Dynamic routing protocols calculate routes dynamically based on information exchanged between routers. Routing Information Protocol (RIP) is an example of a distance vector routing protocol. Distance vector protocols work by having each router periodically send its full routing table to neighbors. This can allow routes to increase without bound in the presence of failures, known as the count-to-infinity problem. Solutions include advertising the full path a route takes, not just the next hop.
destination. The network layer must know the topology of the subnet and choos...Ashish Gupta
The document discusses routing in computer networks at the network layer. It covers key topics such as routing algorithms, distance vector routing, link state routing, OSPF, and BGP. The main points are:
1) Routing algorithms determine the best path between source and destination networks and involve exchanging routing information between routers.
2) Distance vector algorithms like RIP use hop count as the metric and exchange full routing tables periodically between neighbors. Link state algorithms like OSPF flood link state information to all routers.
3) OSPF divides domains into areas to reduce routing overhead and uses different LSA types to distribute routing information within and between areas. BGP handles interdomain routing between autonomous systems
The document discusses routing in computer networks at the network layer. It covers routing algorithms like distance vector routing, link state routing, OSPF, and BGP. Distance vector routing uses hop counts as the metric and is prone to slow convergence. Link state routing floods link state information to all routers to compute shortest paths more quickly. OSPF and BGP are examples of link state and path vector routing protocols used between autonomous systems on the Internet.
The document discusses network layer concepts including network layer design issues, routing algorithms, and protocols. It provides 3 key points:
1) The network layer is responsible for delivering packets between endpoints over multiple links using store-and-forward packet switching. It implements both connectionless and connection-oriented services for the transport layer.
2) Common routing algorithms discussed include shortest path algorithms like Dijkstra's algorithm, flooding, and distance vector routing. Flooding broadcasts all packets while distance vector uses the Bellman-Ford equation to iteratively calculate the shortest paths.
3) Protocols discussed include IPv4, IPv6, ARP, RARP, DHCP, and ICMP. Connectionless transmission uses datagrams while connection
The document discusses routing algorithms in computer networks. It describes the functions of the network layer, including internetworking, addressing, routing, and packetizing. It then focuses on routing algorithms, classifying them as either adaptive or non-adaptive. Adaptive algorithms make routing decisions dynamically based on network conditions, while non-adaptive algorithms use static routing tables. Specific adaptive algorithms discussed include distance vector routing and link state routing, along with explanations of how each works.
The document discusses network layer design issues and protocols. It covers store-and-forward packet switching, the functions of the network layer including routing and congestion control. It then describes the implementation of connectionless and connection-oriented services, comparing virtual circuits and datagrams. Various routing algorithms are also summarized, such as shortest path, flooding, distance vector, and link state routing.
A routing table can be either static or dynamic. A dynamic table is updated automatically when there is a change on the internet. A routing protocol lets routers inform each other of changes. Distance vector routing uses hop counts as the metric and each router maintains a table of minimum distances. Link state routing uses flooding to disseminate link state packets and each router builds a shortest path tree to calculate routes.
The document discusses the network layer and routing. It begins by stating the goals of understanding network layer services like routing, dealing with scale, and router functionality. It then provides an overview of network layer services, routing principles, hierarchical routing, IP, routing protocols, and functions of routers. The key abstraction provided by the network layer is the service model, which can be either virtual circuits or datagrams. Routing determines the path between source and destination, and algorithms like Dijkstra's algorithm are used to find the least cost path through a graph of routers and links.
destination. The network layer must know the topology of the subnet and choos...Ashish Gupta
The document discusses routing in computer networks at the network layer. It covers key topics such as routing algorithms, distance vector routing, link state routing, OSPF, and BGP. The main points are:
1) Routing algorithms determine the best path between source and destination networks and involve exchanging routing information between routers.
2) Distance vector algorithms like RIP use hop count as the metric and exchange full routing tables periodically between neighbors. Link state algorithms like OSPF flood link state information to all routers.
3) OSPF divides domains into areas to reduce routing overhead and uses different LSA types to distribute routing information within and between areas. BGP handles interdomain routing between autonomous systems
The document discusses routing in computer networks at the network layer. It covers routing algorithms like distance vector routing, link state routing, OSPF, and BGP. Distance vector routing uses hop counts as the metric and is prone to slow convergence. Link state routing floods link state information to all routers to compute shortest paths more quickly. OSPF and BGP are examples of link state and path vector routing protocols used between autonomous systems on the Internet.
The document discusses network layer concepts including network layer design issues, routing algorithms, and protocols. It provides 3 key points:
1) The network layer is responsible for delivering packets between endpoints over multiple links using store-and-forward packet switching. It implements both connectionless and connection-oriented services for the transport layer.
2) Common routing algorithms discussed include shortest path algorithms like Dijkstra's algorithm, flooding, and distance vector routing. Flooding broadcasts all packets while distance vector uses the Bellman-Ford equation to iteratively calculate the shortest paths.
