Introduction to two common routing protocols

At present, the development of the routing protocol is very rapid, so I have studied the introduction of the routing protocol, here to share with you, hope to be useful to everyone. With 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 Routing Protocol

1) Introduction to OSPF Routing Protocol

OSPF is the abbreviation of "Open Shortest Path First. 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.

Each router that runs the OSPF protocol always broadcasts the connection status of the local network, such as available interface information and accessible neighbor information, and broadcast it to the entire autonomous system. In this way, each vro receives the LSA generated by all vrouters 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:
In a variety of networks that can be accessed by multiple access, if there are two or more routers, a "designated Router" (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 AREA areas according to the topology of the autonomous system. In this way, the Regional Border Router (ABR) generates a digest LSA in units of network segments when sending route information to other areas. This can reduce the number of LSA in the Autonomous System and the complexity of route computing. Intra-and inter-region routes describe the internal network structure of the autonomous system, while external routes describe how to select routes to destinations outside 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.

Ii) Advantages of the OSPF routing protocol:

1. OSPF is a real LOOP-FREE self-LOOP routing protocol. Derived from the advantages of the algorithm itself. Link Status and Shortest Path Tree Algorithm)
2. Fast OSPF convergence: route changes can be transmitted to the entire Autonomous System in the shortest time.
3. propose the concept of regional area division. After dividing the autonomous system into different regions, the routing 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.

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. It is sent only when there is a route change ). However, to enhance the robustness of the Protocol, all requests are resold once every 1800 seconds.
2) in a broadcast network, use multicast addresses instead of broadcasts to send packets to reduce interference with other network devices that do not run ospf.
3) broadcast in various networks that can access multiple access, NBMA). By selecting DR, You can synchronize the route exchange between routers in the same network segment) reduced to o n times.
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 border router of the ABR region to further reduce route information transmission between regions.
6) in the point-to-point interface type, OSPF over On Demand Circuits is configured by configuring the On-Demand signal play attribute), 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 options by strictly dividing the route levels.
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. Introduction

The earlier IGRP protocol was invented by Cisco and is 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 is much better than IGRP, and its convergence characteristics and operation efficiency are significantly higher than 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 VPN Protocol has the following features:

1. Precise route computing and multi-route support

The VPN protocol inherits 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.

2. less bandwidth usage

A small hello packet is periodically sent between the peer vrouters using the OSPF protocol 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 API.