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Versions: (draft-moncaster-conex-concepts-uses)
00 01 02 03 04 05 RFC 6789
ConEx B. Briscoe, Ed.
Internet-Draft BT
Intended status: Informational R. Woundy, Ed.
Expires: April 24, 2012 Comcast
A. Cooper, Ed.
CDT
October 22, 2011
ConEx Concepts and Use Cases
draft-ietf-conex-concepts-uses-03
Abstract
This document provides the entry point to the set of documentation
about the Congestion Exposure (ConEx) protocol. It explains the
motivation for including a ConEx field at the IP layer: to expose
information about congestion to network nodes. Although such
information may have a number of uses, this document focuses on how
the information communicated in the ConEx field can serve as the
basis for significantly more efficient and effective traffic
management than what exists on the Internet today.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 24, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Congestion . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Congestion-Volume . . . . . . . . . . . . . . . . . . . . 5
2.3. Rest-of-Path Congestion . . . . . . . . . . . . . . . . . 5
2.4. Definitions . . . . . . . . . . . . . . . . . . . . . . . 6
3. Core Use Case: Informing Traffic Management . . . . . . . . . 7
3.1. Use Case Description . . . . . . . . . . . . . . . . . . . 7
3.2. Additional Benefits . . . . . . . . . . . . . . . . . . . 8
3.3. Comparison with Existing Approaches . . . . . . . . . . . 8
4. Other Use Cases . . . . . . . . . . . . . . . . . . . . . . . 10
5. Deployment Arrangements . . . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Contributors . . . . . . . . . . . . . . . . . . . . . . . 12
9. Informative References . . . . . . . . . . . . . . . . . . . . 13
Appendix A. Changes from previous drafts (to be removed by
the RFC Editor) . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
The power of Internet technology comes from multiplexing shared
capacity with packets rather than circuits. Network operators aim to
provide sufficient shared capacity, but when too much packet load
meets too little shared capacity, congestion results. Congestion
appears as either increased delay, dropped packets or packets
explicitly marked with Explicit Congestion Notification (ECN)
markings [RFC3168]. As described in Figure 1, congestion control
currently relies on the transport receiver detecting these
'Congestion Signals' and informing the transport sender in
'Congestion Feedback Signals.' The sender is then expected to reduce
its rate in response.
This document provides the entry point to the set of documentation
about the Congestion Exposure (ConEx) protocol. It focuses on the
motivation for including a ConEx field at the IP layer. (A companion
document, [ConEx-Abstract-Mech], focuses on the mechanics of the
protocol.) Briefly, the idea is for the sender to continually signal
expected congestion in the headers of any data it sends. To a first
approximation, the sender does this by relaying the 'Congestion
Feedback Signals' back into the IP layer. They then travel unchanged
across the network to the receiver (shown as 'IP-Layer-ConEx-Signals'
in Figure 1). This enables IP layer devices on the path to see
information about the whole path congestion.
,---------. ,---------.
|Transport| |Transport|
| Sender | . |Receiver |
| | /|___________________________________________| |
| ,-<---------------Congestion-Feedback-Signals--<--------. |
| | |/ | | |
| | |\ Transport Layer Feedback Flow | | |
| | | \ ___________________________________________| | |
| | | \| | | |
| | | ' ,-----------. . | | |
| | |_____________| |_______________|\ | | |
| | | IP Layer | | Data Flow \ | | |
| | | |(Congested)| \ | | |
| | | | Network |--Congestion-Signals--->-' |
| | | | Device | \| |
| | | | | /| |
| `----------->--(new)-IP-Layer-ConEx-Signals-------->| |
| | | | / | |
| |_____________| |_______________ / | |
| | | | |/ | |
`---------' `-----------' ' `---------'
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Figure 1: The ConEx Protocol in the Internet Architecture
One of the key benefits of exposing this congestion information at
the IP layer is that it makes the information available to network
operators for use as input into their traffic management procedures.