3) Protocols discussed include IPv4, IPv6, ARP, RARP, DHCP, and ICMP. Connectionless transmission uses datagrams while connection
The document discusses routing algorithms in computer networks. It describes the functions of the network layer, including internetworking, addressing, routing, and packetizing. It then focuses on routing algorithms, classifying them as either adaptive or non-adaptive. Adaptive algorithms make routing decisions dynamically based on network conditions, while non-adaptive algorithms use static routing tables. Specific adaptive algorithms discussed include distance vector routing and link state routing, along with explanations of how each works.
The document discusses network layer design issues and protocols. It covers store-and-forward packet switching, the functions of the network layer including routing and congestion control. It then describes the implementation of connectionless and connection-oriented services, comparing virtual circuits and datagrams. Various routing algorithms are also summarized, such as shortest path, flooding, distance vector, and link state routing.
A routing table can be either static or dynamic. A dynamic table is updated automatically when there is a change on the internet. A routing protocol lets routers inform each other of changes. Distance vector routing uses hop counts as the metric and each router maintains a table of minimum distances. Link state routing uses flooding to disseminate link state packets and each router builds a shortest path tree to calculate routes.
The document discusses the network layer and routing. It begins by stating the goals of understanding network layer services like routing, dealing with scale, and router functionality. It then provides an overview of network layer services, routing principles, hierarchical routing, IP, routing protocols, and functions of routers. The key abstraction provided by the network layer is the service model, which can be either virtual circuits or datagrams. Routing determines the path between source and destination, and algorithms like Dijkstra's algorithm are used to find the least cost path through a graph of routers and links.
- Routing protocols are used by routers to communicate and determine the best paths between networks. They update routing tables but do not actually transmit data.
- There are static and dynamic routing protocols. Static routing uses manually configured paths while dynamic routing automatically updates paths in response to network changes.
- Common routing protocols include RIP, OSPF, BGP, which use different algorithms like distance vector or link state to calculate paths. Dijkstra's algorithm is an example used in link state routing to find shortest paths through a network.
The document discusses routing protocols used in internets and autonomous systems. It describes how distance vector routing protocols like RIP work by sharing routing tables between neighbors. It also explains link state routing protocols like OSPF, where each router shares information about connected links and all routers can independently calculate optimal routes. Finally, it outlines path vector routing and BGP, which is used for inter-domain routing between autonomous systems and considers routing policies.
Module 3 Part B - computer networks module 2 pptanushaj46
The document discusses several key issues in network layer design including store-and-forward packet switching, services provided to the transport layer, implementation of connectionless and connection-oriented services, and comparison of virtual-circuit and datagram networks. It also covers routing algorithms such as shortest path, flooding, distance vector, link state, and hierarchical routing.
This PPT focuses on the basic concepts of routing protocols including the executive summary of basic computer networks.
Regarding to the routing protocol concepts, it gives us a brief information of routing, protocol, routing protocol, types of routing protocol, metrics of a routing protocol algorithms...
A routing algorithm determines the best path for data packets to travel between a source and destination on the Internet. This document discusses and compares different routing algorithms used within autonomous systems (ASes) and between ASes. It covers link-state algorithms like OSPF that use flooding to share full topology information, distance-vector algorithms like RIP that share routing tables with neighbors, and BGP which connects different ASes and allows policies to influence path selection.
- Routing protocols allow routers to learn the best paths to different networks. Routers use routing tables to store this path information.
- Dynamic routing protocols allow routers to automatically share routing information with each other. This allows the routers to adapt to network changes. RIP is an example of a dynamic distance vector routing protocol.
- With RIP, each router sends its full routing table to neighboring routers every 30 seconds. The routers use the hop count as the routing metric to determine the best path. The maximum hop count allowed is 15.
Distance Vector & Link state Routing AlgorithmMOHIT AGARWAL
1) Each router maintains a routing table containing the outgoing link and distance to reach each destination node. 2) Routers periodically share their routing tables with neighbors so each can update its own table. 3) This allows routers to continuously determine the shortest paths to all destinations as network conditions change.
The document provides an overview of the network layer chapter from the textbook "Computer Networking: A Top Down Approach". It outlines the key topics covered in the chapter including network layer service models, how routers work, routing algorithms, IP addressing, and routing protocols used in the Internet. The chapter goals are to understand the principles of the network layer and how these concepts are implemented in the Internet.
The document summarizes key aspects of network layer functionality in computer networks. It discusses the differences between virtual circuit and datagram networks, and how they provide different types of connection-oriented and connectionless services. It also describes the basic functions of routers in forwarding packets using destination addresses and routing algorithms to determine optimal paths through the network.
The document discusses different routing methods used in computer networks, including:
- Network-specific routing which treats all hosts on the same network as a single entity in the routing table.
