ecn Parameter

Description

Controls Explicit Congestion Notification (ECN) support.

If this parameter is set to never TCP does not negotiate with a peer that supports the ECN mechanism.

If this parameter is set to passivewhen initiating a connection, TCP does not tell a peer that it supports ECN mechanism.

However, TCP tells a peer that it supports ECN mechanism when accepting a new incoming connection request if the peer indicates that it supports ECN mechanism in the SYN segment.

If this parameter is set to active, in addition to negotiating with a peer on the ECN mechanism when accepting connections, TCP indicates in the outgoing SYN segment that it supports the ECN mechanism when TCP makes active outgoing connections.

Refer to RFC 3168 for information about ECN.

Default

Active

Range

never, passive, or active

Dynamic?

Yes

When to Change

ECN can help TCP better handle congestion control. However, there might be existing TCP implementations, firewalls, NATs, and other non-conforming network devices that are confused by this mechanism. These devices do not comply to the IETF standard. It is suggested that these devices be replaced. In situations where replacing non-conforming devices is not feasible, this parameter value can be set to passive or never.

Commitment Level

Stable