One document matched: draft-ietf-netext-logical-interface-support-00.txt
NETEXT WG T. Melia, Ed.
Internet-Draft Alcatel-Lucent
Intended status: Informational S. Gundavelli, Ed.
Expires: February 26, 2011 Cisco
August 25, 2010
Logical Interface Support for multi-mode IP Hosts
draft-ietf-netext-logical-interface-support-00.txt
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 desirable 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.
Furthermore, this document identifies the applicability of this
approach to various link-layer technologies and analyses the issues
around it when used in context with various mobility management
features.
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 February 26, 2011.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . 7
3.2.2. Logical Interface . . . . . . . . . . . . . . . . . . 7
4. Logical Interface Operation . . . . . . . . . . . . . . . . . 9
5. Logical Interface Use-cases in Proxy Mobile IPv6 . . . . . . . 12
5.1. Multihoming Support . . . . . . . . . . . . . . . . . . . 12
5.2. Inter-Technology Handoff Support . . . . . . . . . . . . . 13
5.3. Flow Mobility Support . . . . . . . . . . . . . . . . . . 15
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
8. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.1. Normative References . . . . . . . . . . . . . . . . . . . 18
10.2. Informative References . . . . . . . . . . . . . . . . . . 19
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 PMIPv6 extensions chartered in the NETEXT WG) 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 (sequentially or
simultaneously), or perform flow movement from one access technology
to another. This document analyses 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 the link-layer implementations hide the
physical interfaces from the IP stack and from the network nodes.
This semantic is widely available in all popular operating systems.
Many applications such as Mobile IP client [RFC3775], IPsec VPN
client [RFC4301] and L2TP client [RFC3931] all rely on this semantic
for their protocol implementation and the same semantic can also be
useful in this context. Specifically, the mobile node [RFC5213] can
use the logical interface configuration for leveraging various
network-based mobility management features provided by the Proxy
Mobile IPv6 domain. The rest of the document provides the
operational details of the Logical Interface on the mobile node and
the inter-working between a mobile node using logical interface and
network elements in the Proxy Mobile IPv6 domain. It also analyzes
the issues involved with this approach and characterizes the contexts
in which such use is appropriate.
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2. Requirements Language
In this document, the key words "MAY", "MUST, "MUST NOT", "OPTIONAL",
"RECOMMENDED", "SHOULD", and "SHOULD NOT", are to be interpreted as
described in [RFC2119].
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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.
We then refer to these generic mechanisms later in the document, when
analyzing their applicability to inter-access technology and flow
mobility purposes in PMIPv6.
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 (see Figure 1).
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 (APs) 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.
Mobile Node
+-----------------------+
| TCP/UDP | AR1 AR2
+-----------------------+ +-----+ +-----+
| IP | | IP | | IP |
+-----------------------+ +-----+ +-----+
| Link Layer (L2) | | L2 | | L2 |
+-----+-----+-----+-----+ +-----+ +-----+
| L1a | L1b | L1c | L1d |<---------->| L1d | | L1b |
+-----+-----+-----+-----+ +-----+ +-----+
^ ^
|_________________________________________|
Figure 1: Link layer support solution architecture
There are also other examples with more complicated architectures,
like for instance, 3GPP EPC. In this case, a UE can move
(inter-RA handover) between GERAN/UTRAN/E-UTRAN, being this
movement invisible to the IP layer at the UE, and also to the LMA
logical component at the PGW. The link layer stack at the UE
(i.e. PDCP and RLC layers), and the GTP between the RAN and the
SGW (which plays the role of inter-3GPP AN mobility anchor) hide
this kind of mobility, which is not visible to the IP layer of the
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UE (see Figure 2).
---------
| Appl. |<----------------------------------------------------->
--------- ----------
| |<+ - - - - - - - - - - - - - - - - - - - - +>| |
| IP | . ----------------- . ------------------- . | IP |
| |<+>| relay |<+>| relay | . | |
--------- . ----------------- . ------------------- . ----------
| PDCP |<+>| PDCP | GTP-U |<+>| GTP-U | GTP-U |<+>| GTP-U |
--------- . ----------------- . ------------------- . ----------
| RLC |<+>| RLC | UDP/IP |<+>| UDP/IP | UDP/IP |<+>| UDP/IP |
--------- . ----------------- . ------------------- . ----------
| MAC |<+>| MAC | L2 |<+>| L2 | L2 |<+>| L2 |
--------- . ----------------- . ------------------- . ----------
| L1 |<+>| L1 | L1 |<+>| L1 | L1 |<+>| L1 |
--------- . ----------------- . ------------------- . ----------
UE Uu E-UTRAN S1-U SGW S5/S8a PGW
Figure 2: 3GPP LTE/EPC data plane architecture (GTP option)
o Logical interface: this refers to solutions (see Figure 3) that
logically group/bond several physical interfaces so they appear to
the upper layers (i.e. IP) as one single interface (where
application sockets bind). Depending on the OS support, it might
be possible to use more than one physical interface at a time --
so the node is simultaneously attached to different media -- or
just to provide a fail-over mode. Controlling the way the
different media is used (simultaneous, sequential attachment, etc)
is not trivial and requires additional intelligence and/or
configuration at the logical interface device driver. An example
of this type of solution is the Logical interface, which is
defined in this document, or the bonding driver (a Linux
implementation).
