Routing Protocols Explained

Preface:

This article will explain many different routing protocols and give some
details and the basic characteristics about them. This document should not be considered
a source of all the details on any of the listed protocols. For more detailed information
information about routing protocols I would suggest you look at the Request For
Comments (RFC) for this protocol, goggling them, or maybe visiting different
vendor websites such as Cisco, Juniper, or Bay Networks. Most vendors' web
sites have detailed explanations of all the protocols there equipment
support the functionality. Before you can understand the routing protocol must be
have a basic knowledge of networks or IP, variable length subnet mask (VLSM)
Network topologies (bus, star, hub, etc. ..), and the OSI model. If you are not
familiar with any of the subjects mentioned above, you might want to read and know
first entering the routing protocols. Routing protocols are what makes the
internet work by moving traffic from one network to another. With the routing
protocols of the Internet could not function because the networks would only be separated
Wi-Fi/Wireless LAN connection to other networks. Internet in terms of base is only a
lots of wired LANs together to make a huge WAN.

Protocol types:

Distance Vector: distance vector routing is a type of
routing protocol that discovers routes on interconnected networks. The Distance
Vector is the routing algorithm based on Bellman-Ford algorithm. Examples of
distance-vector routing protocols are RIP (Routing Information Protocol),
Cisco's IGRP (Internet Gateway Routing Protocol) try Google to see all
different protocols Distance Vector family. Distance vector protocols are
suitable for smaller networks, like many of the protocols of this family are not
scalable in lager complex networks as they are limited. The main limitation
Distance vector protocols is that the method requires that each router simply
inform its neighbors of its routing table. This update the routing table to other
members is to banda to lager networks.

RIP (Routing Information Protocol):

Routing Information Protocol (RIP) is one of the first protocols to be used in
networking and is classified as a distance vector routing protocol. RIP uses
transmission User Datagram Protocol (UDP) data packets for the exchange of routing
Information. There are two versions of RIP v1 and v2. RIP version 1 is the original
version and has many limitations. The metric that RIP uses to assess the value of
different routes is hop count. The hop count metric works by assigning static
routes with a value of 0 and all other values ​​are set by the number of routers
hops (up to 15) that even if the data must travel to reach an end point. RIP
Version 2 supports plain text and MD5 authentication, route summarization,
Classless Inter-Domain Routing (CIDR), variable-length subnet mask (VLSMs)
Multicast support. Some vendors support other non-standard features for RIP but
pay attention to how many features focused vendors are not compatible in a mixed vendor
network.

IGRP (Inter Gateway Routing Protocol):

Interior Gateway Routing Protocol (IGRP) is a distance vector routing protocol
who is an owner and invented by Cisco. It is used by routers to exchange
routing data within an autonomous system (AS). IGRP supports multiple metrics
for the routes, including the bandwidth, load, delay and MTU. This improves the reliability
than RIP because IGRP uses advanced metrics to compare two paths in a
combined path. The two paths together are combined into a single metric, using
a formula that can be set via command line. The maximum hop count of IGRP
is 255 which is an improvement over RIP 15 max hop. Keep in mind that IGRP is a
Cisco proprietary protocol and can not be used in a mixed network provider.

State Links: Link State routing protocol requires each
router (peer) to maintain at least a partial map of the network. When a network
link state changes (down, or vice versa), a notification, called a link
Advertising was (LSA) is flooded throughout the network. All routers
note the change, and recalculate the paths accordingly. This method is more
reliable, easier to debug and less bandwidth than distance vector. It
is also more complex and computation-intensive and memory. Link state routing
protocols found in many lager networks and provide scalable solutions for
more complex networks.

OSPF (Open Shortest Path First):

Open Shortest Path First (OSPF) is a link-state routing protocol that provides
sending link-state advertisements (LSA) to all other routers within the
same hierarchical area or autonomous system (AS). An AS may be divided into a
number of areas, which are groups of contiguous networks and attached hosts.
About interfaces connected, the metrics used, and other variables are
included in OSPF LSAs. As OSPF routers accumulate link-state information, which
use the SPF algorithm to calculate the shortest path for each node.

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

Intermediate System to Intermediate System (IS-IS) routing protocol is a
developed by ISO and is native to a service network or ISO
CLNS protocol so that does not use IP for routing of information messages. It
uses OSI protocols to deliver its packets and establish its adjacencies. IS-IS
has been enhanced to bring IP (Internet Protocol) and this is called Integrated
IS-IS. Integrated IS-IS supports VLSM and converges rapidly. It is also scalable
to support large networks and is the key protocol in many large ISPs.

Hybrid: Hybrid routing protocols are a combination or
both protocols, distance vector and link state, and only one protocol fits into
this field. EIGRP is Cisco Systems proprietary protocol based on their origin
IGRP. For more information on hybrid protocols look under the section "EIGRP".

EIGRP (Enhanced Inter Gateway Routing Protocol):

Major Inter Gateway Routing Protocol (EIGRP) is Cisco Systems Proprietary
protocol based on their original IGRP. EIGRP is a balanced hybrid IP routing
protocol, with optimizations to minimize both the routing instability incurred
after the changes of topology, as well as the use of bandwidth and processing power in
the router. EIGRP is a function of the protocol modules that can treat AppleTalk
as well as IP and IPX. The advantage of this is that only a process of routing
needed instead of running a routing process for each report. EIGRP provides
loop-free and almost instant simultaneous synchronization of routers.

Inter-Autonomous System: Inter-Autonomous System routing protocols are designed
to connect lager networks or Autonomous Systems (AS) together and allow
muitiple autonomous systems network. An example for the need for a
inter-autonomous system protocol to connect two or more Internet Service
Provider (ISP) together in a non-client can connect to each other. Without
to get into too much detail both "Link State and Distance Vector" protocols are
considered intra-autonomous system protocols as they are designed for just route
traffic in a singal AS. The main objective Inter-autonomous system protocols is to
propergate intra-autonomous system information between the various autonomous
systems.

BGP4 (Border Gateway Protocol Version 4):

Border Gateway Protocol is the routing protocol backbone for the most part
Internet and allows peering and carrier networks for the connection. BGP is
explained as a path vector protocol. With BGP attributes for the policy or
perform the actual route selections among the interconnected autonomous systems
is based on weight, local preference, multi-exit discriminator, Origin, as the path,
Next hop, and community. BGP information propagates through the network
exchanges of BGP messages (4 types: open, update, notification and Keep Alive)
peer. Another key feature is that the BGP supports Classless Inter
Domain Routing (CIDR), with the support of CIDR BGP can reduce the size of
Internet routing tables. BGP neighbors exchange full routing information when
's (port 179) TCP connection between neighbors is first established. When
changes to the routing table accrue, the BGP routers send to their neighbors
only those routes that have changed. BGP routers do not send periodic routing
updates and advertise only the optimal paths to a destination .......