tailieunhanh - The Complete IS-IS Routing Protocol- P20

The Complete IS-IS Routing Protocol- P20: IS-IS has always been my favourite Interior Gateway Protocol. Its elegant simplicity, its well-structured data formats, its flexibility and easy extensibility are all appealing – IS-IS epitomizes link-state routing. Whether for this reason or others, IS-IS is the IGP of choice in some of the world’s largest networks. | Flow Control and Throttling of LSPs 177 JUNOS software configuration hannes@Frankfurt show configuration . protocols isis interface at-4 0 lsp-interval 50 . LSP throttling by use of the lsp-interval command is a powerful mechanism to control the flooding pace to neighbouring routers in order to not overload them. There is another issue that has not yet been discussed control traffic LSP and related packets may push back the user traffic information packets because control traffic always has precedence in terms of scheduling on the router interface cards. Unfortunately the control traffic transmission rate does not get lower on low-bandwidth interfaces such as DS0 or fractional T1 E1 line - control traffic stays the same. You can easily imagine that on a low-bandwidth circuit transmitting 30 full-MTU sized packets does not leave much room for other types of packets. So it would be nice if there were a way to tell the router just to utilize a certain percentage of the interface bandwidth for control traffic. In IOS you can configure the bandwidth bw statement on a sub -interface so that the router makes sure that there is not more than 50 per cent for instance of the interface bandwidth utilized for LSP transmission. This is the recommended option to use for low-bandwidth circuits. IOS configuration In IOS LSP throttling is calculated automatically by setting the bandwidth parameter in interface configuration mode - this makes sure that not more than 50 per cent for example of the configured interface Bandwidth is dedicated to the routing protocol. This example sets the total bandwidth available for IS-IS traffic to 256 Kbps which might be only a fraction of the total bandwidth available on the link perhaps 2 Mbps London show running-config . interface Serial1 2 ip router isisu bandwidth 256 . JUNOS software does not support automated calculation of LSP throttling because the lowest-speed interface cards on a Juniper Networks router starts at T1 E1 speeds .