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Versions: 00 01 02 03                                                   
Network Working Group                                             L. Xue
Internet-Draft                                                    D. Guo
Intended status: Standards Track                                  Huawei
Expires: January 5, 2015                                    July 4, 2014


                      Dynamic Stateless GRE Tunnel
                      draft-xue-dhc-dynamic-gre-02

Abstract

   Generic Routing Encapsulation (GRE) is regarded as a popular
   encapsulation tunnel technology because of simpleness and easy
   implementation.  When a node tries to encapsulate the user traffic in
   a GRE tunnel, it needs to first obtain the IP address of the
   destination node which need to decapsulate the GRE packets.  In
   practice, the GRE tunnel destination IP address may be manually
   configured.  This configuration introduces efficiency issues for
   operators, especially, in the scenarios where there are a large
   number entities need to deploy GRE tunnels.  This work proposes an
   approach to configure the GRE information dynamiclly.

Requirements Language

   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 [RFC2119]

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 January 5, 2015.







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Copyright Notice

   Copyright (c) 2014 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
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Use Case  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Dynamic GRE Tunnel  . . . . . . . . . . . . . . . . . . . . .   4
   5.  DHCP Option Definition  . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Generic Routing Encapsulation (GRE) [RFC1701][RFC2784] is widely
   deployed in the operators' networks.  When a node tries to
   encapuslate the user traffic in a GRE tunnel, it needs to first
   obtain the IP address of the destination node which can decapsulate
   the GRE packets.

   In practice, the decapsulation node IP address of GRE may be manually
   configured.  This configuration introduces efficiency issues for
   operators, espeically, in the scenarios where there are large amount
   of GRE tunnels needed.  This work describes a case about large amount
   of GRE tunnels deployment required and proposes a solution which
   extends Dynamic Host Configuration Protocol (DHCP) so as to enable to
   configure the GRE destination node IP address dynamically.








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2.  Terminology

   The following terminologies are used in this document.

   Access Controller (AC)

   The network entity that provides Wireless Termination Point (WTP)
   access to the network infrastructure in the data plane, control
   plane, management plane, or a combination therein.

   Customer Premises Equipment (CPE)

   The CPE equipment is the box that a provider may distribute to the
   customers, which could be Home Gateway (HG), Cable Modem (CM), etc.
   When CPE is using DHCP to obtain network address, CPE is acting as
   "DHCP Client"

   Network Facing Equipment (NPE)

   The NPE is the device to be deployed with the signalling and control
   functions.  It is kind of Service Gateway.

   User Equipment (UE)

   The UE is the a device of the customers, which could be PC or Mobile
   Phone.

   User Facing Equipment (UPE)

   The UPE is the device to make forwarding decisions at the ingress of
   the provider network, which could be Cable Modem Termination Systems
   (CMTS).  UPE is the "DHCP Server" or "DHCP relay agent" in DHCP
   framework.

   Wireless Termination Point (WTP)

   The physical or logical network entity that contains an RF antenna
   and wireless physical layer (PHY) to transmit and receive station
   traffic for wireless access networks.

3.  Use Case

   Wireless Local Area Network (WLAN) has emerged as an important access
   technology for service operators.  Some operators deploy a large
   number of WTPs in the specific environments with the dense crowd.  In
   this scenario, WTPs are preferred to be managed and controlled in a
   centralized location by AC.  The traffic of WTPs are generally
   handled on the access router of the network, which is a different



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   node from AC.  This architecture can avoid the overload for traffic
   management on the AC.  This motivates the need for the WTP to support
   some tunnel encapsulation technologies to the Access Router.  GRE is
   one of the preferred tunnel solution, because of simple and easy
   deployment reasons.

   Currently, several tunnel mechanisms have been standardized, for
   example Layer Two Tunneling Protocol version 3 (L2TPv3) [RFC3931].
   L2TPv3 supports IP/UDP encapsulation and fulfills the tunnel
   requirements.  However, as a multi-layers encapsulation protocol,
   L2TPv3 has to carry multiple protocol headers per data packet.  It is
   complicated and costly, mostly used for Virtual Private Network
   (VPN).  Most CPE devices are too simple to be a L2TPv3 initiator.

