TCP Control Block Interdependence (RFC2140)
Original Publication Date: 1997-Apr-01
Included in the Prior Art Database: 2019-Feb-15
Internet Society Requests For Comment (RFCs)
This memo makes the case for interdependent TCP control blocks, where part of the TCP state is shared among similar concurrent connections, or across similar connection instances. TCP state includes a combination of parameters, such as connection state, current round-trip time estimates, congestion control information, and process information. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind.
Network Working Group J. Touch Request for Comments: 2140 ISI Category: Informational April 1997
TCP Control Block Interdependence
Status of this Memo
This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
This memo makes the case for interdependent TCP control blocks, where part of the TCP state is shared among similar concurrent connections, or across similar connection instances. TCP state includes a combination of parameters, such as connection state, current round- trip time estimates, congestion control information, and process information. This state is currently maintained on a per-connection basis in the TCP control block, but should be shared across connections to the same host. The goal is to improve transient transport performance, while maintaining backward-compatibility with existing implementations.
This document is a product of the LSAM project at ISI.
TCP is a connection-oriented reliable transport protocol layered over IP . Each TCP connection maintains state, usually in a data structure called the TCP Control Block (TCB). The TCB contains information about the connection state, its associated local process, and feedback parameters about the connection’s transmission properties. As originally specified and usually implemented, the TCB is maintained on a per-connection basis. This document discusses the implications of that decision, and argues for an alternate implementation that shares some of this state across similar connection instances and among similar simultaneous connections. The resulting implementation can have better transient performance, especially for numerous short-lived and simultaneous connections, as often used in the World-Wide Web . These changes affect only the TCB initialization, and so have no effect on the long-term behavior of TCP after a connection has been established.
Touch Informational [Page 1]
RFC 2140 TCP Control Block Interdependence April 1997
The TCP Control Block (TCB)
A TCB is associated with each connection, i.e., with each association of a pair of applications across the network. The TCB can be summarized as containing :
Local process state
pointers to send and receive buffers pointers to retransmission queue and current segment pointers to Internet Protocol (IP) PCB
Per-connection shared state
connection state timers flags local and remote host numbers and ports
send and receive window state (size*, current number) round-trip time and variance cong. window size* cong. window size threshold* max windows seen* MSS# round-trip time and variance#
The per-connection information is shown as split into macro-state and micro-state, terminology borrowed from . Macro-state describes the finite state machine; we include the endpoint numbers and components (timers, flags) used to help maintain that state. This includes the protocol for e...