Dynamic GRE Tunnel
draft-jiang-intarea-dynamic-gre-00
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| Authors | Sheng Jiang , Dayong Guo , Li Xue | ||
| Last updated | 2015-05-26 | ||
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draft-jiang-intarea-dynamic-gre-00
Network Working Group S. Jiang, Ed.
Internet-Draft D. Guo
Intended status: Standards Track Huawei Technologies Co., Ltd
Expires: November 27, 2015 L. Xue
May 26, 2015
Dynamic GRE Tunnel
draft-jiang-intarea-dynamic-gre-00
Abstract
Generic Routing Encapsulation (GRE) is regarded as a popular
encapsulation tunnel technology. When a node tries to encapsulate
the user traffic in GRE, it needs the IP address of the destination
node which decapsulates the GRE packets. In practice, the GRE tunnel
destination IP addresses are mainly configured manually. This
configuration mechanism causes efficiency issues for operators. This
document proposes an approach to configure the GRE information
dynamically.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on November 27, 2015.
Copyright Notice
Copyright (c) 2015 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
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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to this document. Code Components extracted from this document must
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. Requirements Language and Terminology . . . . . . . . . . . . 3
3. GRE Use Case - WLAN Network . . . . . . . . . . . . . . . . . 3
4. Dynamic GRE Tunnel Overview . . . . . . . . . . . . . . . . . 4
5. DHCP Options Definition . . . . . . . . . . . . . . . . . . . 6
5.1. DHCPv4 GRE Discovery Option . . . . . . . . . . . . . . . 6
5.2. DHCPv4 GRE Information Option . . . . . . . . . . . . . . 6
5.3. DHCPv6 GRE Discovery Option . . . . . . . . . . . . . . . 7
5.4. DHCPv6 GRE Information Option . . . . . . . . . . . . . . 8
6. DHCP/DHCPv6 server and client behaviors . . . . . . . . . . . 8
6.1. DHCP Server Behavior . . . . . . . . . . . . . . . . . . 8
6.2. DHCP Client Behavior . . . . . . . . . . . . . . . . . . 9
6.3. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . 9
6.4. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Generic Routing Encapsulation (GRE, [RFC1701], [RFC2784]) is widely
deployed in the operators' networks. When a node tries to
encapsulate the user traffic in a GRE tunnel, it needs the IP address
of the destination node which decapsulates the GRE packets.
In practice, the GRE tunnel destination IP addresses are mainly
configured manually on the nodes. This configuration mechanism
causes efficiency issues for operators. As an example, when GRE
tunneling is used in the access network, there may a large amount of
configuration needed at the access side. Also, the configuration is
rigid. It may cause more issues in renumbering scenarios.
This document introduces a use case requiring the deployment of a
large amount of GRE tunnels, which motivates a dynamic approach.
This document proposes a solution to enable the dynamic discovery of
the GRE decapsulation device using Dynamic Host Configuration
Protocol (DHCP).
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2. Requirements Language and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119] when they appear in ALL CAPS. When these words are not in
ALL CAPS (such as "should" or "Should"), they have their usual
English meanings, and are not to be interpreted as [RFC2119] key
words.
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 box that a provider may
distribute to the customers. When CPE is using DHCP to obtain
network address, CPE is acting as "DHCP Client".
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. GRE Use Case - WLAN Network
Wireless Local Area Network (WLAN) has emerged as an important access
technology for service operators. A typical WLAN network contains a
large number of WTPs, centrally managed and controlled by the Access
Controller (AC). It is desirable to distribute customer data frames
to an endpoint through an Access Router (AR) different from the AC.
GRE encapsulation can be used between a WTP and an AR as one of the
optional tunneling technologies shown in
[I-D.ietf-opsawg-capwap-alt-tunnel]
An illustration of a WLAN network is shown in Figure 1. In order for
a WTP to encapsulate the user traffic in a GRE tunnel, it needs to
know the Access Router (AR) IP address. This IP address is usually
configured on WTPs manually. An AC may dynamically configure the WTP
with the AR address via extended CAPWAP message elements (see
[I-D.ietf-opsawg-capwap-alt-tunnel]).
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CAPWAP +--------+
++========+ AC |
// +--------+
//
+-----+// DATA Tunnel (GRE) +--------------+
| WTP |===========================| Access Router|
+-----+ +--------------+
Figure 1: GRE Use Case - WLAN Network 1
However, this approach does not apply to a WLAN network where the
CAPWAP protocol is not deployed, as the network shown in Figure 2.
In fact, it is quite common for operators to have their own private
control plane between the WTP and the AC rather than CAPWAP.
Private Control +--------+
++========+ AC |
// +--------+
//
+-----+// DATA Tunnel (GRE) +--------------+
| WTP |===========================| Access Router|
+-----+ +--------------+
Figure 2: GRE Use Case - WLAN Network 2
Moreover, there are also WLAN deployments without AC, as in the fat
WTPs scenario (see Figure 3). A general approach to resolve this
problem is desirable.
