NETEXT WG S. Gundavelli, Ed.
Internet-Draft Cisco
Intended status: Standards Track X. Zhou
Expires: March 16, 2013 ZTE Corporation
J. Korhonen
Nokia Siemens Networks
G. Feige
R. Koodli
Cisco
September 12, 2012
IPv4 Traffic Offload Selector Option for Proxy Mobile IPv6
draft-ietf-netext-pmipv6-sipto-option-06.txt
Abstract
This specification defines a mechanism and a related mobility option
for carrying IPv4 Offload traffic selectors between a mobile access
gateway and a local mobility anchor in a Proxy Mobile IPv6 domain.
Based on the received offload flow selectors from the local mobility
anchor, a mobile access gateway can enable offload traffic rule on
the selected IPv4 flows.
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 March 16, 2013.
Copyright Notice
Copyright (c) 2012 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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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
2.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 5
3.1. LMA Considerations . . . . . . . . . . . . . . . . . . . . 7
3.2. MAG Considerations . . . . . . . . . . . . . . . . . . . . 8
4. IP Traffic Offload Selector Option . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Protocol Configuration Variables . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9.1. Normative References . . . . . . . . . . . . . . . . . . . 12
9.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
Mobile Operators are expanding their network coverage by integrating
various access technology domains (Ex: Wireless LAN, LTE) into a
common IP mobile core. For providing IP mobility support to a mobile
node irrespective of the access network to which it is attached. For
example, the 3GPP S2a Proxy Mobile IPv6 [TS23402] reference point,
specified by the 3GPP system architecture, is providing the needed
protocol inter-working. When this protocol interface based on Proxy
Mobile IPv6 [RFC5213] is used, the mobile node is topologically
anchored at the local mobility anchor [RFC5213] in the home network.
The mobile node's IPv4 traffic is always tunneled back from the
mobile access gateway [RFC5213] in the access network to the local
mobility anchor in the home network. This may not be the case with
IPv6 traffic, as the mobile node can be assigned an IPv6 prefix from
the access network in addition to the IPv6 prefix from the home
network and thereby allowing the mobile node to use an IPv6 address
from the access network for traffic that needs to be offloaded in the
access network.
However, with the exponential growth in the mobile data traffic,
mobile operators are exploring new ways to offload some of the IP
traffic flows at the nearest access edge where ever there is an
internet peering point, as supposed to carrying it all the way to the
mobility anchor in the home network. Not all IP traffic need to be
routed back to the home network, some of the non-essential traffic
which does not require IP mobility support can be offloaded at the
mobile access gateway in the access network. This approach allows
efficient usage of the mobile packet core which helps in lowering
transport costs. The local mobility anchor in the home network can
potentially deliver the IP flow selectors to the mobile access
gateway in the access network, for identifying the IP flows that need
to be offloaded. Example of such non-essential traffic is entirely a
policy decision. A given operator may choose to offload all traffic
except that requires QoS services (Ex: Voice over IP traffic), or may
choose to offload all HTTP traffic. From the point of view of this
specification, its only about traffic matching a given flow selector
and classification for offload. This approach has one limitation
with respect to identifying encrypted traffic. IPsec encrypted
traffic with no visibility into the application payload cannot be
selected for offload.
This document defines a new mobility option, IP Traffic Offload
Selector option for Proxy Mobile IPv6 (PMIPv6). This option can be
used by the local mobility anchor to notify the mobile access gateway
with the flow selectors that can used for selecting the flows for
offloading them at the access edge. Since, the mobile node's IP
address topologically belongs to the home network, the offloaded IP
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traffic flows need to be NAT [RFC2663] translated. These offloaded
flows will not have mobility support as the NAT becomes the anchor
point for those flows. Given this NAT translation requirement for
the offloaded traffic, this approach will be limited to mobile node's
IPv4 flows. There are better ways to solve this problem for IPv6 and
with the goal not to create NAT66 requirement, this specification
does not support traffic offload support for IPv6 flows. This
document also does not define any new semantics for flow selectors.
The flow identification and the related semantics are all leveraged
from [RFC6088].
2. Conventions and Terminology
2.1. Conventions
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].
2.2. Terminology
All the mobility related terms used in this document are to be
interpreted as defined in the base Proxy Mobile IPv6 specifications
[RFC5213] and [RFC5844]. Additionally, this document uses the
following abbreviations:
IP Flow
IP Flow represents a set of IP packets that match a traffic
selector. The selector is typically based on the source IP
address, destination IP address, source port, destination port and
other fields in upper layer headers.