As shown in Figure 1, a ConEx-enabled sender signals whole path
congestion, which is (approximately) the congestion one round trip
time earlier as reported by the receiver to the sender. The ConEx
signal is a mark in the IP header that is easy for any IP device to
read. Therefore a node performing traffic management can count
congestion as easily as it might count data volume today by simply
counting the volume of packets with ConEx markings.
ConEx-based traffic management can make highly efficient use of
capacity. In times of no congestion, all traffic management
restraints can be removed, leaving the network's full capacity
available to all its users. If some users on the network cause
disproportionate congestion, the traffic management function can
learn about this and directly limit those users' traffic in order to
protect the service of other users sharing the same capacity. ConEx-
based traffic management thus presents a step change in terms of the
options available to operators for managing traffic on their
networks.
The remainder of this document explains the concepts behind ConEx and
how exposing congestion can significantly improve Internet traffic
management, among other benefits. Section 2 introduces a number of
concepts that are fundamental to understanding how ConEx-based
traffic management works. Section 3 shows how ConEx can be used for
traffic management, discusses additional benefits from such usage,
and compares ConEx-based traffic management to existing traffic
management approaches. Section 4 discusses other related use cases.
Section 5 briefly discusses deployment arrangements. The final
sections are standard RFC back matter.
2. Concepts
ConEx relies on a precise definition of congestion and a number of
newer concepts that are introduced and defined in this section.
2.1. Congestion
Despite its central role in network control and management,
congestion is a remarkably difficult concept to define. Experts in
different disciplines and with different perspectives define
congestion in a variety of ways [Bauer09].
The definition used for the purposes of ConEx is expressed as the
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probability of packet loss (or the probability of packet marking if
ECN is in use). This definition focuses on how congestion is
measured, rather than describing congestion as a condition or state.
2.2. Congestion-Volume
The metric that ConEx exposes is congestion-volume: the volume of
bytes dropped or ECN-marked in a given period of time. Counting
congestion-volume allows each user to be held responsible for his or
her contribution to causing congestion. Congestion-volume is a
property of traffic, whereas congestion is a property of a link or a
path.
To understand congestion-volume, consider a simple example. Imagine
Alice sends 1GB while the loss-probability is a constant 0.2%. Her
contribution to congestion -- her congestion-volume -- is 1GB x 0.2%
= 2MB. If she then sends 3GB while the loss-probability is 0.1%,
this adds 3MB to her congestion-volume. Her total contribution to
congestion is then 2MB+3MB = 5MB.
Fortunately, measuring Alice's congestion-volume on a real network
does not require the kind of arithmetic shown above because
congestion-volume can be directly measured by counting the total
volume of Alice's traffic that gets discarded or ECN-marked. (A
queue with a percentage loss involves multiplication inherently.)
2.3. Rest-of-Path Congestion
At a particular measurement point within a network, "rest-of-path
congestion" (also known as "downstream congestion") measures the
level of congestion that a traffic flow is expected to experience
between the measurement point and its final destination. "Upstream
congestion" measures the level of congestion experienced up to the
measurement point.
Measurement points that only observe ECN marks are capable of
measuring upstream congestion, whereas measurement points that
observe ConEx marks in addition to ECN marks can use both kinds of
marks to calculate rest-of-path congestion. When ECN signals are
monitored in the middle of a network, they indicate the level of
congestion experienced so far on the path (upstream congestion). In
contrast, the ConEx signals inserted into IP headers as shown in
Figure 1 indicate the level of congestion along a whole path from
source to destination. Therefore if a measurement point detects both
of these signals, it can subtract the level of ECN (upstream
congestion) from the level of ConEx (whole path) to derive a measure
of the congestion that packets are likely to experience between the
monitoring point and their destination (rest-of-path congestion).
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[ConEx-Abstract-Mech] has further discussion of the constraints
around the network's ability to measure rest-of-path congestion.
