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Network Layer – Open Shortest Path First Protocol (Ospf Protocol)? Best 16 Answer

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The OSPF (Open Shortest Path First) protocol is one of a family of IP Routing protocols, and is an Interior Gateway Protocol (IGP) for the Internet, used to distribute IP routing information throughout a single Autonomous System (AS) in an IP network.Open Shortest Path First (OSPF) is a link-state routing protocol that was developed for IP networks and is based on the Shortest Path First (SPF) algorithm. OSPF is an Interior Gateway Protocol (IGP).OSPF and BGP belong to the Application Layer.


L47: Open Shortest Path First(OSPF) Protocol | OSPF Links, Packets, Frame Format | DCN Lectures

L47: Open Shortest Path First(OSPF) Protocol | OSPF Links, Packets, Frame Format | DCN Lectures
L47: Open Shortest Path First(OSPF) Protocol | OSPF Links, Packets, Frame Format | DCN Lectures

Images related to the topicL47: Open Shortest Path First(OSPF) Protocol | OSPF Links, Packets, Frame Format | DCN Lectures

L47: Open Shortest Path First(Ospf) Protocol | Ospf Links, Packets, Frame Format | Dcn Lectures
L47: Open Shortest Path First(Ospf) Protocol | Ospf Links, Packets, Frame Format | Dcn Lectures

In the previous article, we looked at the network layer RIP protocol. The next major intra-domain protocol is Open Shortest Path First (OSPF). This is another internal routing protocol. It is an intra-domain protocol based on link-state routing. In order to process routes efficiently and in a timely manner, OSPF dives the A.S (Autonomous System) into multiple areas. OSPF dives an autonomous system into multiple areas. A realm is basically a collection of networks, hosts, and routers, all contained within an autonomous system. An autonomous system can be further dived into many different domains. All networks within range must be connected. First, let’s take a look at some related terms used in this protocol: Scope: Networks, hosts, and routers are collectively referred to as scopes. An autonomous system can be imagined from different domains. All networks within range should be connected. Area Border Routers: These are special types of routers used for area borders. Backbone: A special area in an autonomous system is called the backbone. All areas within the A.S. should be connected to the backbone. So the backbone is the primary area and the other areas are called secondary areas. Backbone routers: The routers within the backbone are called backbone routers. Backbone routers can also be used as area border routers. Zone ID: Each zone has a zone ID. The area entifier of the backbone is zero. Autonomous systems are as follows: Link Type In OSPF terminology: a connection is called a link. Four types of links have been defined: point-to-point, transient, stub, and virtual. Disadvantages of RIP Protocol The cost of the destination network is measured in terms of hops. RIP determines the route based on the hop count and does not conser it. Criteria other than the number of routers between the source and destination networks. RIP sends its updates using 576-byte datagrams. If the entry is more than 512 bytes, multiple datagrams must be sent. The main disadvantage of RIP is slow convergence. In the worst case, a RIP update can take more than 15 minutes. This can lead to black holes, loops, etc. RIP periodically updates its entire table with broadcast addresses. (RIPvl, RlPv2 use multicast or broadcast). However, this consumes bandwth.

Remedies with the implementation of OSPF protocol 

OSPF proves solutions to most of RIP’s shortcomings. Using OSPF, we can extend the routing architecture well beyond the maximum 16 hops supported by RIP. Through link state information, each router maintains its own copy of the network topology. From this link state database the shortest routing path can be found.

Features of OSPF Protocol: 

Service routing type: Different routers can be configured to support different types of service requests. For example, one router can be configured to have high throughput, while another router can be configured to support minimal transmission latency for another application. Load Balancing: When multiple routes are available, traffic can be evenly distributed among routes. This obviously leads to higher network efficiency. Subdivision of Autonomous Systems: The system can be further subdived into logical areas. This will improve the management of large autonomous systems. Security: Data exchanges in OSPF are authenticated. Accental or malicious transmissions from external routing nodes are discarded. Host: OSPF supports specific, network, and subnet routing. Special features are proved to support LAN environments: Although the relationship between routers is maintained on a logical link basis, the architecture minimizes link state transfers.

Concept of Area in OSPF  

OSPF dives the network into groups called areas. The rest of the autonomous system is unaware of an area’s topology. This technique minimizes the routing traffic required by the protocol. If multiple scopes are used, each scope has its own copy of the topology database. RIP treats an autonomous system as a whole collection of routes and subnets, but OSPF introduces the concept of ranges. It also introduces the concept of hing routing information within an OSPF (Internet Autonomous System) routing domain. By diving an autonomous system into a collection of logical areas, OSPF can support different types of routing nodes (routers), such as internal routers, area border routers, backbone routers, and autonomous system (AS) border routers.

Metric in OSPF 

The cost that the OSPF administrator assigns to each route is called the metric for that route. In the OSPF protocol, metrics can be based on service types. A router can have multiple routing tables based on different types of services.