IP Traffic Offload
The approach of selecting specific IP flows and routing them
through the access network, instead of tunneling them to the home
network. Offload can also be between two access networks
(Example: moving some of the traffic from LTE access to WLAN
access).
NAT (Network Address Translation)
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Network Address Translation [RFC2663] is a method by which IP
addresses are mapped from one address realm to another, providing
transparent routing to end hosts.
3. Solution Overview
The following illustrates the scenario where the mobile access
gateway in an access network has the ability to offload some of the
IPv4 traffic flows, based on the traffic selectors it received from
the local mobility anchor in the home network. For example, all the
HTTP flows may be offloaded at the mobile access gateway and all the
other flows for that mobility session are tunneled back to the local
mobility anchor. The offloaded flows have to be NAT translated and
this specification does not impose any restrictions on the location
of the NAT function. It is possible, the NAT function is collocated
with the mobile access gateway, or its located some where in the edge
of the access network. When the NAT is not collocated on the mobile
access gateway, the NAT function should have the ability to identify
the offloaded IP traffic for NAT policy enforcement. This could be
achieved by configuring a specific VLAN between the mobile access
gateway and the NAT device and ensuring all the traffic on that VLAN
is NAT translated. This can also be achieved through other means and
the details are outside the scope of this document.
The selectors that are delivered to the mobile access gateway can be
used to classify the traffic, so it can be offloaded to the access
network. The parameters in the IP traffic selectors can be used to
match against the header fields in the data packets. These
parameters include Source IP address, Destination IP address, TCP/UDP
Port numbers, and other fields.
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_----_
_( )_
( Internet )
(_ _)
'----'
|
:
(IPv4 Traffic Offload Point)
:
|
.........................................................
| |
+--------+ | +---------------------+
| Local |-| | Services requiring |
|Services| | | mobility, or service|
+--------+ | | treatment |
| +---------------------+
+---+ |
|NAT| |
+---+ |
| _----_ |
+-----+ _( )_ +-----+
[MN]----| MAG |======( IP )======| LMA |-- Internet
+-----+ (_ _) +-----+
'----'
.
.
[Access Network] . [Home Network]
..........................................................
Figure 1: IP Traffic Offload Support at the MAG
Figure 2 explains the operational sequence of the Proxy Mobile IPv6
protocol signaling message exchange between the mobile access gateway
and the local mobility anchor for negotiating the IP Traffic Offload
selectors. The details related to DHCP transactions, or Router
Advertisements on the access link are not shown here as that is not
the key focus of this specification.
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MN MAG(NAT) LMA
|------>| | 1. Mobile Node Attach
| |------->| 2. Proxy Binding Update
| |<-------| 3. Proxy Binding Acknowledgement (IPTS Option)
| |========| 4. Tunnel/Route Setup
| + | 5. Installing the traffic offload rules
|------>| | 6. IPv4 packet from mobile node
| + | 7. Forwarding rule - Tunnel home/offload
| | |
Figure 2: Exchange of IP Traffic Offload Selectors
3.1. LMA Considerations
The following considerations apply to the local mobility anchor.
o If the received Proxy Binding Update includes the IP Traffic
Offload Selector option (Section 4), but if the configuration
variable, EnableIPTrafficOffloadSupport (Section 6) on the local
mobility anchor is set to a value of (0), then the local mobility
anchor MUST ignore the IP Traffic Offload Selector option and
process the rest of the packet as per [RFC5213]. This would have
no effect on the operation of the rest of the protocol.
o If the received Proxy Binding Update includes the IP Traffic
Offload Selector option (Section 4), and if the configuration
variable, EnableIPTrafficOffloadSupport (Section 6) on the local
mobility anchor is set to a value of (1), then the local mobility
anchor can acquire the offload policy from a network function (Ex:
AAA or PCRF) and can construct the traffic selectors based on the
offload policy and deliver those selectors in the Proxy Binding
Acknowledgement message using the IP Traffic Offload Selector
option. The specific details on how the offload policy for a
mobile node is provisioned on the local mobility anchor is out of
the scope for this document. However, if the received Proxy
Binding Update included a proposed Offload traffic selectors, the
local mobility anchor MAY choose to honor that request and include
the proposed selectors in the reply.
o If the received Proxy Binding Update does not include the IP
Traffic Offload Selector option (Section 4), and if the
configuration variable, EnableIPTrafficOffloadSupport (Section 6)
on the local mobility anchor is set to a value of (1), then the
local mobility anchor SHOULD NOT include the IP Traffic Offload
Selector option in the Proxy Binding Acknowledgement.
