The same Routing Protocol affects the network speed.

We usually think that the speed of the network is affected by hardware devices such as routers, switches, and network cables. You may think that other factors will also affect the speed of the network.

Not long ago, a coal mine system was upgrading its network. The Network has 300 or 400 vrouters of different sizes, most of which are Cisco Series. The overall network topology is a flat structure similar to a star or tree structure, the network-wide routing protocol is a popular OSPF protocol in recent years. As a result, it brings about a serious problem: the use of OSPF in a flat network slows down the network operation speed. This wastes system resources and is not conducive to system stability.

Application Scope of OSPF

OSPFOpen Shortest Path First) has been quite popular in recent years. Currently, OSPF version 2 is widely used. The latest standard is RFC 2328.

There is a trend that OSPF is required for all routes regardless of the size unit and network type. It seems that non-OSPF is not advanced. However, in the routing protocol, OSPF has its own application scope. In an OSPF network, Each router pays attention to every change in the Network Area of the router. For example, the Network shown in the right figure can be seen from the network topology structure, the relationship between Route 1 and Route 2 is not close. any downtime between the two will not affect the other, the only impact is that the other router cannot see the downtime.) But in OSPF, Each router is closely related. Even if Route 2 stops temporarily, Route 1 will soon know, every vro on the entire network will know and modify its Route table. After a while, Route 2 will slow down again, and Route 1 and all vrouters on the entire network will be modified again.

In addition, in the autonomous region AS), each vro maintains an identical and complete full-link database. This database is huge. When looking for paths, the router uses itself as the root to construct the shortest path tree, and then constructs the route table based on the shortest path. Routers exchange with each other and save the link information of the entire network to master the topology of the entire network and calculate routes independently.

OSPF, a flat and simple network topology, is characterized by its dynamic, open, and global nature. This is an excellent feature for large networks with complex topology structures. For example, on a complex Internet, if a router breaks down, other routers can be automatically adjusted immediately without the network administrator's effort to detect and reset the path; however, if it runs on a flat network with a relatively simple topology, this advantage becomes a critical weakness, seriously affecting the speed and stability of network operation, that is to say, the failure and downtime of any port on the network will affect the entire network and cause re-calculation of all routers. The cost is very high. For example, we just saw Route 1 and Route 2. At present, there are three most common routing algorithms, namely, Point-to-Point Protocol (PPP) and route information protocol (RIP), based on the complexity) and Open Shortest Path protocol (OSPF ).
The PPP protocol is one of the earliest routing protocols. It only requires the routers to operate on each other without any routing options. This applies to connecting two networks, and each network uses different routing protocols. The PPP protocol can transmit the basic structure information of data groups between two routers. RIP Protocol is a static Route Selection Based on Distance Vector Algorithm D-V), always make the same choice according to the shortest routing. This Protocol provides more functions than PPP, but the routing function is not strong. It does not consider the current network communication status and communication costs.
Different from OSPF, a router using this Protocol only cares about the world around itself, and only exchanges information with its adjacent vrouters. The range is limited to 15 hops, so it does not care. This limits the size of the network. Therefore, the RIP Protocol is not suitable for large networks. The OSPF protocol overcomes some shortcomings of RIP and does not need to send detection signals frequently. It is only sent in case of an accident. For example, if a link is damaged, all routers need to be notified, to avoid further grouping to damaged link routing. OSPF not only calculates the shortest path between two network nodes, but also calculates the communication fee. You can balance the cost and performance according to the requirements of network users to select the corresponding route. OSPF protocol has been widely used. Therefore, many manufacturers such as Cisco, Nortel, and Huawei provide such router products. At present, OSPF is regarded as an indispensable Routing Protocol in both traditional Router Design and MPLS Multi-Protocol Label Switching.

Compared with other protocols, OSPFv3 supports forwarding IPv6 data. OSPF supports various authentication mechanisms, such as simple password verification and MD5 encryption verification), and allows different systems or regions to adopt different authentication mechanisms; provides the load balancing function, if several routes with the same cost are calculated to a destination station, the OSPF router distributes communication traffic evenly to these routes and sends the packets along these routes; in an autonomous system, several regions can be divided. Each region calculates the shortest path based on its own topology, which reduces the workload of OSPF routing. OSPF is a dynamic adaptive protocol, the network topology changes can be quickly reflected and adjusted to provide a short convergence period, so that the route table can be stabilized as soon as possible, and compared with other routing protocols, OSPF only requires the least traffic during the process of handling network topology changes. OSPF provides point-to-point interfaces and supports CIDR classless Inter-Domain Routing) addresses.

Recently, OSPF has also been fully upgraded. OSPFv3OSPF 3rd) supports forwarding IPv6 data on the network. OSPFv3 improves versatility and enables the network to adapt to changing requirements. This simplifies the complex network and takes some enhancement measures to ensure easy upgrade. OSPFv3 is also optimized and the security is also improved. It is undeniable that OSPF has become one of the most widely used routing protocols for Internet Wide Area Networks and Intranet enterprise networks.

A small network requires RIP. Although OSPF has the above advantages, it cannot completely replace RIP, because this algorithm also has many defects and limitations.

The first is that it has a high overhead and consumes a lot of resources such as CPU and memory, which is the cost. Because each router must save the topology of the entire network in the LSDB form), the failure or downtime of each endpoint must cause a chain reaction of all the routers in the entire network, it consumes a lot of resources.

Secondly, OSPF configuration is very complex, and there are many commands, and the configurations of different brands of routers are also different, which has high requirements on the professional configuration personnel. Also, OSPF has its applicability, that is, large networks. What is a large network? There are many machines or large networks, but the topology structure is complex. The most typical structure is the mesh structure. In addition, there are large scales and many routing sites.

Let's look at RIP. Although it was launched earlier, it cannot be regarded as outdated because it has its own irreplaceable advantages. It is very practical and stable. For small networks, RIP consumes less bandwidth, and uses routing protocols based on distance vector algorithms for ease of configuration, management, and implementation. In addition, RIP is widely used, there is still a lot of use, and RIP is still used on the Internet.

To this end, the router protocol does not stand out in OSPF, but is still a coexistence of multiple protocols. In terms of the choice of the routing protocol, do not blindly fashion, but should carefully consider, select the protocol for network characteristics. OSPF can be used only for large networks with complex topology structures. Traditional manual configuration is still the best option for networks with simple topology, multiple nodes, and relatively fixed relationships.