Internet Engineering Task Force X. Wei
INTERNET-DRAFT Huawei Technologies
Intended Status: Informational L.Zhu
Expires: July 29, 2017 Huawei Technologies
L.Deng
China Mobile
January 25, 2017
Tunnel Congestion Feedback
draft-ietf-tsvwg-tunnel-congestion-feedback-04
Abstract
This document describes a method to measure congestion on a tunnel
segment based on recommendations from RFC 6040, "Tunneling of
Explicit Congestion Notification", and to use IPFIX to communicate
the congestion measurements from the tunnel's egress to a controller
which can respond by modifying the traffic control policies at the
tunnel's ingress.
Status of this Memo
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Copyright and License Notice
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Copyright (c) 2017 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
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to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions And Terminologies . . . . . . . . . . . . . . . . . 3
3. Congestion Information Feedback Models . . . . . . . . . . . . 3
4. Congestion Level Measurement . . . . . . . . . . . . . . . . . 4
5. Congestion Information Delivery . . . . . . . . . . . . . . . . 6
5.1 IPFIX Extensions . . . . . . . . . . . . . . . . . . . . . . 7
5.1.1 tunnelEcnCeCePacketTotalCount . . . . . . . . . . . . . 8
5.1.2 tunnelEcnEct0NectPacketTotalCount . . . . . . . . . . . 8
5.1.3 tunnelEcnEct1NectPacketTotalCount . . . . . . . . . . . 8
5.1.4 tunnelEcnCeNectPacketTotalCount . . . . . . . . . . . . 9
5.1.5 tunnelEcnCeEct0PacketTotalCount . . . . . . . . . . . . 9
5.1.6 tunnelEcnCeEct1PacketTotalCount . . . . . . . . . . . . 9
5.1.7 tunnelEcnEct0Ect0PacketTotalCount . . . . . . . . . . . 10
5.1.8 tunnelEcnEct1Ect1PacketTotalCount . . . . . . . . . . . 10
6. Congestion Management . . . . . . . . . . . . . . . . . . . . . 10
6.1 Example . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 14
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.1 Normative References . . . . . . . . . . . . . . . . . . . 16
9.2 Informative References . . . . . . . . . . . . . . . . . . 17
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
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1. Introduction
In IP networks, persistent congestion[RFC2914] lowers transport
throughput, leading to waste of network resource. Appropriate
congestion control mechanisms are therefore critical to prevent the
network from falling into the persistent congestion state. Currently,
transport protocols such as TCP[RFC793], SCTP[RFC4960],
DCCP[RFC4340], have their built-in congestion control mechanisms, and
even for certain single transport protocol like TCP there can be a
couple of different congestion control mechanisms to choose from. All
these congestion control mechanisms are implemented on host side, and
there are reasons that only host side congestion control is not
sufficient for the whole network to keep away from persistent
congestion. For example, (1) some protocol's congestion control
scheme may have internal design flaws; (2) improper software
implementation of protocol; (3) some transport protocols, e.g.
RTP[RFC3550] do not even provide congestion control at all.
Tunnels are widely deployed in various networks including public
Internet, data center network, and enterprise network etc. A tunnel
consists of ingress, egress and a set of intermediate routers. For
the tunnel scenario, a tunnel-based mechanism is introduced for
network traffic control to keep the network from persistent
congestion. Here, tunnel ingress will implement congestion
management function to control the traffic entering the tunnel.
This document provides a mechanism of feeding back inner tunnel
congestion level to the ingress. Using this mechanism the egress can
feed the tunnel congestion level information it collects back to the
ingress. After receiving this information the ingress will be able to
perform congestion management according to network management policy.
2. Conventions And Terminologies
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]
DP: Decision Point, an logical entity that makes congestion
management decision based on the received congestion feedback
information.
AP: Action Point, an logical entity that implements congestion
management action according to the decision made by Decision Point.
ECT: ECN-Capable Transport code point defined in RFC3168.
3. Congestion Information Feedback Models
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The feedback model mainly consists of tunnel egress and tunnel
ingress. The tunnel egress composes of meter function and exporter
function; tunnel ingress composes AP (Action Point) function,
collector function and DP (Decision Point) function.
