Bandwidth management

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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,^[1] which would result in network congestion and poor performance of the network. Bandwidth is described by bit rate and measured in units of bits per second (bit/s) or bytes per second (B/s).^[2]

Bandwidth management mechanisms and techniques

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

• Traffic shaping^[3] (rate limiting):^[4]
  • 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^[5][6]
• Scheduling algorithms
  :
  • Weighted fair queuing (WFQ)^[7]
  • Class based weighted fair queuing
  • Weighted round robin (WRR)
  • Deficit weighted round robin
    (DWRR)
  • Hierarchical Fair Service Curve
    (HFSC)
• Congestion avoidance:^[1]
  • 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)[8]
  • Explicit congestion notification
  • Buffer tuning - ^[9] allows you to modify the way a router allocates buffers from its available memory, and helps prevent packet drops during a temporary burst of traffic.
• Bandwidth reservation protocols / algorithms
  • Resource reservation protocol (RSVP) - is the means by which applications communicate their requirements to the network in an efficient and robust manner.^[10]
  • 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 to each class of traffic differently

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^[11]
  is a program or a device that eavesdrops on the network traffic by grabbing information traveling over a network
• Network traffic measurement

See also

• Bandwidth cap
• Bandwidth management is a subset of
  performance management
• Bandwidth management using NetFlow and IPFIX data
• Bandwidth throttling
• Customer service unit a device to balance the data rate on user's telecommunication equipment
• INASP runs bandwidth management training workshops and produces reports
• Network congestion avoidance
  lists some techniques for prevention and management of congestion on routers
• Network traffic measurement is a subset of network monitoring
• Traffic shaping and rate limiting are bandwidth management (traffic control) techniques

References