Translator (NAT) Terminology and Considerations", RFC
2663, August 1999.
[RFC2760] Allman, M., Dawkins, S., Glover, D., Griner, J.,
Henderson, T., Heidemann, J., Kruse, H., Ostermann, S.,
Scott, K., Semke, J., Touch, J. and D. Tran, "Ongoing TCP
Research Related to Satellites", RFC2760, February 2000.
[RFC3002] Mitzel, D., "Overview of 2000 IAB Wireless
Internetworking Workshop", RFC3002, December 2000.
[RFC3042] Allman, M., Balakrishnan, H. and S. Floyd, "Enhancing
TCP's Loss Recovery Using Limited Transmit", RFC3042,
January 2001.
[SHEL00] Z. Shelby, T. Saarinen, P. Mahonen, D. Melpignano, A.
Marshall, L. Munoz, "Wireless IPv6 Networks - WINE," IST
Mobile Summit, Ireland, October 2000.
[SNOOP] H. Balakrishnan, S. Seshan, E. Amir, R. Katz, "Improving
TCP/IP Performance over Wireless Networks," Proc. 1st ACM
Conference on Mobile Communications and Networking
(Mobicom), Berkeley, California, November 1995.
[SNOOPELN] H. Balakrishnan, R. Katz, "Explicit Loss Notification and
Wireless Web Performance," Proc. IEEE Globecom 1998,
Internet Mini-Conference, Sydney, Australia, November
1998.
[SPACENET] Spacenet, VSAT technology vendor based in Mclean,
Virginia. Website at http://www.spacenet.com.
[SRC84] J.H. Saltzer, D.P. Reed, D.D. Clark, "End-To-End
Arguments in System Design," ACM TOCS, Vol. 2, No. 4, pp.
277-288, November 1984.
[WAPARCH] Wireless Application Protocol Architecture Specification,
April 1998, http://www.wapforum.org.
[WAPPROXY] Wireless Application Protocol Push Proxy Gateway Service
Specification, August 1999, http://www.wapforum.org.
[WAPWAE] Wireless Application Protocol Wireless Application
Environment Overview, March 2000,
http://www.wapforum.org.
[WAPWDP] Wireless Application Protocol Wireless Datagram Protocol
Specification, February 2000, http://www.wapforum.org.
[WAPWSP] Wireless Application Protocol Wireless Session Protocol
Specification, May 2000, http://www.wapforum.org.
[WAPWTLS] Wireless Application Protocol Wireless Transport Layer
Security Specification, February 2000,
http://www.wapforum.org.
[WAPWTP] Wireless Application Protocol Wireless Transaction
Protocol Specification, February 2000,
http://www.wapforum.org.
[Zhang00] Y. Zhang, B. Singh, "A Multi-Layer IPsec Protocol," Proc.
proceedings of 9th USENIX Security Symposium, Denver,
Colorado, August 2000. Available at
http://www.wins.hrl.com/people/ygz/papers/usenix00.html.
10. Authors' Addresses
Questions about this document may be directed to:
John Border
Hughes Network Systems
11717 Exploration Lane
Germantown, Maryland 20876
Phone: +1-301-548-6819
Fax: +1-301-548-1196
EMail: border@hns.com
Markku Kojo
Department of Computer Science
University of Helsinki
P.O. Box 26 (Teollisuuskatu 23)
FIN-00014 HELSINKI
Finland
Phone: +358-9-1914-4179
Fax: +358-9-1914-4441
EMail: kojo@cs.helsinki.fi
Jim Griner
NASA Glenn Research Center
MS: 54-5
21000 Brookpark Orad
Cleveland, Ohio 44135-3191
Phone: +1-216-433-5787
Fax: +1-216-433-8705
EMail: jgriner@grc.nasa.gov
Gabriel Montenegro
Sun Microsystems Laboratories, Europe
29, chemin du Vieux Chene
38240 Meylan, FRANCE
Phone: +33 476 18 80 45
EMail: gab@sun.com
Zach Shelby
University of Oulu
Center for Wireless Communications
PO Box 4500
FIN-90014
Finland
Phone: +358-40-779-6297
EMail: zach.shelby@ee.oulu.fi
Appendix A - PEP Terminology Summary
This appendix provides a summary of terminology frequently used
during discussion of Performance Enhancing Proxies. (In some cases,
these terms have different meanings from their non-PEP related
usage.)
