This paper discusses the use of Explicit Congestion Notification (ECN) mechanisms in TCP/IP networks. It proposes new guidelines for TCP's response to ECN mechanisms, such as Source Quench packets and ECN fields in packet headers. The paper explores the benefits and drawbacks of ECN through simulations, using RED gateways modified to set an ECN bit in IP packet headers. The simulations show that ECN can reduce unnecessary packet drops and delays for low-bandwidth, delay-sensitive TCP connections. ECN is also beneficial in networks where TCP retransmit timers are limited by coarse granularity. The paper discusses implementation issues, including the comparison between Source Quench and ECN fields, incremental deployment of ECN-capable TCP, and the use of ECN in heterogeneous environments. The simulations demonstrate that ECN can improve performance in both LAN and WAN environments, reducing packet delay and increasing throughput. The paper concludes by discussing the advantages and disadvantages of ECN and its potential impact on future network environments.This paper discusses the use of Explicit Congestion Notification (ECN) mechanisms in TCP/IP networks. It proposes new guidelines for TCP's response to ECN mechanisms, such as Source Quench packets and ECN fields in packet headers. The paper explores the benefits and drawbacks of ECN through simulations, using RED gateways modified to set an ECN bit in IP packet headers. The simulations show that ECN can reduce unnecessary packet drops and delays for low-bandwidth, delay-sensitive TCP connections. ECN is also beneficial in networks where TCP retransmit timers are limited by coarse granularity. The paper discusses implementation issues, including the comparison between Source Quench and ECN fields, incremental deployment of ECN-capable TCP, and the use of ECN in heterogeneous environments. The simulations demonstrate that ECN can improve performance in both LAN and WAN environments, reducing packet delay and increasing throughput. The paper concludes by discussing the advantages and disadvantages of ECN and its potential impact on future network environments.