The Meter function collects network congestion level information, and
conveys the information to Exporter which feeds back the information
to the collector function.
The collector collects congestion level information from exporter,
after that congestion management Decision Point (DP) function will
make congestion management decision based on the information from
collector.
The action point controls the traffic entering tunnel, and it
implements traffic control decision of DP.
Feedback
+-----------------------------------+
| |
| |
| V
+--------------+ +-------------+
| +--------+ | | +---------+ |
| |Exporter| | | |Collector| |
| +---|----+ | | +---|-----+ |
| +--|--+ | | +|-+ |
| |Meter| | | |DP| |
| +-----+ | | +--+ |
| | | +--+ |
| | | |AP| |
| | | +--+ |
|Egress | | Ingress |
+--------------+ +-------------+
Figure 1: Feedback Model.
4. Congestion Level Measurement
This section describes how to measure congestion level in a
tunnel.
The congestion level measurement is based on ECN (Explicit
Congestion Notification) [RFC3168] and packet drop. If the routers
support ECN, after router's queue length is over a predefined
threshold, the routers will mark the ECN-capable packets as
Congestion Experienced (CE) or drop not-ECT packets with the
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probability proportional to queue length; if the queue overflows
all packets will be dropped. If the routers do not support ECN,
after router's queue length is over a predefined threshold, the
routers will drop both the ECN-capable packets and the not-ECT
packets with the probability proportional to the queue length.
The network congestion level could be indicated through the ratio
of CE-marked packet and the ratio of packet drop, the relationship
between these two kinds of indicator is complementary. If the
congestion level in tunnel is not high enough, the packets would
be marked as CE instead of being dropped, and then it is easy to
calculate congestion level according to the ratio of CE-marked
packets. If the congestion level is so high that ECT packet will
be dropped, then the packet loss ratio could be calculated by
comparing total packets entering ingress and total packets
arriving at egress over the same span of packets, if packet loss
is detected, it could be assumed that severe congestion has
occurred in the tunnel. Because loss is only ever a sign of
serious congestion, so it doesn't need to measure loss ratio
accurately.
Faked ECN-capable transport (ECT) is used at ingress to defer
packet loss to egress. The basic idea of faked ECT is that, when
encapsulating packets, ingress first marks tunnel outer header
according to RFC6040, and then remarks outer header of Not-ECT
packet as ECT, there will be three kinds of combination of outer
header ECN field and inner header ECN field: CE|CE, ECT|N-ECT,
ECT|ECT (in the form of outer ECN| inner ECN); when decapsulating
packets at egress, RFC6040 defined decapsulation behavior is used,
and according to RFC6040, the packets marked as CE|N-ECT will be
dropped by egress.
To calculate congestion level, for the same span of packets, the
number of each kind of ECN marking packet at ingress and egress
will be compared to get the volume of CE-marked packet in the
tunnel; and the total number of packets at ingress and egress will
be compared to detect the packet loss.
The basic procedure of congestion level measurement is as follows:
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+-------+ +------+
|Ingress| |Egress|
+-------+ +------+
| |
+----------------+ |
|cumulative count| |
+----------------+ |
| |
| <node id-i, ECN counts> |
|------------------------>|
|<node id-e, ECN counts> |
|<------------------------|
| |
| |
Figure 2: Procedure of Congestion Level Measurement
Ingress encapsulates packets and marks outer header according to
faked ECT as described above. Ingress cumulatively counts packets for
three types of ECN combination (CE|CE, ECT|N-ECT, ECT|ECT) and then
the ingress regularly sends cumulative packet counts message of each
type of ECN combination to the egress. When each message arrives, the
egress cumulatively counts packets coming from the ingress and adds
its own packet counts of each type of ECN combination (CE|CE, ECT|N-
ECT, CE|N-ECT, CE|ECT, ECT|ECT) to the message and returns the whole
message to the ingress.