- Host-specific routing which explicitly defines routes to individual host addresses in the routing table.
- Default routing which uses a single default route for all unknown destinations.
It also covers routing protocols like RIP and OSPF, explaining how they establish and maintain routing tables dynamically as the network changes. Distance vector protocols like RIP propagate full routing tables between routers, while link-state protocols like OSPF flood link state information to build independent views of the network topology.
Tcil_Concept of Routing_n_protocols.pptxVINAYTANWAR18
Routing allows data to be transferred between different networks and subnets. Routers use routing tables to determine the best path for packets to travel. Routing tables can be populated through static or dynamic routing protocols. Dynamic routing protocols use metrics like hop count or bandwidth to calculate the optimal route and update routing tables automatically based on network changes. Common routing protocols include RIP, OSPF, and BGP.
The document discusses different routing protocols used in computer networks. It begins with an introduction to routing protocols and their purpose of communicating between source and destination networks by updating routing tables. It then categorizes routing protocols as static or dynamic and discusses examples in each category. For dynamic routing protocols, it further divides them into interior gateway protocols used within an autonomous system and exterior gateway protocols used between autonomous systems. Specific dynamic interior routing protocols discussed in detail include distance vector protocols like RIP and link state protocols like OSPF.
Networking issues for distributed systemskingGovindi
The document provides an overview of networking issues for distributed systems, basic networking concepts, and Internet protocols. It discusses performance parameters like latency and data transfer rate that affect message transfer speed. It also describes various wired and wireless network types and their typical bandwidth and latency ranges. The document introduces the OSI 7-layer model and summarizes each layer's functions. It explains concepts like routing, routing algorithms, encapsulation, and the TCP/IP protocol stack. The document provides examples of routing tables, packet encapsulation, and how NAT enables private addressing on local networks.
1. Asynchronous Transfer Mode (ATM) is a cell-switching and multiplexing technology that combines the benefits of circuit switching and packet switching. It uses fixed-length cells to carry information across networks.
2. ATM networks are built using ATM switches and end-points. Switches are connected via User-Network Interfaces (UNI) and Network-Network Interfaces (NNI). Common ATM end-points include workstations, routers, and video codecs.
3. ATM provides guaranteed bandwidth through virtual circuits established over packet-switched networks. It is highly scalable and efficient for transmitting voice and video due to its small, fixed-length cells.
The network layer is concerned with routing packets from the source to the destination across multiple networks. It must understand the topology of connected networks and choose optimal paths while avoiding overloading some lines. The network layer provides either connection-oriented or connectionless services to the transport layer and deals with differences when sources and destinations are in different networks. Dynamic routing algorithms like distance vector routing are used to adaptively route packets based on current network conditions.
The network layer is responsible for transporting data segments from source to destination hosts. It encapsulates segments into datagrams and delivers them to the transport layer. Network layer protocols run on every host and router. Routers examine header fields to forward datagrams appropriately based on destination addresses. The network layer handles addressing, routing, and intermediate forwarding of datagrams between source and destination hosts.
The document discusses several topics related to computer networks including:
1. The network layer, including design issues like store-and-forward and connection-oriented services. Routing algorithms like shortest path routing and flooding are also discussed.
2. Congestion control principles and policies for preventing congestion in virtual circuits and datagram subnets.
3. Transport layer protocols like TCP and UDP, and how they provide services and manage connections and transmissions.
4. Application layer protocols like DNS for managing domain names and resource records.
Routing is the process of selecting the best path to send data from a source to a destination. Routers perform routing by using routing protocols and algorithms to determine the optimal path. Distance vector routing uses hop count as the metric to calculate the best path, while link state routing uses the least cost path based on metrics like bandwidth and delay. Key differences are that distance vector routing shares distance vectors with neighbors periodically, while link state routing shares complete topology information and triggers updates when links change state.
- Routing protocols are used by routers to communicate and determine the best paths between networks. They update routing tables but do not actually transmit data.
- There are static and dynamic routing protocols. Static routing uses manually configured paths while dynamic routing automatically updates paths in response to network changes.
- Common routing protocols include RIP, OSPF, BGP, which use different algorithms like distance vector or link state to calculate paths. Dijkstra's algorithm is an example used in link state routing to find shortest paths through a network.
The document discusses routing protocols used in internets and autonomous systems. It describes how distance vector routing protocols like RIP work by sharing routing tables between neighbors. It also explains link state routing protocols like OSPF, where each router shares information about connected links and all routers can independently calculate optimal routes. Finally, it outlines path vector routing and BGP, which is used for inter-domain routing between autonomous systems and considers routing policies.
Module 3 Part B - computer networks module 2 pptanushaj46
The document discusses several key issues in network layer design including store-and-forward packet switching, services provided to the transport layer, implementation of connectionless and connection-oriented services, and comparison of virtual-circuit and datagram networks. It also covers routing algorithms such as shortest path, flooding, distance vector, link state, and hierarchical routing.
