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 C D H BGF E

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.