The counting of packets can be at the granularity of the all traffic
from the ingress to the egress to learn about the overall congestion
status of the path between the ingress and the egress. The counting
can also be at the granularity of individual customer's traffic or a
specific set of flows to learn about their congestion contribution.
5. Congestion Information Delivery
As described above, the tunnel ingress needs to convey a message
containing cumulative packet counts of each type of ECN combination
to tunnel egress, and the tunnel egress also needs to feed back the
message of cumulative packet counts of each type of ECN combination
to the ingress. This section describes how the messages should be
conveyed.
The message travels along the same path with network data traffic,
referred as in-band signal. Because the message is transmitted in
band, so the message packet may get lost in case of network
congestion. To cope with the situation that the message packet gets
lost, the packet counts values are sent as cumulative counters. Then
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if a message is lost the next message will recover the missing
information. Even though the missing information could be recovered,
the message should be transmitted in a much higher priority than
users' traffic flows.
IPFIX [RFC7011] is selected as information feedback protocol. IPFIX
uses preferably SCTP as transport. SCTP allows partially reliable
delivery [RFC3758], which ensures the feedback message will not be
blocked in case of packet loss due to network congestion.
Ingress can do congestion management at different granularity which
means both the overall aggregated inner tunnel congestion level and
congestion level contributed by certain traffic(s) could be measured
for different congestion management purpose. For example, if the
ingress only wants to limit congestion volume caused by certain
traffic(s),e.g UDP-based traffic, then congestion volume for the
traffic will be fed back; or if the ingress do overall congestion
management, the aggregated congestion volume will be fed back.
When sending message from ingress to egress, the ingress acts as
IPFIX exporter and egress acts as IPFIX collector; When feedback
congestion level information from egress to ingress, then the egress
acts as IPFIX exporter and ingress acts as IPFIX collector.
The combination of congestion level measurement and congestion
information delivery procedure should be as following:
# The ingress determines IPFIX template record to be used. The
template record can be preconfigured or determined at runtime, the
content of template record will be determined according to the
granularity of congestion management, if the ingress wants to limit
congestion volume contributed by specific traffic flow then the
elements such as source IP address, destination IP address, flow id
and CE-marked packet volume of the flow etc will be included in the
template record.
# Meter on ingress measures traffic volume according to template
record chosen and then the measurement records are sent to egress in
band.
# Meter on egress measures congestion level information according to
template record, the content of template record should be the same
as template record of ingress.
# Exporter of egress sends measurement record together with the
measurement record of ingress back to the ingress.
5.1 IPFIX Extensions
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This sub-section defines a list of new IPFIX Information Elements
according to RFC7013 [RFC7013].
5.1.1 tunnelEcnCeCePacketTotalCount
Description: The total number of incoming packets with CE|CE ECN
marking combination for this Flow at the Observation Point since the
Metering Process (re-)initialization for this Observation Point.
Abstract Data Type: unsigned64
Data Type Semantics: totalCounter
ElementId: TBD1
Statues: current
Units: packets
5.1.2 tunnelEcnEct0NectPacketTotalCount
Description: The total number of incoming packets with ECT(0)|N-ECT
ECN marking combination for this Flow at the Observation Point since
the Metering Process (re-)initialization for this Observation Point.
Abstract Data Type: unsigned64
Data Type Semantics: totalCounter
ElementId: TBD2
Statues: current
Units: packets
5.1.3 tunnelEcnEct1NectPacketTotalCount
Description: The total number of incoming packets with ECT(1)|N-ECT
ECN marking combination for this Flow at the Observation Point since
the Metering Process (re-)initialization for this Observation Point.
Abstract Data Type: unsigned64
Data Type Semantics: totalCounter
ElementId: TBD3
Statues: current
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Units: packets
5.1.4 tunnelEcnCeNectPacketTotalCount
Description: The total number of incoming packets with CE|N-ECT ECN
marking combination for this Flow at the Observation Point since the
Metering Process (re-)initialization for this Observation Point.
Abstract Data Type: unsigned64
Data Type Semantics: totalCounter
ElementId: TBD4
Statues: current
Units: packets
5.1.5 tunnelEcnCeEct0PacketTotalCount
Description: The total number of incoming packets with CE|ECT(0) ECN
marking combination for this Flow at the Observation Point since the
Metering Process (re-)initialization for this Observation Point.
