One document matched: draft-bernardos-mif-pmip-01.txt
Differences from draft-bernardos-mif-pmip-00.txt
NETEXT Working Group C. Bernardos
Internet-Draft UC3M
Intended status: Experimental T. Melia
Expires: April 29, 2010 Alcatel-Lucent Bell Labs
P. Seite
France Telecom
J. Korhonen
Nokia Siemens Networks
October 26, 2009
Multihoming extensions for Proxy Mobile IPv6
draft-bernardos-mif-pmip-01
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Abstract
The IETF standardized Proxy Mobile IPv6 (PMIPv6). PMIPv6 enables
mobile devices to connect to a PMIPv6 domain and roam across gateways
without changing the IP address. PMIPv6 also provides limited multi-
homing support to multi-mode mobile devices. The IETF is working on
optimizations for PMIPv6. While multi-homing item has been proposed
to be part of the approved work, discussions showed there are still
many controversial issues to be addressed (i.e. the no-host
modification theorem). This document explores solutions for the
multi-homing use case aiming at helping PMIPv6 development where
possible.
Requirements Language
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].
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. MIF scope and PMIPv6 . . . . . . . . . . . . . . . . . . . . . 5
3. A use case . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Considerations on feasibility and approach overview . . . . . 7
4.1. MN considerations . . . . . . . . . . . . . . . . . . . . 8
4.2. LMA considerations . . . . . . . . . . . . . . . . . . . . 9
4.3. MAG considerations . . . . . . . . . . . . . . . . . . . . 9
4.4. Downlink and Uplink considerations . . . . . . . . . . . . 10
4.5. IPv4 considerations . . . . . . . . . . . . . . . . . . . 10
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
Proxy Mobile IPv6 (PMIPv6), specified in RFC 5213 [RFC5213] and
[I-D.ietf-netlmm-pmip6-ipv4-support], provides network based mobility
management to hosts connecting to a PMIPv6 domain. PMIPv6 introduces
two new functional entities, the Local Mobility Anchor (LMA) and the
Mobility Access Gateway (MAG). The MAG is the first layer three hop
detecting Mobile Node (MN) attachment and providing IP connectivity.
The LMA is the entity assigning one or more Home Network Prefixes
(HNPs) and zero or one IPv4 Home Address (IPv4-MN-HoA)to the MN and
is the topological anchor for all traffic from/to the MN.
PMIPv6 allows an MN to connect to the same PMIPv6 domain through
different interfaces. ID
[I-D.devarapalli-netext-multi-interface-support] identifies at least
three possible scenarios, namely i) unique prefix per interface, ii)
same prefix but different global addresses per interface, iii) shared
address across multiple interfaces. The ID further describes issues
associated with each scenario. The first two scenarios are similar,
and bring similar issues, whereas the third one is more complex to
tackle, since it requires to deal with the sharing of the same IP
address across different interfaces. This document focuses on the
two first scenarios, as depicted in Figure 1. However, if [RFC1918]
defined private IPv4 addresses are used as IPv4 Home Addresses, the
scenario iii) may happen implicitly. Unless the LMA coordinates
private IPv4 Home Addresses across different access technologies and
mobility session, then there is a possibility that the same private
IPv4 Home Address would be assigned to both if1 and if2 of the MN.
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LMA Binding Cache
+----+ -----------------
|LMA | MN:if1 [prefix1 or addr1] --> MAG1
+----+ MN:if2 [prefix2 or addr1] --> MAG2
//\\
+---------//--\\-------------+
( // \\ ) PMIPv6 domain
( // \\ )
+------//--------\\----------+
// \\
// \\
+----+ +----+
|MAG1| |MAG2|
+----+ +----+
| |
| |
| if1 if2 |
+------[MN]------+
Figure 1: Unique prefix and Unique address per Interface scenarios
The fact is that many (client) hosts currently have the ability to
attach to multiple networks simultaneously, and that implies benefits
(e.g., enables load balancing, improved connectivity, higher
throughput and better reliability, etc.), but also brings some
operation issues (e.g., default router selection, address selection,
DNS server selection, choice of interface for packet transmission,
the treatment of configuration information received from the various
networks, etc.). Configuration decisions about how to deal with the
different information from each of the interface might have a very
strong impact on the connectivity experienced by a node with multiple
network interfaces (from now on we refer a node with multiple network
interfaces as a MIF node).
