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[RPRWG] Comments on Definitions




The following are my comments against the file bs_terms_03a.pdf, posted on 
the web site by Bob Sultan.  I probably won't have a chance to be at the 
Monday 9 - 11am meeting.  Please review these comments there.

R.D. Love's comments against file bs_terms_03a.pdf

network (data transmission points interconnected by communication channels.
Proposed change: "points" to "nodes" in definition #2.

Resilient Packet Ring definition:  Footnote question:  Should this be 
specifically the protocol standardized by IEEE802?
My answer, YES! When used in our standard, it ought to refer specifically to 
standard implementations.

station (data station): [adapted15 from IEEE 100 (C/EMB/LM) 1073.3.1-1994, 
1073.4.1-1994, 8802-5-1995] A device that may be attached to a network for 
the purpose of transmitting and receiving information on that network. A 
station is identified by a MAC address.
    Change the last sentence to:
A station is identified by one or more MAC address. - See the definition of 
dual ring station for rationale behind this request.  I believe that some 
dual ring stations may be built with at least two MACs (as was done in IEEE 
802.5.)

Encoding (The following definition appears in 802.5: 'symbol: [802.5-1998 
1.3.68] In this standard a symbol consists of two signal elements. Four 
symbols are defined: data_zero, data_one, non-data_J, and non-data_K.'. Does 
this (or some analog of this) apply to 802.17?)   NO!
 and 
signal element:: [802.5-1998 1.3.61] The logical signal during one half of a 
bit time which may take on the values of Logic_1 or Logic_0.

These are definitions that are 802.5 specific.  Since we will be picking up 
existing PHY layers, the encoding and the characteristics of the symbol 
elements will be variable.  Delete the definition of signal element until we 
see that we need one.

layer agnosticism - Mark these terms as ones to be deleted when the draft 
goes out to ballot.  They are useful in understanding our objectives.


link: (1) [IEEE 100 (C/LM) 802.5c-1991] A unidirectional physical and media 
connection between two stations. (2) [IEEE 802.3-2000 1.4.153] The 
transmission path between any two interfaces of generic cabling.
        Based on the definitions of link segment and link partner, the second 
definition of link should be removed.

Footnote 31: A link aggregation group appears to the MAC Client as a single 
link, so I assume that a link can refer to a link aggregation group. Is that 
correct? - Based on definition 1, the assumption appears correct.

ring: (1)The collection of stations and links forming a resilient packet 
ring. (2) A set of congruent ringlets forming a resilient packet ring
-   NO! You have now defined a ring as a MAC protocol (refer to the 
definition of resilient packet ring).  
-   I believe you need a definition that more specifically talks about the 
allowable topology, i.e. 
I would suggest defining a ring as a set of congruent ringlets, at least two 
of which are opposing.  I see that this is what your definition is for 
multi-ring.  I would suggest dropping the definition of multi ring.

ring medium: The abstraction of a ring as a continuous transmission medium 
having a closed path.
Or more simply:  The transmission medium used by a ringlet or congruent 
ringlets.


ring segment (segment) : (1) The portion of a ring bounded by two stations 
interconnected by one or more links. (2) [802.5-1998 1.3.57] Section of 
transmission path bounded by repeaters or converters38. Ring segment 
boundaries are critical for determining the transmission limits that apply to 
the devices within the segment. (3) [IEEE 100 (C/LM) 802.3u-1995, 
802.9a-1995] The portion of a ringlet39 between the producer and consumer 
along which a packet is sent. The segment traversed by a send packet is the 
send segment, and the segment traversed by an echo is the echo segment. (4) 
[IEEE 100 (C) 610.6-1991] The medium connection40, including connectors, 
between medium dependent interfaces in a LAN.

Drop Definitions 2 and 3.

dual-ring: (1) [(C/LM) 802.5c-1991] A topology in which stations are linked 
by link pairs and, from any one station to another, there are exactly two 
distinct paths, where a path is defined as a sequence of consecutive links in 
which no link pair is traversed more than once. (2) A ring composed of 
exactly two congruent ringlets whose transmission paths have opposite 
orientations.

Drop Definition 1.  Definition 2 for dual ring is much better.

<dual-ring station: [(C/LM) 802.5c-1991] A station that attaches link pairs 
that have opposite directions of data flow with respect to the adjacent dual 
ring stations. It consists of MACs, a crosspoint function, and dual ring 
management. It may have other attachments.>
        With this definition you run into trouble defining "station" as 
having only a single MAC. 

multi-ring: A ring composed of multiple congruent ringlets, at least two of 
which are opposing ringlets.
        I suggest dropping this definition in favor of ringlet and ring.


