Transcript Internet Traffic Engineering
Internet Traffic Engineering • Motivation: – The Fish problem, congested links. – Two properties of IP routing • Destination based • Local optimization • TE: optimizing performance of operational networks. • Reduce hot spots • Improve resource utilization • Approach: carefully select the route for the flows. • TE solutions: – Need mechanisms to explicitly manage the traffic inside a network – The overlay model: • IP on top of ATM (or other link layer technologies) • Use ATM VCs to construct a virtual network between edge nodes. • Traffic distribution is managed by carefully mapping VCs to the physical network topology. – MPLS explicit route • Work well with BGP (BGP NEXT HOP information) • Overlay model: An example A E F G H D C B • Overlay Model: – Some problems • N square problem. a large ISP can be 20 PoPs with each has 10 edge nodes, how many explicit routes do we need to manage? • Too many neighbors also increase the load on IP routers. • Peer model: – Use native IP routing, but manipulate the link weights on the network. • TE optimization objectives: – Different algorithms need to be developed for different optimization objectives • • • • Minimizing congestion and pack losses in the network Improving link utilization Minimizing the total delay experienced by packets Increasing the number of customers • The architecture of a typical TE system: Demand Estimation Route Computation Data Repository Graphical user interface Topology and State discovery Network Interface • Topology and State Discovery • Static information: usually can be determined when the network is configured. • Dynamic information: TE need accurate up-to-date information about traffic and capacity on each link, such information must be maintained in some way. – OSPF based schemes • OSPF is widely deployed for IP routing • LSAs in OSPF may not carry sufficient information for TE. – Local and remote interface IP addresses (to distinguish between multiple links) – Traffic engineering metrics – Maximum bandwidth – Maximum reservable bandwdith – Unreserved bandwidth – Resource classes.