Static routing refers to routing information configured manually by a network manager. When a topology structure of a network or a link state has a change, the network manager needs to manually modify the related static routing information in a routing table. The static routing information is private by default, and will not be transferred to other routers. Of course, the network manager can also make the static routing information become shared by setting a router.
Strategy routing is a data packet routing forward mechanism which is more flexible than routing based on a target network. Using the strategy routing, the router will determine how to process a data packet needed to be routed through a routing map, wherein the routing map determines a next-hop forwarding router of one data packet. With the strategy routing, the routing map used by the strategy routing must be specified, and the routing map needs to be created. One routing map is comprised of lots of strategies, and each strategy defines one or more matching rules and corresponding operations. After the strategy routing is applied on one interface, all packets received by this interface are detected, and a data packet which does not comply with any strategy in the routing map will be processed in accordance with a usual routing forward, and a data packets which complies with a certain strategy in the routing map will be processed in accordance with the operation defined in the strategy.
Equal-Cost Multipath Routing (ECMP) exists in a network environment where a plurality of different links arrive at the same destination address. If a traditional routing technology is used, the data packets transmitted to the destination address can only use one link therein, and other links are in a standby state or a failure state, and it is needed a certain time for switching with each other in a dynamic routing environment; however, an equal-cost or equal-value multipath routing protocol can use a plurality of links at the same time in the above-mentioned network environment, which not only increases transmission bandwidth, but also can back up the data transmission of the failure link without delay and packet loss. The greatest characteristic of the ECMP is to implement the purpose of multipath load balancing and link backup with equal-cost or equal-value, and both the strategy routing and the static routing substantially support the ECMP function.
The ARP is to transform an Internet address of a machine into a physical address. The IP data packet passes through physical networks one after another when being propagation in the Internet, and when arriving at the destination network, the IP data packet needs to be transmitted through the last physical network to a destination host. When passing through the physical network, the data packet needs the physical address of the machine, while the IP address of the machine is used for the transmission of the data packet, so one mechanism is needed to transform the IP address of the machine into the physical address.
Both the static routing and the strategy routing are based on configuration, and cannot transmit messages actively, and after an outcoming interface of the routing (a physical port of a home terminal to which a link corresponds) is from down to up, the link can be used theoretically. However, in fact, the outcoming interface of the routing being up does not represent that the link is available.
For example, when the home terminal and the opposite terminal connect using a layer 1 or layer 2 device, the method of detecting whether the next hop is available using a state of the outcoming interface of the routing is not able to detect the connectivity of the next hop; when the outcoming interface of the routing is up but the link is abnormal, the ECMP uses this link, which results in that all traffic which selects this link is discarded; and, in addition, if the outcoming interface of the routing is up, the link is normal, but forwarding information (e.g., ARP) of the opposite terminal cannot be learned immediately, then it will be also resulted in discarding the traffic which is transmitted in a certain time before learning the forwarding information.
A protocol of being able to detect the link state based on IP messages is needed to detect the state of the physical link and be able to be cooperated with the static routing and the strategy routing. A Chinese patent with an application No. CN200710187500.0 (a method for fault detection and link recovery based on a bidirectional forwarding link) provides a method for detecting the physical link based on Bidirectional Forwarding Detection (BFD). The BFD supports fast detecting the link state with a message transmission interval being a minimal value of 3.3 ms, so the BFD has natural advantages in terms of fast fault detection. In the respect of fault recovery, the BFD transmits a unicast IP message to trigger ARP learning, which ensures that the traffic can be normally forwarded on the link when the BFD detects that the link fault is recovered.
However, there are some disadvantages for using the BFD to detect the link state, that is: the detection parameters need to be configured, the configured detection parameters must be consistent with those of the next hop of the routing, a plurality of the next hops need to correspond to a plurality of BFD detections, the BFD messages need to be transmitted periodically, and the shorter the detection time is, the larger the system overhead which is occupied is.
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