ACK filtering
Removing acknowledgments to prevent congestion of a low speed
link, usually used with paths which include a highly asymmetric
link. Sometimes also called ACK reduction. See Section 3.1.4.
ACK spacing
Delayed forwarding of acknowledgments in order to space them
appropriately, for example, to help minimize the burstiness of
TCP data. See Section 3.1.1.
application layer PEP
A Performance Enhancing Proxy operating above the transport
layer. May be aimed at improving application or transport
protocol performance (or both). Described in detail in Section
2.1.2.
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).
available bandwidth
The total capacity of a link available to carry information at any
given time. May be lower than the raw bandwidth due to competing
traffic.
bandwidth utilization
The actual amount of information delivered over a link in a given
period, usually expressed as a percent of the raw bandwidth of
the link.
gateway
Has several meanings with respect to PEPs, depending on context:
- An access point to a particular link;
- A device capable of initiating and terminating connections
on
behalf of a user or end system (e.g., a firewall or proxy).
Not necessarily, but could be, a router.
in flight (data)
Data sent but not yet acknowledged. More precisely, data sent for
which the sender has not yet received the acknowledgement.
link layer PEP
A Performance Enhancing Proxy operating below the network layer.
local acknowledgement
The generation of acknowledgments by an entity in the path
between two end systems in order to allow the sending system to
transmit more data without waiting for end-to-end
acknowledgments. Described (in the context of TCP) in Section
3.1.2.
performance enhancing proxy
An entity in the network acting on behalf of an end system or user
(with or without the knowledge of the end system or user) in order
to enhance protocol performance. Section 2 describes various
types of performance enhancing proxies. Section 3 describes the
mechanisms performance enhancing proxies use to improve
performance.
raw bandwidth
The total capacity of an unloaded link available to carry
information.
Snoop
A TCP-aware link layer developed for wireless packet radio and
cellular networks. It works by caching segments at a wireless
base station. If the base station sees duplicate acknowledgments
for a segment that it has cached, it retransmits the missing
segment while suppressing the duplicate acknowledgement stream
being forwarded back to the sender until the wireless receiver
starts to acknowledge new data. Described in detail in Section
5.3.2 and [SNOOP].
split connection
A connection that has been terminated before reaching the intended
destination end system in order to initiate another connection
towards the end system. This allows the use of different
connection characteristics for different parts of the path of
the originally intended connection. See Section 2.4.
TCP PEP
A Performance Enhancing Proxy operating at the transport layer
with TCP. Aimed at improving TCP performance.
TCP splitting
Using one or more split TCP connections to improve TCP
performance.
TCP spoofing
Sometimes used as a synonym for TCP PEP. More accurately, TCP
spoofing refers to using transparent (to the TCP stacks in the
end systems) mechanisms to improve TCP performance. See Section
2.1.1.
transparent
In the context of a PEP, transparent refers to not requiring
changes to be made to the end systems, transport endpoints
and/or applications involved in a connection. See Section 2.5
for a more detailed explanation.
transport layer PEP
A Performance Enhancing Proxy operating at the transport layer.
Described in detail in Section 2.1.1.
tunneling
In the context of PEPs, tunneling refers to the process of
wrapping a packet for transmission over a particular link
between two PEPs. See Section 3.2.
WAP
The Wireless Application Protocol specifies an application
framework and network protocols intended to work across
differing narrow-band wireless network technologies. See
Section 5.2.2.2.
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