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
o no impact to the IP layer (e.g. Neighbor Discovery, path MTU)
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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 these layers.
One example is the case where several 802.11 APs are deployed in the
same subnet and all of them share higher layer resources such as DHCP
server, IP gateway, etc. In this case the APs can autonomously (or
with the help of a central box) communicate and control the STA
association changes from one AP to another, without the STA being
aware of the movement. This type of scenario is applicable to cases
when the different points of attachment (i.e. APs) belong to the
same network domain, e.g. enterprise, hotspots from same operator,
etc.
This type of solution does not typically allow for simultaneous
attachment to different access networks, and therefore can only be
considered for inter-access technology handovers, but not for flow
mobility. Existing RFC 5213 handover hint mechanisms could benefit
from link layer information (e.g. triggers) to detect and identify MN
handovers.
Link layer support is not applicable when two different access
technologies are involved (e.g. 802.11 WLAN and 802.16 WiMAX) and the
same is true when the same access technology expands over multiple
network domains. This solution does not impose any change at the IP
layer since changes in the access technology occur at layer two.
3.2.2. Logical Interface
The use of a logical interface allows the mobile node to provide a
single interface view to the layers above IP (thus not changing the
IP layer itself). Upper layers can bind to this interface, which
hides inner inter-access technology handovers or data flow transfers
among different physical interfaces.
This type of solution 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 physical
interfaces, instead to IP interfaces as current RFC5213 does.
RFC5213 assumes that each physical interface capable of attaching to
a MAG is an IP interface, while the logical interface solution groups
several physical interfaces under the same IP logical interface.
Neighbor discovery in conjunction with the logical interface concept
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has been widely studied for IPv4. Link awareness and gratuitous ARP
messages ensure neighbor reachability in case of media change. The
same apply to IPv6 where Router Solicitation/Router Advertisement can
be sent/received to efficiently manage neighbor cache population.
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4. Logical Interface Operation
On most operating systems, a network interface is associated with a
physical device that provides the capability for transmitting and
receiving network packets. In some cases a network interface can
also be implemented as a logical interface which does not feature any
packet transmission or receive capabilities, but relies on other
network interfaces for such capabilities. A logical interface can be
realized by that means. General overview of a logical interface is
shown in Figure 3.
The logical interface allows heterogeneous attachment while leaving
the change in the media transparent to the IP stack. Simultaneous
and sequential network attachment procedures are possible enabling
inter-technology and flow mobility scenarios. Through link awareness
the logical interface can keep consistent neighbor caches and move
flows across access networks transparently to the upper layers.
+----------------------------+
| TCP/UDP |
Session to IP +---->| |
Address binding | +----------------------------+
+---->| IP |
IP Address +---->| |
binding | +----------------------------+
+---->| Logical Interface |
Logical to +---->| (MN-HoA) |
Physical | +----------------------------+
Interface +---->| L2 | L2 | | L2 |
binding |(IF#1)|(IF#2)| ..... |(IF#n)|
+------+------+ +------+
| L1 | L1 | | L1 |
| | | | |
+------+------+ +------+
Figure 3: General overview of logical interface
From the perspective of the IP stack and the applications, a Logical
interface is just another interface. A host does not see any
difference between a Logical and a physical interface. All
interfaces are represented as software objects 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:
o Logical interface appears to the host stack as any other
interface. IP address configuration can be bound to this
interface by configuring one or more IPv4 and/or IPv6 addresses to
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this interface.
o Logical interface has a relation to a set of physical interfaces
on the host. These physical interfaces in the context of Logical
interface are called sub-interfaces in this document. These sub-
interfaces provide transmit and receive functions for sending and
receiving packets over physical links. A Logical interface can
receive packets sent to any of its sub-interfaces. In other words
the MN accepts packets on any physical interface as long as the IP
address is valid (downlink).
o The link-layer identifier of the Logical interface is used in the
link-layer header of the IP packets sent through this interface,
and the link-layer address of the physical interface will not be
used.
o The send/receive vectors of a Logical interface are managed
dynamically and are tied to the sub-interfaces. The mapping
between this Logical interface and the sub-interfaces can change
dynamically and this change will not be visible to the
applications. The side effect of this is the ability for the
application bound to the address configuration on the Logical
interface, to survive across inter-technology handoffs.
Applications will survive across the mapping change between a
Logical interface and its sub interfaces.
o An IP link as seen by the applications that the Logical interface
is being part of through specific sub interface(s), when changed
to be as part of through a different set of sub interface(s), will
not trigger session loss, address loss, as long as the IP prefix
is valid, and the host continues to exchange Neighbor Discovery
messages [RFC4861] from the IP routers to the Logical interface
over the sub-interface(s).
o The host has the path awareness of an IPv4/IPv6 link through a
sub-interface and standard routing table(s) lookup (via the
logical interface) uses the sub-interfaces for packet forwarding.
