Subject: [multipathtcp] [MPTCP] draft-deng-mptcp-mobile-network-proxy-00

From: "Xiongchunshan (Sam)" <[email-masked]>
Date: Tue, 25 Feb 2014 01:01:07 +0000

Hello folks,

Here I have some comments on this document:

1)
5.2  Traffic mediation
   (a) Anchoring of sub-flow traffic: On one hand, it is not always
   possible for a single GW be sitting on the path of every sub-flow
   from a MPTCP session, hence explicit traffic anchoring to enable a
   single point of general control over MPTCP sub-flows should be
   considered.
   (b) Mediation of sub-flow traffic: On the other hand, for fine-
   grained mediation of sub-flow traffic, both static and dynamic
   selection/offloading/pooling policies should be allowed. For
   instance, "always prefer Wi-Fi over 3GPP" could be a static policy
   for bulk data transfer services, while "use 3GPP only for backup
   unless Wi-Fi is congested" could be a dynamic offloading policy for a
   un-prioritized VoIP service.
[xcs]Question for clarification: How does the MPTCP proxy know the binding information between the IP and RAT ?  The mobile node knows which IP is allocated from which RAT, but it is very hard for the MPTCP Proxy in the core network to know these mapping information.
One possible solution is the PCRF (defined in the 3GPP) to provide these binding information to the MPTCP proxy if the MPTCP proxy performance the traffic mediation or let the mobile to do the traffic mediation.

Another question is how the rules (e.g. "always prefer Wi-Fi over 3GPP") are provided to the MPTCP Proxy or the mobile ? For the MPTCP proxy, it is again the PCRF; for the mobile , it is the ANDSF ?

2)
4.2 Resource pooling for reduced expense
   Due to its low construction and operation expenses, Wi-Fi has been
   adopted by mobile operators as a complementary RAT for their
   traditional 3GPP networks. However, different construction and
   operation expenses of various radio networks result in differences in
   charging rates/policies for different RATs.
   For instance, Wi-Fi access may be charged by the access duration,
   while the 3GPP access may be charged by the consumed data volume.
   Even if using the same policy, Wi-Fi service is expected to be much
   cheaper than 3GPP data service.
   Moreover, different subscription packages may offer various data
   plans for various RATs. For instance, a basic 4G package may contain
   free data volume as well free Wi-Fi access too.
   By enabling MPTCP session between UE and network proxy, via mediating
   sub-flow data traffic based on their Radio access types and the
   user’s subscription package, it is possible to further reduce the
   usage expenses from both sides of the network and user.

[xcs] it will benefit the user if the user’s expense of data usage is reduced, if the WiFi connection is available and charging fee is very low, maybe all the traffic from the 4G are moved to the WiFi by the MPTCP proxy, and the mobility and QoS of the service maybe aren’t ensured, so it is proposed to adding the following sentence to the end of this chapter:
The QoS/QoE/Service continuity of the current data services are still kept when the MPTCP proxy is used to reduce the user’s usage expenses.

A assumption for reducing user expense is that the WiFi connection is activated beforehand, but sometimes the WiFi connection isn’t activated or a wrong WiFi AP is selected by the user( that MPTCP Proxy can’t access the WiFi IP flow), that is, one hand, the network need to control the MPTCP Proxy to mediate the IP flows, another hand, the network should tell the mobile to open which RAT/WiFi to make the MPTCP Proxy work.  i.e. the network should provide some information to the UE , to guide the UE to select and open another RAT to enable the MPTCP.

3)
4.1 Dynamic traffic offloading based on network information
   For real-time interactive services with higher QoS requirements it is
   expected that 3GPP network can provide better guarantees on the
   average case. For bulk data transfer who is satisfied with best-
   effort delivery, Wi-Fi would be a great choice. But the vertical
   partition does not fit everywhere for the wireless condition itself
   is quite dynamic and hard to predict. It is important to implement
   adaptive offloading mechanisms in order to achieve higher resource
   utility with ever changing radio environment for a possibly moving
   terminal based on network status, e.g. cell load, AP’s signal
   intensity, user’s subscription type, etc.
[xcs]The same question from 1):  How does the MPTCP Proxy/UE know the network status ? The PCRF/ANDSF provides these information to the MPTCP Proxy/UE ?