This PPT focuses on the basic concepts of routing protocols including the executive summary of basic computer networks.
Regarding to the routing protocol concepts, it gives us a brief information of routing, protocol, routing protocol, types of routing protocol, metrics of a routing protocol algorithms...
A routing algorithm determines the best path for data packets to travel between a source and destination on the Internet. This document discusses and compares different routing algorithms used within autonomous systems (ASes) and between ASes. It covers link-state algorithms like OSPF that use flooding to share full topology information, distance-vector algorithms like RIP that share routing tables with neighbors, and BGP which connects different ASes and allows policies to influence path selection.
- Routing protocols allow routers to learn the best paths to different networks. Routers use routing tables to store this path information.
- Dynamic routing protocols allow routers to automatically share routing information with each other. This allows the routers to adapt to network changes. RIP is an example of a dynamic distance vector routing protocol.
- With RIP, each router sends its full routing table to neighboring routers every 30 seconds. The routers use the hop count as the routing metric to determine the best path. The maximum hop count allowed is 15.
Distance Vector & Link state Routing AlgorithmMOHIT AGARWAL
1) Each router maintains a routing table containing the outgoing link and distance to reach each destination node. 2) Routers periodically share their routing tables with neighbors so each can update its own table. 3) This allows routers to continuously determine the shortest paths to all destinations as network conditions change.
The document provides an overview of the network layer chapter from the textbook "Computer Networking: A Top Down Approach". It outlines the key topics covered in the chapter including network layer service models, how routers work, routing algorithms, IP addressing, and routing protocols used in the Internet. The chapter goals are to understand the principles of the network layer and how these concepts are implemented in the Internet.
The document summarizes key aspects of network layer functionality in computer networks. It discusses the differences between virtual circuit and datagram networks, and how they provide different types of connection-oriented and connectionless services. It also describes the basic functions of routers in forwarding packets using destination addresses and routing algorithms to determine optimal paths through the network.
The document discusses different routing methods used in computer networks, including:
- Network-specific routing which treats all hosts on the same network as a single entity in the routing table.
- Host-specific routing which explicitly defines routes to individual host addresses in the routing table.
- Default routing which uses a single default route for all unknown destinations.
It also covers routing protocols like RIP and OSPF, explaining how they establish and maintain routing tables dynamically as the network changes. Distance vector protocols like RIP propagate full routing tables between routers, while link-state protocols like OSPF flood link state information to build independent views of the network topology.
Tcil_Concept of Routing_n_protocols.pptxVINAYTANWAR18
Routing allows data to be transferred between different networks and subnets. Routers use routing tables to determine the best path for packets to travel. Routing tables can be populated through static or dynamic routing protocols. Dynamic routing protocols use metrics like hop count or bandwidth to calculate the optimal route and update routing tables automatically based on network changes. Common routing protocols include RIP, OSPF, and BGP.
The document discusses different routing protocols used in computer networks. It begins with an introduction to routing protocols and their purpose of communicating between source and destination networks by updating routing tables. It then categorizes routing protocols as static or dynamic and discusses examples in each category. For dynamic routing protocols, it further divides them into interior gateway protocols used within an autonomous system and exterior gateway protocols used between autonomous systems. Specific dynamic interior routing protocols discussed in detail include distance vector protocols like RIP and link state protocols like OSPF.
Networking issues for distributed systemskingGovindi
The document provides an overview of networking issues for distributed systems, basic networking concepts, and Internet protocols. It discusses performance parameters like latency and data transfer rate that affect message transfer speed. It also describes various wired and wireless network types and their typical bandwidth and latency ranges. The document introduces the OSI 7-layer model and summarizes each layer's functions. It explains concepts like routing, routing algorithms, encapsulation, and the TCP/IP protocol stack. The document provides examples of routing tables, packet encapsulation, and how NAT enables private addressing on local networks.
1. Asynchronous Transfer Mode (ATM) is a cell-switching and multiplexing technology that combines the benefits of circuit switching and packet switching. It uses fixed-length cells to carry information across networks.
2. ATM networks are built using ATM switches and end-points. Switches are connected via User-Network Interfaces (UNI) and Network-Network Interfaces (NNI). Common ATM end-points include workstations, routers, and video codecs.
3. ATM provides guaranteed bandwidth through virtual circuits established over packet-switched networks. It is highly scalable and efficient for transmitting voice and video due to its small, fixed-length cells.
The network layer is concerned with routing packets from the source to the destination across multiple networks. It must understand the topology of connected networks and choose optimal paths while avoiding overloading some lines. The network layer provides either connection-oriented or connectionless services to the transport layer and deals with differences when sources and destinations are in different networks. Dynamic routing algorithms like distance vector routing are used to adaptively route packets based on current network conditions.
