noticable difference over RIPs 15 hop max. Bear in mind that IGRP is really a
'cisco' proprietary protocol and cannot be utilized in an assorted vendor network.

Link Condition: Link Condition routing protocol requires each
router (peer) to keep a minimum of an incomplete map from the network. Whenever a network
link changes condition (as much as lower, or the other way around), a notification, known as a hyperlink
condition advertisement (LSA) is flooded through the network. All of the hubs
note the modification, and recompute their routes accordingly. This process is much more
reliable, simpler to debug and fewer bandwidth-intensive than Distance-Vector. It
can also be more complicated and much more compute- and memory-intensive. Link condition routing
methods are located in lots of lager systems and supply Scalable solutions for
more complicated systems.

OSPF (Open Least Path First):

Open least path first (OSPF) is really a link-condition routing protocol that requires
the delivering of link-condition ads (LSAs) to any or all other hubs inside the
same hierarchical area or autonomous system (AS). An As possible split into a
quantity of areas, that are categories of contiguous systems and attached hosts.
Info on attached connects, metrics used, along with other variables are
incorporated in OSPF LSAs. As OSPF hubs accumulate link-condition information, they
make use of the SPF formula to calculate the least road to each node.

(IS-IS) Intermediate System-to-Intermediate System:

Intermediate System-to-Intermediate System (IS-IS) is really a routing protocol
produced by the ISO and it is natively an ISO Connectionless Network Service or
CLNS protocol so it doesn't use IP to hold routing information messages. It
uses OSI methods to provide its packets and establish its adjacencies. IS-IS
continues to be enhanced to hold IP (Ip Address) which is known as Integrated
IS-IS. Integrated IS-IS supports VLSM and converges quickly. It's also scalable
to aid large systems and is paramount protocol in lots of bigger ISP's.

Hybrid: Hybrid routing Methods really are a combination or
both Distance Vector and Link condition methods and just one protocol suits
this area. EIGRP is 'cisco' Systems Proprietary protocol according to their original
IGRP. For additional info on Hybrid Methods look below towards the section on "EIGRP".

EIGRP (Enhanced Inter Gateway Routing Protocol):

Enhanced Inter Gateway Routing Protocol (EIGRP) is 'cisco' Systems Proprietary
protocol according to their original IGRP. EIGRP is really a balanced hybrid IP routing
protocol, with optimizations to reduce both routing instability incurred
after topology changes, along with the utilization of bandwidth and processing energy in
the router. EIGRP has Protocol-Dependent Modules that may cope with AppleTalk
and IPX in addition to IP. The benefit with this particular is the fact that just one routing process
need run rather than a routing process for each one of the methods. EIGRP provides
loop-free operation and almost instant synchronised synchronization of hubs.

Inter-Autonomous System: Inter-Autonomous System routing methods are made
for connecting lager systems or Autonomous Systems (AS) together and permit
muitiple Autonomous Systems to network. An example for the necessity of an
inter-autonomous system protocol would be to connect several Online Sites
Companies (Web service provider) together there customer can connect with one another. Without
getting into to an excessive amount of detail both "Link Condition &lifier Distance Vector" methods are
considered intra-autonomous system methods because they are made to just route
traffic inside a singal AS. Inter-Autonomous System methods primary goal would be to
propergate the intra-autonomous system information between different autonomous
systems.

BGP4 (Border Gateway Protocol Version 4):

Border Gateway Protocol may be the backbone routing protocol for the majority of the
internet and enables for peering and company systems for connecting. BGP is
described like a path vector protocol. With BGP the insurance policy or characteristics for
making the particular route choices one of the interconnected autonomous systems
is dependant on Weight ,Local preference, Multi-exit discriminator, Origin, AS path,
Next hop, &lifier Community. BGP details are propagated with the network by
trades of BGP messages (4 types: Open, Update, Notification, &lifier Keep Alive)
between peers. Another key feature to BGP is that's supports Classless Inter
Domain Routing (CIDR) using the support of CIDR BGP can help to eliminate how big the
Internet routing tables. BGP neighbors exchange full routing information when
the TCP (port 179) link between neighbors is first established. When
changes towards the routing table accrue, the BGP hubs send for their neighbors
only individuals routes which have transformed. BGP hubs don't send periodic routing
updates and advertise just the optimal pathways to some destination.