+-----+ DATA Tunnel (GRE) +--------------+
| WTP |===========================| Access Router|
+-----+ +--------------+
Figure 3: GRE Use Case - WLAN Network 3
4. Dynamic GRE Tunnel Overview
The DHCP options defined in Section 5 enable an automated way to
inform the GRE encapsulator with the GRE destination IP address.
Additionally, some other GRE tunnel information may be provided. In
this way, a GRE tunnel can be setup dynamically.
Figure 4 illustrates the procedure to set up a dynamic GRE tunnel in
the network (only in IPv4 netweork scenario).
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/ \ IPv4-x.x.x.x IPv4-y.y.y.y / \
/ \ +-------+ +-------+ +-------+ / \
| | | | | | | | | |
| Host +------+ CPE +-------+ DHCP +------+ AR +------+Internet
\ / | | | Server| | | \ /
\ / +-------+ +-------+ +-------+ \ /
DHCP Client DHCP Server
| | | |
| | DHCPREQUEST | |
| (1) + ------------->| |
| | | |
| | DHCPACK | |
| + <-------------| |
| | with y.y.y.y and |
|information (optional) |
| | |
| *-------------------------------*
|<-User Packet->+<---User Packet-in-GRE-Encap.->|
| (2) *----with x.x.x.x -------------*
| | / \
| | | Tunnel Client |
| | \ List Config. /
| | |
| *-------------------------------*
| (3) |<-------Keepalive Packet------>|
| *-------------------------------*
Figure 4: Dynamic GRE Tunnel
The steps to set up a GRE tunnel between the CPE and the AR are as
follows:
1. The CPE, as one endpoint of GRE tunnel, sends the DHCPREQUEST
message to the DHCP server to acquire the AR access. The GRE
DHCP Option should be included in Parameter List Option, as
defined in Section 6.2. When the DHCP server receives this
request, it replies to the CPE the DHCPACK message, containing
the AR address and the tunnel information if needed.
2. The CPE can encapsulate the upstream packets from the hosts
within GRE tunnel packets. Generally, upstream packets are
either data packets or control packets. When the AR gets an
encapsulated GRE tunnel packet, the AR checks whether there is an
existing GRE tunnel with the CPE. If this is a new endpoint
without GRE record, the AR should add this CPE into the tunnel
client list. This would be mainly used for the correspondent
downstream packets.
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3. A keepalive mechanism may be required for a GRE tunnel between
the CPE and the AR. If there is neither keepalive packet nor
data packet, when a keepalive timer expires, the AR or the CPE
will tear down the tunnel and release resources.
5. DHCP Options Definition
This section defines the new DHCPv4 and DHCPv6 options that support
the Dynamic stateless GRE tunnel.
5.1. DHCPv4 GRE Discovery Option
The DHCPv4 GRE Discovery option provides to a GRE encapsulator a list
of one or more IPv4 addresses of a GRE decapsulator. According to
[RFC2131], the DHCPv4 GRE Discovery Option is structured as shown in
Figure 5.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code | Option Len | AR IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR IPv4 Address | AR IPv4 Address (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: DHCPv4 GRE Discovery Option
option-code OPTION_V4_GRE_DISCOVERY (TBA1).
option-len 4 + 4*n (in octets).
AR IPv4 Address AR IPv4 address, an endpoint of GRE tunnel. More than
one AR IPv4 addresses may be provided for redundancy
reasons. The default priority of the listed AR IPv4
addresses may be from highest to lowest.
5.2. DHCPv4 GRE Information Option
The DHCPv4 GRE Information option provides a list of the GRE
information as defined in and [RFC2784][RFC2890]. The GRE
information may include the key. According to [RFC2131], the DHCPv4
GRE Information Option is structured as shown in Figure 6.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code | Option Len | GRE Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key (cont.) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: DHCPv4 GRE Information Option
option-code OPTION_V4_GRE_INFO (TBA2).
option-len 6 (in octets).
GRE Key The Key field contains a four octet number which is
inserted by the GRE encapsulator according to [RFC2890].
Reserved This field is reserved for future use. These bits MUST
be sent as zero and MUST be ignored on receipt.
5.3. DHCPv6 GRE Discovery Option
The DHCPv6 GRE Discovery option provides to a GRE encapsulator a list
of one or more IPv6 addresses of a GRE decapsulator. According to
[RFC7227], the DHCPv6 GRE Discovery Option is structured as shown in
Figure 7.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code | Option Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address (Optional) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: DHCPv6 GRE Discovery Option
option-code OPTION_V6_GRE_DISCOVERY (TBA3).
option-len 16 + 16*n (in octets).
