BANANA N. Leymann
INTERNET-DRAFT C. Heidemann
Intended Category: Standards Track Deutsche Telekom AG
J. Shen
China Telecom Co., Ltd
L. Geng
China Mobile
L. Chen
M. Zhang
X. Geng
Huawei
Expires: September 20, 2018 March 19, 2018
BANdwidth Aggregation for interNet Access (BANANA)
ECN Operations for Bonding Tunnels
draft-leymann-banana-ecn-01
Abstract
This document specifies a Bonding Tunnel ECN Mechanism that uses
Explicit Congestion Notification (ECN) in bonding tunnels to notify
congestion of a tunnel so that the load-balancing strategy of the
tunnel ingress can be adjusted accordingly. Attributes for the
control protocol of BANANA are defined to support this mechanism.
Status of this Memo
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Copyright and License Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. ECN Features of IP-in-IP Bonding Tunnels . . . . . . . . . . . 3
2.1. ECN Features . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. ECN Features of IP-in-IP Tunnels . . . . . . . . . . . . . 4
2.3. Bonding Tunnel ECN Mechanism . . . . . . . . . . . . . . . 5
3. ECN Capability in Bonding Tunnels . . . . . . . . . . . . . . . 6
4. Congestion Notification in Bonding Tunnels . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
Conventionally, ECN allows end-to-end notification of network
congestion without dropping packets [RFC3168], and the sender reduces
its transmission rate when it receives the congestion indication. ECN
may be used between two ECN-enabled endpoints when the underlying
network infrastructure also supports it. [RFC6040] redefines how the
ECN field of the IP header should be constructed on entry to and exit
from any IP-in-IP tunnel.
This document, however, focuses on load-balancing adjustment between
bonding tunnels rather than end-to-end transmission rate adjustment.
When establishing the bonding tunnels, the local BANANA box and the
remote BANANA box negotiate whether the Bonding Tunnel ECN Mechanism
is supported. When this is successfully negotiated, an ECN-aware
router may set a mark on the ECN field of the outer IP header of any
packets in the tunnel. As soon as the bonding tunnel egress (one of
the BANANA boxes) receives the packet with that mark, it will send an
Congestion Notification to the bonding tunnel ingress (the other
BANANA box) to inform congestion so that the ingress can change the
load-balancing strategy accordingly.
ECN Capability and Congestion Notification are two attributes for the
control protocol of BANANA defined to support the Bonding Tunnel ECN
Mechanism.
1.1. Terminology
AQM: Active Queue Management
CE: Congestion Experienced
ECN: Explicit Congestion Notification
ECT: ECN-Capable Transport
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].
2. ECN Features of IP-in-IP Bonding Tunnels
2.1. ECN Features
The ECN field in the IP header has two bits, making four ECN
codepoints, '00' to '11', as shown in Figure 1. The not-ECT (ECN-
Capable Transport) codepoint '00' indicates a packet that is not
using ECN. The ECT codepoints '10' and '01' are set by the data
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sender to indicate that the end-points of the transport protocol are
ECN-capable. Senders are free to use either the ECT(0) or ECT(1) and
routers treat ECT(0) and ECT(1) as equivalent. AQM allows routers to
use the CE (Congestion Experienced) codepoint '11' in a packet header
as an indication of congestion, instead of relying solely on packet
drops. [RFC 3168]
+----+----+
|ECN FIELD|
+----+----+
0 0 Not-ECT
0 1 ECT(1)
1 0 ECT(0)
1 1 CE
Figure 1 The ECN Field in IP
2.2. ECN Features of IP-in-IP Tunnels
While the outer header of an IP packet can encapsulate one or more IP
headers for IP-in-IP tunneling, routers using ECN to signify
congestion only mark the immediately visible outer IP header. When
the tunnel decapsulator later removes this outer header, it follows
rules to propagate congestion markings by combining the ECN fields of
the inner and outer IP header into one outgoing IP header. [RFC 6040]
Figure 2 shows an example about how ECN works in the IP-in-IP tunnel
scenario.
