| Good questions, Glen.
Working from the bottom up (using current block labels):
1. The UMT Sublayer uses the Type field to determine whether the frame is UMT or not. If it is not UMT the frame is passed to the MAC Client side. If it is UMT the UMT Sublayer passes the frame to the UMT Tunnel Multiplexer block.
2. The UMT Tunnel Multiplexer block looks at the Source MAC and Destination MAC to determine the Tunnel Instance to which this frame is associated. The get_tid(SA,DA) function defined in 4.3.1.4rand used in state diagram 4-9, returns a tunnel identifier. Based on the returned TID, the UMT Tunnel Multiplexer passes the frame to the selected UMT Tunnel Adapter (there are one or more instances of the UMT Tunnel Adapter).
3. The selected UMT Tunnel Adapter looks at the UMT Subtype to determine the UMT User/User Adaptation to which the PDU should be passed.
4. The UMT User Adaptation block simply transforms the decapsulated UMT data into a format that can be consumed by the UMT User. This is an abstract and unspecified function as far as the standard is concerned.
Early on I considered combining some of the blocks, but ultimately decided against it because doing so didn’t simplify the actual specification language and, in fact, seemed to make it more complex.
For example, I considered using the tuple (SA, DA, UMT Subtype) to identify a tunnel. Doing so made the state diagrams an order of magnitude more complex. I also think doing this would complicate future enhancements to specify tunnel maintenance functions and tunnel discovery and automatic setup.
—kan—
Before deciding how to name individual functional blocks, let’s discuss if we even need them all. When each block is expanded, they all look identical inside: Parser in the Rx direction, Multiplexor in the Tx direction. This parsing and multiplexing is shown to happen to UMTPDUs 3 times: in what is currently called “UMT sublayer”, “UMT Tunnel Multiplexor” and “UMT Tunnel Adapter” (see figure below). Each Parser (demultiplexor, really) demultiplexes frames to different outputs based on a value of one or several specific fields in the received UMTPDU. So, I would like to clarify first which fields each of the three boxes operate on. This will clarify if we need them all and how to name them. <image001.png> Hmmm…. There is currently already a UMT Tunnel Multiplexer, so I guess UMT PDU Multiplexer would work.
The block only does PDU (frame) multiplexing, correct? So how about “UMT Multiplexer” or “UMT PDU Multiplexer”? I’m okay with this approach. What would we call the functional block that is currently labeled “UMT Sublayer”? We probably should not use the word “layer” in this case. Layers are defined in OSI reference model and there are exactly seven of them (Physical, Data Link, Network, Transport, etc.) What 802 did and what we should do as well, define sublayers for those OSI layers. For example, 802.3 split the physical layer into several sublayers: PMD, PMA, PCS, and RS. Similarly Data Link was split into MAC, MAC Control, OAM, MAC Client sublayers. We also should not use the word “system”, as it generally encompasses operations at both the transmitting end and the receiving end and includes all layers in a device. To keep the terminology and the layering model consistent with other closely-related standards, I suggest we enclose the entire UMT functionality in a sublayer called “UMT sublayer”. That will be the total thing that 1904.2 will define. Within the UMT sublayer, as it is typically done, we will define multiple “functional blocks”. These blocks, as well as their connections will be illustrated in a figure called “UMT functional block diagram”. That figure will be similar to what is now shown in Figure 4-2. UMT Layer is the entire UMT system. UMT Sublayer is a component in the UMT layer. Now that you’ve asked the question, I notice that Fig 4-1 does not make that very clear because the tunnel adapters are shown outside the UMT Layer, and the UMT Layer is not properly labeled as "UMT Layer”. In the baseline text proposal, is "UMT Layer" and "UMT Sublayer" the same thing? I see about 50 instances of UMT Sublayer and 6 instances of UMT layer. Specifically, my question is (in reference to the picture below): Are UMT Tunnel Multiplexors and UMT Tunnel Adaptors part of UMT Layer or not? They are not shown to be part of UMT Sublayer, since the UMT sublayer is shown as a separate box. Per the agreement in our meeting yesterday, I am forwarding the MS Word and PDF versions of the baseline text presented during the meeting. Please review and send comments directly to me or to the list for discussion. When commenting, please include the line number of the text for which the comment is directed and supply suggested changes to the text. Please send me comments by 17 August so I have time to update the text before the next meeting. ________________________________________________________________________
To unsubscribe from the STDS-1904-2-TF list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-1904-2-TF&A=1
To unsubscribe from the STDS-1904-2-TF list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-1904-2-TF&A=1
|