DMM Working Group A. Yegin
Internet-Draft K. Kweon
Intended status: Standards Track J. Lee
Expires: January 04, 2014 J. Park
Samsung
July 03, 2013
On Demand Mobility Management
draft-yegin-dmm-ondemand-mobility-00
Abstract
Applications differ with respect to whether they need IP session
continuity and/or IP address reachability. The network providing the
same type of service to any mobile host and any application running
on the host yields inefficiencies. This document describes a
solution for taking the application needs into account in selectively
providing IP session continuity and IP address reachability on a per-
socket basis.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 3
3. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Types of IP Addresses . . . . . . . . . . . . . . . . . . 4
3.2. Granularity of Selection . . . . . . . . . . . . . . . . 5
3.3. On Demand Nature . . . . . . . . . . . . . . . . . . . . 5
3.4. Conveying the Selection . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Normative References . . . . . . . . . . . . . . . . . . 8
6.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
In the context of Mobile IP [RFC5563][RFC6275][RFC5213][RFC5944],
following two attributes are defined for the IP service provided to
the mobile hosts:
IP session continuity: The ability to maintain an ongoing IP session
by keeping the same local end-point IP address throughout the session
despite moving among different IP networks. The IP address of the
host may change between two independent IP sessions, but that does
not jeopardize the IP session continuity. IP session continuity is
essential for mobile hosts to maintain ongoing IP sessions without
any interruption.
IP address reachability: The ability to maintain the same IP address
for an extended period of time. The IP address shall stay the same
across independent IP sessions, and even in the absence of any IP
session. The IP address may be published in a long-term registry
(e.g., DNS), and it shall be available for serving incoming (e.g.,
TCP) connections. IP address reachability is essential for mobile
hosts to use specific/published IP addresses.
Mobile IP is designed to provide both IP session continuity and IP
address reachability to mobile hosts. Architectures utilizing these
protocols (e.g., 3GPP, 3GPP2, WIMAX) ensure that every one of the
mobile hosts attached to the compliant networks enjoy these benefits.
Every application running on each one of those mobile hosts is
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subjected to the same treatment with respect to the IP session
continuity and IP address reachability.
It should be noted that in reality not every application may need
those benefits. IP address reachability is required for applications
running as servers (e.g., a camera mounted on a bus). But, a typical
client application (e.g., web browser) does not necessarily require
IP address reachability. Similarly, IP session continuity is not
required for all types of applications either. Applications
performing brief communication (e.g., DNS client) can survive without
having IP session continuity support.
Achieving IP session continuity and IP address reachability by using
Mobile IP incur some cost. This solution forces the mobile host's IP
traffic to traverse a centrally-located router (Home Agent, HA),
which incurs additional transmission latency and use of additional
network resources, adds to the network CAPEX and OPEX, and decreases
the reliability of the network with the introduction of a single
point of failure [I-D.ietf-dmm-requirements]. Therefore, IP session
continuity and IP address reachability should be used selectively.
Furthermore, even when an application needs IP session continuity, it
may be able to satisfy that need by using a solution above the IP
layer, such as MPTCP [RFC6824], SIP mobility [RFC3261], or an
application-layer mobility solution. Those higher-layer solutions
are not subject to the same issues that arise with the use of Mobile
IP since they can utilize the most direct data path between the end-
points. But, if Mobile IP is being applied to the mobile host, those
higher-layer protocols are rendered useless because their operation
is inhibited by the Mobile IP. Since Mobile IP ensures the IP
address of the mobile host remains fixed (despite the location and
movement of the mobile host), the higher-layer protocols never detect
the IP-layer movement and never engage in mobility management.
This document proposes a solution where the applications running on
the mobile host can indicate whether they need IP session continuity
or IP address reachability. The IP stack on the mobile host, in
conjunction with the network, would provide the required type of IP
service. It is for the benefit of both the users and the network
operators not to engage an extra level of service unless it is
absolutely necessary. So it is expected that applications and
networks compliant with this specification would utilize this
solution to use network resources more efficiently.
2. Notational Conventions
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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 [RFC2119].
