PCP Working Group Z. Cao
Internet-Draft G. Chen
Intended status: Informational H. Deng
Expires: September 7, 2011 T. Sun
China Mobile
March 6, 2011
Requirements for Always Online Applications
draft-cao-pcp-mobapp-online-00
Abstract
This document discusses several requirements for always online mobile
applications which reveals that PCP only solution does not fill the
gap.
Status of this Memo
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This Internet-Draft will expire on September 7, 2011.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . . 3
2. Scenario and Problems . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements for Always-online Mobile Applications . . . . . . 4
3.1. R1: Support for NAT and Firewall State Keep-alive . . . . . 4
3.2. R2: Keep the State on Mobile App Server . . . . . . . . . . 4
3.3. R3: Keep the State on Mobile Network Gateway . . . . . . . 4
3.4. R4: Relieve Burden on Air Interface . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
6. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5
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1. Introduction
This document discusses several requirements for always online mobile
applications which reveals that PCP only solution does not fill the
gap.
1.1. Conventions used in this document
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].
2. Scenario and Problems
Figure 1 depicts the secenario of the mobile network environment. BS
is the radio Base Station which provides wireless connectivity to the
MN. The MNG/FW is the MN's default router which provides IP address
management and NAT/Firewall functionality. The Border Router (BR) as
the name implies, borders the Internet for the mobile network. The
BR does not perform subscriber management for the mobile network.
The mobile application server is server on the Internet that provides
application layer service to the MN.
To make the mobile application behave like always online, there are
several states that need to be kept. Below, we take Instant Message
applications as an example,
1. Mobile App Server: the server needs to know if the mobile client
is still active and if the mobile node is still on-line. Mobile
application developers always make the mobile client send keep
alive messages at an interval.
2. NAT state: The GW/FW needs to keep the NAT binding state for the
TCP/UDP mappings. Once the NAT states staled, the mobile
application server is not able to push messages to the mobile
client.
3. IP address state: the mobile network normally uses the so called
"packet data protocol (PDP)" to manage the IP connection with the
MN.
4. Wireless Channel State: when packets are ready, the mobile node
needs to acquire the wireless channel in order to receive or
transmit those packet.
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MN BS +----+
| /\ /---------\ +------+ /-----------\ +--+ / \
+-+ /_ \---/ Internal \|MNG/FW|/ Operator's \|BR|/Internet\
| |---/ \ \IP Network /+------+\ IP Network /+--+\ /
+-+ \---------/ \-----------/ \ /
+----+
|
+--------+ |
|Mob App |---+
|Server |
+--------+
MNG: Mobile Network Gateway
FW: Firewall
BR: Border Router
Figure 1: Mobile Client/Server Applications
3. Requirements for Always-online Mobile Applications
The requirements that need to be addressed by an always-online mobile
applications.
3.1. R1: Support for NAT and Firewall State Keep-alive
Mapping states on the NAT box or Firewall should be retained in order
to make the MN visible and reachable from outside. PCP
[I-D.ietf-pcp-base] is an instant solution this problem, however it
does not take into account the other problems as list below.
3.2. R2: Keep the State on Mobile App Server
The mobile application server needs to keep track of the mobile node
in order to know the status of the mobile application. For example,
mobile Instant Message servers need to know the MN's presence status
and notify their friends accordingly.
Note: most mobile applications send keep alive messages between the
MN and the server in order to keep the state on both the App Server
and the NAT/FW.
3.3. R3: Keep the State on Mobile Network Gateway
The IP connection between the MN and Mobile Network Gateway (MNG) is
managed by a certain Packet Data Protocol (PDP) in the mobile
network. The MNG frequently releases the resources and state of IP
connection after a setup timeout. In order to make the mobile
applications always online, the state on the MNG should be
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maintained.
3.4. R4: Relieve Burden on Air Interface
In order to maintain any states mentioned above, it necessarily send
many small packets between the MN and MNG or MN and the APP Server
which incurs a huge burden on the air interface. Whenever
transmitting packets, one dedicated channel is required. When the
channel is released, the paging procedure is triggered. Both of
these incur a lot of signalling on the air interface. It is highly
indispensable to relieve the burden on air interface.
4. Security Considerations
TBD.
5. IANA Considerations
This document does not require any IANA actions.
6. Normative References
[I-D.ietf-pcp-base]
Wing, D., Cheshire, S., Boucadair, M., Penno, R., and F.
Dupont, "Port Control Protocol (PCP)",
draft-ietf-pcp-base-06 (work in progress), February 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Authors' Addresses
Zhen Cao
China Mobile
Unit2, 28 Xuanwumenxi Ave,Xuanwu District
Beijing 100053
China
Email: zehn.cao@gmail.com
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Gang Chen
China Mobile
Unit2, 28 Xuanwumenxi Ave,Xuanwu District
Beijing 100053
China
Email: chengang@chinamobile.com
Hui Deng
China Mobile
Unit2, 28 Xuanwumenxi Ave,Xuanwu District
Beijing 100053
China
Email: denghui@chinamobile.com
Tao Sun
China Mobile
Unit2, 28 Xuanwumenxi Ave,Xuanwu District
Beijing 100053
China
Email: suntao@chinamobile.com
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