2.4. Definitions
Congestion: In general, congestion occurs when any user's traffic
suffers loss, ECN marking, or increased delay as a result of one
or more network resources becoming overloaded. For the purposes
of ConEx, congestion is measured using the concrete signals
provided by loss and ECN markings (delay is not considered).
Congestion is measured as the probability of loss or the
probability of ECN marking, usually expressed as a dimensionless
percentage.
Congestion-volume: For any granularity of traffic (packet, flow,
aggregate, link, etc.), the volume of bytes dropped or ECN-marked
in a given period of time. Conceptually, data volume multiplied
by the congestion each packet of the volume experienced. Usually
expressed in bytes (or MB or GB).
Rest-of-path congestion (or downstream congestion): The level of
congestion a flow of traffic is expected to experience on the
remainder of its path. In other words, at a measurement point in
the network the rest-of-path congestion is the level of congestion
the traffic flow has yet to experience as it travels from that
point to the receiver.
Upstream congestion: The accumulated level of congestion experienced
by a traffic flow thus far, relative to a point along its path.
In other words, at a measurement point in the network the upstream
congestion is the accumulated level of congestion the traffic flow
has experienced as it travels from the sender to that point. At
the receiver this is equivalent to the end-to-end congestion level
that (usually) is reported back to the sender.
Network provider (or operator): Operator of a residential,
commercial, enterprise, campus or other network.
User: The contractual entity that represents an individual,
household, business, or institution that uses the service of a
network provider. There is no implication that the contract has
to be commercial; for instance, the users of a university or
enterprise network service could be students or employees who do
not pay for access but may be required to comply with some form of
contract or acceptable use policy. There is also no implication
that every user is an end user. Where two networks form a
customer-provider relationship, the term user applies to the
customer network.
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[ConEx-Abstract-Mech] gives further definitions for aspects of ConEx
related to protocol mechanisms.
3. Core Use Case: Informing Traffic Management
This section explains how ConEx could be used as the basis for
traffic management, highlights additional benefits derived from
having ConEx-aware nodes on the network, and compares ConEx-based
traffic management to existing approaches.
3.1. Use Case Description
One of the key benefits that ConEx can deliver is in helping network
operators to improve how they manage traffic on their networks.
Consider the common case of a commercial broadband network where a
relatively small number of users place disproportionate demand on
network resources, at times resulting in congestion. The network
operator seeks a way to manage traffic such that the traffic that
contributes more to congestion bears more of the brunt of the
management.
Assuming ConEx signals are visible at the IP layer, the operator can
accomplish this by placing a congestion policer at an enforcement
point within the network and configuring it with a traffic management
policy that monitors each user's contribution to congestion. As
described in [ConEx-Abstract-Mech] and elaborated in [CongPol], a
congestion policer can be implemented in a similar way to a bit-rate
policer, except that it monitors and polices congestion-volume rather
than bit-rate. When implemented as a token bucket, the tokens
provide users with the right to cause bits of congestion-volume,
rather than to send bits of data volume. The fill rate represents
each user's congestion-volume quota.
The congestion policer monitors the ConEx signals of the traffic
entering the network. As long as the network remains uncongested and
users stay within their quotas, no action is taken. When the network
becomes congested and a user exhausts his quota, some action is taken
against the traffic that breached the quota in accordance with the
operator's traffic management policy. For example, the traffic may
be dropped, delayed, or marked with a lower QoS class. In this way,
traffic is managed according to its contribution to congestion -- not
some application- or flow-specific policy -- and is not managed at
all during times of no congestion.
As an example of how a network operator might employ a ConEx-based
traffic management system, consider a typical DSL network
architecture (as elaborated in [TR-059] and [TR-101]). Traffic is
routed from regional and global IP networks to an operator-controlled
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IP node, the Broadband Remote Access Server (BRAS). From the BRAS,
traffic is delivered to access nodes. The BRAS carries enhanced
functionality including IP QoS and traffic management capabilities.
