The initial window MAY be two packets (instead of the current initial window of one packet). For packets of at most 1460 bytes, the initial window MAY be three packets. For packets of at most 1095 bytes, the initial window MAY be four packets. 2 The Burstiness of Current TCP in Slow-Start: cwnd = 1 packet:) send one data packet ( receive one ACK increase cwnd to 2 packets:) send two back-to-back packets ( receive one ACK (a delayed ACK) increase cwnd to 3 packets:) send three back-to-back packets 3 The Burstiness of Current TCP with a Dropped Ack: cwnd = N packets, N packets are in pipe: ( receive one ACK, acking two packets) send two back-to-back packets ( receive one ACK, acking two packets) send two back-to-back packets ONE ACK IS DROPPED IN THE NETWORK

An increase in the permissible initial window size of a TCP connection, from one segment to three or four segments, has been under discussion in the tcp-impl working group. This document covers some simulation studies of the effects of increasing the initial window size of TCP. Both long-lived TCP connections (file transfers) and short-lived web-browsing style connections were modeled. The simulations were performed using the publicly available ns-2 simulator and our custom models and files are also available. A pdf version of this document is available and recommended for the figures it contains.

Packet networks require queues (buffers) to absorb short term arrival rate fluctuations. Yet network implementors have always observed that queues at bottlenecks tend to fill and stay filled, which contributes extra delay and removes the ability to absorb bursts. In [1] Floyd and Jacobson proposed the RED (Random Early Detection) active queue management algorithm. RED is simple, robust and quite effective at reducing persistent queues. However, while it has been used widely and successfully on Internet routers, [1] offers little guidance on how to set configuration parameters and RED has gained the reputation of being very difficult to tune. This paper develops RED in different way, treating it as a servo control loop and deriving all the loop parameters from measurable properties of a router. The result is a `self-tuning' RED whose parameters are completely determined by the queue output bandwidth (average departure rate). This new RED performs substantially better than the original version and works for a much wider variety of traffic and link bandwidths. It also admits a substantially simpler and more efficient implementation, one particularly well suited for ASIC forwarding engines. Please note: This is an early draft of an in-progress paper. Several important sections are still missing and the simulation data needs to be reorganized so that the story it tells is clearer. 1.0

This document specifies an optional standard for TCP to increase the permitted initial window from one or two segment(s) to roughly 4K bytes, replacing RFC 2414. It discusses the advantages and disadvantages of the higher initial window, and includes discussion of experiments and simulations showing that the higher initial window does not lead to congestion collapse. Finally, this document provides guidance on implementation issues.

An increase in the permissible initial window size of a TCP connection, from one segment to three or four segments, has been under discussion in the tcp-impl working group. This document covers some simulation studies of the effects of increasing the initial window size of TCP. Both long-lived TCP connections (file transfers) and short-lived web-browsing style connections were modeled. The simulations were performed using the publicly available ns-2 simulator and our custom models and files are also available.