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Re: [STDS-802-16] Issues for the usage of the Secondary management connection

Dear Chulsik,
 
I think our disagreement results from a very fundamental fact. This fact is that I believe that the management function of the mobile device can be done on top of the MAC rather than inside it. What this means is that it is not necessary for the MAC to define DHCP or Mobile-IP or TFTP download or any of these things. It is sufficient to define a management interface (like a MIB), and then after the MSS is connected to the network, open a management connection (which is a normal transport connection from the MAC point of view, but used for management from the system point of view) and manage the MSS to your heart's desire. This approach simplifies things, since in the MAC level there is no special treatment to this connection (not to mention that it does not need an IP stack now, HO is faster, etc.).
I hope this clarifies what I said in the meeting.
 
BR,
Yigal

From: owner-stds-802-16@listserv.ieee.org [mailto:owner-stds-802-16@listserv.ieee.org] On Behalf Of ???
Sent: Friday, October 15, 2004 4:09 AM
To: STDS-802-16@listserv.ieee.org
Subject: [STDS-802-16] Issues for the usage of the Secondary management connection

Hello Yigal,

 

I would like to discuss the usage of the Secondary Management Connection.

 

In the current draft standard, the usage of the secondary management connection is described like this (it is the result of the last meeting in Seoul, comment #580):

¡°Finally, the Secondary Management Connection is used by the BS and MSS to transfer delay tolerant, standards-based [Dynamic Host Configuration Protocol (DHCP), Trivial File Transfer Protocol (TFTP), SNMP, etc.] management messages.¡±

-- The text having the meaning that Mobile IP messages and router prefix advertisement are not transferred through the secondary management connection.

 

We have talked about the issues in the meeting, but we have found out some differences in our understanding, and the problems in the current specification.

 

You said:
The Secondary Management Connection can be used only for the management purposes, not for a user traffic transport, such as the SNMP messages for the SS. The IP address allocated by using the DHCP is used only for the management for the SS, not for the user traffic. The IP address for the user service can be allocated using the ¡°default¡± Transport Connection. And the parameters for default Transport Connection is pre-assigned in each Base Station (BS).

 

But, these ideas have some problems:

1)       You mean that the protocol layer for the SS management (i.e., SNMP) is within the layer 2 (MAC) of the SS, and the path to that is on the Secondary Management Connection. And the user traffic (even in the case of DHCP or Mobile IP message for the IP address allocation for the user traffic) cannot use the secondary management connection.
In that case the protocol layers for the IP and above should be duplicated in the user plane and the management plane. But, the SNMP for the SS management and the Mobile IP for the IP connectivity management for user traffic can be discriminated in the IP layer by the ¡°protocol¡± field. So, the two protocols can be well harmonized using the secondary management connection. And, it is not required to implement the duplicated protocol layers for the management plane and the user plane. The SNMP and the Mobile IP can be distinguished as a different application on the same IP layer. It is the better approach.

2)      If we shall use the default transport connection for the IP connectivity management for the user traffic, then the DSA procedure should be proceeded before the allocation of the ¡°default transport CID¡± for the user. But, generally DSA procedure requires the IP address for the transport connection, and even if it is not required, the ¡°default transport connection¡± allocation is not possible. If we use the transport connection for the transfer of the Mobile IP and/or DHCP messages for the IP connectivity for the user traffic, then the IP address related parameters for the DSA procedure cannot be set. That means the parameters required should already be known to the SSs and the BSs. The default parameters should be used.
Because, the procedure is not described in anywhere in the specification, the BS cannot provide the allocated ¡°default transport CID¡± to the user. In what management message? Using what parameter?

3)      If we should use the (default) Transport CID for IP connectivity management for the user traffic, then every terminal shall maintain the Basic CID, Primary Management CID, Secondary Management CID, and default Transport CID for signaling/control. That means SS should have minimum 4 CIDs , but the specification say that the minimum required CIDs each SS should have shall be not four but three. So, the usage of default Transport CID violates the specification.  

4)      If we use Transport CID instead of Secondary Management CID for the IP connectivity management for the user traffic, then the additional DSA-REQ/RSP procedures should be included in the network entry process. The DSA (connection establishment) procedure must be preceded for the transaction of the IP connectivity management procedures (DHCP or Mobile IP), because we should use the connection established before the transaction. But, if we use the Secondary management CID for that transaction, then the connection establishment procedure is not required. That means, the usage of the (default) Transport connection have more signaling overhead and causes more delay during the network entry process.

5)      In the fixed environment, a subscriber station (SS) can be separated with equipment for the user traffic (such as multiple TEs) and the equipment for the air interface (such as MT), so that the Secondary management connection for the IP-based external management for the SS is feasible. But, generally in the mobile environment, the two equipment (TE and MT) should be integrated and used by only one user, so the separation of the path for the user traffic IP connectivity management  (default transport CID) and for the external management for the MSS (Secondary Management CID) is not a good approach.
Therefore, even in the case of the Secondary management connection is used for the external management for the MSS, the Secondary management connection should also be used as the transfer of the user traffic IP connectivity management and management (Mobile IP or DHCP).
-- We need to define the concept of MSS clearly. I think that the Mobile Router (One modem and multiple user equipment in mobile situation) concept is not appropriate for the current 16e specification.

6)      If we use the Secondary management connection only for the IP-based management of the SS externally, then the IP address for the SS management and the IP address for the user traffic (you mean, using the default transport connection) should be different. But, the IP address for the user traffic and the SS management can be shared, and has no problem. So, the separate IP address allocation procedure is duplicated and cause wasting up the IP address resources, especially in the case of MSS.

7)      If we use the transport connection for the user traffic IP connectivity management, then the CID resources should be thrown away unnecessarily. If we can reuse the Secondary management connection, then we can save the CID resources.

8)      If we should proceed the handover process in the mobile environment over the subnets, then the transport connection for the user traffic IP connectivity management should be preceded before the transfer of the Mobile IP messages, that gives us a large unwanted delay for the handover process, and the system performance shall be greatly degraded.

 

In summary, I would like to say my understanding and concept, and the specification should be reflected to support that:

1)       Secondary management connection can be used as a user traffic IP connectivity management (DHCP or Mobile IP).

2)      The IP address allocated by the DHCP procedure using the Secondary management connection, can be shared for the user traffic and the external management for the SS. So, there is no need to separate the path to the SS management and the user traffic by secondary management connection and the transport connection. 

3)      Mobile IP should be supported for the seamless HO across the subnets, and for the swift handover process, the Secondary management connection should also be used for the Mobile IP message transfer and the external management for the MSS for the managed MSS.

 

Best Regards,

 

Chulsik Yoon

 

Senior Engineer, ETRI