Differences between OSPF and OSPF

The difference between OSPF and VPN is clearly the result of the rapid development of the Internet. TCP/IP has become the mainstream protocol for data network interconnection. Vrouters running on various networks are responsible for controlling traffic that may be the most important information of this century. The collaboration between hundreds of vrouters is inseparable from the routing protocol. OSPF and OSPF are both good dynamic routing protocols in recent years. OSPF has been widely used in many manufacturers with high protocol standardization. However, the OSPF protocol was invented by Cisco, a leading provider in the network industry, it is also widely recognized by users based on its influence in the industry and its absolute market share. However, which of the two Protocols is better? Who is more suitable for the future development of the network? This article analyzes the advantages and disadvantages of these two protocols from a technical perspective on users' concerns, so that network integrators and enterprise users can serve as a reference in network design and planning. I. OSPF protocol (I). OSPF is the abbreviation of Open Shortest Path First ("Open Shortest routing Priority Protocol. It is a link-based autonomous system internal routing protocol developed by IETF. On an IP network, it dynamically discovers and transmits routes by collecting and passing the link status of the autonomous system. Www.2cto.com Each router that runs the OSPF protocol always describes the connection status of the local network (such as available interface information and accessible neighbor information) in LSA (link status broadcast, and broadcast it to the entire autonomous system. In this way, each router receives the LSA generated by all the routers in the autonomous system. These LSA sets constitute the LSDB (link status database ). Since each LSA describes the network topology around a vro, the entire LSDB is a true reflection of the network topology of the autonomous system. Based on LSDB, Each router runs the SPF (Shortest Path First) algorithm. Build a self-rooted Shortest Path Tree that provides routes to nodes in the autonomous system. In graph theory, "Tree" is a non-loop join graph. Therefore, the routes calculated by OSPF are also non-loop routes. To reduce the overhead of OSPF, the following concepts are proposed: (1 ). DR: if there are two or more vrouters in various networks that can be accessed by multiple access, a "designated vro" (DR) should be selected on the network ). The "specified vro" synchronizes the LSDB with all vrouters in this segment. In this way, no LSDB synchronization is performed between two non-DR routers. This greatly saves the bandwidth overhead within the same network segment. (2 ). AREA: OSPF can be divided into different regions according to the topology of the autonomous system. In this way, when the Regional Border Router (ABR) sends route information to other regions, the Digest LSA is generated in units of network segments. This can reduce the number of LSA in the Autonomous System and the complexity of route computing. OSPF uses four different types of routes, which are in priority order: routes in the www.2cto.com region are the first type of external routes. routes in the second type of external routes are described in the network structure of the autonomous system, external routes describe how to select a route to a destination other than the autonomous system. Generally, the first type of external routes correspond to the information introduced by OSPF from other internal routing protocols. The cost of these routes is comparable to that of OSPF routes; the second type of external routes correspond to the information introduced by OSPF from the external routing protocol. Their cost is much higher than the OSPF route cost. Therefore, only the external cost is considered during computing. (2) Main advantages of OSPF: 1. OSPF is a real LOOP-FREE (no routing self-ring) routing protocol. Derived from the advantages of the algorithm itself. (Link status and Shortest Path Tree Algorithm) 2. Fast OSPF convergence speed: route changes can be transmitted to the entire Autonomous System in the shortest time. 3. The concept of area Division is proposed. After the autonomous system is divided into different regions, the route information digest between regions greatly reduces the number of route information to be transmitted. In addition, the routing information does not expand rapidly as the network size expands. 4. Minimize the Protocol overhead. See: 1) The hello messages without routing information are sent regularly to discover and maintain the neighbor relationship, which is very short. The update mechanism is triggered when packets containing route information are sent. (Sent only when there is a route change ). However, to enhance the robustness of the Protocol, all requests are resold once every 1800 seconds. Www.2cto.com 2) in the broadcast network, the multicast address (rather than the broadcast) is used to send packets to reduce interference to other network devices that do not run ospf. 3) in various networks (broadcast, NBMA) that can be accessed by multiple access, the number of Route switching (synchronization) times between routers in the same network segment is changed from O (N * N) the number of times is reduced to O (N. 4) propose the STUB region concept so that the introduced ASE route will not be transmitted in the STUB region. 5) supports route aggregation on the ABR (Regional Border Router) to further reduce route information transmission between regions. 6) in the point-to-point interface type, OSPF over On Demand Circuits is configured so that ospf no longer regularly sends hello packets and regularly updates route information. Update information is sent only when the network topology changes. 5. Provide more trusted routing choices by strictly dividing the route levels (which can be divided into four poles. 6. Good security. ospf supports interface-based plaintext and md5 verification. 7. OSPF can adapt to a variety of networks, with a maximum of thousands. II. The earlier IGRP protocol and the protocol used in the Protocol are both invented by Cisco and are a dynamic routing protocol based on the distance vector algorithm. The Enhanced Interior Gateway Routing Protocol is an Enhanced version of the IGRP Protocol. It belongs to the dynamic Internal Gateway Routing Protocol and still uses the vector-distance algorithm. However, its implementation has been greatly improved compared with IGRP, and its convergence characteristics and * work efficiency have been significantly improved compared with IGRP. The Convergence feature of network replication is based on the DUAL (Distributed Update Algorithm) Algorithm. The DUAL algorithm makes it impossible to form a loop in route computing. Its convergence time can rival any other existing routing protocols.