AR IPv4 Address AR IPv64 address(es), an endpoint of GRE tunnel.
More than one AR IPv6 addresses may be provided for
redundancy reasons. The default priority of the listed
AR IPv6 addresses may be from highest to lowest.
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5.4. DHCPv6 GRE Information Option
The DHCPv6 GRE Information option provides a list of the GRE
information as defined in and [RFC2784][RFC2890]. The GRE
information may include the key.
According to [RFC7227], the DHCPv6 GRE Information Option is
structured as shown in Figure 8.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code | Option Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: DHCPv6 GRE Information Option
option-code OPTION_V6_GRE_INFO (TBA4).
option-len 8 (in octets).
GRE Key The Key field contains a four octet number which is
inserted by the GRE encapsulator according to [RFC2890].
Reserved This field is reserved for future use. These bits MUST
be sent as zero and MUST be ignored on receipt.
6. DHCP/DHCPv6 server and client behaviors
This section defines the DHCP/DHCPv6 server and client behaviors
during the procedure of configure GRE options.
6.1. DHCP Server Behavior
Section 3.5 of [RFC2131] describes how a DHCP client and server
negotiate configuration values using the Parameter List (55) option
[RFC2132]. By default, a server will not reply with a GRE option if
the client has not explicitly enumerated one in its Parameter List
option.
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6.2. DHCP Client Behavior
A WTP/CPE acting as DHCP client will request DHCP GRE configuration
parameters from the DHCP server located in the IPv4 network. Such a
client MUST request the DHCP GRE option(s) that it is configured for
in Parameter List option in its DHCPDISCOVER, DHCPREQUEST, or
DHCPINFORM messages.
The client SHOULD use the received GRE destination address and
information to establish GRE tunnels.
6.3. DHCPv6 Server Behavior
Section 17.2.2 of [RFC3315] describes how a DHCPv6 client and server
negotiate configuration values using the Option Request (6)
Option[RFC3315]. By default, a server will not reply with a GRE
option if the client has not explicitly enumerated one in its ORO.
6.4. DHCPv6 Client Behavior
A WTP/CPE acting as DHCPv6 client will request DHCPv6 GRE
configuration parameters from the DHCPv6 server located in the IPv6
network. Such a client MUST request the GRE option(s) that it is
configured for in its ORO in SOLICIT, REQUEST, RENEW, REBIND or
INFORMATION-REQUEST messages.
The client SHOULD use the received GRE destination address and
information to establish GRE tunnels.
7. Security Considerations
Section 23 of [RFC3315] discusses DHCPv6-related security issues. As
with all DHCPv6-derived configuration state, it is possible that
configuration is actually being delivered by a third party (Man In
The Middle). As such, there is no basis on which access over the
stateless GRE tunnel can be trusted. Therefore, the stateless GRE
tunnel should not bypass any security mechanisms such as IP firewalls
or user authentication.
8. IANA Considerations
This document defines two new DHCPv4 [RFC2131] options. The IANA is
requested to assign values for these four options from the DHCPv4
Option Codes table of the DHCPv4 Parameters registry maintained in
http://www.iana.org/assignments/bootp-dhcp-parameters. The four
options are:
The GRE Discovery Option (TBA1), described in Section 5.1.
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The GRE Information Option (TBA2), described in Section 5.2.
This document defines three new DHCPv6 [RFC3315] options. The IANA
is requested to assign values for these three options from the DHCPv6
Option Codes table of the DHCPv6 Parameters registry maintained in
http://www.iana.org/assignments/dhcpv6-parameters. The three options
are:
The GRE Discovery Option (TBA3), described in Section 5.3.
The GRE Information Option (TBA4), described in described in
Section 5.4.
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.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, 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.
[RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
BCP 187, RFC 7227, May 2014.
9.2. Informative References
[I-D.ietf-opsawg-capwap-alt-tunnel]
Zhang, R., Cao, Z., Deng, H., Pazhyannur, R., Gundavelli,
S., and L. Xue, "Alternate Tunnel Encapsulation for Data
Frames in CAPWAP", draft-ietf-opsawg-capwap-alt-tunnel-05
(work in progress), April 2015.
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[RFC1701] Hanks, S., Li, T., Farinacci, D., and P. Traina, "Generic
Routing Encapsulation (GRE)", RFC 1701, October 1994.
Authors' Addresses
Sheng Jiang (editor)
Huawei Technologies Co., Ltd
Q14, Huawei Campus, No.156 Beiqing Road
Hai-Dian District, Beijing, 100095
CN
Email: jiangsheng@huawei.com
Dayong Guo
Huawei Technologies Co., Ltd
Q14, Huawei Campus, No.156 Beiqing Road, Hai-Dian District
Beijing, 100095
China
Email: guoseu@huawei.com
Li Xue
Email: xueli_jas@163.com
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