NETEXT WG T. Melia, Ed.
Internet-Draft Alcatel-Lucent
Intended status: Informational S. Gundavelli, Ed.
Expires: April 21, 2014 Cisco
October 18, 2013
Logical Interface Support for multi-mode IP Hosts
draft-ietf-netext-logical-interface-support-08
Abstract
A Logical Interface is a software semantic internal to the host
operating system. This semantic is available in all popular
operating systems and is used in various protocol implementations.
The Logical Interface support is required on the mobile node
operating in a Proxy Mobile IPv6 domain, for leveraging various
network-based mobility management features such as inter-technology
handoffs, multihoming and flow mobility support. This document
explains the operational details of Logical Interface construct and
the specifics on how the link-layer implementations hide the physical
interfaces from the IP stack and from the network nodes on the
attached access networks. Furthermore, this document identifies the
applicability of this approach to various link-layer technologies and
analyzes the issues around it when used in context with various
mobility management features.
Status of this Memo
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This Internet-Draft will expire on April 21, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Hiding Link-layer Technologies - Approaches and
Applicability . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Link-layer Abstraction - Approaches . . . . . . . . . . . 5
3.2. Applicability Statement . . . . . . . . . . . . . . . . . 6
3.2.1. Link layer support . . . . . . . . . . . . . . . . . . 6
3.2.2. Logical Interface . . . . . . . . . . . . . . . . . . 6
4. Technology Use cases . . . . . . . . . . . . . . . . . . . . . 8
5. Logical Interface Functional Details . . . . . . . . . . . . . 9
5.1. Configuration of a Logical Interface . . . . . . . . . . . 10
5.2. Logical Interface Forwarding Conceptual Data Structures . 10
6. Logical Interface Use-cases in Proxy Mobile IPv6 . . . . . . . 12
6.1. Multihoming Support . . . . . . . . . . . . . . . . . . . 12
6.2. Inter-Technology Handoff Support . . . . . . . . . . . . . 13
6.3. Flow Mobility Support . . . . . . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Normative References . . . . . . . . . . . . . . . . . . . 18
11.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
Proxy Mobile IPv6 [RFC5213] is a network-based mobility protocol.
Some of the key goals of the protocol include support for
multihoming, inter-technology handoffs and flow mobility support.
The base protocol features specified in [RFC5213] and [RFC5844] allow
the mobile node to attach to the network using multiple interfaces
(simultaneously or sequentially), or to perform handoff between
different interfaces of the mobile node. However, for supporting
these features, the mobile node is required to be activated with
specific software configuration that allows the mobile node to either
perform inter-technology handoffs between different interfaces,
attach to the network using multiple interfaces, or perform flow
movement from one access technology to another. This document
analyzes from the mobile node's perspective a specific approach that
allows the mobile node to leverage these mobility features.
Specifically, it explores the use of the Logical Interface support, a
semantic available on most operating systems.
A Logical Interface is a construct internal to the operating system.
It is an approach where a logical link-layer implementation hides a
variety of physical interfaces from the IP stack. This semantic has
been used on a variety of operating systems to implement applications
such as Mobile IP clients [RFC6275] and IPsec VPN clients [RFC4301].
In the context of an access infrastructure providing network network-
based mobility management services across a variety of access
technologies, as provided by a Proxy Mobile IPv6 domain [RFC5213], a
logical interface can be used to afford inter-technology handover,
multihoming, and/or flow mobility without requiring from the mobile
node IP stack specific support to that effect.
The rest of the document provides a functional description of a
Logical Interface on the mobile node and the interworking between a
mobile node using logical interface and network elements in the Proxy
Mobile IPv6 domain when supporting the aforementioned mobility
management features. It also analyzes the issues involved with this
approach and characterizes the contexts in which such usage is
appropriate.
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2. Terminology
All the mobility related terms used in this document are to be
interpreted as defined in Proxy Mobile IPv6 specifications, [RFC5213]
and [RFC5844]. In addition, this document introduces the following
terms:
PIF (Physical Interface) - a network interface card attached to an
an host providing network connectivity (e.g. an Ethernet card, a
WLAN card, an LTE interface).