Based on typical network designs and current traffic patterns, the
BRAS is located at a point in the network where congestion may be
most likely to occur. As a consequence, the BRAS is a logical choice
of location for deploying traffic management functionality. By
deploying a congestion policer at the BRAS location, the operator can
measure the congestion-volume created by users within the access
nodes. The policer would be provisioned with a traffic management
policy, perhaps directing the BRAS to drop packets from users that
exceed their congestion-volume quotas during times of congestion.
Those users would be expected to react in the typical way to drops,
backing off (assuming use of standard TCP), and thereby lowering
their congestion-volumes back within the quota limits.
3.2. Additional Benefits
The ConEx-based approach to traffic management has a number of
benefits in addition to efficient management of traffic. It provides
incentives for users to make use of scavenger transport protocols,
such as [LEDBAT], that provide ways for bulk-transfer applications to
rapidly yield when interactive applications require capacity. With a
congestion policer in place as described in Section 3.1, users of
these protocols will be less likely to run afoul of the operator's
traffic management policy than those whose bulk-transfer applications
generate the same volume of traffic without being sensitive to
congestion.
ConEx-based traffic management also makes it possible for a user to
control the relative performance among its own traffic flows. If a
user wants some flows to have more bandwidth than others, it can
allow the higher bandwidth traffic to generate more congestion
signals, leaving less congestion "budget" for the user to "spend" on
other traffic. This approach is most relevant if congestion is
signalled by ECN, because no impairment due to loss is involved and
delay can remain low.
3.3. Comparison with Existing Approaches
A variety of approaches already exist for network operators to manage
congestion, traffic, and the disproportionate usage of scarce
capacity by a small number of users. Common approaches can be
categorized as rate-based, volume-based, or application-based.
Rate-based approaches constrain the traffic rate per user or per
network. A user's peak and average (or "committed") rate may be
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limited. These approaches have the potential to either over- or
under-constrain the network, suppressing rates even when the network
is uncongested or not suppressing them enough during heavy usage
periods.
Round-robin scheduling and fair queuing were developed to address
these problems. They equalize relative rates between active users
(or flows) at a known bottleneck. The bit-rate allocated to any one
user depends on the number of active users at each instant. The
drawback of these approaches is that they favor heavy users over
light users over time, because they do not have any memory of usage.
Heavy users will be active at every instant whereas light users will
only occupy their share of the link occassionally, but bit-rate is
shared instant by instant.
Volume-based approaches measure the overall volume of traffic a user
sends (and/or receives) over time. Users may be subject to an
absolute volume cap (for example, 10GB per month) or the "heaviest"
users may be sanctioned in some other manner. Many providers use
monthly volume limits and count volume regardless of whether the
network is congested or not, creating the potential for over- or
under-constraining problems, as with the original rate-based
approaches.
ConEx-based approaches, by comparison, only react during times of
congestion and in proportion to each user's congestion contribution,
making more efficient use of capacity and more proportionate
management decisions.
Unlike ConEx-based approaches, neither rate-based nor volume-based
approaches provide incentives for applications to use scavenger
transports. They may even penalize users of applications that employ
scavenger services for the large amount of volume they send, rather
than rewarding them for carefully avoiding congestion while sending
it. While the volume-based approach described in Comcast's Protocol-
Agnostic Congestion Management System [RFC6057] aims to overcome the
over/under-constraining problem by only measuring volume and
triggering traffic management action during periods of high
utilization, it still does not provide incentives to use scavenger
transports because congestion-causing volume cannot be distinguished
from volume overall. ConEx provides this ability.
