Performance Implications of Link Characteristics (pilc)

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Last Modified: 2003-03-11


Spencer Dawkins <>
Aaron Falk <>

Transport Area Director(s):

Allison Mankin <>
Jon Peterson <>

Transport Area Advisor:

Allison Mankin <>

Mailing Lists:

General Discussion:
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Description of Working Group:

Erik Nordmark ( is the Technical Advisor.

The Internet network-layer and transport-layer protocols are
designed to accommodate a very wide range of networking
technologies and characteristics.  Nevertheless, experience has shown
that the particular properties of different network links can have a
significant impact on the performance of Internet protocols operating
over those links, and on the performance of connections along paths
include such links.  This is especially of concern to the wireless
networking community.

The PILC working group will produce several BCP/Informational
documents.  The first document will discuss considerations for
link-layer designers from the perspective of best supporting existing
IETF protocols will be produced.  The next document will discuss the
capabilities, limitations and pitfalls of 'performance enhancing
proxies' (PEPs), that is, active network elements that modify or splice
end-to-end flows in an attempt to enhance the performance they attain
the face of particular link characteristics.  The remaining documents
will either discuss the impact and mitigations for a problematic
link-layer characteristic (or group of closely related
or provide overviews of which other PILC documents apply to particular
problem domains.

As one of its first work items, the WG will review an existing
I-D on considerations for "long, thin" networks (one of the salient
characteristics of terrestrial wireless links).  This will be
published as a preliminary assessment of the problem domain, to
be refined by later PILC documents.

All documents will identify which of their considerations remain
research topics versus which are established as advanced
development.  Research topics will be explicitly flagged as not
part of any recommendations.  All documents will also identify
any security implications associated with their considerations.

The working group will also serve as a forum for discussing
possible modifications to IETF protocols to improve performance
in environments with problematic link characteristics - however,
not to the detriment of performance and stability in the general
Internet, nor to undermine existing security models.

It is incumbent upon the chairs to ensure that the WG maintains
good communications with other groups interested in related
technology issues, such as wireless forums.

Goals and Milestones:

Done    Submit Internet-Draft on significantly low bandwidth links.
Done    Submit Internet-Draft on significantly lossy links.
Done    Submit Internet-Draft on long-thin networks (based on draft-montenegro-pilc-ltn-01.txt) submitted to the IESG for publication.
Done    Draft of link-layer design considerations document.
Done    Draft of PEP capabilities and limitations document.
Done    Draft on asymmetric network paths.
Done    Document on lossy links to IESG for publication as BCP.
Done    Document on PEP capabilities and limitations submitted for publication as Informational.
Done    Document on low bandwidth links to IESG for publication as BCP.
Done    Draft of TCP Over Wireless document to the IESG as BCP
Done    Document on link-layer design considerations submitted for publication as BCP.
Done    Document on asymmetric network paths submitted to the IESG for publication as BCP.

Request For Comments:

Advice for Internet Subnetwork Designers (RFC 3819) (15174 bytes)
Performance Enhancing Proxies Intended to Mitigate Link-Related Degradations (RFC 3135) (114825 bytes)
End-to-end Performance Implications of Slow Links (RFC 3150) (39942 bytes)
End-to-end Performance Implications of Links with Errors (RFC 3155) (36388 bytes)
Advice to link designers on link Automatic Repeat reQues (ARQ) (RFC 3366) (66097 bytes)
TCP Performance Implications of Network Path Asymmetry (RFC 3449) (108839 bytes)
TCP over Second (2.5G) and Third (3G) Generation Wireless Networks (RFC 3481) (61528 bytes)