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3.2. MAG Considerations
o If the configuration variable, EnableIPTrafficOffloadSupport on
the mobile access gateway is set to a value of (0), then the
mobile access gateway MUST NOT include the IP Traffic Offload
Selector option (Section 4) in the Proxy Binding Update message
that it sends to the local mobility anchor. Otherwise, the option
MUST be included in the Proxy Binding Update message. When this
option is included, it is an indication to the local mobility
anchor that the mobile access gateway is capable of supporting IP
Traffic Offload support. The TS format field of the IP Traffic
Offload Selector option MUST be set to a value of (255),
indicating that the mobile access gateway is not proposing any
specific offload policy for that mobility session, but a request
to the local mobility anchor to provide the IP traffic offload
flow selectors for that mobility session.
o The mobile access gateway MAY choose to include its proposed IP
traffic offload flow selectors in the IP Traffic Offload Selector
option (Section 4). Including this offload traffic selectors
serves as a proposal to the local mobility anchor, which the local
mobility anchor can override with its own offload policy, or agree
to the proposed policy. When including the offload traffic
selectors, the TS format field of the IP Traffic Offload Selector
option MUST be set to the respective flow specification type.
o If there is no IP Traffic Offload Selector option in the
corresponding Proxy Binding Acknowledgement message, that the
mobile access gateway receives in response to a Proxy Binding
Update, it serves as an indication that the local mobility anchor
does not support IP Traffic Offload support for that mobility
session, and it implies the local mobility anchor cannot deliver
IP flow selectors for that mobility session. The mobile access
gateway upon accepting the Proxy Binding Acknowledgement message
MUST NOT enable any offload policy for that mobility session. All
the mobile node's IP flows MUST be tunneled back to the local
mobility anchor.
o If there is an IP Traffic Offload Selector option in the
corresponding Proxy Binding Acknowledgement message, it is an
indication that the local mobility anchor has provided the IP
traffic Offload selectors for that mobility session [RFC5213] and
the identified IP flows have to be offloaded. Considerations
related to (M) flag MUST be applied. The mobile access gateway
SHOULD enable traffic offload for those identified flows. The
delivered offload selectors rules MUST be applied only for the
flows associated to that mobility session.
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o If the mobile access gateway is not capable, or enabled to support
IP Traffic Offload support, but if the received Proxy Binding
Acknowledgement message has the IP Traffic Offload Selector
option, the mobile access gateway SHOULD ignore the option and
process the rest of the packet as per [RFC5213].
4. IP Traffic Offload Selector Option
A new mobility option, IP Traffic Offload Selector option, is defined
for using it in Proxy Binding Update (PBU) and Proxy Binding
Acknowledgement (PBA) messages exchanged between a mobile access
gateway and a local mobility anchor. This option is used for
carrying the flow selectors for enabling IP traffic offload function
at the mobile access gateway.
The alignment requirement for this option is 4n.
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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M| Reserved | TS Format |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Selector ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: IP Traffic Offload Selector Option
Type
<IANA-1>
Length
8-bit unsigned integer indicating the length in octets of the
option, excluding the type and length fields.
Reserved
This field is unused for now. The value MUST be initialized to 0
by the sender and MUST be ignored by the receiver.
IP Traffic Offload Mode Flag
This field indicates the offload mode. If the (M) flag value is
set to a value of (1), it is an indication that all the IP flows
associated to that mobility session except the identified IP
flow(s) in this mobility option SHOULD be offloaded at the mobile
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access gateway. If the (M) flag value is set to a value of (0),
it is an indication that the identified IP flow(s) in this
mobility option SHOULD be offloaded at the mobile access gateway
and all other IP flows associated with that mobility session need
to be tunneled to the local mobility anchor.
TS Format
An 8-bit unsigned integer indicating the Traffic Selector Format.
The values for this field are maintained by the "Traffic Selector
Format" namespace defined in [RFC6089]. The value of "255" is
reserved and is used when there are no selectors to carry. In
this case, the option is used only as a capability indicator.
When the value of TS Format field is set to (1), the format that
follows is the IPv4 Binary Traffic Selector specified in section
3.1 of [RFC6088].