In the context of PMIPv6, current specification [RFC5213] does not
address the case of a MIF node attaching to a PMIPv6 domain other
than stating it is possible. We argue it is important to enable
PMIPv6 to bring MIF nodes the advantages related to the simultaneous
use of multiple interfaces. Moreover a MIF node could be seen as a
not-modified host implementing the right technology for multi-
interface handling.
2. MIF scope and PMIPv6
Current scope of MIF nodes as described in
[I-D.ietf-mif-problem-statement] only covers the issues of host
attaching to multiple networks. The current work is focused on
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documenting the system level effects to host IP stacks and
identification of gaps between the existing IETF recommendations and
existing practice, both for IPv4 and IPv6.
While [I-D.ietf-mif-problem-statement]is not addressing any (neither
flow nor host nor network) mobility, a MIF node might find itself
connected to a PMIPv6 domain. PMIPv6 should be extended to
efficiently support MIF nodes attaching to a PMIPv6 domain, enabling
features such as the ones identified in
[I-D.jeyatharan-netext-multihoming-ps], e.g., dynamic mobility
sessions between different interfaces, allowing traffic to be
forwarded to any of the interfaces of a MIF node, not only to the one
configured with the destination prefix/address of that traffic).
3. A use case
This section describes a simple use case of a MIF node in a PMIPv6
domain, as an example of a situation where PMIPv6 needs to be
extended.
+-----+
| CN1 |
+-----+
| LMA Binding Cache
| =====================
| MN:if1, pref1, MAG1
+-----+ +-----+ :if2, pref2, MAG2
| CN2 |--------| LMA |
+-----+ +-----+
//\\
+---------//--\\-------------+
( // \\ ) PMIPv6 domain
( // \\ )
+------//--------\\----------+
// \\
// \\
+----+ +----+
|MAG1| |MAG2|
+----+ +----+
| |
| |
| if1 if2 |
+-------[MN]------+
(WLAN) (3G)
Figure 2: Use case
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Figure 2 shows a potential use case of interest involving an MIF
mobile node attached to a PMIPv6 domain. The MN is attached to MAG1
through its WLAN interface (if1), and to MAG2 through its 3G
interface (if2). Lets consider the case in which each interface has
been assigned a different prefix by the LMA (for the sake of
simplicity we have left the IPv4 case out of this example). Two
different mobility bindings are created in the LMA referring to the
MN. In this scenario, if the MN decides to move if1 from MAG1 to a
different MAG of the same domain, the PMIPv6 support would take care
of ensuring that the same prefix (pref1) is assigned at the new MAG
(we assume that there is an L2 identifier for if1 that the new MAG
can include in the PBU).
Lets assume for the sake of this example that the MN starts a
communication with CN1, using as source IPv6 address (pref1::if1) the
one assigned to its WLAN interface (if1), and that it also starts a
different communication with CN2, using as source IPv6 address
(pref2::if2) the one assigned to its 3G interface (if2). In this
scenario, it would be useful to enable the MN be able to receive
traffic addressed to pref1::if1 via if2 and vice versa. However,
current PMIPv6 specification does not support this. Analogously, it
would be also useful to allow the MN send traffic with source address
pref1::if1 through if2 and vice versa.
We argue in the next section that PMIPv6 could benefit from MIF
outcomes to support the previous scenario while limiting impact on
the LMA and MAG operation.
4. Considerations on feasibility and approach overview
We analyse in the next sections the feasibility of the scenario
presented in Section 3, by identifying the requirements and changes
that would be needed in PMIPv6 to support it. In this version of the
document we do not specify with all the required details the
solution, but rather concentrate on the concept, with the goal of
triggering the discussion within the IETF.
Figure 3 shows in a glimpse the extensions to PMIPv6 required to
support the MIF example scenario shown in Section 3.
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+-----+
| CN1 |
+-----+
| LMA Binding Cache LMA policy/routing table
| ===================== ============================
| MN:if1, pref1, MAG1 flow1(CN1,MN[pref1])->MAG2
+-----+ +-----+ :if2, pref2, MAG2 flow2(CN1,MN[pref2])->MAG2
| CN2 |-----| LMA | ...
