Internet Engineering Task Force J. Griner
INTERNET DRAFT NASA Lewis
16 November 1998
TCP Performance Enhancing Proxy Terminology
draft-griner-tcppep-term-00.txt
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Abstract
This document presents definitions for many terms to be used during
the discussion of various TCP Performance Enhancing Proxies (PEP).
A PEP, located between two end-systems, is used to, in some way,
enhance a TCP connection. PEP's are commonly referred to as
spoofing, connection splitting gateways, etc.
1. Introduction
This document presents definitions for many terms to be used during
the discussion of various TCP Performance Enhancing Proxies (PEP).
A PEP, located between two end-systems, is used to enhance a TCP
connection. PEP's are commonly referred to as spoofing, a
connection splitting gateway, etc. With commonly agreed
definitions, it is expected that PEP designers will be able to
discuss more clearly the advantages and disadvantages of their PEP
methods.
This document is a strawman, based on conversations conducted on the
tcppep mailing list. For information on subscribing to the tcppep
mailing list reference: http://tcppep.lerc.nasa.gov
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2. Definitions for TCP Performance Enhancing Proxy Terms
asymmetric link
A link which has different rates for the forward channel (used
for data segments) and the back, or return, channel (used for
ACKs).
raw bandwidth
The total capacity (bytes/sec) of an unloaded link available to
carry information.
available bandwidth
The total capacity (bytes/sec) of a link that is available at
any given time. May be lower than raw bandwidth due to competing
traffic.
bandwidth utilization
The actual amount of information delivered over a link, in a
given period, expressed as a percent of the raw bandwidth on
that link.
gateway
A device capable of initiating and terminating IP connections on
behalf of a user. (eg. firewall, proxy, etc.) Not necessarily,
but could be, the same as a "router".
opaque
A modification that requires changes to be made to both
end-systems.
protocol tunneling
When a packet from an originating host is subsequently wrapped
for transmission, and the wrapper later removed for final
delivery to an end host.
proxies
An entity in the network acting on behalf of a user (with or
without the user's knowledge)
Type 1: Traditional web proxy, which contains content and
requires a configuration change on the client end. (mirrors seem
like a brute force/higher level implementation of this)
Type 2: Does not break the end-to-end TCP connection, but
modifies things like ACK spacing to improve performance. This
proxy is invisible to client and server.
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Type 3: Uses TCP splitting for communications between two
end-systems, and is invisible to client and server.
router
A device for routing IP packets through an internetwork.
Snoop
A TCP-aware link layer developed for wireless packet radio or
cellular networks. It works by caching segments at a wireless
base station. If the base station sees dupacks for a segment
that it has cached, it retransmits the missing segment while
suppressing the dupack stream back to the sender until the
wireless receiver starts to ack new data. [BSK95]
split-connection
A TCP connection that has been terminated, before reaching the
destination end-system, in order to initiate a second connection
towards the end-system. [BB95]
TCP splitting
Using one or more split-connections, for communications between
two unaltered end-systems.
translucent
A modification that requires changes to be made at only one
end-system.
transparent
No changes are necessary in either of the end-systems.
Acknowledgements
I would like to thank the people who contributed to the tcppep
mailing list. Most of the definitions were extracted from
discussions on this list.
References
[BSK95] Hari Balakrishnan, Srinivasan Seshan, Randy
H. Katz. Improving Reliable Transport and Handoff Performance in
Cellular Wireless Networks. ACM Wireless Networks, 1(4),
December 1995.
[BB95] A. Bakre and B. R. Badrinath. I-TCP: Indirect TCP for Mobile
Hosts. In Proceedings of the 15th International Conference on
Distributed Computing Systems (ICDCS), May 1995.
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Author's Address
Jim Griner
NASA Lewis Research Center
MS: 54-2
21000 Brookpark Rd.
Cleveland, OH 44135
+1-216-433-5787
jgriner@lerc.nasa.gov
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Jim Griner