Application-based approaches use deep packet inspection or other
techniques to determine what application a given traffic flow is
associated with. Operators may then use this information to rate-
limit or otherwise sanction certain applications, in some cases only
during peak hours. These approaches suffer from being at odds with
IPSec and some application-layer encryption, and they may raise
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additional policy concerns. In contrast, ConEx offers an
application-agnostic metric to serve as the basis for traffic
management decisions.
The existing types of approaches share a further limitation that
ConEx can help to overcome: performance uncertainty. Flat-rate
pricing plans are popular because users appreciate the certainty of
having their monthly bill amount remain the same for each billing
period, allowing them to plan their costs accordingly. But while
flat-rate pricing avoids billing uncertainty, it creates performance
uncertainty: users cannot know whether the performance of their
connections is being altered or degraded based on how the network
operator is attempting to manage congestion. By exposing congestion
information at the IP layer, ConEx instead provides a metric that can
serve as an open, transparent basis for traffic management policies
that both providers and their customers can measure and verify.
4. Other Use Cases
ConEx information can be put to a number of uses other than informing
traffic management. These include:
Informing inter-operator contracts: ConEx information is made
visible to every IP node, including border nodes between networks.
Network operators can use this information to measure how much
traffic from each network contributes to congestion in the other.
As such, congestion-volume could be included as a metric in inter-
operator contracts, just as volume or bit-rate are included today.
Enabling more efficient capacity provisioning: Operators currently
provision capacity based on observations of a number of network
characteristics, including averaged utilization and congestion.
Without ConEx, a user may have little incentive to back off during
times of congestion, even if the reduction in performance
resulting from backing off certain applications (bulk transfer,
for example) would go largely unnoticed by the user. Using ConEx
to ration congestion-volume directly creates incentives where
appropriate for users and applications to switch to scavenger
transports, resulting in traffic demand that more accurately
reflects the actual capacity needed for the mix of applications on
the network to perform well. This enables capacity to be
provisioned more efficiently because traffic more closely tracks
users' real capacity needs.
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5. Deployment Arrangements
ConEx is designed so that it can be incrementally deployed in the
Internet and still be valuable for early adopters. As long as some
senders are ConEx-enabled, a network on the path can unilaterally use
ConEx-aware policy devices for traffic management; no changes to
network forwarding elements are needed and ConEx still works if there
are other networks on the path that are unaware of ConEx marks.
The above two steps seem to represent a stand-off where neither step
is useful until the other has made the first move: i) some sending
hosts must be modifed to give information to the network and ii) a
network must deploy policy devices to monitor this information and
act on it. Nonetheless, the developer of a scavenger transport
protocol like LEDBAT does have a strong incentive to tell the network
how little congestion it is causing despite sending large volumes of
data. In this case the developer makes the first move expecting it
will prompt at least some networks to move in response--so that they
use the ConEx information to reward users of the scavenger protocol.
On the host side, we have already shown (Figure Figure 1) how the
sender piggy-backs ConEx signals on normal data packets to re-insert
feedback about packet drops (and/or ECN) back into the IP layer. In
the case of TCP, [I-D.conex-tcp-mods] specifies the required sender
modifications. ConEx works with any TCP receiver as long as it uses
SACK, which most do. There is a receiver optimisation
[I-D.conex-accurate-ecn] that improves ConEx precision when using
ECN, but ConEx can still use ECN without it.
On the network side the operator solely needs to place ConEx
congestion policers at each ingress to its network, in a similar
arrangement to the edge-policed architecture of Diffserv [RFC2475].
A sender can choose whether to send ConEx or Not-ConEx packets.
ConEx packets bring information to the policer about congestion
expected on the rest of the path beyond the policer. Not-ConEx
packets bring no such information. Therefore the network will tend
to rate-limit not-ConEx packets conservatively in order to manage the
unknown risk of congestion. In contrast, a network doesn't normally
need to rate-limit ConEx-enabled packets unless they reveal a
persistently high contribution to congestion. This natural tendency
for networks to favour senders that provide ConEx information
reinforces ConEx deployment.