The network layer is responsible for transporting data segments from source to destination hosts. It encapsulates segments into datagrams and delivers them to the transport layer. Network layer protocols run on every host and router. Routers examine header fields to forward datagrams appropriately based on destination addresses. The network layer handles addressing, routing, and intermediate forwarding of datagrams between source and destination hosts.
The document discusses several topics related to computer networks including:
1. The network layer, including design issues like store-and-forward and connection-oriented services. Routing algorithms like shortest path routing and flooding are also discussed.
2. Congestion control principles and policies for preventing congestion in virtual circuits and datagram subnets.
3. Transport layer protocols like TCP and UDP, and how they provide services and manage connections and transmissions.
4. Application layer protocols like DNS for managing domain names and resource records.
Routing is the process of selecting the best path to send data from a source to a destination. Routers perform routing by using routing protocols and algorithms to determine the optimal path. Distance vector routing uses hop count as the metric to calculate the best path, while link state routing uses the least cost path based on metrics like bandwidth and delay. Key differences are that distance vector routing shares distance vectors with neighbors periodically, while link state routing shares complete topology information and triggers updates when links change state.
Temple of Asclepius in Thrace. Excavation resultsKrassimira Luka
The temple and the sanctuary around were dedicated to Asklepios Zmidrenus. This name has been known since 1875 when an inscription dedicated to him was discovered in Rome. The inscription is dated in 227 AD and was left by soldiers originating from the city of Philippopolis (modern Plovdiv).
Communicating effectively and consistently with students can help them feel at ease during their learning experience and provide the instructor with a communication trail to track the course's progress. This workshop will take you through constructing an engaging course container to facilitate effective communication.
Leveraging Generative AI to Drive Nonprofit InnovationTechSoup
In this webinar, participants learned how to utilize Generative AI to streamline operations and elevate member engagement. Amazon Web Service experts provided a customer specific use cases and dived into low/no-code tools that are quick and easy to deploy through Amazon Web Service (AWS.)
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
हिंदी वर्णमाला पीपीटी, hindi alphabet PPT presentation, hindi varnamala PPT, Hindi Varnamala pdf, हिंदी स्वर, हिंदी व्यंजन, sikhiye hindi varnmala, dr. mulla adam ali, hindi language and literature, hindi alphabet with drawing, hindi alphabet pdf, hindi varnamala for childrens, hindi language, hindi varnamala practice for kids, https://www.drmullaadamali.com
Beyond Degrees - Empowering the Workforce in the Context of Skills-First.pptxEduSkills OECD
Iván Bornacelly, Policy Analyst at the OECD Centre for Skills, OECD, presents at the webinar 'Tackling job market gaps with a skills-first approach' on 12 June 2024
Gender and Mental Health - Counselling and Family Therapy Applications and In...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
This document provides an overview of wound healing, its functions, stages, mechanisms, factors affecting it, and complications.
A wound is a break in the integrity of the skin or tissues, which may be associated with disruption of the structure and function.
Healing is the body’s response to injury in an attempt to restore normal structure and functions.
Healing can occur in two ways: Regeneration and Repair
There are 4 phases of wound healing: hemostasis, inflammation, proliferation, and remodeling. This document also describes the mechanism of wound healing. Factors that affect healing include infection, uncontrolled diabetes, poor nutrition, age, anemia, the presence of foreign bodies, etc.
Complications of wound healing like infection, hyperpigmentation of scar, contractures, and keloid formation.
Bed Making ( Introduction, Purpose, Types, Articles, Scientific principles, N...
module10-rip (1).ppt
1. 1
Dynamic Routing Protocols I
RIP
Relates to Lab 4.
The first module on dynamic routing protocols. This module provides an
overview of routing, introduces terminology (interdomain, intradomain,
autonomous system),
2. 2
Routing
• Recall: There are two parts to routing IP packets:
1. How to pass a packet from an input interface to the output
interface of a router (packet forwarding) ?
2. How to find and setup a route ?
• We already discussed the packet forwarding part
• There are two approaches for calculating the routing tables:
– Static Routing
– Dynamic Routing: Routes are calculated by a routing protocol
3. 3
IP Routing
TCP
Network Interfaces
IP Input
Queue
IP Output: Calculate
Next Hop Router
ICMP
routing
daemon
Process IP
Options
IP Layer
For me ?
UDP
route
comman d
netstat
comman d
routing
table
ICM
P
Redirect
Source
Routing
NO:
if forwarding enabled
YES
4. 4
Autonomous Systems
• An autonomous system is a region of the Internet that is
administered by a single entity.
• Examples of autonomous regions are:
• UVA’s campus network
• MCI’s backbone network
• Regional Internet Service Provider
• Routing is done differently within an autonomous system
(intradomain routing) and between autonomous system
(interdomain routing).