LIF (Logical Interface) - It is a virtual interface in the IP stack.
It appears just as any other physical interface, provides similar
semantics with respect to packet transmit and receive functions to
the upper layers in the IP stack. However, it is only logical
construct and is not a representation of an instance of any
physical hardware.
Sub-If (Sub Interface) - a physical interface that is part of a
logical interface construct. For example, a logical interface may
have been created abstracting two physical interfaces, LTE and
WLAN. These physical interfaces, LTE and WLAN are referred to as
sub-interfaces of that logical interface. In some cases, a sub-
interface can also be another logical interface, such as an IPsec
tunnel interface.
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3. Hiding Link-layer Technologies - Approaches and Applicability
There are several techniques/mechanisms that allow hiding access
technology changes or movement from host IP layer. This section
classifies these existing techniques into a set of generic
approaches, according to their most representative characteristics.
Later sections of this document analyze the applicability of these
solution approaches for supporting features such as, inter-technology
handovers and IP flow mobility support for a mobile node in a Proxy
Mobile IPv6 domain [RFC5213].
3.1. Link-layer Abstraction - Approaches
The following generic mechanisms can hide access technology changes
from host IP layer:
o Link-layer Support - Certain link-layer technologies are able to
hide physical media changes from the upper layers. For example,
IEEE 802.11 is able to seamlessly change between IEEE 802.11a/b/g
physical layers. Also, an 802.11 STA can move between different
Access Points within the same domain without the IP stack being
aware of the movement. In this case, the IEEE 802.11 MAC layer
takes care of the mobility, making the media change invisible to
the upper layers. Another example is IEEE 802.3, that supports
changing the rate from 10Mbps to 100Mbps and to 1000Mbps. Another
example is the situation in the 3GPP Evolved Packet
System[TS23401] where a UE can perform inter-access handovers
between three different access technologies (2G GERAN, 3G UTRAN,
and 4G E-UTRAN) that are invisible to the IP layer at the UE.
o A logical interface denotes a mechanism that that logically group/
bond several physical interfaces so they appear to the IP layer as
a single interface (see Figure 1). Depending on the type of
access technologies, it might be possible to use more than one
physical interface at a time -- such that the node is
simultaneously attached via different access technologies -- or
just to perform handovers across a variety of physical interfaces.
Controlling the way the different access technologies are used
(simultaneous, sequential attachment, etc) is not trivial and
requires additional intelligence and/or configuration within the
logical interface implementation. The configuration is typically
handled via a connection manager, and based on a combination of
user preferences on one hand, and operator preferences such as
those provisionned by the Access Network Discovery and Selection
Function (ANDSF) [TS23402] on the other hand.
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3.2. Applicability Statement
We now focus on the applicability of the above solutions against the
following requirements:
o multi technology support
o sequential vs. simultaneous access
3.2.1. Link layer support
Link layer mobility support applies to cases when the same link layer
technology is used and mobility can be fully handled at that layer.
One example is the case where several 802.11 access points are
deployed in the same subnet with a common IP layer configuration
(DHCP server, default router, etc.). In this case the handover
across access points need not to be hidden to the IP layer since the
IP layer configuration remains the same after a handover. This type
of scenario is applicable to cases when the different points of
attachment (i.e. access points) belong to the same network domain,
e.g. Enterprise, hotspots from same operator, etc.
Since this type of link layer technology does not typically allow for
simultaneous attachment to different access networks of the same
technology, the logical interface would not be used to provide
simultaneous access for purposes of multihoming or flow mobility.
Instead, the logical interface can be used to provide inter-access
technology handover between this type of link layer technology and
another link layer technology, e.g., between IEEE 802.11 and IEEE
802.16.
3.2.2. Logical Interface
The use of a logical interface allows the mobile node to provide a
single interface perspective to the IP layer and its upper layers
(transport and application). Doing so allows to hide inter-access
technology handovers or application flow handovers across different
physical interfaces.
