We consider the sizing of network buffers in 802.11 based networks. Wireless networks face a number of fundamental issues that do not arise in wired networks. We demonstrate that the use of fixed size buffers in 802.11 networks inevitably leads to either undesirable channel under-utilization or unnecessary high delays. We present two novel dynamic buffer sizing algorithms that achieve high throughput while maintaining low delay across a wide range of network conditions. Experimental measurements demonstrate the utility of the proposed algorithms in a production WLAN and a lab test bed.
The distribution of packet service times is also strongly dependent on the WLAN offered load. This directly affects the burstiness of transmissions and so buffering requirements.
IEEE 802.11b support up to 11 MBps, sometimes this is not enough – far lower than 100 Mbps fast Ethernet.
In co-existing environment, the probability of frequency collision for one 802.11 frame vary from 48% ~62%
In this paper we demonstrate the major performance costs associated with the use of fixed buffer sizes in 802.11WLANs and present two novel dynamic buffer sizing algorithms that achieve significant performance gains. The stability of the feedback loop induced by the adaptation is analyzed, including when cascaded with the feedback loop created by TCP congestion control action. using the A* algorithm proposed in this paper, the RTTs observed when repeating the same experiment fall to only 90-130 ms. This reduction in delay does not come at the cost of reduced throughput, i.e., the measured throughput with the A* algorithm and the default buffers is similar.
In this paper is on TCP traffic since this continues to constitute the bulk of traffic in modern networks (80–90% of current Internet traffic and also of WLAN traffic), although we extend consideration to UDP traffic at various points during the discussion and also during our experimental tests.
- Buffer Sizing
- IEEE 802.11 Media Access Control (MAC)
- TCP/IP packet in 802.11
- IEEE 802.11e Simulation
- Traffic Mix, Adaptive Limit Tuning (ALT)