1. ROUTING INFOMARTION PROTOCOL
a. WHAT IS THE MEANING OF RIP?
Routing Information Protocol (RIP) is a dynamic protocol used to find
the best route or path from end-to-end (source to destination) over a network
by using a routing metric/hop count algorithm. This algorithm is used to
determine the shortest path from the source to destination, which allows the
data to be delivered at high speed in the shortest time. A router running RIP
sends the contents of its routing table to each of its adjacent routers every
30 seconds. When a route is removed from the routing table, it is flagged as
unusable by the receiving routers after 180 seconds, and removed from their
tables after an additional 120 seconds.
b. WHO IS THE INVENTOR?
The
Routing Information Protocol (RIP) was written by C. Hedrick from Rutgers
University in June 1988, and has since become the most common Internet routing
protocol for routing within networks.
RIP
is based on the computer program "routed", which was widely
distributed with the Unix 4.3 Berkeley Software Distribution (BSD) operating system, and became the de-facto standard for
routing in research labs supported by vendors of network gateways.
All
RIP routing protocols are based on a distance vector algorithm called the
Bellman-Ford algorithm, after Bellman's development of the equation used as the
basis of dynamic programming, and Ford's early work in the area.
Software
based on these algorithms was used as early as 1969 on the ARPANET, but the
main protocol development was done by the Xerox network research and
development division. The earliest RIP protocol was the PUP protocol, which
used the Gateway Information Protocol to exchange routing information, and was
invented by a team that included R. M. Metcalfe, who later developed the Ethernet physical layer network protocol. The PUP protocol was
later upgraded to support the Xerox Network
Systems (XNS) architecture, and named "Routing Information
Protocol", usually just called RIP.
c. WHERE IS INVENTED?
The Routing Information
Protocol (RIP) was written by C. Hedrick from Rutgers University in June 1988,
and has since become the most common Internet routing
protocol for routing within networks.
d. WHEN IS INVENTED?
June 1988
e. HOW TO WORK RIP?
1.
The host hears the
broadcast address if there is a routing update from the gateway.
2.
The host will check
first the local routing table if it receives routing updates.
3.
If the route does
not exist yet, information is immediately entered into the routing table.
4.
If the route already
exists, the smallest metric will be taken as a reference.
5.
The route through a
gateway will be deleted if there is no update from the gateway within a certain
time
6.
Especially for
gateways, RIP will send routing updates to the broadcast address on each
connected network
2. INTERIOR GATEWAY ROUTING PROTOCOL
a. WHAT IS THE MEANING?
Interior
Gateway Routing Protocol (IGRP) is a proprietary distance vector routing
protocol used to communicate routing information within a host network. It was
invented by Cisco.
IGRP manages the flow of routing information within connected routers
in the host network or autonomous system. The protocol ensures that every
router has routing tables updated with the best available path. IGRP also
avoids routing loops by updating itself with the changes occurring over the
network and by error management.
b. WHO IS THE INVENTOR?
Cisco created Interior Gateway
Routing Protocol (IGRP) in response to the limitations in Routing Information
Protocol (RIP), which handles a maximum hop count of 15. IGRP supports a
maximum hop count of up to 255. The primary two purposes of IGRP are to:
•
Communicate routing
information to all connected routers within its boundary or autonomous system
•
Continue updating
whenever there is a topological, network or path change that occurs
IGRP sends a notification of any new changes, and information about
its status, to its neighbors every 90 seconds.
IGRP manages a routing table with the most optimal path
to respective nodes and to networks within the parent network. Because it is a
distance vector protocol, IGRP uses several parameters to calculate the metric
for the best path to a specific destination. These parameters include delay,
bandwidth, reliability, load and maximum transmission unit (MTU).
c. WHEN IS INVENTED?
Cisco developed IGRP in the 1980s to
provide an alternative to RIP (Routing Information Protocol).
[source: https://www.linktionary.com/i/igrp.html]
d. HOW DOES IT WORK?
Enhanced
IGRP uses the same distance vector algorithm and distance information as IGRP.
However, the convergence properties and the operating efficiency of enhanced
IGRP have improved significantly.
