Ospf - Hirschmann MACH 4000 User Manual

OSPF

7 OSPF
Open Shortest Path First (OSPF) is a dynamic routing protocol based on the
Link State Algorithm. This algorithm is based on the link states between the
routers involved.
The significant metric in OSPF is the "OSPF costs", which is calculated from
the available bit rate of a link.
OSPF was developed by IETF. OSPF is currently specified as OSPFv2 in
RFC 2328. Along with many other advantages of OSPF, the fact that it is an
open standard has contributed to the wide usage of this protocol. OSPF has
replaced the Routing Information Protocol (RIP) as the standard Interior
Gateway Protocol (IGP) in large networks.
OSPF has a number of significant advantages to offer:
Cost-based routing metrics: In contrast to RIP, OSPF provides clear
metrics based on the bandwidth of each individual network connection.
OSPF provides major flexibility in designing a network, because the user
can simply change these costs.
Routing via multiple paths (equal cost multiple path/ECMP): OSPF is able
to support a number of equal paths to a given destination. OSPF thus
provides efficient utilization of the network resources (load distribution)
and improves the availability (redundancy).
Hierarchical routing: By logically dividing the network into areas, OSPF
shortens the time required to distribute routing information. The
messages about changes in a subnetwork remain within the subnetwork,
without putting any load on the rest of the network.
Support of Classless Inter-Domain Routing (CIDR) and Variable Length
Subnet Mask (VLSM): This allows the network administrator to assign the
IP address resources efficiently.
Fast tuning time: OSPF supports the fast distribution of messages about
route changes. This speeds up the tuning time for updating the network
topology.
Saving network resources / bandwidth optimization: Because OSPF, in
contrast to RIP, does not exchange the routing tables at regular, short
intervals, no bandwidth is unnecessarily "wasted" between the routers.
Support of authentication: OSPF supports the authentication of all nodes
that send routing information.
Routing L3P
Release 4.0 11/07
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