OSPF Packet Types

The OSPF protocol runs directly over IP and uses the assigned number 89. Each OSPF packet consists of an OSPF header followed by a body of a specific packet type. OSPF packets must be sent to specific IP addresses on a non-broadcast multi-access network. Different types of OSPF packages: hello. Database description. Connection status request. Update connection status. Confirm link status.

OSPF Packet Format :

All OSPF packets have the same common header, as shown in the following figure. This header is the same for all five OSPF packet types. The fields in the OSPF header are as follows: Version: The content of this 8-bit field proves information about the version of the OSPF protocol. Currently at version 2. Input: This 8-bit field definition. Type of package. There are five types of OSPF packets, which can be defined from 1 to 5 by the content of the custom type field. Message Length: This 16-bit field defines the length of the entire message, including headers and body. Source Router IP Address: This 32-bit field defines the IP address of the router that sent the packet. Area ID: This 32-bit field defines the area in which routing occurs. Checksum: This field is used for error detection of the entire packet, with the exception of the Authentication Type and Authentication Data fields. Authentication Type: This 16-bit field defines the authentication method used in this field. Two authentication methods are currently defined: “0” in this field means no authentication is used, and “1” means password is used for authentication. Authentication: This 64-bit field is the actual value of the authentication data. If more authentication types are defined later, this field will contain the result of the authentication calculation. I hope you really enjoyed this informative article on the OSPF protocol. In the next article, we will learn more about the BGP protocol. stay tuned. report this ad


What is Open Shortest Path First OSPF protocol?

Open Shortest Path First (OSPF) is a link-state routing protocol that was developed for IP networks and is based on the Shortest Path First (SPF) algorithm. OSPF is an Interior Gateway Protocol (IGP).

Which layer is OSPF?

OSPF and BGP belong to the Application Layer.

How does OSPF find shortest path?

OSPF routers rely on cost to compute the shortest path through the network between themselves and a remote router or network destination. The shortest path computation is done using Djikstra’s algorithm. This algorithm isn’t unique to OSPF.

What OSPF is used for?

Routers connect networks using the Internet Protocol (IP), and OSPF (Open Shortest Path First) is a router protocol used to find the best path for packets as they pass through a set of connected networks.

What are the features of OSPF protocol?

OSPF supports/provides/advantages –
  • Both IPv4 and IPv6 routed protocols.
  • Load balancing with equal-cost routes for the same destination.
  • VLSM and route summarization.
  • Unlimited hop counts.
  • Trigger updates for fast convergence.
  • A loop-free topology using SPF algorithm.
  • Run-on most routers.
  • Classless protocol.

What are the OSPF States?

Following are the OSPF States we’ll be examining:
  • Down state.
  • Attempt state.
  • Init state.
  • 2-Way state.
  • Exstart state.
  • Exchange state.
  • Loading state.
  • Full state.

Is OSPF Layer 2?

There is a common understanding that OSPF operates at Layer 3. However, as per wikipedia, it operates at Link Layer i.e., Layer 2.

Is OSPF a Layer 4 protocol?

OSPF is implemented as a layer 4 protocol, so it sits directly on top of IP. Neither TCP nor UDP are used, so to implement reliability OSPF has a checksum and its own built-in ACK. To troubleshoot by sniffing traffic, we need to know that the OSPF multicast address is 224.0. 0.5, and DRs use 224.0.

Which type of routing protocol uses the shortest path first algorithm?

OSPF uses the shortest path first (SPF) algorithm to determine routes that should be added to the routing table. OSPF routers maintain a map of the internetwork called the link state database.

How Open Shortest Path First works?

Open Shortest Path First (OSPF) is a routing protocol for Internet Protocol (IP) networks. It uses a link state routing (LSR) algorithm and falls into the group of interior gateway protocols (IGPs), operating within a single autonomous system (AS).

How does OSPF choose best path?

OSPF uses cost values to determine the best path to a particular destination – the lower the cost value, the more likely the interface will be used to forward data traffic.

Is OSPF open protocol?

The OSPF (Open Shortest Path First) protocol is one of a family of IP Routing protocols, and is an Interior Gateway Protocol (IGP) for the Internet, used to distribute IP routing information throughout a single Autonomous System (AS) in an IP network.

Is OSPF a layer 3 protocol?

At Layer 3, routers will use dynamic routing protocols (generally Open Shortest Path First or OSPF and BGP in most enterprises) to present a robust network that handles site-to-site link failures and minimizes the burden of IP management.

What port is OSPF?

Difference between OSPF and BGP
S.NO OSPF
7. It works in 89 port number.
8. OSPF is a Link State type.
9. In OSPF Dijkstra algorithm is used.
10. OSPF prefers fastest path rather than shortest path.
27 thg 5, 2019

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