Sender reduces rate Receiver reports the CE packet
+-------------------- <------------------------------+
| Outer IP +-+-+ +-+-+ +-+-+ |
| ECN field |1 0| |1 0| |1 1| |
| +-+-+ +-+-+ +-+-+ |
v +-------+ +------+ |
+------+ |Tunnel | +------+ +------+ |Tunnel| +--------+
|Sender|->-|Ingress|->-|Router|->-|Router|->-|Egress|->-|Receiver|
+------+ +-------+ +------+ +------+ +------+ +--------+
+-+-+ +-+-+ +-+-+ ^ +-+-+ +-+-+
ECN |1 0| |1 0| |1 0| | |1 0| |1 1|
field +-+-+ +-+-+ +-+-+ | +-+-+ +-+-+
|
congestion
Figure 2 An IP-in-IP Tunnel ECN example
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2.3. Bonding Tunnel ECN Mechanism
In the IP-in-IP bonding tunnel scenario, the tunnel ingress has an
additional load balancing function compared to the single tunnel
scenario. Thus, ECN can be used to notify congestion within the
bonding tunnels. As Figure 3 shows, the tunnel egress receives a
packet with the CE codepoint from Tunnel 2. Then, the tunnel egress
reports this situation to the tunnel ingress by sending an Congestion
Notification through Tunnel 2 so that the tunnel ingress can change
its load balancing strategy, e.g., temporarily reducing the load-
balance proportion for Tunnel 2. As the tunnel ingress may receive
more than one Congestion Notification during a certain time period,
the load-balance strategy of the next time period can be made based
on the number of received Congestion Notifications.
Outer IP +-+-+ +-+-+ +-+-+
ECN field |1 0| |1 0| |1 0|
+-+-+ +-+-+ +-+-+
+------+ +------+
+-->--|Router|-->--|Router|-->--+ Tunnel 1
| +------+ +------+ |
+-------+ +------+
+------+ |Tunnel | |Tunnel| +--------+
|Sender|->-|Ingress| --<-- Congestion --<-- |Egress|->-|Receiver|
+------+ +-------+ Notification +------+ +--------+
| +------+ +------+ |
+-->--|Router|-->--|Router|-->--+ Tunnel 2
+------+ +------+
Outer IP +-+-+ +-+-+ ^ +-+-+
ECN field |1 0| |1 0| | |1 1|
+-+-+ +-+-+ | +-+-+
|
congestion
Figure 3 An IP-in-IP Bonding Tunnel ECN example
At the tunnel ingress, the ECN field of the incoming packets will be
copied to the inner IP headers. The outer IP headers will be set to
the ECT or not-ECT codepoint, according to whether the bonding tunnel
supports the Bonding Tunnel ECN Mechanism or not.
At the tunnel egress, if the outer IP headers from Tunnel 1 and
Tunnel 2 are both CE and the inner IP headers are ECT, the ECN field
of the outgoing packet will be set to CE. Otherwise the ECN field of
the outgoing packet will be copied from the inner IP headers.
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3. ECN Capability in Bonding Tunnels
The local BANANA box (could be either the tunnel ingress or the
tunnel egress) uses the ECN Capability to notify the remote BANANA
box (could be either the tunnel egress or the tunnel ingress) that
the local BANANA box supports the Bonding Tunnel ECN Mechanism. The
first GRE Tunnel Setup Request message [RFC8157] MAY include the ECN
Capability attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type
ECN Capability, set to 36.
Attribute Length
Set to 0
If the remote BANANA box receives the GRE Tunnel Setup Request
message with the ECN Capability attribute included, the remote BANANA
box could use the ECN Capability to inform the local BANANA box that
the remote BANANA box supports the Bonding Tunnel ECN Mechanism as
well. The first GRE Tunnel Setup Accept message MAY include the ECN
Capability attribute.
The remote BANANA box activates the Bonding Tunnel ECN Mechanism when
it sends out the ECN Capability attribute. The local BANANA box
activates the Bonding Tunnel ECN Mechanism when it receives the ECN
Capability attribute from the remote BANANA box.