   An illustration of WLAN network is shown in figure 1.  When WTP tries
   to encapsulate the user traffic in a GRE tunnel, it needs to first
   obtain the Access Router (AR) IP address.  In practice, this IP
   address is usually deployed on WTP manually, which introduces
   efficiency issues for operators.  Especially, a large number of WTPs
   are deployed with the dense crowd.

                 CAPWAP   +--------+
                ++========+   AC   |
               //         +--------+
              //
      +-----+//   DATA Tunnel (GRE)     +--------------+
      | WTP |===========================| Access Router|
      +-----+                           +--------------+

                        Figure 1: WLAN Illustration

4.  Dynamic GRE Tunnel

   This work proposes an automatic solution which extends Dynamic Host
   Configuration Protocol (DHCP) so as to configure the GRE destination
   IP address.  Due to successful IP address configuration, GRE tunnel
   can be setup dynamically.

   Figure 2 illustrates the procedure for dynamic GRE tunnel in WLAN
   network.  The WTP, AR in the picture are respectively the CPE and
   NPE.










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     /    \      IPv4-x.x.x.x                   IPv4-y.y.y.y     /    \
   /      \      +-------+       +-------+      +-------+      /      \
   |       |     |       |       |       |      |       |      |       |
   |  UE   +-----+  CPE  +-------+  DHCP +------+  NPE  +------+Internet
   \       /     |       |       |       |      |       |      \       /
    \     /      +-------+       +-------+      +-------+       \     /
                 DHCP Client     DHCP Server
      |              |               |               |
      |              |DHCPv4 Request |               |
      |  Preliminary + ------------->                |
      |    Phase     |               |               |
      | (Discovery)  | DHCPv4 Reply  |               |
      |              + <-------------|               |
      |              | with y.y.y.y  |               |
                     |
      |              |                               |
      |              *-------------------------------*
      |--------------+----User Packet-in-GRE-Encap.->|
      | Establishment*----with  x.x.x.x -------------*
      |    Phase     |                       /               \
      |              |                       | Tunnel Client |
      |              |                       \ List Config.  /
      |              |                               |
      |   Keepalive  *-------------------------------*
      |     Phase    |<-------Keepalive Packet------>|
      |              *-------------------------------*


               Figure 2: Dynamic GRE Tunnel in WLAN Network

   At Preliminary Phase, the CPE as one endpoint of GRE tunnel, may get
   information of NPE by the DHCP approach.  CPE sends the DHCP request
   to initiate a IPv4 address request.  When a DHCP server replies the
   CPE request message, the NPE information can be carried in a DHCP
   reply message via DHCP options.  Thus CPE configures the NPE address
   y.y.y.y and tunnel parameter of GRE tunnel, such as GRE key etc if
   they are carried in the DHCP message.  For load sharing or single-
   point failure recovery purposes, a DHCP reply message may carry
   information of more than one NPEs.

   Consequently, NPE can discover CPE via the received GRE encapsulated
   packet from CPE.  Then the GRE tunnel information, such as IP address
   of CPE as source address is checked and restored as destination of
   GRE tunnel on NPE side.  Generally, CPE can encapsulate UE's first
   packet with GRE, no matter data packet or control packet.  For
   example, during a User Equipment (UE) subscriber attached initiates
   the DHCP procedure for an inner address, CPE should encapsulated this
   DHCP message via GRE.



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   When NPE receives the packet with GRE encapsulation, it should look
   up the outer source IP of the packet in its tunnel client list.  If
   it is a new client, the NPE adds source IP into the tunnel client
   list, decapsulates GRE header and deals with the packet encapsulated
   by GRE.

   There could be a keepalive mechanism for GRE tunnel between CPE and
   NPE.  If there is neither keepalive packet nor data packet when the
   deployed timer expires, the NPE will tear down the tunnel and
   releases resource

5.  DHCP Option Definition

   As introduced above, The DHCPv4 GRE Discovery (GD) Option is defined,
   when CPE wants to obtain an NPE address in IPv4 network.  This Option
   is carried in DHCPv4.

   The DHCPv4 GD Option is structured as follows:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    Code       |      Len      | Ver |Reserved |Protocol Type  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    cont.      |     NPE address                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    cont.      |
    +---------------+


                        DHCPv4 GRE Discovery Option

   Code: TBD1

   Len: The length of value field.  If there are several instance for
   multiple NPE address considering redundancy, the length should be
   Len1 + Len2 + ... + Len n +Len of sub option in octets.