Addresses from Prefix P1, P2 tied to the Logical interface, may
have two different link paths, Prefix P1 over E0, Prefix P2 over
E1, and this mapping may be reversed, without applications being
aware of, and with the needed path changes on the network side.
o The Logical interface MUST transmit uplink packets on the same
physical interface on which the downlink packet was received for
the particular prefix/flow. This will guarantee that packets
belonging to the same session (e.g. TCP connection) are routed
along the same path (downlink and uplink). In other words a flow
mobility decision taken at the LMA will be understood at the MN as
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an implicit decision when packets belonging to the same flow will
arrive at a new interface.
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5. 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.
5.1. Multihoming Support
A mobile node in the Proxy Mobile IPv6 domain can potentially attach
to the Proxy Mobile IPv6 domain, simultaneously through multiple
interfaces. Each of the attachment links are assigned a unique set
of IPv6 prefixes. 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 LL-ID |
|LMA | +================================+
+----+ | HNP-1 MN-1 PCoA-1 5 ZZZ |
//\\ | HNP-2 MN-1 PCoA-2 4 ZZZ |
+---------//--\\-----------+
( // \\ )
( // \\ )
+------//--------\\--------+
// \\
PCoA-1 // \\ PCoA-2
+----+ +----+
(WLAN) |MAG1| |MAG2| (WiMAX)
+----+ +----+
\ /
\ /
HNP-1 \ / HNP-2
\ /
\ /
+-------+ +-------+
| if_1 | | if_2 |
|(WLAN) | |(WiMAX)|
+-------+-+-------+
| Logical |
(LL-ID: ZZZ) | Interface | HNP-1::zzz/128
+-----------------| HNP-2::zzz/128
| MN |
+-----------------+
Figure 4: Multihoming Support
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o The mobile node detects the advertised prefixes from the MAG1 and
MAG2 as the onlink prefixes on the link to which the Logical
interface is attached.
o The mobile node can generate address configuration using stateless
auto configuration mode from any of those prefixes.
o The applications can be bound to any of the addresses bound to the
Logical interface and that is determined based on the source
address selection rules.
o The host has path awareness for the hosted prefixes based on the
received Router Advertisement messages. Any packets with source
address generated using HNP_1 will be routed through the interface
if_1 and for packets using source address from HNP_2 will be
routed through the interface if_2.
5.2. 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.
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LMA's Binding Table
+================================+
+----+ | HNP MN-ID CoA ATT LL-ID |
|LMA | +================================+
+----+ | HNP-1 MN-1 PCoA-1 5 ZZZ |
//\\ (pCoA-2)(4) <-change
+---------//--\\-----------+
( // \\ )
( // \\ )
+------//--------\\--------+
// \\
PCoA-1 // \\ PCoA-2
+----+ +----+
(WLAN) |MAG1| |MAG2| (WiMAX)
+----+ +----+
\ /
\ Handoff /
\ ----> / HNP-1
\ /
\ /
+-------+ +-------+
| if_1 | | if_2 |
|(WLAN) | |(WiMAX)|
+-------+-+-------+
| Logical |
(LL-ID: ZZZ) | Interface | HNP-1::zzz/128
+-----------------|
| MN |
+-----------------+
Figure 5: 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. It will continue to receive Router Advertisements from the
network, but from a different sub-interface path.
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.
o The MAG2 will host the prefix on the attached link and will
include the home network prefixes in the Router Advertisements
that it sends on the link.
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5.3. 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 5.2, 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.
As an example of mobile-based triggers, the LMA could receive input
(e.g.by means of a layer 2.5 function via L3 signalling [RFC5677])
from the MN detecting changes in the mobile wireless environment
(e.g. weak radio signal, new network detected, etc.). Upon receiving
these triggers, the LMA can initiate the flow mobility procedures.
For instance, when the mobile node only supports single-radio
operation (i.e. one radio transmitting at a time), only sequential
(i.e. not simultaneous) attachment to different MAGs over different
media is possible. In this case layer 2.5 signalling can be used to
perform the inter-access technology handover and communicate to the
LMA the desired target access technology, MN-ID, Flow-ID and prefix.
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6. IANA Considerations
This specification does not require any IANA Actions.
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7. 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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8. Authors
This document reflects contributions from the following authors:
Hidetoshi Yokota
yokota@kddilabs.jp
Tran Minh Trung
trungtm2909@gmail.com
Yong-Geun Hong
yonggeun.hong@gmail.com
Kent Leung
kleung@cisco.com
Carlos Jess Bernardos Cano
cjbc@it.uc3m.es
Antonio de la Oliva
aoliva@it.uc3m.es
Juan Carlos Zuniga
JuanCarlos.Zuniga@InterDigital.com
9. 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,
Julien Laganier for all the discussions on this topic.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
10.2. Informative References
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC5677] Melia, T., Bajko, G., Das, S., Golmie, N., and JC. Zuniga,
"IEEE 802.21 Mobility Services Framework Design (MSFD)",
RFC 5677, December 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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