The
convergence technology is based on research conducted at SRI International and
employs an algorithm referred to as the Diffusing Update Algorithm (DUAL). This
algorithm guarantees loop-free operation at every instant throughout a route
computation and allows all routers involved in a topology change to synchronize
at the same time. Routers that are not affected by topology changes are not
involved in recomputations.
The
convergence time with DUAL rivals that of any other existing routing protocol.
The initial implementation of IGRP operated in Internet Protocol (IP) networks.
Enhanced IGRP extends IGRP so that it is independent of the network-layer
protocol. In addition to IP, it now also operates in AppleTalk and Novell IPX
networks.
3. OPEN SHORTEST PATH FIRST
a. WHAT IS THE MEANING?
Stands
for "Open Shortest Path First." OSPF is a method of finding the
shortest path from one router to another in a local area network (LAN). As long as a network is IP-based, the OSPF algorithm will calculate the most efficient
way for data to be transmitted.
If
there are several routers on a network, OSPF builds a table (or topography) of
the router connections. When data is sent from one location to another, the
OSPF algorithm compares the available options and chooses the most efficient
way for the data to be sent. This limits unnecessary delays in data
transmission and prevents infinite loops.
[source: https://techterms.com/definition/ospf]
b. WHO IS INVENTED?
The OSPF routing algorithm was created to provide an alternative to RIP,
based on Shortest Path First algorithms instead of the Bellman-Ford algorithm.
It uses a tree that describes the network topology to define the shortest path
from each router to
each destination address. Since OSPF keeps track of entire paths, it has more
overhead than RIP, but provides more options.
c. HOW DOES IT WORK?
The main difference between
OSPF and RIP is that RIP only keeps track of the closest router for each
destination address, while OSPF keeps track of a complete topological database
of all connections in the local network. The OSPF algorithm works as described
below.
•
Startup. When a
router is turned on it sends Hello packets to all of its neighbors, receives
their Hello packets in return, and establishes routing connections by
synchronizing databases with adjacent routers that agree to synchronize.
•
Update. At regular
intervals each router sends an update message called its "link state"
describing its routing database to all the other routers, so that all routers
have the same description of the topology of the local network.
•
Shortest path tree.
Each router then calculates a mathematical data structure called a
"shortest path tree" that describes the shortest path to each
destination address and therefore indicates the closest router to send to for
each communication; in other words -- "open shortest path first".
4. ENHANCED INTERIOR GATEWAY ROUTING PROTOCOL
a. WHAT IS THE MEANING?
Enhanced
Interior Gateway Routing Protocol (EIGRP) is an advanced distance vector
routing protocol based on the principles of the Interior Gateway Routing
Protocol (IGRP).
EIGRP is a successor to the Interior Gateway Routing Protocol (IGRP).
Both are owned by Cisco and operate only on their devices. Cisco introduced
EIGRP because it needed a protocol with faster converging abilities, route
selection and calculation and the ability to record information from
neighboring devices.
[source:
https://www.techopedia.com/definition/16186/enhanced-interior-gateway-routing-protocol-eigrp]
b. WHO IS INVENTED?
Enhanced
Interior Gateway Routing Protocol (EIGRP) or Enhanced IGRP is a Cisco proprietary routing
protocol utilizing the Diffusing Update Algorithm (DUAL). The DUAL algorithim
was invented by Dr. J.J. Garcia-Luna Aceves of SRI International as an
improvement to the IGRP routing protocol. EIGRP was designed to be
interoperable with standard IGRP. EIGRP is a hybrid protocol as it incorporates
features of a Distance Vector routing protocol and features of a Link State
routing protocol. EIGRP is often used in Cisco-based networks running multiple
network-layer protocols.
EIGRP can redistribute its routes (and metrics) intoother routing
protocols and accepts redistribution from other routing protocols as well.
c. HOW DOES IT WORK?
EIGRP is a distance vector routing protocol that uses the diffusing update algorithm (DUAL) (based on work from SRI
International) to
improve the efficiency of the protocol and to help prevent calculation errors
when attempting to determine the best path to a remote network.
EIGRP determines the value of the path using five metrics: bandwidth, load,
delay, reliability and MTU.
EIGRP routing information exchanged to a router from
another router within the same autonomous system has a default administrative distance of 90. EIGRP routing information that has come from an
EIGRP-enabled router outside the autonomous system has a default administrative distance of 170.