   Ver: The Version Number field which is contained in GRE header,
   defined in [RFC2784].

   Reserved: This field is reserved for future use.  A receiver MUST
   discard a packet where this field is non-zero.  These bits MUST be
   sent as zero and MUST be ignored on receipt.

   Protocol Type: The Protocol Type field contains the protocol type of
   the payload packet.  This field is defined in [RFC2784].




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   NPE Address: IPv4 address of NPE, the endpoint of GRE tunnel.

   Sub-Option (Optional): DHCPv4 GRE Key Suboption is structured in TLV
   style shown as follows.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Type = 1     | Len = 4       |       GRE Key                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     GRE Key (cont.)           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         DHCPv4 GRE Key Suboption

   Based on requirement defined in [RFC2784] [RFC2890], GRE Key
   Suboption is used in this document to configure the complementary
   tunnel information.  GRE Key is generated from [RFC2890].  If the
   client receives the GRE Key suboption, the key MUST be inserted into
   the GRE encapsulation header.  It is used for identifying extra
   context information about the received payload.  The payload packets
   without the correspondent GRE Key or with an unmatched GRE Key will
   be silently dropped.

   Code 1 for GRE Key Suboption.

   Len (1 octet): The total octets of the suboption value field.

   Suboption Value : GRE Key according definition in [RFC2890].

   The DHCPv6 GRE Discovery (GD) Option is mainly used when CPE wants to
   obtain an NPE address in IPv6 network.  This option is carried in
   DHCPv6.  According to [I-D.ietf-dhc-option-guidelines]The DHCPv6 GD
   Option is structured as follows.

















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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         Code                  |        Len                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Ver |Reserved |       Protocol Type           |  NPE IPv6 Add |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                NPE IPv6 Address (cont.)                       .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    cont.      |
    +-+-+-+-+-+-+-+-+


                        DHCPv6 GRE Discovery Option

   Code: TBD2

   Len: The length of the option value.

   Ver: The Version Number field which is contained in GRE header,
   defined in [RFC2784].

   Reserved: This field is reserved for future use.  A receiver MUST
   discard a packet where this field is non-zero.  These bits MUST be
   sent as zero and MUST be ignored on receipt.

   Protocol Type: The Protocol Type field contains the protocol type of
   the payload packet.  This field is defined in [RFC2784].

   NPE Address: IPv6 address of NPE, the endpoint of GRE tunnel.

   Based on requirement defined in [RFC2784] [RFC2890], DHCPv6 GRE Key
   Option is used in this document to configure the complementary tunnel
   information.  Optionally, the DHCPv6 GRE Key Option is encapsulated
   in DHCPv6 GRE Discovery Option.  It is structured in TLV style shown
   as follows.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Code                |       Len = 4                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           GRE Key                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           DHCPv6 GRE Key Option

   Code 1 for DHCPv6 GRE Key Option: TBD3



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   Len (1 octet): The total octets of the option value field.

   Option Value : GRE Key according definition in [RFC2890].

6.  IANA Considerations

   TBD

7.  References

7.1.  Normative References

   [RFC1701]  Hanks, S., Li, T., Farinacci, D., and P. Traina, "Generic
              Routing Encapsulation (GRE)", RFC 1701, October 1994.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol", RFC
              2131, March 1997.

   [RFC2784]  Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
              Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
              March 2000.

   [RFC2890]  Dommety, G., "Key and Sequence Number Extensions to GRE",
              RFC 2890, September 2000.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3931]  Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
              Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.

7.2.  Informative References

   [I-D.ietf-dhc-option-guidelines]
              Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
              S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
              draft-ietf-dhc-option-guidelines-17 (work in progress),
              January 2014.

Authors' Addresses







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Li Xue
Huawei
No.156 Beiqing Rd. Z-park, Shi-Chuang-Ke-Ji-Shi-Fan-Yuan,HaiDian District
Beijing  100095
China

Email: xueli@huawei.com


Dayong Guo
Huawei
No.156 Beiqing Rd. Z-park, Shi-Chuang-Ke-Ji-Shi-Fan-Yuan,HaiDian District
Beijing  100095
China

Email: guoseu@huawei.com



































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