Internet Traffic Engineering

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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
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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
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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.