EIGRP does not operate using the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP). This means that EIGRP does not use a port number to identify traffic. Rather,
EIGRP is designed to work on top of layer 3 (i.e. the IP protocol). Since EIGRP
does not use TCP for communication, it implements Cisco's Reliable Transport
Protocol (RTP) to ensure that EIGRP router updates are delivered to all
neighbors completely. The reliable transport protocol also contains other
mechanisms to maximize efficiency and support multicasting. EIGRP uses 224.0.0.10 as its
multicast address and protocol number 88.
[source: https://en.wikipedia.org/wiki/Enhanced_Interior_Gateway_Routing_Protocol#Technical_details]
5. BORDER GATEWAY PROTOCOL
a. WHAT IS THE MEANING?
Border
Gateway Protocol (BGP) is a routing protocol used to transfer data and
information between different host gateways, the Internet or autonomous
systems. BGP is a Path Vector Protocol (PVP), which maintains paths to
different hosts, networks and gateway routers and determines the routing
decision based on that. It does not use Interior Gateway Protocol (IGP) metrics
for routing decisions, but only decides the route based on path, network
policies and rule sets.
Sometimes, BGP is described as a reachability protocol rather than a
routing protocol.
b. WHO IS INVENTED?
How BGP was
invented. BGP was initially created in three different
implementations. Then, in a standard Internet approach, they were used together
to show that separate implementations of the protocol could interoperate
without problems.
•
Kirk Lougheed of
Cisco systems developed a proprietary version of BGP for Cisco router
equipment.
•
Jeff Honig from
Cornell University and Dennis Ferguson from the University of Toronto developed
a BGP version called "gated" to run on Unix computers, enabling Unix
machines to become BGP routers, and then put the code in the public domain for
others to use.
•
Yakov Rekhter from
the IBM Thomas J. Watson Research Center wrote a BGP version for the NSFNET
backbone.
c. HOW DOES IT WORK?
When a BGP
router first comes up on the Internet, either for the first time or after being
turned off, it establishes connections with the other BGP routers with which it
directly communicates. The first thing it does is download the entire routing
table of each neighboring router. After that it only exchanges much shorter
update messages with other routers.
BGP routers
send and receive update messages to indicate a change in the preferred path to
reach a computer with a given IP address. If the router decides to update its
own routing tables because this new path is better, then it will subsequently
propagate this information to all of the other neighboring BGP routers to which
it is connected, and they will in turn decide whether to update their own
tables and propagate the information further.
BGP uses the TCP/IP protocol on port 179 to
establish connections. It has strong security features, including the
incorporation of a digital signature in all communications between BGP routers.
Each BGP
router contains a Routing Information Base (RIB) that contains the routing
information maintained by that router. The RIB contains three types of
information:
•
Adj-RIBs-In.
The unedited routing information sent by neighboring routers.
•
Loc-RIB.
The actual routing information the router uses, developed from Adj-RIBs-In.
•
Adj-RIBs-Out.
The information the router chooses to send to neighboring routers.
BGP routers
exchange information using four types of messages:
•
Open. Used to open an initial connection
with a neighboring router.
•
Update. These messages do most of the work,
exchanging routing information between neighboring routers, and contain one of
the following pieces of information.
•
Withdrawn Routes. The IP addresses of computers that
the router no longer can route messages to.
•
Paths. A new preferred route for an IP
address. This path consists of two pieces of information -- the IP address, and
the address of the next router in the path that is used to route messages
destined for that address.
•
Notification. Used to indicate errors, such as an
incorrect or unreadable message received, and are followed by an immediate
close of the connection with the neighboring router.
•
Keepalive. Each BGP router sends a 19 byte
Keepalive message to each neighboring router to let them know that it is still
operational about every 30 seconds, and no more often than every three seconds.
If any router does not receive a Keepalive message from a neighboring router
within a set amount of time, it closes its connection with that router, and
removes it from its Routing Information Base, repairing what it perceives as
damage to the network.
Routing messages are the highest precedence traffic on the Internet, and
each BGP router gives them first priority over all other traffic. This makes
sense -- if routing information can't make it through, then nothing else will.