+-----+ +-----+ flowN(CN2,MN[pref1])->MAG1
//\\
+---------//--\\-------------+
( // \\ ) PMIPv6 domain
( // \\ )
+------//--------\\----------+
// \\
// \\ MAG2 routing table
+----+ +----+ ================================
|MAG1| |MAG2| (dest) (next hop)
+----+ +----+ pref2::/64 directly connected
| | pref1::/64 directly connected
| |
| if1 if2 |
+-------[MN]------+ MN implements the weak host model
(WLAN) (3G)
Figure 3: Solution overview
4.1. MN considerations
In order to support the reception of traffic addressed to pref1::if1
at the interface if2, the MN MUST follow the Weak host model
[RFC1122], [I-D.thaler-ip-model-evolution]. This model does not
limit traffic reception at a host only to IP packets whose
destination address matches the IP address assigned to the interface
receiving the packets, but allows to receive and process packets
whose IP destination address corresponds to that of any of the local
interfaces of the host.
By implementing the Weak host model, the MN in Figure 3 would be able
to process traffic addressed to any of its IP addresses (i.e.,
pref1::if1 and pref2::if2), no matter to which interface that traffic
arrives to.
We have performed some tests with different operating systems, and
the results show that both Linux (tested with Linux-2.6.26) and Mac
OS X (tested with Leopard) implements the Weak host model for both
IPv4 and IPv6 traffic. We have not performed tests with Windows, but
some results have been reported in [I-D.ietf-mif-current-practices].
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It should be noted that Windows XP and Windows Server 2003 use the
weak host model for sends and receives for all IPv4 interfaces and
the strong host model for sends and receives for all IPv6 interfaces.
This behavior cannot be modified. The Next Generation TCP/IP stack
in Windows Vista and Windows Server 2008 supports strong host sends
and receives for both IPv4 and IPv6 by default on all interfaces.
The stack can be configured to use weak host model.
Generally it should be possible to enable automatic configuration of
the weak model during network attachment/entry according to policies
configured in the operator's network. Signaling exchanged between
the MAG and the LMA (PUB, PBA) needs to be extended to configure the
MN (via RS/RA or DHCP) to use the weak host model on a specific
interface. As an example according to RFC 5175 [RFC5175] a bit can
be assigned in the RA message indicating such option. The access
provider could then decide to configure the MAGs to advertise the MN
for weak model configuration. Obviously, understanding a new RA/RS
bit or a DHCP option would require new functionality in the MN`s IP
stack, or at minimum some kind of a networking configuration manager
running in a MIF node.
4.2. LMA considerations
The LMA MUST be able to identify all the mobility bindings at its
Binding Cache (BC) that refer to the same MN, using the MN-
identifier. The LMA SHOULD have an additional policy/routing table.
This table is used by the LMA to store and look up information about
how to route packets to a certain MN. With current PMIPv6
specification, the LMA decides on the next hop towards a particular
MN based only on the destination prefix (that would result on an
outgoing tunnel interface to reach the MAG where that prefix is
currently reachable). In order to allow the LMA to dynamically
decide which is the best path for a certain traffic to reach the MN,
a policy/routing table SHOULD be used. By using this table, the LMA
would be able to send different flows addressed to the same
destination IP address (e.g. pref1::if1) via different MAGs.
4.3. MAG considerations
The MAG MUST support routing packets addressed to MNs locally
attached to the MAG, but using a destination prefix or address that
is not on-link. In order to do that, the MAG SHOULD be informed by
the LMA about the set of IP addresses that the MN has acquired from
the PMIPv6 domain, so the MAG can add the required entries on its
routing table. The PBA MAY be extended to include such information.
The prefixes advertised in the Router Advertisement (RA) sent from
the MAG to the MN include only those that would be advertised in case
of base RFC 5213 operation without any flow/policy routing
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extensions.
4.4. Downlink and Uplink considerations
The extensions outlined in this document would allow an MN to
simultaneously receive traffic through all of its interfaces that are
attached to the same PMIPv6 domain. Enabling such a feature in the
Downlink (DL) makes sense when several access networks are available
at the same time, as for example in heterogeneous PMIPv6 domains
where several access technologies exhibiting different DL capacities
are found (e.g., WLAN and 3G).
Enabling the feature on the Uplink (UL) is also possible. Enabling
the network (i.e., the LMA) to have the control on which MN's
outgoing interface it used for a certain flow requires changes on the
MN side, as well as signaling on the MN-AR interface or configuring
explicit routes on the MN using existing host configuration protocols
at IP level (e.g. DHCP). Nevertheless, if the decision is on the MN
side, this might be easily supported by the solution outlined in this
document, by properly configuring the routing and ingress filtering
at the MAGs.
