Routing traffic control
Length congested network traffic statistical multiplexing through the results contained in providing access to circuit users and service providers access to the information flow through the transmission circuit should be the average transmission rate agreed conventions and burst transfer rates, As long as production in full compliance with this agreement and in accordance with the service level agreement (SLA) to transmit the packet, the service provider will attempt to promptly transfer their information flow in the network, timely transmission of this kind are not asking for traditional data applications, but at present emerging real-time applications, such as Voice over IP (VolP) and desktop conferencing requirements, these transfer applications when playing on the transmission delay and delay jitter caused by network congestion has a very stringent requirements.
In order to support special for all users of the SLA, the service provider must restrict information flow through the same network in order to avoid overload and cause congestion, and must ensure that each user can not excessive network bandwidth, so as not to affect the service to other users, in order to achieve had this goal, the service provider needs to be able to help them determine whether each user their SLA compliance measures and tools the user to the network transmission of information within the specified flow rate should be taken to find. Currently, there are two basic methods for sharing resources protection SP network, they are traffic shaping and traffic control.
Control traffic allow service providers to detect user traffic, discard or mark exceeds SLA user packets. Information flow control token bucket algorithm, but the packet queue or substituted with packets discarded packets vertical marker function block. If the traffic control function block determines that the user rate of arrival packets within the network service level allows, let the packet enters the network, if the traffic control function block determines that the user rate exceeds the packet reaches the level permitted by the network service, or packet immediately discarded (hard control), or allow it to enter the network, but it is marked (soft control), the procedure as shown below:
Mark beyond the level allowed by the network service allows packets downstream node when performing traffic control function, the marked packets and normal packets to take different processing methods, e.g., by the configuration, the access router information flow control function block exceeds the allowed network service levels for packets dropped preferentially, so that, in the core router congested, the priority bits disposed worry Xiandiu bits discarded packets.
When you use the stream is controlled to mark packets, you must maintain the order of the packet stream, but increases the likelihood of marking core router the packet is discarded during congestion, the transmission path may be via packets across the network when hop router, all packets in the same order in the stream is stored in the same queue for each. You should avoid using such a notation, in a network such that this labeling method allows packets within and beyond the network service level allows established service class packets are assigned to different output queues. A single stream of information distributed to different output queues lead to packet reordering issues, which will have negative impact on the flow of information is the main raw throughput.
Traffic shaping tool using flow restriction information, to precisely control the flow of information into the information flow rate of the network, but they do not support dynamic feedback mechanism, such a dynamic feedback mechanism can adapt to changes in network conditions and to use a temporary core network has excess capacity information flow control than the rate limit provides a more flexible approach that allows resource protection mechanisms to adapt to changes in network conditions.
But hard information flow control method is similar to traffic shaping, control and information flow fundamentally different from that of soft regulation Hard regulation deferred its decision to discard the packet, so that messages continue to transmit on the network only when network congestion actually occurs, just throw it away. In the bandwidth is Kuanyu situations, traffic control soft approach allows service providers to protect shared resources to meet the SLA for all users at the same time, for a number of users of the service beyond the SLA.