1. IEEE 802.21 MEDIA INDEPENDENT HANDOVER DCN: 21-07-0199-01-0000
Title: Comments on NET-SAP
Date Submitted: May, 15, 2007
Presented at IEEE session #20 in Montreal
Authors or Source(s):
Angelo Centonza, Eleanor Hepworth, Robert Hancock
Abstract: This contribution suggests some modifications to the NET_SAP to reduce complexity, and remove ambiguities (also addresses comment 4150)

2. IEEE 802.21 presentation release statements
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3. MIH_NET_SAP
Currently the MIH_NET_SAP provides primitives to manage connection oriented transport sessions, and to send data.
Downside of requiring the MIH to explicitly manage the transport layer in this way is that it has to do things like decide when to listen/set up the socket, when to invoke L3 security mechanisms etc. which is unnecessary complexity in the MIH layer.
We’ve also half re-invented the sockets API, and it’s not clear why this is necessary in the standard.
Why does the MIH need to have visibility of transport layer state – what benefit does this provide?

4. MIH_NET_SAP and MIH_LINK_SAP
P25, link 38, P33 line 14 state:
Replace “For all transport services over L2, the MIH_NET_SAP uses the primitives specified by the MIH_LINK_SAP” with
“For all transport services over L2, the MIH_NET_SAP shall rely on the primitives specified by the MIH_LINK_SAP”

5. Proposal Make it simpler.
A single interface that the MIH layer invokes to send a message using whatever transport is available below (TCP, UDP, DCCP, SCTP, aYetToBeInventedP)
Flags in the primitive indicate to the transport *how* the message should be sent (reliably etc.) but makes no assumption about what protocols are used to achieve it
Better future proofing properties
The MIH can operate in blissful ignorance of things like socket status, whether the socket needs to be reset, etc. etc. – makes MIH stateless
MIH_LINK_SAP and MIH_NET_SAP are better aligned
MIH
Send message
(send reliably)
Message sent successfully
Comment: the MIH shall still be able to know which L2 is used and whether the L4 is reliable or not.
Transport (black box)

6. Suggested Modifications #1
Modify the “description” field for the Reliable Delivery Flag in MIH_TP_Data.request ( ) and MIH_TP_Data.indication ( ) from:
“Indicate whether an acknowledgement is required.” to
“Indicate that the data MUST be sent reliably and an error generated if delivery fails”
Substitute the status row in the semantics section MIH_TP_Data.confirm ( ) with the following:
Status
Enumerated
0-5
Status of operation:
0 Success
1 Unspecified Failure
2 Rejected
3 Authorization Failure
4 Network Error
5 Success with unacknowledged transport only
General positive feeling that a FALSE flag shall be present.
Question from Roger Communication (operator): the data sent via TP_DATA are only signalling. Why there shall be an unreliable delivery if the only messages transported are signalling? (I quite do not understand why only signalling messages are transported)

7. Suggested Modifications #2
The following primitives should be removed ( ):
TP_Connect
TP_Reset
TP_Disconnect