Open Shortest Path First (OSPF) - 5 : Routing Basics
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4 سال پیش
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This playlist provides an overview
This playlist provides an overview of the Open Shortest Path First (OSPF) routing protocol and its advantages and disadvantages:
26 : OSPF - Fundamentals of Communica...
Before we get into the specifics of the OSPF protocol let's review a little about routing. (If you've just finished the RIP lesson, you'll find this is a review of what we've just learned.)
As we discussed, routers are used to separate networks based on logical assigned addresses. These are layer 3 addresses, not the static layer 2 addresses. Using logical addresses, the network manager can create separate networks and subnetworks to divide up users. The division of networks can be done locally or between remote sites. The division of networks results in keeping traffic local and provides higher levels of security by allowing the network manager to decide which users can communicate where.
Networks and subnetworks can only connect to other networks via a router. The only way for routers to learn about networks to which they are not directly connected is to exchange this information with their neighboring routers. To support this, multiple protocols have been developed to allow routers to tell each other which networks they are connected to or are aware of. These routing protocols are designed to send out updates to other routers, either on a regular timed cycle or when a change occurs - and some do both.
When a network change like a link failure is detected by a router, the router generates a routing update to alert all other routers of the change. The time it takes for this information to be distributed to all routers in the network is called the convergence time. (Remember, this use of the term "convergence" relates to routed networks from our routing lesson.)
Convergence time is very important, because until convergence has occurred, some routers may be forwarding packets based on outdated information. Obviously, convergence time should be as short as possible.
26 : OSPF - Fundamentals of Communica...
Before we get into the specifics of the OSPF protocol let's review a little about routing. (If you've just finished the RIP lesson, you'll find this is a review of what we've just learned.)
As we discussed, routers are used to separate networks based on logical assigned addresses. These are layer 3 addresses, not the static layer 2 addresses. Using logical addresses, the network manager can create separate networks and subnetworks to divide up users. The division of networks can be done locally or between remote sites. The division of networks results in keeping traffic local and provides higher levels of security by allowing the network manager to decide which users can communicate where.
Networks and subnetworks can only connect to other networks via a router. The only way for routers to learn about networks to which they are not directly connected is to exchange this information with their neighboring routers. To support this, multiple protocols have been developed to allow routers to tell each other which networks they are connected to or are aware of. These routing protocols are designed to send out updates to other routers, either on a regular timed cycle or when a change occurs - and some do both.
When a network change like a link failure is detected by a router, the router generates a routing update to alert all other routers of the change. The time it takes for this information to be distributed to all routers in the network is called the convergence time. (Remember, this use of the term "convergence" relates to routed networks from our routing lesson.)
Convergence time is very important, because until convergence has occurred, some routers may be forwarding packets based on outdated information. Obviously, convergence time should be as short as possible.
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در تاریخ 1399/07/10 منتشر شده
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