[permalink] [id link]
OSPF is perhaps the most widely used interior gateway protocol ( IGP ) in large enterprise networks.
from
Wikipedia
Some Related Sentences
OSPF and is
Dijkstra's algorithm is used in SPF, Shortest Path First, which is used in the routing protocols OSPF and IS-IS.
While OSPF is natively built to route IP and is itself a Layer 3 protocol that runs on top of IP, IS-IS is natively an OSI network layer protocol ( it is at the same layer as CLNS ).
In OSPF, areas are delineated on the interface such that an area border router ( ABR ) is actually in two or more areas at once, effectively creating the borders between areas inside the ABR, whereas in IS-IS area borders are in between routers, designated as Level 2 or Level 1-2.
The logical view is that OSPF creates something of a spider web or star topology of many areas all attached directly to Area Zero and IS-IS by contrast creates a logical topology of a backbone of Level 2 routers with branches of Level 1-2 and Level 1 routers forming the individual areas.
Open Shortest Path First ( OSPF ) is an adaptive routing protocol for Internet Protocol ( IP ) networks.
It is defined as OSPF Version 2 in RFC 2328 ( 1998 ) for IPv4.
OSPF is an interior gateway protocol that routes Internet Protocol ( IP ) packets solely within a single routing domain ( autonomous system ).
OSPF does not use a TCP / IP transport protocol ( UDP, TCP ), but is encapsulated directly in IP datagrams with protocol number 89.
PIM ( Protocol Independent Multicast ) in conjunction with OSPF or other IGPs, ( Interior Gateway Protocol ), is widely deployed.
The neighbor relationship table is called an adjacency database in OSPF.
Provided that OSPF is configured correctly, OSPF forms neighbor relationships only with the routers directly connected to it.
An OSPF domain is divided into areas that are labeled with 32-bit area identifiers.
While most OSPF implementations will right-justify an area number written in a format other than dotted decimal format ( e. g., area 1 ), it is wise to always use dotted-decimal formats.
It is the logical and physical structure for the ' OSPF domain ' and is attached to all nonzero areas in the OSPF domain.
Note that in OSPF the term Autonomous System Boundary Router ( ASBR ) is historic, in the sense that many OSPF domains can coexist in the same Internet-visible autonomous system, RFC1996.
OSPF and most
In most current networking environments, RIP is not the preferred choice for routing as its time to converge and scalability are poor compared to EIGRP, OSPF, or IS-IS ( the latter two being link-state routing protocols ), and ( without RMTI ) a hop limit severely limits the size of network it can be used in.
As a result, the shortest path first is widely used in network routing protocols, most notably IS-IS and OSPF ( Open Shortest Path First ).
OSPF and used
PNNI uses the same shortest-path-first algorithm used by OSPF and IS-IS to route IP packets to share topology information between switches and select a route through a network.
A transit area is an area with two or more OSPF border routers and is used to pass network traffic from one adjacent area to another.
RouterOS supports many applications used by Internet service providers, for example OSPF, BGP, Multiprotocol Label Switching ( VPLS / MPLS ).
Protocols that support some form of adjacency setup, such as OSPF or IS-IS, may also be used to bootstrap a BFD session.
Raw sockets are typically available in network equipment, and used for routing protocols such as the Internet Group Management Protocol ( IGMP ) and Open Shortest Path First ( OSPF ), and in the Internet Control Message Protocol ( ICMP, best known for the ping suboperation ).
While the papers describing HSLS do not focus on security, techniques such as digital signatures on routing updates can be used with HSLS ( similar to OSPF with Digital Signatures ), and BBN has implemented HSLS with digital signatures on neighbor discovery messages and link state updates.
OSPF and interior
One version of RIP served as one of the initial so-called interior gateway protocols for the growing Internet, before the arrival of the more modern OSPF and IS-IS.
OSPF and gateway
The protocol establishes a framework between network routers in order to achieve default gateway failover if the primary gateway becomes inaccessible, in close association with a rapid-converging routing protocol like EIGRP or OSPF.
OSPF and protocol
Examples of adaptive-routing algorithms are the Routing Information Protocol ( RIP ) and the Open-Shortest-Path-First protocol ( OSPF ).
Like the OSPF protocol, IS-IS uses Dijkstra's algorithm for computing the best path through the network.
IS-IS was developed at roughly the same time that the Internet Engineering Task Force IETF was developing a similar protocol called OSPF.
To operate with IPv6 networks, the OSPF protocol was rewritten in OSPF v3 ( as specificed in RFC 2740 ).
For routing multicast IP traffic, OSPF supports the Multicast Open Shortest Path First protocol ( MOSPF ) as defined in RFC 1584.
The OSPF protocol, when running on IPv4, can operate securely between routers, optionally using a variety of authentication methods to allow only trusted routers to participate in routing.
OSPF version 3 introduces modifications to the IPv4 implementation of the protocol.
This detection occurs when a router identifies itself in a hello OSPF protocol packet.
As a link state routing protocol, OSPF establishes and maintains neighbor relationships in order to exchange routing updates with other routers.
* Link-state advertisement, communication mechanism of the OSPF routing protocol for IP
To many, it is not clear whether a whole new protocol is needed, or whether OSPF could be extended with support for wireless interfaces.
While starting up, CUWiN relies on Dijkstra's Open Shortest Path First ( OSPF ), though they are in the process of implementing a much more amenable routing protocol named Hazy-Sighted Link State ( HSLS ), and then, later, implementing a modification to it named Adaptive Hazy-Sighted Link State ( A-HSLS ).
ROSPF does not use the OSPF hello protocol for link discovery, etc.
Long before anoNet reaches that number of routers the network will have to be split into OSPF clouds, or switched to a completely different routing protocol or alter the BGP protocol to use a 32bit integer for ASNs, like the rest of the Internet will do, since 32-bit AS numbers now are standardised.
OSPF and IGP
In some cases this is done by the actual servers announcing the anycast prefix to the router over OSPF or another IGP.
OSPF and large
An example would be the joining of a number of large OSPF ( Open Shortest Path First ) networks where OSPF by itself would not scale to size.
0.244 seconds.