The above gives only the most salient aspects of ConEx deployment.
For further detail, [ConEx-Abstract-Mech] describes the incremental
deployment features of the ConEx protocol and the components that
need to be deployed for ConEx to work. Then [I-D.conex-init-deploy]
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gives concrete examples of feasible initial deployment scenarios.
6. Security Considerations
This document does not specify a mechanism, it merely motivates
congestion exposure at the IP layer. Therefore security
considerations are described in the companion document that gives an
abstract description of the ConEx protocol and the components that
would use it [ConEx-Abstract-Mech].
7. IANA Considerations
This document does not require actions by IANA.
8. Acknowledgments
Bob Briscoe was partly funded by Trilogy, a research project (ICT-
216372) supported by the European Community under its Seventh
Framework Programme. The views expressed here are those of the
author only.
The authors would like to thank the many people that have commented
on this document: Bernard Aboba, Mikael Abrahamsson, Joao Taveira
Araujo, Marcelo Bagnulo Braun, Steve Bauer, Caitlin Bestler, Steven
Blake, Louise Burness, Ken Carlberg, Nandita Dukkipati, Dave McDysan,
Wes Eddy, Matthew Ford, Ingemar Johansson, Georgios Karagiannis,
Mirja Kuehlewind, Dirk Kutscher, Zhu Lei, Kevin Mason, Matt Mathis,
Michael Menth, Chris Morrow, Tim Shepard, Hannes Tschofenig and
Stuart Venters. Please accept our apologies if your name has been
missed off this list.
8.1. Contributors
Philip Eardley and Andrea Soppera made helpful text contributions to
this document.
The following co-edited this document through most of its life:
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Toby Moncaster
Computer Laboratory
William Gates Building
JJ Thomson Avenue
Cambridge, CB3 0FD
UK
EMail: toby.moncaster@cl.cam.ac.uk
John Leslie
JLC.net
10 Souhegan Street
Milford, NH 03055
US
EMail: john@jlc.net
9. Informative References
[Bauer09] Bauer, S., Clark, D., and W. Lehr, "The
Evolution of Internet Congestion", 2009.
[ConEx-Abstract-Mech] Mathis, M. and B. Briscoe, "Congestion
Exposure (ConEx) Concepts and Abstract
Mechanism",
draft-ietf-conex-abstract-mech-02 (work in
progress), July 2011.
[CongPol] Briscoe, B., Jacquet, A., and T. Moncaster,
"Policing Freedom to Use the Internet
Resource Pool", RE-Arch 2008 hosted at the
2008 CoNEXT conference , December 2008.
[I-D.conex-accurate-ecn] Kuehlewind, M. and R. Scheffenegger,
"Accurate ECN Feedback in TCP",
draft-kuehlewind-conex-accurate-ecn-00
(work in progress), July 2011.
[I-D.conex-init-deploy] Briscoe, B., "Initial Congestion Exposure
(ConEx) Deployment Examples",
draft-briscoe-conex-initial-deploy-00 (work
in progress), October 2011.
[I-D.conex-tcp-mods] Kuehlewind, M. and R. Scheffenegger, "TCP
modifications for Congestion Exposure",
draft-kuehlewind-conex-tcp-modifications-00
(work in progress), July 2011.
[LEDBAT] Shalunov, S., Hazel, G., Iyengar, J., and
M. Kuehlewind, "Low Extra Delay Background
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Transport (LEDBAT)",
draft-ietf-ledbat-congestion-08 (work in
progress), May 2011.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies,
E., Wang, Z., and W. Weiss, "An
Architecture for Differentiated Services",
RFC 2475, December 1998.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black,
"The Addition of Explicit Congestion
Notification (ECN) to IP", RFC 3168,
September 2001.
[RFC6057] Bastian, C., Klieber, T., Livingood, J.,
Mills, J., and R. Woundy, "Comcast's
Protocol-Agnostic Congestion Management
System", RFC 6057, December 2010.