The logical interface may support simultaneous attachment, in
addition to sequential attachment. It requires additional support at
the node and the network in order to benefit from simultaneous
attachment. For example special mechanisms are required to enable
addressing a particular interface from the network (e.g. for flow
mobility). In particular extensions to PMIPv6 are required in order
to enable the network (i.e., the MAG and LMA) to deal with logical
interface, instead to IP interfaces as current RFC5213 does. RFC5213
assumes that each physical interface capable of attaching to a MAG is
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an IP interface, while the logical interface solution groups several
physical interfaces under the same IP logical interface.
It is therefore clear that the Logical Interface approach satisfies
the multi technology and the sequential vs: simultaneous access
support.
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4. Technology Use cases
3GPP has defined the Evolved Packet System (EPS) for heterogeneous
wireless access. A mobile device equipped with 3GPP and non-3GPP
wireless technologies can simultaneously or sequentially connect any
of the available devices and receive IP services through any of them.
This document focuses on employing a logical interface for
simultaneous and sequential use of a variety of access technologies.
As mentioned in the previous sections the Logical Interface construct
is able to hide to the IP layer the specifics of each technology in
the context of network based mobility (e.g. in multi-access
technology networks based on PMIPv6). The LIF concept can be used
with at least the following technologies: 3GPP access technologies
(3G, LTE), IEEE 802.16 access technology, and IEEE 802.11 access
technology.
In some UE implementations the wireless connection setup is based on
creation of a PPP interface between the IP layer and the wireless
modem that is configured with the IPCP and IPv6CP protocol [RFC5072].
In this case the PPP interface does not have any L2 address assigned.
In some other implementations the wireless modem is presented to the
IP layer as a virtual Ethernet interface.
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5. Logical Interface Functional Details
This section identifies the functional details of a logical interface
and provides some implementation considerations.
On most operating systems, a network interface is associated with a
physical device that offers the services for transmitting and
receiving IP packets from the network. In some configurations, a
network interface can also be implemented as a logical interface
which does not have the inherent capability to transmit, or receive
packets on a physical medium, but relies on other physical interfaces
for such services. Example of such configuration is an IP tunnel
interface.
An overview of a logical interface is shown in Figure 1. The logical
interface allows heterogeneous attachment while making changes in the
underlying media transparent to the IP stack. Simultaneous and
sequential network attachment procedures are therefore possible,
enabling inter-technology and flow mobility scenarios.
+----------------------------+
| TCP/UDP |
Session to IP +---->| |
Address binding | +----------------------------+
+---->| IP |
IP Address +---->| |
binding | +----------------------------+
+---->| Logical Interface |
Logical to +---->| IPv4/IPv6 Address |
Physical | +----------------------------+
Interface +---->| L2 | L2 | | L2 |
binding |(IF#1)|(IF#2)| ..... |(IF#n)|
+------+------+ +------+
| L1 | L1 | | L1 |
| | | | |
+------+------+ +------+
Figure 1: General overview of logical interface
From the perspective of the IP stack and the applications, a Logical
interface is just another interface. In fact, the logical interface
is only visible to the IP and upper layers when enabled. A host does
not see any operational difference between a Logical and a physical
interface. As with physical interfaces, a Logical interface is
represented as a software object to which IP address configuration is
bound. However, the Logical interface has some special properties
which are essential for enabling inter-technology handover and flow-
mobility features. Following are those properties:
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1. The logical interface has a relation to a set of physical
interfaces (sub-interfaces) on the host that it is abstracting.
These sub-interfaces can be attached or detached from the Logical
Interface at any time. The sub-interfaces attached to a Logical
interface are not visible to the IP and upper layers.
2. The logical interface may be attached to multiple access
technologies.
3. The Transmit/Receive functions of the logical interface are
mapped to the Transmit/Receive services exposed by the sub-
interfaces. This mapping is dynamic and any change is not
visible to the upper layers of the IP stack.
4. The logical interface maintains IP flow information for each of
its sub-interfaces. A conceptual data structure is maintained
for this purpose. The host may populate this information based
on tracking each of the sub-interface for the active flows.