3. Solution
3.1. Types of IP Addresses
Three types of IP addresses are defined with respect to the mobility
management.
- Home Network Anchored Address
This is what standard Mobile IP provides with a Home Address (HoA).
The mobile host is configured a HoA from a centrally-located Home
Network. Both IP session continuity and IP address reachability are
provided to the mobile host with the help of a router in the Home
Network (Home Agent, HA). This router acts as an anchor for the IP
address of the mobile host.
- Access Network Anchored Address
This type of IP address provides IP session continuity but not IP
address reachability. It is achieved by ensuring that the IP address
used at the beginning of the session remains usable despite the
movement of the mobile host. But the IP address may change after the
end of ongoing IP sessions, therefore it does not exhibit
persistence.
The IP address is allocated by a serving IP gateway. When the mobile
host moves to another network, the previously serving gateway becomes
an anchor gateway and starts treating the IP address as a Home
Address with the help of the received binding updates. A tunnel is
established between the anchor gateway and the current care-of
address of the mobile host (whether configured on the host itself
[RFC5944][RFC6275], or on the serving gateway [RFC5213][RFC5563]) for
ensuring the session continuity using the same IP address.
- Unanchored Address
This type of IP address provides neither IP session continuity nor IP
address reachability. The IP address is obtained from the serving IP
gateway and it is not maintained across gateway changes. In other
words, the IP address may be released and replaced by a new IP
address when the IP gateway changes due to the mobile host's
mobility.
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Applications running as servers at a published IP address require
Home Network Anchored Address. Long-standing applications (e.g., an
SSH session) may also require this type of address. They could use
Access Network Anchored Address, but that can produce sub-optimal
results if the mobile host ends up far from the anchor gateway.
Enterprise applications that connect to an enterprise network via
virtual LAN require Home Network Anchored Address.
Applications with short-lived transient IP sessions can use Access
Network Anchored Address. For example: Email client, web browser,
calendar, app store client, etc.
Applications with very short IP sessions, such as DNS client and
instant messengers, can utilize Unanchored Address. Even though they
could very well use Home or Access Network Anchored Addresses, the
transmission latency would be the minimum when an Unanchored Address
is used.
3.2. Granularity of Selection
The IP address type selection is made at per-socket granularity.
Different parts of the same application may have different needs.
For example, control part of the application may require Home Network
Anchored Address in order to stay reachable, whereas data part of the
application may be satisfied with Access Network Anchored Address.
3.3. On Demand Nature
At any point in time, a mobile host may have any mixture of IP
addresses configured. Zero or more Unanchored, zero or more Access
Network Anchored, and zero or more Home Network Anchored IP addresses
may be available on the IP stack of the host. The mixture may be as
a result of the host policy, or as a result of the application
demand.
If an IP address of the requested type is not available, then the IP
stack shall attempt to configure one. For example, a host may not
always have a Home Network Anchored IP address available as this is
rarely used. In case an application requests one, then the IP stack
shall make an attempt to configure one using Mobile IP. If Mobile IP
is not available to the host, or if its operation fails, then the IP
stack shall fail the associated socket request. In case of
successful Mobile IP operation, a Home Network Anchored IP Address
gets configured on the mobile host. If another socket requests a
Home Network Anchored IP address at a later time, then the same IP
address may be served to that socket as well. When the last socket
using the requested IP address is closed, the IP address may be
released.
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The following are matters of policy, which may be dictated by the
host itself, the network operator, or the compliant network
architecture:
- The initial set of IP addresses configured on the host at the boot
time.
- Permission to grant various types of IP addresses to a requesting
application.
- Determination of a default address type when an application does
not make any explicit indication, whether it already supports the
required API or it is a legacy application.
3.4. Conveying the Selection
The selection of the address type is conveyed from the applications
to the IP stack in a way to influence the source address selection
algorithm [RFC6724].