6. 6
Interdomain and Intradomain Routing
Intradomain Routing
• Routing within an AS
• Ignores the Internet outside the
AS
• Protocols for Intradomain routing
are also called Interior Gateway
Protocols or IGP’s.
• Popular protocols are
– RIP (simple, old)
– OSPF (better)
Interdomain Routing
• Routing between AS’s
• Assumes that the Internet
consists of a collection of
interconnected AS’s
• Normally, there is one dedicated
router in each AS that handles
interdomain traffic.
• Protocols for interdomain routing
are also called Exterior Gateway
Protocols or EGP’s.
• Routing protocols:
– EGP
– BGP (more recent)
7. 7
Components of a Routing Algorithm
• A procedure for sending and receiving reachability information
about network to other routers
• A procedure for calculating optimal routes
– Routes are calculated using a shortest path algorithm:
• Goal: Given a network were each link is assigned a
cost. Find the path with the least cost between two
networks with minimum cost.
• A procedure for reacting to and advertising topology changes
8. 8
Approaches to Shortest Path Routing
• There are two basic routing algorithms found on the Internet.
1. Distance Vector Routing
• Each node knows the distance (=cost) to its directly connected neighbors
• A node sends periodically a list of routing updates to its neighbors.
• If all nodes update their distances, the routing tables eventually converge
• New nodes advertise themselves to their neighbors
2. Link State Routing
• Each node knows the distance to its neighbors
• The distance information (=link state) is broadcast to all nodes in the
network
• Each node calculates the routing tables independently
9. 9
Routing Algorithms in the Internet
Distance Vector
• Routing Information Protocol
(RIP)
• Gateway-to-Gateway Protocol
(GGP)
• Exterior Gateway Protocol (EGP)
• Interior Gateway Routing Protocol
(IGRP)
Link State
• Intermediate System -
Intermediate System (IS-IS)
• Open Shortest Path First
(OSPF)
10. 10
Dynamic IP Routing Protocols
• In Unix systems, the dynamic setting of routing tables is done
by the routed or gated daemons
• The routing daemons execute the following intradomain and
interdomain routing protocols
intradomain interdomain
11. 11
A network as a graph
• In the following, networks are represented as a network
graph:
– nodes are connected by networks
– network can be a link or a LAN
– network interface has cost
– networks are destinations
– Net(v,w) is an IP address of a network
• For ease of notation,
we often replace the
clouds between nodes
by simple links. n
v
w
Net
Net(v,w)
Net(v,n)
c(v,w)
c(v,n)
12. 12
Distance Vector Algorithm: Routing Table
Dest
n
v
w
D(v,Net)
n
cost
via
(next hop)
Net
RoutingTable of node v
Net
Net(v,w)
c(v,w)
Net(v,n)
c(v,n)
Net(v,w): Network address of the network between v
and w
The network can be a link, but could also be a LAN
c(v,w): cost to transmit on the
interface to network Net(v,w)
13. 13
Distance Vector Algorithm: Messages
Dest
D(v,Net)
n
cost
via
(next hop)
Net
RoutingTable of node v
• Nodes send messages to their neighbors which contain
routing table entries
• A message has the format: [Net , D(v,Net)] means“My cost to
go to Net is D (v,Net)”
v n
[Net , D(v,Net)]
14. 14
Distance Vector Algorithm: Sending Updates
Dest
D(v,Net2)
n
cost
via
(next hop)
Net2
RoutingTable of node v
D(v,Net1)
m
Net1
D(v,NetN)
w
NetN
Periodically, each node v
sends the content of its routing
table to its neighbors:
n
v w
m
[NetN,D(v,NetN)]
[Net1,D(v,Net1)]
[NetN,D(v,NetN)]
[Net1,D(v,Net1)]
[NetN,D(v,NetN)]
[Net1,D(v,Net1)]
15. 15
Initiating Routing Table I
Dest
c (v,w)
Net(v,w)
0
m
cost
via
(next hop)
Net(v,m)
RoutingTable
c(v,m)
Net(v,m)
c(v,n)
Net(v,n) 0
w
Net(v,w)
0
n
Net(v,n)
n
v w
m
• Suppose a new node v becomes active.