BRs
Chunshan Xiong
Huawei Technologies Co., Ltd.

---

From: lingli deng <[email-masked]>
Date: Wed, 26 Feb 2014 13:20:40 +0800

Hi Sam,

Thanks for your review and comments.
Plz see some initial comments inline:

Lingli

2014-02-25 9:01 GMT+08:00 Xiongchunshan (Sam) <[email-masked]>
:

> [xcs]Question for clarification: How does the MPTCP proxy know the binding
> information between the IP and RAT ?  The mobile node knows which IP is
> allocated from which RAT, but it is very hard for the MPTCP Proxy in the
> core network to know these mapping information.
>

*[dll] For 3GPP access networks, the core knows the RAT type as the time of
PDP connection setup. For WLAN, there has been interworking standards via
PDG (packet data gateway) which does the IP binding. So the core network
knows the mapping, and there is a need to integrate MPTCP proxy with
existing architecture to get this information.*

>  One possible solution is the PCRF (defined in the 3GPP) to provide these
> binding information to the MPTCP proxy if the MPTCP proxy performance the
> traffic mediation or let the mobile to do the traffic mediation.
>

*[dll] I agree that interface with PCRF could be a solution to provide
binding information from the network side, as well as acquiring mediation
policy.*

>
>
> Another question is how the rules (e.g. "always prefer Wi-Fi over 3GPP")
> are provided to the MPTCP Proxy or the mobile ? For the MPTCP proxy, it is
> again the PCRF; for the mobile , it is the ANDSF ?
>
>
>

*[dll] Yes, PCRF would be a candidate in the case of proxy mediation and
ANDSF has been proposed to be used by 3GPP for network selection. However,
just for discussion, I personally prefer proxy-based mediation, as it may
not always be proper to rely on the terminal for network-driven policy
enforcement. Therefore, I would suggest we **currently **focuse on
proxy-mediation case. Would you agree?*

> [xcs] it will benefit the user if the user’s expense of data usage is
> reduced, if the WiFi connection is available and charging fee is very low,
> maybe all the traffic from the 4G are moved to the WiFi by the MPTCP proxy,
> and the mobility and QoS of the service maybe aren’t ensured, so it is
> proposed to adding the following sentence to the end of this chapter:
>
> *The QoS/QoE/Service continuity of the current data services are still
> kept when the MPTCP proxy is used to reduce the user’s usage expenses.*
>

*[dll] Good point. I agree.*

>
>
> A assumption for reducing user expense is that the WiFi connection is
> activated beforehand, but sometimes the WiFi connection isn’t activated or
> a wrong WiFi AP is selected by the user( that MPTCP Proxy can’t access the
> WiFi IP flow), that is, one hand, the network need to control the MPTCP
> Proxy to mediate the IP flows, another hand, the network should tell the
> mobile to open which RAT/WiFi to make the MPTCP Proxy work.  i.e. the
> network should provide some information to the UE , to guide the UE to
> select and open another RAT to enable the MPTCP.
>
>
>
*[dll] I agree that it is of great value for mobile terminals to be more
intelligent in enabling multiple interfaces based on network provided
information. But how it is done seems to be out of scope of a MPTCP proxy
discussion.*

> [xcs]The same question from 1):  How does the MPTCP Proxy/UE know the
> network status ? The PCRF/ANDSF provides these information to the MPTCP
> Proxy/UE ?
>

 *[dll] Plz refer to the above comments^^*

> _______________________________________________
> multipathtcp mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/multipathtcp
>
>

-- 
邓灵莉/Lingli Deng
中国移动通信研究院/China Mobile Research Institute
e-mail: [email-masked]
tel: 15801696688-3367
mobile: 13810597148

---

From: Olivier Bonaventure <[email-masked]>
Date: Thu, 27 Feb 2014 09:45:32 +0100

Hello,

>
>     [xcs]Question for clarification: How does the MPTCP proxy know the
>     binding information between the IP and RAT ?  The mobile node knows
>     which IP is allocated from which RAT, but it is very hard for the
>     MPTCP Proxy in the core network to know these mapping information.
>
>
> *[dll] For 3GPP access networks, the core knows the RAT type as the time
> of PDP connection setup. For WLAN, there has been interworking standards
> via PDG (packet data gateway) which does the IP binding. So the core
> network knows the mapping, and there is a need to integrate MPTCP proxy
> with existing architecture to get this information.*

For MPTCP, the client gets several IP addresses, say one from the WLAN 
and one from the 3G network. A proxy solution should allow the client to 
start the MPTCP connection through the proxy either via the WLAN 
interface or via the 3G interface. It should not be bound to a specific 
network (say 3G) and force the client to always start over this network. 
There are mobility scenarios where only one network is available when a 
connection starts and this connection must pass through the proxy to 
benefit from mptcp in the future.