The mapping of a flow to an interface may be driven by the terminal,
the LMA or both:
1. driven by the terminal: the terminal establishes the policy and
selects the interface to send packets. The LMA must be aware of
the flow/interface mapping policy to keep consistency in routing
(the terminal would expect receiving traffic on a specific
interface). So the terminal may provide its policy to the LMA.
2. driven by the LMA: the LMA have the control on which MN's
outgoing interface is used for a certain flow. In such a case
the MN's routing table is updated according to the policy which
must be provided to the MN by the LMA.
3. MN driven but assisted by the LMA: the terminal controls the
mapping of the flows to the possible interfaces. However the LMA
provides some default policies which can be updated by the MN.
The policies must be exchanged in both directions (from LMA to MN
and vice versa).
4.5. IPv4 considerations
IPv4 Home Addresses work mostly in a similar manner as IPv6 HNPs in
the context of PMIPv6 and MIF nodes. Though, a MIF node may by
default apply a different host model depending on the IP version.
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One problem with IPv4 Home Addresses is the possible use of private
IPv4 addresses [RFC1918]. It is possible for a MIF node to configure
overlapping public IPv4 Addresses on multiple interfaces. This is
not a new issue as it has been possible since the introduction of
[RFC1918] and any multi-homed IPv4 node. Still, the host operation
is not generally clearly defined in case of multiple overlapping
addresses. The only common advice is to avoid overlapping [RFC1918]
private IPv4 Home Addresses within PMIPv6 domain, unless the MIF
nodes are known to be able to handle such situation gracefully. This
situation resembles the scenario iii) of
[I-D.devarapalli-netext-multi-interface-support] and therefore is out
of scope of this document.
5. IANA Considerations
This document makes no request of IANA.
6. Security Considerations
None.
7. Acknowledgements
The authors would like to thank Paulo Ferrer and Marco Liebsch for
their comments and discussion on this document.
The research of Carlos J. Bernardos leading to these results has
received funding from the European Community's Seventh Framework
Programme (FP7/2007-2013) under grant agreement n. 214994 (CARMEN
project) and also from the Ministry of Science and Innovation of
Spain, under the QUARTET project (TIN2009-13992-C02-01).
8. References
8.1. Normative References
[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
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Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5175] Haberman, B. and R. Hinden, "IPv6 Router Advertisement
Flags Option", RFC 5175, March 2008.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
8.2. Informative References
[I-D.devarapalli-netext-multi-interface-support]
Devarapalli, V., Kant, N., Lim, H., and C. Vogt, "Multiple
Interface Support with Proxy Mobile IPv6",
draft-devarapalli-netext-multi-interface-support-00 (work
in progress), March 2009.
[I-D.ietf-mif-current-practices]
Wasserman, M., "Current Practices for Multiple Interface
Hosts", draft-ietf-mif-current-practices-00 (work in
progress), October 2009.
[I-D.ietf-mif-problem-statement]
Blanchet, M. and P. Seite, "Multiple Interfaces Problem
Statement", draft-ietf-mif-problem-statement-01 (work in
progress), October 2009.
[I-D.ietf-netlmm-pmip6-ipv4-support]
Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
Mobile IPv6", draft-ietf-netlmm-pmip6-ipv4-support-17
(work in progress), September 2009.
[I-D.jeyatharan-netext-multihoming-ps]
Jeyatharan, M. and C. Ng, "Multihoming Problem Statement
in NetLMM", draft-jeyatharan-netext-multihoming-ps-01
(work in progress), March 2009.
[I-D.thaler-ip-model-evolution]
Thaler, D., "Evolution of the IP Model",
draft-thaler-ip-model-evolution-01 (work in progress),
July 2008.
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Authors' Addresses
Carlos J. Bernardos
Universidad Carlos III de Madrid
Av. Universidad, 30
Leganes, Madrid 28911
Spain
Phone: +34 91624 6236
Email: cjbc@it.uc3m.es
URI: http://www.it.uc3m.es/cjbc/
Telemaco Melia
Alcatel-Lucent Bell Labs
Email: Telemaco.Melia@alcatel-lucent.com
Pierrick Seite
France Telecom
Email: pierrick.seite@orange-ftgroup.com
Jouni Korhonen
Nokia Siemens Networks
Email: jouni.korhonen@nsn.com
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