BANdwidth Aggregation for interNet Access (BANANA) ECN Operations for Bonding Tunnels
draft-leymann-banana-ecn-00

Versions: 00                                                            
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: March 16, 2018                               September 12, 2017


           BANdwidth Aggregation for interNet Access (BANANA)
                   ECN Operations for Bonding Tunnels
                      draft-leymann-banana-ecn-00

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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              <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>.

   [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
   China Telecom Co., Ltd
   109 West Zhongshan Ave, Tianhe District
   Guangzhou 510630
   P.R. China

   EMail: shenjun@gsta.com



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   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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