Bandwidth management

Bandwidth management is the process of measuring and controlling the communications (traffic, packets) on a network link, to avoid filling the link to capacity or overfilling the link, which would result in network congestion and poor performance of the network.

Contents 1 Bandwidth management mechanisms and techniques 2 Link performance 3 Tools and techniques 4 See also 5 Notes 6 References 7 External links

Bandwidth management mechanisms and techniques

Bandwidth management mechanisms may be used to further engineer performance and includes:

• Traffic shaping (rate limiting):
  • Token bucket
  • Leaky bucket
  • TCP rate control - artificially adjusting TCP window size as well as controlling the rate of ACKs being returned to the sender
• Scheduling algorithms:
  • Weighted fair queuing (WFQ)
  • Class based weighted fair queuing
  • Weighted round robin (WRR)
  • Deficit weighted round robin (DWRR)
  • Hierarchical Fair Service Curve (HFSC)
• Congestion avoidance:
  • RED, WRED - Lessens the possibility of port queue buffer tail-drops and this lowers the likelihood of TCP global synchronization
  • Policing (marking/dropping the packet in excess of the committed traffic rate and burst size)
  • Explicit congestion notification
  • Buffer tuning
• Bandwidth reservation protocols / algorithms
  • Resource reservation protocol (RSVP)
  • Constraint-based Routing Label Distribution Protocol (CR-LDP)
  • Top-nodes algorithm
• Traffic classification - categorising traffic according to some policy in order that the above techniques can be applied differently to each class of traffic

Link performance

Issues which may limit the performance of a given link include:

• TCP determines the capacity of a connection by flooding it until packets start being dropped (Slow-start)
• Queueing in routers results in higher latency and jitter as the network approaches (and occasionally exceeds) capacity
• TCP global synchronization when the network reaches capacity results in waste of bandwidth
• Burstiness of web traffic requires spare bandwidth to rapidly accommodate the bursty traffic
• Lack of widespread support for explicit congestion notification and Quality of Service management on the Internet
• Internet Service Providers typically retain control over queue management and quality of service at their end of the link
• Window Shaping allows higher end products to reduce traffic flows, which reduce queue depth and allow more users to share more bandwidth fairly

Tools and techniques

• Packet sniffer
• Network traffic measurement

See also

• INASP runs bandwidth management training workshops and produces reports
• Bandwidth management using NetFlow and IPFIX data
• Network congestion avoidance lists some techniques for prevention and management of congestion on routers
• Traffic shaping and Rate limiting are bandwidth management (traffic control) techniques
• Bandwidth management is a subset of Network management and Performance management
• Network traffic measurement is a subset of Network monitoring
• Bandwidth throttling
• Bandwidth cap

Notes

References

• "Deploying IP and MPLS QoS for Multiservice Networks: Theory and Practice" by John Evans, Clarence Filsfils (Morgan Kaufmann, 2007, ISBN 0-12-370549-5)

External links

• Bandwidth Management Tools, Strategies, and Issues
• TechSoup for Libraries: Bandwidth Management
• The True Price of Bandwidth Monitoring