Abstract Data Type: unsigned64
Data Type Semantics: totalCounter
ElementId: TBD5
Statues: current
Units: packets
5.1.6 tunnelEcnCeEct1PacketTotalCount
Description: The total number of incoming packets with CE|ECT(1) ECN
marking combination for this Flow at the Observation Point since the
Metering Process (re-)initialization for this Observation Point.
Abstract Data Type: unsigned64
Data Type Semantics: totalCounter
ElementId: TBD6
Statues: current
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Units: packets
5.1.7 tunnelEcnEct0Ect0PacketTotalCount
Description: The total number of incoming packets with ECT(0)|ECT(0)
ECN marking combination for this Flow at the Observation Point since
the Metering Process (re-)initialization for this Observation Point.
Abstract Data Type: unsigned64
Data Type Semantics: totalCounter
ElementId: TBD7
Statues: current
Units: packets
5.1.8 tunnelEcnEct1Ect1PacketTotalCount
Description: The total number of incoming packets with ECT(1)|ECT(1)
ECN marking combination for this Flow at the Observation Point since
the Metering Process (re-)initialization for this Observation Point.
Abstract Data Type: unsigned64
Data Type Semantics: totalCounter
ElementId: TBD8
Statues: current
Units: packets
6. Congestion Management
After tunnel ingress receives congestion level information, then
congestion management actions could be taken based on the
information, e.g. if the congestion level is higher than a predefined
threshold, then action could be taken to reduce the congestion level.
The design of network side congestion management SHOULD take host
side e2e congestion control mechanism into consideration, which means
the congestion management needs to avoid the impacts on e2e
congestion control. For instance, congestion management action must
be delayed by more than a worst-case global RTT (e.g. 100ms),
otherwise tunnel traffic management will not give normal e2e
congestion control enough time to do its job, and the system could go
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unstable.
The detailed description of congestion management is out of scope of
this document, as examples, congestion management such as circuit
breaker [CB] could be applied. Circuit breaker is an automatic
mechanism to estimate congestion, and to terminate flow(s) when
persistent congestion is detected to prevent network congestion
collapse.
6.1 Example
This subsection provides an example of how the solution described in
this document could work.
First of all, IPFIX template records are exchanged between ingress
and egress to negotiate the format of data record, the example here
is to measure the congestion level for the overall tunnel (caused by
all the traffic in tunnel). After the negotiation is finished,
ingress sends in-band message to egress, the message contains the
number of each kind of ECN-marked packets (i.e. CE|CE, ECT|N-ECT and
ECT|ECT) received until the sending of message.
After egress receives the message, the egress counts number of
different kinds of ECN-marking packets received until receiving the
message, then the egress sends a feedback message containing the
counts together with the information in ingress's message to ingress.
Figure 3 to Figure 6 below show the example procedure between ingress
and egress.