4. Congestion Notification in Bonding Tunnels
The tunnel egress (could be either the local BANANA box or the remote
BANANA box) uses the Congestion Notification to notify congestion on
Tunnel 1 or Tunnel 2 to the tunnel ingress. GRE Tunnel Notify
messages sent over both Tunnel 1 and Tunnel 2 MAY include the
Congestion Notification attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Attribute Type
Congestion Notification, set to 37.
Attribute Length
Set to 0.
5. Security Considerations
<TBD>
6. IANA Considerations
No IANA action is required in this document. RFC Editor: please
remove this section before publication.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI
10.17487/RFC2119, March 1997, <http://www.rfc-
editor.org/info/rfc2119>.
[RFC3168] Ramakrishnan, K., "The Addition of Explicit Congestion
Notification (ECN) to IP", RFC3168, DOI 10.17487/RFC3168,
September 2001, <http://www.rfc-editor.org/info/rfc3168>.
[RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion
Notification", RFC6040, DOI 10.17487/RFC6040, November
2010, <http://www.rfc-editor.org/info/rfc3168>.
[RFC8157] Leymann, N., "Huawei's GRE Tunnel Bonding Protocol",
RFC8157, DOI 10.17487/RFC8157, May 2017, <http://www.rfc-
editor.org/info/rfc8157>.
7.2. Informative References
[RFC2784] Farinacci, D., "Generic Routing Encapsulation (GRE)",
RFC2784, DOI 10.17487/RFC2784, March 2000,
<http://www.rfc-editor.org/info/rfc2784>.
[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC2890, DOI 10.17487/RFC2890, September 2000,
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INTERNET DRAFT ECN Operations for Bonding Tunnels March 19, 2018
<http://www.rfc-editor.org/info/rfc2890>.
[TSVWG-ECN]
Briscoe, B., "Layered Encapsulation of Congestion
Notification", draft-briscoe-tsvwg-ecn-tunnel-01,
<https://tools.ietf.org/pdf/draft-briscoe-tsvwg-ecn-
tunnel-01.pdf>.
[TSVWG-TCF]
Wei, X., "Tunnel Congestion Feedback",
draft-ietf-tsvwg-tunnel-congestion-feedback-05,
<https://www.ietf.org/id/draft-ietf-tsvwg-tunnel
-congestion-feedback-05.txt>.
[BANANA-signaling]
Leymann, N., Heidemann, C., et al, "BANdwidth Aggregation
for interNet Access (BANANA) The Control Protocol of
Bonding Tunnels", draft-leymann-banana-signaling, work in
progress.
[BANANA-attributes]
Leymann, N., Heidemann, C., et al, "BANdwidth Aggregation
for interNet Access (BANANA) Attributes for the Control
Protocol of Bonding Tunnels", draft-leymann-banana-
signaling-attributes, work in progress.
Authors' Addresses
Nicolai Leymann
Deutsche Telekom AG
Winterfeldtstrasse 21-27
Berlin 10781
Germany
Phone: +49-170-2275345
EMail: n.leymann@telekom.de
Cornelius Heidemann
Deutsche Telekom AG
Heinrich-Hertz-Strasse 3-7
Darmstadt 64295
Germany
Phone: +4961515812721
EMail:heidemannc@telekom.de
Jun Shen
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China Telecom Co., Ltd
109 West Zhongshan Ave, Tianhe District
Guangzhou 510630
P.R. China
EMail: shenjun@gsta.com
Liang Geng
China Mobile
32 Xuanwumen West Street,
Xicheng District, Beijing, 100053,
P.R. China
EMail: gengliang@chinamobile.com
Lihao Chen
Huawei Technologies
No.156 Beiqing Rd. Haidian District,
Beijing 100095
P.R. China
EMail: lihao.chen@huawei.com
Mingui Zhang
Huawei Technologies
No.156 Beiqing Rd. Haidian District,
Beijing 100095
P.R. China
EMail: zhangmingui@huawei.com
Xuesong Geng
Huawei Technologies
No.156 Beiqing Rd. Haidian District,
Beijing 100095
P.R. China
EMail: gengxuesong@huawei.com
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