NETEXT WG S. Gundavelli, Ed.
Internet-Draft Cisco
Intended status: Standards Track X. Zhou
Expires: July 30, 2012 ZTE Corporation
J. Korhonen
Nokia Siemens Networks
G. Feige
R. Koodli
Cisco
January 27, 2012
IPv4 Traffic Offload Selector Option for Proxy Mobile IPv6
draft-ietf-netext-pmipv6-sipto-option-01.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 July 30, 2012.
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 . . . . . . . . . . . . . . . . . 3
2.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 4
3.1. LMA Considerations . . . . . . . . . . . . . . . . . . . . 5
3.2. MAG Considerations . . . . . . . . . . . . . . . . . . . . 6
4. IP Traffic Offload Selector Option . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Protocol Configuration Variables . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
Mobile Operators are expanding their network coverage by integrating
various access technology domains 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, the 3GPP S2/a Proxy Mobile
IPv6 [TS23402] interface, specified by the 3GPP system architecture,
is providing the needed protocol glue. When this protocol interface
based on Proxy Mobile IPv6 [RFC5213] is used, the mobile node is
topologically anchored on the local mobility anchor [RFC5213] in the
home network. The mobile node's IP traffic is always tunneled back
from the mobile access gateway [RFC5213] in the access network to the
local mobility anchor in the home 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 needs 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 provides
greater leverage and efficient usage of the mobile packet core with
increased overall network capacity and by 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 needs to be offloaded.
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 for notifying the flow selectors
for that can be used by the local mobility anchor for notifying the
mobile access gateway flows that can be offloaded at the access edge.
Since, the mobile node's IP address topologically belongs to the home
network, the offloaded IP traffic flows need to be NAT [RFC2663]
translated. 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
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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.
Selective IP Traffic Offload (SIPTO)
The approach of selecting specific IP flows and routing them to
the local network, as supposed to tunneling them to the home
network.
NAT (Network Address Translation)
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 having 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 be offloaded at the mobile access gateway and
all the other flows for that mobility session are tunneled back to
the local mobility anchor.
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_----_
_( )_
( Internet )
(_ _)
'----'
|
(IPv4 Traffic Offload Point
at access edge gateway for
non-essential traffic
Ex: HTTP Traffic Offloaded)
|
......................................................
| . +----------------+
+---+ . | Operator Value |
|NAT| . | Added Services |
+---+ . +----------------+
| _----_ |
+-----+ _( )_ +-----+
[MN]----| MAG |======( IP )======| LMA |-- Internet
+-----+ (_ _) +-----+
'----' (
.
.
.
[Access Network] . [Home Network]
......................................................
Figure 1: Access Networks attached to MAG
3.1. LMA Considerations
The following considerations apply to the local mobility anchor and
the mobile access gateway.
Figure 1 explains the operational sequence of the IP Traffic Offload
selectors between the mobile access gateway and the local mobility
anchor.
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
| | |
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Figure 2: Exchange of IP Traffic Offload Selectors
o If the received Proxy Binding Update includes the IP Traffic
Offload Selector Option Section 4, but if the configuration
variable, EnableIPTrafficOffloadSupport 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. This would not 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 on the local mobility
anchor is set to a value of (1), then the local mobility anchor
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. 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.
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 (0), 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 mobility 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 spec 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.
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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 mobility access
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 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 and the
identified IP flows have to be offloaded. Considerations related
to (M) flag MUST be applied.
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 local mobility
anchor and a mobile access gateway. This option is used for carrying
the flow selectors for supporting 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
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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 flows except the identified IP flow(s) in
this mobility option needs to be offloaded at the mobile access
gateway. If the (M) flag value is set to a value of (0), it is an
indication that the identified IP flow(s) needs to be offloaded at
the mobile access gateway and all other IP flows associated with
that mobility session needs to be tunneled to the local mobility
anchor.
TS Format An 8-bit unsigned integer indicating the Traffic Selector
Format. The value of "0" is reserved and is used when there are
no selectors to carry, relevant when the option is used as a
capability indicator. The value of (1) is assigned for IPv4
Binary Traffic Selector [RFC6088].
TS Selector A variable-length opaque field for including the traffic
specification identified by the TS format field. 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].
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 introduces a new number space. This number space needs to
be managed by IANA, under the Registry, IP Traffic Offload
Selector Type Registry. This specification reserves the sub-type
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values of (0) and (1). The value of "0" is reserved and is used
when there are no selectors to carry, relevant when the option is
used just as a capability indicator. The value of (1) is assigned
for IPv4 Binary Traffic Selector [RFC6088]. Approval of new sub-
type values are to be made through IANA Expert Review.
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.
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.
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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 local 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.
8. Acknowledgements
The authors would like to thank Basavaraj Patil, Ryuji Wakikawa,
Carlos Bernardos, Hidetoshi Yokota, Pierrick Seite, Mark Grayson,
Frank Brockners, Woj Dec, 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.
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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.
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
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Rajeev Koodli
Cisco
3650 Cisco Way
San Jose, CA 95134
USA
Email: rkoodli@cisco.com
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