The current source address selection algorithm operates on the
available set of IP addresses when selecting an address. According
to the proposed solution, if the requested type IP address is not
available at the time of the request, then the IP stack shall make an
attempt to configure one such IP address. The selected IP address
shall be compliant with the requested IP address type, whether it is
selected among available addresses or dynamically configured. In the
absence of a matching type (because it is not available and not
configurable on demand), the source address selection algorithm shall
return an empty set.
A Socket API-based interface for enabling applications to influence
the source address selection algorithm is described in [RFC5014].
That specification defines IPV6_ADDR_PREFERENCES option at the
IPPROTO_IPV6 level. That option can be used with setsockopt() and
getsockopt() calls to set and get address selection preferences.
Furthermore, that RFC also specifies two flags that relate to IP
mobility management: IPV6_PREFER_SRC_HOME and IPV6_PREFER_SRC_COA.
These flags are used for influencing the source address selection to
prefer either a Home Address or a Care-of Address.
Unfortunately, these flags do not satisfy the aforementioned needs
due to the following reasons, therefore new flags are proposed in
this document:
- Current flags indicate a "preference" whereas there is a need for
indicating "requirement". Source address selection algorithm does
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not have to produce an IP address compliant with the "preference" ,
but it has to produce an IP address compliant with the "requirement".
- Current flags influence the selection made among available IP
addresses. The new flags force the IP stack to configure a compliant
IP address if none is available at the time of the request.
- The Home vs. Care-of Address distinction is not sufficient to
capture the three different types of IP addresses described in
Section 2.1.
The following new flags are defined in this document and they shall
be used with Socket API in compliance with the [RFC5014]:
IPV6_REQUIRE_HOME_ANCHORED /* Require Home Anchored address as source
*/
IPV6_REQUIRE_ACCESS_ANCHORED /* Require Access Anchored address as
source */
IPV6_REQUIRE_UNANCHORED /* Require Unanchored address as source */
More than one of these flags may be set on the same socket. In that
case, an IP address compliant with any one of them shall be selected.
When any of these new flags is used, then the IPV6_PREFER_SRC_HOME
and IPV6_PREFER_SRC_COA flags, if used, shall be ignored.
These new flags are used with setsockopt()/getsockopt(),
getaddrinfo(), and inet6_is_srcaddr() functions [RFC5014]. Similar
with the setsockopt()/getsockopt() calls, getaddrinfo() call shall
also trigger configuration of the required type IP address, if one is
not already available. When the new flags are used with
getaddrinfo() and the triggered configuration fails, the
getaddrinfo() call shall ignore that failure (i.e., not return an
error code to indicate that failure). Only the setsockopt() shall
return an error when configuration of the requested type IP address
fails.
Application of this solution to IPv4 is TBD.
4. Security Considerations
The setting of certain IP address type on a given socket may be
restricted to privileged applications. For example, a Home Anchored
IP Address may be provided as a premium service and only certain
applications may be allowed to use them. Setting and enforcement of
such privileges are outside the scope of this document.
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5. IANA Considerations
TBD
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5014] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6
Socket API for Source Address Selection", RFC 5014,
September 2007.
[RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, September 2012.
6.2. Informative References
[I-D.ietf-dmm-requirements]
Chan, A., Liu, D., Seite, P., Yokota, H., and J. Korhonen,
"Requirements for Distributed Mobility Management", draft-
ietf-dmm-requirements-05 (work in progress), June 2013.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[RFC5563] Leung, K., Dommety, G., Yegani, P., and K. Chowdhury,
"WiMAX Forum / 3GPP2 Proxy Mobile IPv4", RFC 5563,
February 2010.
[RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised", RFC
5944, November 2010.
[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.
[RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
"TCP Extensions for Multipath Operation with Multiple
Addresses", RFC 6824, January 2013.
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Authors' Addresses
Alper Yegin
Samsung
Istanbul
Turkey
Email: alper.yegin@partner.samsung.com
Kisuk Kweon
Samsung
Suwon
South Korea
Email: kisuk.kweon@samsung.com
Jinsung Lee
Samsung
Suwon
South Korea
Email: js81.lee@samsung.com
Jungshin Park
Samsung
Suwon
South Korea
Email: shin02.park@samsung.com
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