>     ____
>
>     One possible solution is the PCRF (defined in the 3GPP) to provide
>     these binding information to the MPTCP proxy if the MPTCP proxy
>     performance the traffic mediation or let the mobile to do the
>     traffic mediation.
>
>
> binding information from the network side, as well as acquiring
> mediation policy.*

An MPTCP proxy should not be restricted to a given technology. The 
client should be able to learn the address of the proxy that it needs to 
use (e.g. based on its location, subscription information or the network 
that it is currently connected to, ...). There could be some way to 
distribute this information from the 3GPP network, but it should not be 
the only way

>     ____
>
>     ____
>
>     Another question is how the rules (e.g. "always prefer Wi-Fi over
>     3GPP") are provided to the MPTCP Proxy or the mobile ? For the MPTCP
>     proxy, it is again the PCRF; for the mobile , it is the ANDSF ?____
>
>
> ANDSF has been proposed to be used by 3GPP for network selection.
> However, just for discussion, I personally prefer proxy-based mediation,
> as it may not always be proper to rely on the terminal for
> network-driven policy enforcement. Therefore, I would suggest we
> **currently **focuse on proxy-mediation case. Would you agree?*
>

In the case of WLANs, and in particular WLANs that are not controlled by 
the network operator, the terminal has often more information about the 
quality of the network (both WLAN and 3G) than the network itself. We 
should exploit this information and not only rely on the network.

>     [xcs] it will benefit the user if the user’s expense of data usage
>     is reduced, if the WiFi connection is available and charging fee is
>     very low, maybe all the traffic from the 4G are moved to the WiFi by
>     the MPTCP proxy, and the mobility and QoS of the service maybe
>     aren’t ensured, so it is proposed to adding the following sentence
>     to the end of this chapter:____
>
>     *The QoS/QoE/Service continuity of the current data services are
>     still kept when the MPTCP proxy is used to reduce the user’s usage
>     expenses.*
>
>

Reducing the user expenses (assuming that WiFi is cheaper than 3G) is 
one use case for an MPTCP proxy, but this is by far not the only one. 
Other use cases include :

  - improving performance by using simultaneously WiFi and 3G
  - improving quality of experience by allowing the terminal to use 
either WiFi or 3G automatically without asking the user to manually 
switch between the two interfaces
  - avoid being stuck with "open" WiFi networks that provide an IP 
address but use a captive portal where the user has to log in. Today, 
many users of smartphones are frustrated when their smartphone stops 3G 
to attach to such a WiFi network that they cannot use (but the 
smartphone tries sometimes for several minutes)
  - ...

>     ____
>
>     ____
>
>     A assumption for reducing user expense is that the WiFi connection
>     is activated beforehand, but sometimes the WiFi connection isn’t
>     activated or a wrong WiFi AP is selected by the user( that MPTCP
>     Proxy can’t access the WiFi IP flow), that is, one hand, the network
>     need to control the MPTCP Proxy to mediate the IP flows, another
>     hand, the network should tell the mobile to open which RAT/WiFi to
>     make the MPTCP Proxy work.  i.e. the network should provide some
>     information to the UE , to guide the UE to select and open another
>     RAT to enable the MPTCP.____
>
> information. But how it is done seems to be out of scope of a MPTCP
> proxy discussion.*

A proxy should not be limited to some specific networks that are 
controlled by the network operator. Users expected to be able to use 
whatever WiFi for which they have the necessary credentials and MPTCP is 
able to use whatever WiFi has long as it provides a reachable IP address.

Olivier

-- 
INL, ICTEAM, UCLouvain, Belgium, http://inl.info.ucl.ac.be