5.1. Configuration of a Logical Interface
A host may be statically configured with the logical interface
configuration, or an application such as a connection manager on the
host may dynamically create it. Furthermore, the set of sub-
interfaces that are part of a logical interface construct may be a
fixed set, or may be kept dynamic, with the sub-interfaces getting
added or deleted as needed. The specific details related to these
configuration aspects are implementation specific and are outside the
scope of this document.
The IP layer should be configured with a default router reachable via
the logical interface. The default router can be internal to the
logical interface, i.e., it is a logical router that in turns decide
which physical interface is to be used to transmit packets.
5.2. Logical Interface Forwarding Conceptual Data Structures
The logical interface maintains the list of sub-interfaces that are
part of the logical interface. This conceptual data strucure is
called as the LIF Table. The logical interface also maintains the
list of flows associated with a given sub-interface and this
conceptual data structure is called as the PIF Table. Both of these
data structures have to be associated with a logical interface, and
are depicted in Figure 2
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LIF TABLE FLOW table
+===============================+ +=============================+
| PIF_ID | FLOW RoutingPolicies | | FLOW ID | Physical_Intf_Id |
| | Link Status | +-----------------------------+
+-------------------------------| | FLOW_ID | Physical_Intf_Id |
| PIF_ID | FLOW RoutingPolicies | +=============================+
| | Link Status | + .... | .... |
+-------------------------------+ +=============================+
| .... | .... |
+===============================+
Figure 2
The LIF table maintains the mapping between the LIF and each PIF
associated to the LIF (refer to property #3, Figure 1). For each PIF
entry the table should store the associated Routing Policies, and the
Link Status of the PIF (e.g. active, not active). The method by
which the Routing Policies are configured on the host is out of scope
for this document.
The FLOW table allows the logical interface to properly route each IP
flow over the right interface. The logical interface can identify
the flows arriving on its sub-interfaces and associate them to those
sub-interfaces. This approach is similar to reflective QoS performed
by the IP routers. For locally generated traffic (e.g. unicast
flows), the logical interface should perform interface selection
based on the Flow Routing Policies. In case traffic of an existing
flow is suddenly received from the network on a different sub-
interface than the one locally stored, the logical interface should
interpret the event as an explicit flow mobility trigger from the
network and it should update the PIF_ID parameter in the FLOW table.
Similarly, locally generated events from the sub-interfaces, or
configuration updates to the local policy rules can cause updates to
the table and hence trigger flow mobility.
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6. Logical Interface Use-cases in Proxy Mobile IPv6
This section explains how the Logical interface support on the mobile
node can be used for enabling some of the Proxy Mobile IPv6 protocol
features.
6.1. Multihoming Support
A mobile node with multiple interfaces can attach simultaneously to
the Proxy Mobile IPv6 domain. If the host is configured to use
Logical interface over the physical interfaces through which it is
attached, following are the related considerations.
LMA Binding Table
+========================+
+----+ | HNP MN-ID CoA ATT |
|LMA | +========================+
+----+ | HNP-1 MN-1 PCoA-1 5 |
//\\ | HNP-1 MN-1 PCoA-2 4 |
+---------//--\\-----------+
( // \\ )
( // \\ )
+------//--------\\--------+
// \\
PCoA-1 // \\ PCoA-2
+----+ +----+
(WLAN) |MAG1| |MAG2| (3GPP)
+----+ +----+
\ /
\ /
\ /
\ /
\ /
+-------+ +-------+
| if_1 | | if_2 |
|(WLAN) | |(3GPP) |
+-------+-+-------+
| Logical |
| Interface |
| (HNP-1) |
+-----------------|
| MN |
+-----------------+
Figure 3: Multihoming Support
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6.2. Inter-Technology Handoff Support
The Proxy Mobile IPv6 protocol enables a mobile node with multiple
network interfaces to move between access technologies, but still
retaining the same address configuration on its attached interface.
The protocol enables a mobile node to achieve address continuity
during handoffs. If the host is configured to use Logical interface
over the physical interface through which it is attached, following
are the related considerations.
