Understanding Traffic Engineering
Congestion is an issue with any network. Unlike the strictly local concept of flow control (no sender should send faster than a receiver can handle), congestion is a global property of the network (no sender is sending fast … there's just too much traffic on this part of the network). Experience with early networks quickly showed that avoiding congestion is much better than trying to alleviate it.
The art of trying to anticipate natural points of congestion in a network and trying to deal with them ahead of time is called traffic engineering. A little traffic engineering can go a long way toward avoiding network congestion.
The universal sign of congestion in a network is when users complain that the network is slow. The problem is that slow to users can mean anything from “The response wasn't instantaneous” to “I pressed Enter yesterday, and I'm still waiting.”
Tools available in the Junos OS for traffic engineering include the following:
- Load balancing on multiple, equal-cost routes
- Features built into routing protocols such as Open Shortest Path First (OSPF)
- Specific switching mechanisms such as Multiprotocol Label Switching (MPLS)
- Interface monitoring for traffic slowing
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