[TR-059] Anschutz, T., Ed., "DSL Forum Technical
Report TR-059: Requirements for the Support
of QoS-Enabled IP Services",
September 2003.
[TR-101] Cohen, A., Ed. and E. Schrum, Ed., "DSL
Forum Technical Report TR-101: Migration to
Ethernet-Based DSL Aggregation",
April 2006.
Appendix A. Changes from previous drafts (to be removed by the RFC
Editor)
From draft-ietf-conex-concepts-uses-02 to -03: Reorganization and
re-write of most sections.
From draft-ietf-conex-concepts-uses-01 to -02: New Abstract &
Introduction. Concepts and Misconceptions sections added around
definitions. Minor clarifications to Existing Traffic Management
and Use-Cases sections, with Other use Cases Added. Deployment
Arrangements Section added.
From draft-ietf-conex-concepts-uses-00 to -01:
Added section on timescales: Section 6
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Revised introduction to clarify congestion definitions
Changed source for congestion definition in Section 2
Other minor changes
From draft-moncaster-conex-concepts-uses-02 to
draft-ietf-conex-concepts-uses-00 (per decisions of working group):
Removed section on DDoS mitigation use case.
Removed appendix on ConEx Architectural Elements. PLEASE NOTE:
Alignment of terminology with the Abstract Mechanism draft has
been deferred to the next version.
From draft-moncaster-conex-concepts-uses-01 to
draft-moncaster-conex-concepts-uses-02:
Updated document to take account of the new Abstract Mechanism
draft [ConEx-Abstract-Mech].
Updated the definitions section.
Removed sections on Requirements and Mechanism.
Moved section on ConEx Architectural Elements to appendix.
Minor changes throughout.
From draft-moncaster-conex-concepts-uses-00 to
draft-moncaster-conex-concepts-uses-01:
Changed end of Abstract to better reflect new title
Created new section describing the architectural elements of
ConEx. Added Edge Monitors and Border Monitors (other elements
are Ingress, Egress and Border Policers).
Extensive re-write of use cases partly in response to suggestions
from Dirk Kutscher
Improved layout of Section 2 and added definitions of Whole Path
Congestion, ConEx-Enabled and ECN-Enabled. Re-wrote definition of
Congestion Volume. Renamed Ingress and Egress Router to Ingress
and Egress Node as these nodes may not actually be routers.
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Improved document structure. Merged sections on Exposing
Congestion and ECN.
Added new section on ConEx requirements with a ConEx Issues
subsection. Text for these came from the start of the old ConEx
Use Cases section
Added a sub-section on Partial vs Full Deployment (Section 5.5)
Added a discussion on ConEx as a Business Secret
From draft-conex-mechanism-00 to
draft-moncaster-conex-concepts-uses-00:
Changed filename to draft-moncaster-conex-concepts-uses.
Changed title to ConEx Concepts and Use Cases.
Chose uniform capitalization of ConEx.
Moved definition of Congestion Volume to list of definitions.
Clarified mechanism section. Changed section title.
Modified text relating to conex-aware policing and policers (which
are NOT defined terms).
Re-worded bullet on distinguishing ConEx and non-ConEx traffic in
use cases section.
Authors' Addresses
Bob Briscoe (editor)
BT
B54/77, Adastral Park
Martlesham Heath
Ipswich IP5 3RE
UK
Phone: +44 1473 645196
EMail: bob.briscoe@bt.com
URI: http://bobbriscoe.net/
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Richard Woundy (editor)
Comcast
1701 John F Kennedy Boulevard
Philadelphia, PA 19103
US
EMail: richard_woundy@cable.comcast.com
URI: http://www.comcast.com
Alissa Cooper (editor)
CDT
1634 Eye St. NW, Suite 1100
Washington, DC 20006
US
EMail: acooper@cdt.org
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