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.

Interior routing mostly uses link-state routing protocols such as OSPF and IS-IS.

Like the OSPF protocol, IS-IS uses Dijkstra's algorithm for computing the best path through the network.

OSPF uses the Dijkstra algorithm.

OSPF uses multicast addressing for route flooding on a broadcast network link.

OSPF uses path cost as its basic routing metric, which was defined by the standard not to equate to any standard value such as speed, so the network designer could pick a metric important to the design.

Both IS-IS and OSPF are link state protocols, and both use the same Dijkstra algorithm for computing the best path through the network.

Instead, OSPF adjacencies are created and destroyed as a function of MANET information that is distributed by the NTDR routers, both cluster heads and cluster members.

OSPF multicast IP packets never traverse IP routers, they never travel more than one hop.

OSPF reserves the multicast addresses < tt > 224. 0. 0. 5 </ tt > for IPv4 or < tt > FF02 :: 5 </ tt > for IPv6 ( all SPF / link state routers, also known as < tt > AllSPFRouters </ tt >) and < tt > 224. 0. 0. 6 </ tt > for IPv4 or < tt > FF02 :: 6 </ tt > for IPv6 ( all Designated Routers, < tt > AllDRouters </ tt >), as specified in RFC 2328 and RFC 5340.

For routing multicast IP traffic, OSPF supports the Multicast Open Shortest Path First protocol ( MOSPF ) as defined in RFC 1584.

In such a case, the ASBR does send externals into the totally stubby area, and they are available to OSPF speakers within that area.

Other routing protocols such as Open Shortest Path First ( OSPF ) and Enhanced Interior Gateway Routing Protocol ( EIGRP ) only send updates when a connection changes.

This detection occurs when a router identifies itself in a hello OSPF protocol packet.

ROSPF does not use the OSPF hello protocol for link discovery, etc.

OSPF is an interior gateway protocol that routes Internet Protocol ( IP ) packets solely within a single routing domain ( autonomous system ).

The " Main OSPF Packet Header " is the same for all 5 types of packets ( with exception of the Type field ) whereas the following sub-headers will vary from type to type and are shown below the Main OSPF Packet Header.

They present a means of detecting false packets, at least to the subnet, by essentially making use of existing OSPF routing state to have routers make intelligent decisions about whether or not a packet should be routed.

OSPF detects changes in the topology, such as link failures, very quickly and converges on a new loop-free routing structure within seconds.

The OSPF routing policies to construct a route table are governed by link cost factors ( external metrics ) associated with each routing interface.

As a link state routing protocol, OSPF establishes and maintains neighbor relationships in order to exchange routing updates with other routers.

Link-state routing protocols such as Open Shortest Path First ( OSPF ) and IS-IS elect a designated router on every link to perform flooding of topology information.

However, protocols like OSPF will propagate a link state update from the failed nodes neighbors, and thus all nodes will learn quickly of the failed node's demise ( or disconnection ).

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.

The updates for IPv6 are specified as OSPF Version 3 in RFC 5340 ( 2008 ).

However, it does synchronize routing tables at start up as OSPF does, and sends specific updates only when topology changes occur.

Dijkstra's algorithm is used in SPF, Shortest Path First, which is used in the routing protocols OSPF and IS-IS.

MPLS Traffic Engineering relies upon the use of TE extensions to Open Shortest Path First ( OSPF ) or Intermediate System To Intermediate System ( IS-IS ) and RSVP.

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.

IS-IS was developed at roughly the same time that the Internet Engineering Task Force IETF was developing a similar protocol called OSPF.

OSPF, on the other hand, was designed for IPv4.

IS-IS differs from OSPF in the way that " areas " are defined and routed between.

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.

IS-IS also differs from OSPF in the methods by which it reliably floods topology and topology change information through the network.

OSPF has a larger set of extensions and optional features.

Given the same set of resources, IS-IS can support more routers in an area than OSPF.

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 perhaps the most widely used interior gateway protocol ( IGP ) in large enterprise networks.

OSPF was designed to support variable-length subnet masking ( VLSM ) or Classless Inter-Domain Routing ( CIDR ) addressing models.

Identical copies of the LSDB are periodically updated through flooding on all OSPF routers.

An OSPF network may be structured, or subdivided, into routing areas to simplify administration and optimize traffic and resource utilization.