• The cost to access directly connected networks is zero:
– D (v, Net(v,m)) = 0
– D (v, Net(v,w)) = 0
– D (v, Net(v,n)) = 0
16. 16
Initiating Routing Table II
Dest
0
m
cost
via
(next hop)
Net(v,m)
RoutingTable
0
w
Net(v,w)
0
n
Net(v,n)
• New node v sends the routing table entry to all its neighbors:
n
v w
m
[w,0]
[n,0] [n,0]
[m,0]
[m,0]
[w,0]
n
v w
m
[Net(v,w),0]
[Net(v,n),0] [Net(v,n),0]
[Net(v,m),0]
[Net(v,w),0]
[Net(v,m),0]
n
v w
m
[Net(v,w),0]
[Net(v,n),0] [Net(v,n),0]
[Net(v,m),0]
[Net(v,w),0]
[Net(v,m),0]
18. 18
Updating Routing Tables I
c(v,m)
Net(v,m)
n
v w
m
Net
[Net,D(m,Net)]
• Suppose node v receives a message from node m: [Net,D(m,Net)]
if ( D(m,Net) + c (v,m) < D (v,Net) ) {
Dnew (v,Net) := D (m,Net) + c (v,m);
Update routing table;
send message [Net, Dnew (v,Net)] to all neighbors
}
Node v updates its routing table and sends out further
messages if the message reduces the cost of a route:
19. 19
Updating Routing Tables II
c(v,m)
Net(v,m)
n
v w
m
Net
[Net,D(m,Net)]
• Before receiving the message:
Dest
D(v,Net)
??
cost
via
(next hop)
Net
RoutingTable
c(v,m)
Net(v,m)
n
v w
m
Net
[Net,Dnew (v,Net)]
[Net,Dnew (v,Net)]
Dest
m
cost
via
(next hop)
Net
RoutingTable
Dnew
(v,Net)
• Suppose D (m,Net) + c (v,m) < D (v,Net):
20. 20
Example
Router A Router B Router C Router D
10.0.2.0/24 10.0.3.0/24 10.0.4.0/24 10.0.5.0/24
10.0.1.0/24
.1
.2
.2
.2
.2 .1
.1
.1
Assume: - link cost is 1, i.e., c(v,w) = 1
- all updates, updates occur simultaneously
- Initially, each router only knows the cost of
connected interfaces
t=0:
10.0.1.0 - 0
10.0.2.0 - 0
Net via
cost
t=0:
10.0.2.0 - 0
10.0.3.0 - 0
Net via
cost
t=0:
10.0.3.0 - 0
10.0.4.0 - 0
Net via
cost
t=0:
10.0.4.0 - 0
10.0.5.0 - 0
Net via
cost
t=1:
10.0.1.0 - 0
10.0.2.0 - 0
10.0.3.0 10.0.2.2 1
t=2:
10.0.1.0 - 0
10.0.2.0 - 0
10.0.3.0 10.0.2.2 1
10.0.4.0 10.0.2.2 2
t=2:
10.0.1.0 10.0.2.1 1
10.0.2.0 - 0
10.0.3.0 - 0
10.0.4.0 10.0.3.2 1
10.0.5.0 10.0.3.2 2
t=1:
10.0.1.0 10.0.2.1 1
10.0.2.0 - 0
10.0.3.0 - 0
10.0.4.0 10.0.3.2 1
t=2:
10.0.1.0 10.0.3.1 2
10.0.2.0 10.0.3.1 1
10.0.3.0 - 0
10.0.4.0 - 0
10.0.5.0 10.0.4.2 1
t=1:
10.0.2.0 10.0.3.1 1
10.0.3.0 - 0
10.0.4.0 - 0
10.0.5.0 10.0.4.2 1
t=2:
10.0.2.0 10.0.4.1 2
10.0.3.0 10.0.4.1 1
10.0.4.0 - 0
10.0.5.0 - 0
t=1:
10.0.3.0 10.0.4.1 1
10.0.4.0 - 0
10.0.5.0 - 0
22. 22
Characteristics of Distance Vector Routing
• Periodic Updates: Updates to the routing tables are sent at
the end of a certain time period. A typical value is 90 seconds.
• Triggered Updates: If a metric changes on a link, a router
immediately sends out an update without waiting for the end
of the update period.
• Full Routing Table Update: Most distance vector routing
protocols send their neighbors the entire routing table (not
only entries which change).
• Route invalidation timers: Routing table entries are invalid if
they are not refreshed. A typical value is to invalidate an entry
if no update is received after 3-6 update periods.
23. 23
The Count-to-Infinity Problem
A B C
1 1
A's Routing Table B's Routing Table
C
to cost
via
(next hop)
2
B C
to cost
via
(next hop)
1
C
now link B-C goes down
C 2 C oo
C oo
-
C 2
B
C oo C 3
C 3
A
C oo
-
C 4 C oo
C oo
-
C 4
B
24. 24
Count-to-Infinity
• The reason for the count-to-infinity problem is that each node
only has a “next-hop-view”
• For example, in the first step, A did not advertise that its route
(with cost 2) to C went through node B
• How can the Count-to-Infinity problem be solved?
25. 25
Count-to-Infinity
• The reason for the count-to-infinity problem is that each node
only has a “next-hop-view”
• For example, in the first step, A did not realize that its route
(with cost 2) to C went through node B
• How can the Count-to-Infinity problem be solved?