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+---------------------------------+----------------------+
|Set ID=2 Length=40 |
|---------------------------------|----------------------|
|Template ID=256 Field Count =8 |
|---------------------------------|----------------------|
|tunnelEcnCeCePacketTotalCount Field Length=8 |
|---------------------------------|----------------------|
|tunnelEcnEctNectPacketTotalCount Field Length=8 |
|---------------------------------|----------------------|
|tunnelEcnEctEctPacketTotalCount Field Length=8 |
|---------------------------------|----------------------|
|tunnelEcnCeCePacketTotalCount Field Length=8 |
|---------------------------------|----------------------|
|tunnelEcnEctNectPacketTotalCount Field Length=8 |
|---------------------------------|----------------------|
|tunnelEcnEctEctPacketTotalCount Field Length=8 |
|---------------------------------|----------------------|
|tunnelEcnCeNectPacketTotalCount Field Length=8 |
|---------------------------------|----------------------|
|tunnelEcnCeEctPacketTotalCount | Field Length=8 |
+---------------------------------+----------------------+
Figure 3: Template Record Sent From Egress to Ingress
+---------------------------------+----------------------+
|Set ID=2 Length=28 |
|---------------------------------|----------------------|
|Template ID=257 Field Count =3 |
|---------------------------------|----------------------|
|tunnelEcnCeCePacketTotalCount Field Length=8 |
|---------------------------------|----------------------|
|tunnelEcnEctNectPacketTotalCount Field Length=8 |
|---------------------------------|----------------------|
|tunnelEcnEctEctPacketTotalCount Field Length=8 |
|---------------------------------|----------------------|
Figure 4: Template Record Sent From Ingress to Egress
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+-------+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-------+
| | |M| |P| |P| |P| |M| |P| |P| | |
| | +-+ +-+ +-+ +-+ +-+ +-+ +-+ | |
| |<---------------------------------------| |
| | | |
| | | |
|egress | +-+ +-+ |ingress|
| | |M| |M| | |
| | +-+ +-+ | |
| |--------------------------------------->| |
| | | |
| | | |
+-------+ +-------+
+-+
|M| : Message Packet
+-+
+-+
|P| : User Packet
+-+
Figure 5 Traffic flow Between Ingress and Egress
Set ID=257, Length=28
+------+ A1 +------+
| | B1 | |
| | C1 | |
| | <----------------------------- | |
| | | |
| | | |
| | SetID=256, Length=68 | |
| | A1 | |
| | B1 | |
|egress| C1 ingress|
| | A2 | |
| | B2 | |
| | C2 | |
| | D | |
| | E | |
| | ----------------------------> | |
| | | |
+------+ +------+
Figure 6: Message Between Ingress and Egress
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The following provides an example of how tunnel congestion level
could be calculated:
Congestion Level could be divided into two categories:(1)slight
congestion(no packets dropped); (2)serious congestion (packet
dropping happen).
For slight congestion, the congestion level is indicated as the
number of CE-marked packet:
ce_marked = (A2 + D + E) - A1;
For serious congestion, the congestion level is indicated as the
number of lost packets:
total_ingress = (A1 + B1 + C1)
total_egress = (A2 + B2 + C2 + D + E)
packet_loss = (total_ingress - total_egress)
7. Security Considerations
This document describes the tunnel congestion calculation and
feedback.
The tunnel endpoints are assumed to be deployed in the same
administrative domain, so the ingress and egress will trust each
other, the signaling traffic between ingress and egress will be
protected utilizing security mechanism provided IPFIX (see section 11
in RFC7011).
From the consideration of privacy point of view, in case of fine
grained congestion management, ingress is aware of the amount of
traffic for specific application flows inside the tunnel which seems
to be an invasion of privacy. But in any way, the ingress could The
solution doesn't introduce more privacy problem.
8. IANA Considerations
This document defines a set of new IPFIX Information Elements
(IE),which need to be registered at IANA IPFIX Information Element
Registry.
ElementID: TBD1
Name:tunnelEcnCeCePacketTotalCount
Data Type: unsigned64
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Data Type Semantics: totalCounter
Status: current
Description:The total number of incoming packets with CE|CE ECN
marking combination for this Flow at the Observation Point since the
Metering Process (re-)initialization for this Observation Point.
Units: packets
ElementID: TBD2
Name:tunnelEcnEct0NectPacketTotalCount
Data Type: unsigned64
Data Type Semantics: totalCounter
Status: current
Description:The total number of incoming packets with ECT(0)|N-ECT
ECN marking combination for this Flow at the Observation Point since
the Metering Process (re-)initialization for this Observation Point.
Units: packets
ElementID: TBD3
Name: tunnelEcnEct1NectPacketTotalCount
Data Type: unsigned64
Data Type Semantics: totalCounter
Status: current
Description:The total number of incoming packets with ECT(1)|N-ECT
ECN marking combination for this Flow at the Observation Point since
the Metering Process (re-)initialization for this Observation Point.
Units: packets
ElementID: TBD4
Name:tunnelEcnCeNectPacketTotalCount
Data Type: unsigned64
Data Type Semantics: totalCounter
Status: current
Description:The total number of incoming packets with CE|N-ECT ECN
marking combination for this Flow at the Observation Point since the
Metering Process (re-)initialization for this Observation Point.