LMA's Binding Table
+==========================+
+----+ | HNP MN-ID CoA ATT |
|LMA | +==========================+
+----+ | HNP-1 MN-1 PCoA-1 5 |
//\\ (pCoA-2)(4) <--change
+---------//--\\-----------+
( // \\ )
( // \\ )
+------//--------\\--------+
// \\
PCoA-1 // \\ PCoA-2
+----+ +----+
(WLAN) |MAG1| |MAG2| (3GPP)
+----+ +----+
\ /
\ Handoff /
\ /
\ /
+-------+ +-------+
| if_1 | | if_2 |
|(WLAN) | |(3GPP) |
+-------+-+-------+
| Logical |
| Interface |
| (HNP-1) |
+-----------------|
| MN |
+-----------------+
Figure 4: Inter-Technology Handoff Support
o When the mobile node performs an handoff between if_1 and if_2,
the change will not be visible to the applications of the mobile
node.
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o The protocol signaling between the network elements will ensure
the local mobility anchor will switch the forwarding for the
advertised prefix set from MAG1 to MAG2.
6.3. Flow Mobility Support
For supporting flow mobility support, there is a need to support
vertical handoff scenarios such as transferring a subset of
prefix(es) (hence the flows associated to it/them) from one interface
to another. The mobile node can support this scenario by using the
Logical interface support. This scenario is similar to the Inter-
technology handoff scenario defined in Section 6.2, only a subset of
the prefixes are moved between interfaces.
Additionally, IP flow mobility in general initiates when the LMA
decides to move a particular flow from its default path to a
different one. The LMA can decide on which is the best MAG that
should be used to forward a particular flow when the flow is
initiated e.g. based on application policy profiles) and/or during
the lifetime of the flow upon receiving a network-based or a mobile-
based trigger.
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7. IANA Considerations
This specification does not require any IANA Actions.
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8. Security Considerations
This specification explains the operational details of Logical
interface on an IP host. The Logical Interface implementation on the
host is not visible to the network and does not require any special
security considerations.
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9. Authors
This document reflects contributions from the following authors
(listed in alphabetical order):
Carlos Jesus Bernardos Cano
cjbc@it.uc3m.es
Antonio De la Oliva
aoliva@it.uc3m.es
Yong-Geun Hong
yonggeun.hong@gmail.com
Kent Leung
kleung@cisco.com
Tran Minh Trung
trungtm2909@gmail.com
Hidetoshi Yokota
yokota@kddilabs.jp
Juan Carlos Zuniga
JuanCarlos.Zuniga@InterDigital.com
Julien Laganier
jlaganier@JUNIPER.NET
10. Acknowledgements
The authors would like to acknowledge prior discussions on this topic
in NETLMM and NETEXT working groups. The authors would also like to
thank Joo-Sang Youn, Pierrick Seite, Rajeev Koodli, Basavaraj Patil,
Peter McCann, and Julien Laganier for all the discussions on this
topic.
11. References
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11.1. Normative References
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
[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.
11.2. Informative References
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC5072] Varada, S., Haskins, D., and E. Allen, "IP Version 6 over
PPP", RFC 5072, September 2007.
[RFC5677] Melia, T., Bajko, G., Das, S., Golmie, N., and JC. Zuniga,
"IEEE 802.21 Mobility Services Framework Design (MSFD)",
RFC 5677, December 2009.
[RFC6085] Gundavelli, S., Townsley, M., Troan, O., and W. Dec,
"Address Mapping of IPv6 Multicast Packets on Ethernet",
RFC 6085, January 2011.
[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.
[RFC6418] Blanchet, M. and P. Seite, "Multiple Interfaces and
Provisioning Domains Problem Statement", RFC 6418,
November 2011.
[TS23401] "3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects; General
Packet Radio Service (GPRS) enhancements for Evolved
Universal Terrestrial Radio Access Network (E-UTRAN)
access.", 2009.
[TS23402] "3rd Generation Partnership Project; Technical
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Specification Group Services and System Aspects;
Architecture Enhancements for non-3GPP Accesses.", 2009.
Authors' Addresses
Telemaco Melia (editor)
Alcatel-Lucent
Route de Villejust
Nozay 91620
France
Email: telemaco.melia@alcatel-lucent.com
Sri Gundavelli (editor)
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sgundave@cisco.com
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