• Solution 1: Always advertise the entire path in an update
message (Path vectors)
– If routing tables are large, the routing messages
require substantial bandwidth
– BGP uses this solution
26. 26
Count-to-Infinity
• The reason for the count-to-infinity problem is that each node
only has a “next-hop-view”
• For example, in the first step, A did not realize that its route
(with cost 2) to C went through node B
• How can the Count-to-Infinity problem be solved?
• Solution 2: Never advertise the cost to a neighbor if this
neighbor is the next hop on the current path (Split Horizon)
– Example: A would not send the first routing update to B, since B
is the next hop on A’s current route to C
– Split Horizon does not solve count-to-infinity in all cases!
27. 27
RIP - Routing Information Protocol
• A simple intradomain protocol
• Straightforward implementation of Distance Vector Routing
• Each router advertises its distance vector every 30 seconds
(or whenever its routing table changes) to all of its neighbors
• RIP always uses 1 as link metric
• Maximum hop count is 15, with “16” equal to “”
• Routes are timeout (set to 16) after 3 minutes if they are not
updated
28. 28
RIP - History
• Late 1960s : Distance Vector protocols were used in the
ARPANET
• Mid-1970s: XNS (Xerox Network system) routing protocol is
the precursor of RIP in IP (and Novell’s IPX RIP
and Apple’s routing protocol)
• 1982 Release of routed for BSD Unix
• 1988 RIPv1 (RFC 1058)
- classful routing
• 1993 RIPv2 (RFC 1388)
- adds subnet masks with each route entry
- allows classless routing
• 1998 Current version of RIPv2 (RFC 2453)
29. 29
RIPv1 Packet Format
IP header UDP header RIP Message
Command Version Set to 00...0
32-bit address
Unused (Set to 00...0)
address family Set to 00.00
Unused (Set to 00...0)
metric (1-16)
one
route
entry
(20
bytes)
Up to 24 more routes (each 20 bytes)
32 bits
One RIP message can
have up to 25 route entries
1: request
2: response
2: for IP
0…0: request full rou-
ting table
Address of destination
Cost (measured in hops)
1: RIPv1
30. 30
RIPv2
• RIPv2 is an extends RIPv1:
– Subnet masks are carried in the route information
– Authentication of routing messages
– Route information carries better next-hop address if it
exists
– Exploites IP multicasting
• Extensions of RIPv2 are carried in unused fields of RIPv1
messages
31. 31
RIPv2 Packet Format
IP header UDP header RIP Message
Command Version Set to 00...0
32-bit address
Unused (Set to 00...0)
address family Set to 00.00
Unused (Set to 00...0)
metric (1-16)
one
route
entry
(20
bytes)
Up to 24 more routes (each 20 bytes)
32 bits
One RIP message can
have up to 25 route entries
1: request
2: response
2: for IP
0…0: request full rou-
ting table
Address of destination
Cost (measured in hops)
2: RIPv2
32. 32
RIPv2 Packet Format
IP header UDP header RIPv2 Message
Command Version Set to 00.00
IP address
Subnet Mask
address family route tag
Next-Hop IP address
metric (1-16)
one
route
entry
(20
bytes)
Up to 24 more routes (each 20 bytes)
32 bits
Used to carry information
from other routing
protocols (e.g.,
autonomous system
number)
Identifies a better next-hop
address on the same
subnet than the advertising
router, if one exists
(otherwise 0….0)
2: RIPv2
Subnet mask for IP
address
33. 33
RIP Messages
• This is the operation of RIP in routed. Dedicated port for
RIP is UDP port 520.
• Two types of messages:
– Request messages
• used to ask neighboring nodes for an update
– Response messages
• contains an update
34. 34
Routing with RIP
• Initialization: Send a request packet (command = 1, address
family=0..0) on all interfaces:
• RIPv1 uses broadcast if possible,
• RIPv2 uses multicast address 224.0.0.9, if possible
requesting routing tables from neighboring routers
• Request received: Routers that receive above request send their entire
routing table
• Response received: Update the routing table
• Regular routing updates: Every 30 seconds, send all or part of the
routing tables to every neighbor in an response message
• Triggered Updates: Whenever the metric for a route change, send entire
routing table.
35. 35
RIP Security
• Issue: Sending bogus routing updates to a router
• RIPv1: No protection
• RIPv2: Simple authentication scheme
IP header UDP header RIPv2 Message
Command Version Set to 00.00
Password (Bytes 0 - 3)
Password (Bytes 4 - 7)
0xffff Authentication Type
Password (Bytes 8- 11)
Password (Bytes 12 - 15)
Authetication
Up to 24 more routes (each 20 bytes)
32 bits
2: plaintext
password
36. 36
RIP Problems
• RIP takes a long time to stabilize
– Even for a small network, it takes several minutes until the
routing tables have settled after a change
• RIP has all the problems of distance vector algorithms, e.g.,
count-to-Infinity
» RIP uses split horizon to avoid count-to-infinity
• The maximum path in RIP is 15 hops