Units: packets
ElementID: TBD5
Name:tunnelEcnCeEct0PacketTotalCount
Data Type: unsigned64
Data Type Semantics: totalCounter
Status: current
Description:The total number of incoming packets with CE|ECT(0) ECN
marking combination for this Flow at the Observation Point since the
Metering Process (re-)initialization for this Observation Point.
Units: packets
ElementID: TBD6
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Name:tunnelEcnCeEct1PacketTotalCount
Data Type: unsigned64
Data Type Semantics: totalCounter
Status: current
Description:The total number of incoming packets with CE|ECT(1) ECN
marking combination for this Flow at the Observation Point since the
Metering Process (re-)initialization for this Observation Point.
Units: packets
ElementID: TBD7
Name:tunnelEcnEct0Ect0PacketTotalCount
Data Type: unsigned64
Data Type Semantics: totalCounter
Status: current
Description:The total number of incoming packets with ECT(0)|ECT(0)
ECN marking combination for this Flow at the Observation Point since
the Metering Process (re-)initialization for this Observation Point.
Units: packets
ElementID: TBD8
Name:tunnelEcnEct1Ect1PacketTotalCount
Data Type: unsigned64
Data Type Semantics: totalCounter
Status: current
Description:The total number of incoming packets with
ECT(1)|ECT(1)ECN marking combination for this Flow at the Observation
Point since the Metering Process (re-)initialization for this
Observation Point.
Units: packets
[TO BE REMOVED: This registration should take place at the following
location: http://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-
information-elements]
9. References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, September 2001, <http://www.rfc-
editor.org/info/rfc3168>.
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[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003,
<http://www.rfc-editor.org/info/rfc3550>.
[RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP)
Partial Reliability Extension", RFC 3758, May 2004,
<http://www.rfc-editor.org/info/rfc3758>.
[RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram
Congestion Control Protocol (DCCP)", RFC 4340, March 2006,
<http://www.rfc-editor.org/info/rfc4340>.
[RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, September 2007, <http://www.rfc-
editor.org/info/rfc4960>.
[RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion
Notification", RFC 6040, November 2010, <http://www.rfc-
editor.org/info/rfc6040>.
[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
"Specification of the IP Flow Information Export (IPFIX)
Protocol for the Exchange of Flow Information", STD 77,
RFC 7011, September 2013, <http://www.rfc-
editor.org/info/rfc7011>.
[RFC7013] Trammell, B. and B. Claise, "Guidelines for Authors and
Reviewers of IP Flow Information Export (IPFIX)
Information Elements", BCP 184, RFC 7013, September 2013,
<http://www.rfc-editor.org/info/rfc7013>.
[CONEX] Matt Mathis, Bob Briscoe. "Congestion Exposure (ConEx)
Concepts, Abstract Mechanism and Requirements", RFC7713,
December 2015
9.2 Informative References
[CB] G. Fairhurst. "Network Transport Circuit Breakers", draft-ietf-
tsvwg-circuit-breaker-01, April 02, 2015
10. Acknowledgements
Thanks Bob Briscoe for his insightful suggestions on the basic
mechanisms of congestion information collection and many other useful
comments. Thanks David Black for his useful technical suggestions.
Wei Expires July 29, 2017 [Page 17]
INTERNET DRAFT Tunnel Congestion Feedback January 25, 2017
Also, thanks Anthony Chan, Jake Holland, John Kaippallimalil and
Vincent Roca for their careful reviews.
Authors' Addresses
Xinpeng Wei
Beiqing Rd. Z-park No.156, Haidian District,
Beijing, 100095, P. R. China
E-mail: weixinpeng@huawei.com
Zhu Lei
Beiqing Rd. Z-park No.156, Haidian District,
Beijing, 100095, P. R. China
E-mail:lei.zhu@huawei.com
Lingli Deng
Beijing, 100095, P. R. China
E-mail: denglingli@gmail.com
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