The IPSec protocol has the following features: 1. Precise route computing and multi-route support for the IPSec protocol inherit the biggest advantage of the IGRP Protocol: vector routing. In route computing, the network bandwidth, network latency, channel usage, channel reliability, and other factors need to be comprehensively considered by the Protocol. Therefore, the route calculation of the Protocol is more accurate, better reflect the actual situation of the network. At the same time, the OSPF protocol supports multiple routes so that the routers can share the load according to different routes. Www.2cto.com 2. A small amount of bandwidth is used to periodically send small hello packets between the peer vrouters using the VPN protocol, so as to ensure the validity of the previously sent packets. Route sending uses the incremental sending method, that is, only the changed route is sent each time. The route update messages sent are reliably transmitted. If no confirmation message is received, the messages are resent until they are confirmed. It can also control the sent VPN packets to reduce the bandwidth usage of the network interface. This avoids the impact of a large number of consecutive Route packets on normal data services.
3. Loop-free routing and fast convergence rate the Convergence Rate of route computing loops and routes is an important indicator of route computing. Because the DUAL algorithm is used in the Protocol, it is impossible for the Protocol to generate loop routes in route computing. At the same time, the convergence time of route computing is well guaranteed. Because the DUAL algorithm makes it only re-calculate the changed route during route computing. For a route, only the routers affected by this route will be involved in re-calculation of the route. 4. MD5 authentication to ensure the correctness of the route, MD5 authentication can be configured between Routers running the OSPF Protocol process, and the packets that do not conform to the authentication can be discarded to ensure the security of the route. 5. routes with any netmask length can be aggregated using any netmask length routing through configuration, thus reducing route information transmission and saving bandwidth. Www.2cto.com 6. A route entry with the same purpose but with the same priority can be shared by the load to the route table for the same purpose. The route priority can be automatically generated based on the speed, connection quality, reliability, and other attributes of the interface, when a packet is sent, the interface traffic can be automatically matched based on the information to achieve load balancing of Several Interfaces.
7. The Protocol configuration is simple to build a network using the VPN protocol. The router configuration is very simple. It does not have complicated region settings, and you do not need to implement different configuration methods for different network interface types. To use the network protocol, you only need to use the router VPN command to start the OSPF routing process on the router, and then use the network command to enable interfaces within the network range. Iii. Comparison between OSPF and OSPF: OSPF and OSPF are algorithms that converge quickly and do not form loops. They consume a small amount of network bandwidth and use flexible and secure routing protocols. However, from the above analysis, we can see that each has its own advantages and disadvantages. (1) Disadvantages of OSPF 1. complicated configuration. Due to the complexity of network area division and network attributes, the network analyst must have a high level of network knowledge to configure and manage the OSPF network. 2. Weak routing load balancing capabilities. Although OSPF can automatically generate the interface routing priority based on the Interface speed and connection reliability, OSPF only selects the forwarding with a higher priority for routes with different priorities for the same purpose, routes with different priorities cannot be used for load balancing. Only those with the same priority can achieve the purpose of Server Load balancer. Unlike in the case of VPN, traffic can be automatically matched based on different priorities. (2) Disadvantages of the network. 1. The concept of AREA does not exist in the network. However, in the case of a large-scale network, OSPF can plan and limit the network size by dividing areas. Therefore, it is suitable for networks with relatively small network sizes. This is also the limitation of the vector-distance routing algorithm (the RIP Protocol uses this algorithm. Www.2cto.com 2. the routers running the network must send the HELLO message regularly to maintain the relationship between the neighbors. This relationship also needs to send the HELLO Message periodically even on the dial-up network, in this way, on the on-demand dial-up network, it is impossible to locate whether this is a useful service message or a scheduled inquiry message sent by the kernel, which may trigger a connection on the On-Demand dial-up network by mistake, especially on the backup network, causing unnecessary troubles. Therefore, generally, the vroeigrp that runs the OSPF Protocol needs to configure Dialer list and Dialer group on the dial-up backup port to filter unnecessary packets or run the TRIP protocol. This increases the overhead of the vro operation. OSPF supports on-demand dial-up on the dial-up network. Only one routing protocol can meet the needs of various leased lines or dial-up network applications.
3. the loop-free computing and convergence speed of the network are based on the distributed DUAL algorithm, which actually spreads uncertain routing information (active route) (send query Packets to neighbors ), the process of re-convergence after the confirmation of all neighbors is obtained. When the neighbors are not sure about the reliability of the route information, the spread will be repeated, therefore, in some cases, the route information may remain active (this route is called stuck in active route, when the next (successor) metric of the route changes, it enters multiple computations, which will affect the DUAL algorithm.