TS Selector
A variable-length opaque field for including the traffic
specification identified by the TS format field.
5. IANA Considerations
This document requires the following two IANA actions.
o Action-1: This specification defines a new Mobility Header option,
IP Traffic Offload Selector option. This option is described in
Section 4. The Type value for this option needs to be assigned
from the same numbering space as allocated for the other mobility
options [RFC6275].
o Action-2: The Sub-type field of the IP Traffic Offload Selector
option described in Section 4 uses the number space from "Traffic
Selector Format" namespace specified in [RFC6089]. This
specification reserves the value (255) (NULL Selector) from that
number space.
6. Protocol Configuration Variables
This specification defines the following configuration variable that
control the use of IP Traffic Offload support for a mobility session.
The mobility entities, local mobility anchor and the mobile access
gateway MUST allow these variables to be configured by the system
management. The configured values for these protocol variables MUST
survive server reboots and service restarts.
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EnableIPTrafficOffloadSupport
This flag indicates whether or not IP Traffic Offload support
needs to be enabled. This configuration variable is available
at both in the mobile access gateway and at the local mobility
anchor. The default value for this flag is set to (0),
indicating that the support for IP Traffic offload support is
disabled.
When this flag on the mobile access gateway is set to a value
of (1), the mobile access gateway MUST enable the IP Traffic
offload support for a mobility session, specifically it MUST
include the IP Traffic Offload Selector option in the Proxy
Binding Update messages and offload the negotiated IP flows to
the access network. If the value of the flag is set to a value
of (0), mobile access gateway MUST NOT enable IP Traffic
Offload support and it MUST NOT include this option in the
Proxy Binding Update.
Similarly, when this flag on the local mobility anchor is set
to a value of (1), the local mobility anchor SHOULD enable
support for IP Traffic offload support. When the local
mobility anchor chooses to enable IP Traffic offload support
and if there is offload flow policy specified for a mobility
node, it SHOULD deliver the offload selectors to the mobile
access gateway by including the IP Traffic Offload Selector
option in the Proxy Binding Acknowledgement message.
7. Security Considerations
The IP Traffic Offload Selector option defined in this specification
is for use in Proxy Binding Update and Proxy Binding Acknowledgement
messages. This option is carried like any other mobility header
option as specified in [RFC5213] and does not require any special
security considerations. Carrying IP traffic offload selectors does
not introduce any new security vulnerabilities.
When IPv4 traffic offload support is enabled for a mobile node, the
mobile access gateway selectively offloads some of the mobile node's
traffic flows to the access network. Typically, these offloaded
flows get NAT translated and essentially that introduces certain
vulnerabilities which are common to any NAT deployment. These
vulnerabilities and the related considerations have been well
documented in the NAT specification [RFC2663]. There are no
additional considerations above and beyond what is already documented
by the NAT specifications and which are unique to the approach
specified in this document.
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8. Acknowledgements
The authors would like to thank Ahmad Muhanna, Basavaraj Patil,
Carlos Bernardos, Eric Voit, Frank Brockners, Hidetoshi Yokota, Marco
Liebsch, Mark Grayson, Pierrick Seite, Ryuji Wakikawa, and Steve Wood
for all the discussions related to the topic of IP traffic offload.
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.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
Mobile IPv6", RFC 5844, May 2010.
[RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont,
"Traffic Selectors for Flow Bindings", RFC 6088,
January 2011.
[RFC6089] Tsirtsis, G., Soliman, H., Montavont, N., Giaretta, G.,
and K. Kuladinithi, "Flow Bindings in Mobile IPv6 and
Network Mobility (NEMO) Basic Support", RFC 6089,
January 2011.
9.2. Informative References
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations",
RFC 2663, August 1999.
[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.
[TS23402] 3GPP, "Architecture enhancements for non-3GPP accesses",
2010.
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Authors' Addresses
Sri Gundavelli (editor)
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sgundave@cisco.com
Xingyue Zhou
ZTE Corporation
No.68 Zijinghua Rd
Nanjing
China
Email: zhou.xingyue@zte.com.cn
Jouni Korhonen
Nokia Siemens Networks
Linnoitustie 6
Espoo FIN-02600
Finland
Email: jouni.nospam@gmail.com
Gaetan
Cisco
France
Email: gfeige@cisco.com
Rajeev Koodli
Cisco
3650 Cisco Way
San Jose, CA 95134
USA
Email: rkoodli@cisco.com
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