<upstream neighbor's address (UNA):: [802.5-1998 1.3.77] The address of the 
station
functioning upstream from a specific station.>
        Suggest adding at the end:  "for a particular data flow"

broadcast address: [ISO/IEC2382-25 25.01.13] A group address that identifies 
the set of all stations on the network.
        Suggest changing "identifies" to "is recognized by" since a group 
address has no knowledge of, and does not identify any stations on the 
network.
    Make the same change in "Multicast Address" though not in "individual 
address".
For "data frame": define PAD.

maximum transfer unit (MTU): [IEEE 100 610.7-1995] The largest amount of data 
that can be transferred across a given physical network.
    Add "in a single frame" at the end of this definition.

data-stream: [(C) 610.10-1994] A continuous stream (sic) of data elements 
being transmitted, or intended for transmission.
    To avoid circularity, make that "A continuous field …

traffic: (1) The aggregate of frames circulating on a ring.
    I think we need to add "in a specified time interval" for this definition 
to really stand up.  


<ring in : [802.5-1998 1.3.53] A port that receives signals from the main 
ring path on the
trunk cable and transmits signals to the backup path on the trunk cable, and 
provides connectivity to the immediate upstream ring out port.>

<ring out : [802.5-1998 1.3.55] A port that transmits the output signals to 
the main ring path on the trunk cable and receives from the backup ring path 
on the trunk cable, and provides connectivity to the immediate downstream 
ring in port.>

The sins of my past are catching up with me.  I believe I created  these 
definitions of ring in and ring out.  I don't think that they are appropriate 
for 802.17 and I would suggest we drop them entirely.  Token ring had to 
distinguish between trunk and lobe calbing, and between the primary ring path 
and the backup path.  Those concepts just don't apply to RPR.

strip (stripping)  Definition 1 suffices.
definitions 2 and 3 are too limiting.  If we don't use idles, then definition 
4 is wrong.

change
copy (copying) : The receipt and acceptance of a frame from the ring by a 
station after
determination that the frame is addressed to the station.
To
copy (copying) : The receipt and acceptance of a frame from the ring by a 
station 
The last part of the sentence (a) didn't make sense, and (b) would probably 
be superfluous even if written well.

transmit (transmission)
Eliminate definitions 3 and 4.

encapsulation:
Change "must" to "may" in the definition, or delete the term "must" 
altogether.

bit rate:
Delete definition 1.  In an attempt to avoid a circular definition you use 
the term "speed" which is properly a measure of distance/time, and not # of 
bits/time.

bit time: (BT):
Leave out the example for bit time.  We don't need an 802.3 example in an 
802.17 definition list.

bandwidth: [FRF Glossary (modified)] The range of frequencies, expressed in 
Kilobits per second, that can pass over a given data transmission channel 
within a network. The bandwidth determines the rate at which information can 
be sent through a channel - the greater the bandwidth, the more information 
that can be sent in a given amount of time 62.
    This definition is technically incorrect.  Bandwidth is measured in Hz, 
not in bits/second.  Consider changing to a more accurate:
bandwidth: The range of frequencies, expressed in Hertz, used to pass data 
over a given data transmission channel within a network. The bandwidth 
together with the data encoding scheme determine the rate at which 
information can be sent through a channel - the greater the bandwidth, the 
more information that can be sent in a given amount of time.

Consider changing to:
time-to-live (TTL): Value carried in the protocol header of a PDU.  It is 
used to prevent a PDU that has not been stripped from the ring by its 
destination or source station to be removed. The TTL value is generally set 
to an initial value at the source and decremented at each subsequent hop. The 
PDU is discarded when the TTL value reaches zero.

plug-and-play : Consider:  The requirement that a station be capable of 
transferring and receiving frames, and if permitted, sending frames without 
manual intervention other than the physical connection of the equipment. 
(With this definition I am trying to accommodate the conditions where the 
station may or may not require permission to insert data frames onto the ring)

operational :
Delete definition 1.  Definition 2 says it better and is complete.

Change
neighbor : [BH] A station that is exactly one segment away.
To:  The station that is immediately upstream or downstream from the station
Or change "segment" to "link"
Because:  Segment can include intermediate stations (see the definition we 
have above)

partitioned ring
I would like to see a diagram.  What do we call a ring with a break in it?  
Is there a separate name?

path:
Use definition 1, and drop definition 2.  I don't know how to use definition 
2 for a multi-ringlet configuration.

topology database update (TDU):
Add the word Frame after update so we can differentiate the frame from the 
information update.

topology discovery : The process by which the connectivity and capabilities 
of the stations and links on the ring is discovered by a newly added station.
Delete "by a newly added station".  Old stations must do topology discovery 
every time there is a change to the ring.

insertion buffer [HvA-Alt] : A type of transit buffer used to store all or 
part of a transit frame or frames awaiting completion of an ingress frame 
transmission in progress.
Delete the two words "transit" from this definition.  A transit buffer is 
only defined with respect to transit frames.  An insertion buffer holds the 
data BEFORE it is placed on the ring, and therefore, the word "transit" is 
incorrect.
ALSO, Remove the word "transit" from "
shaping buffer, for the same reason.

Replace both definitions of Latency with:
latency: The time it takes for information to get through a network, or 
elements of a network, sometimes referred to as delay.
This definition combines the important features of the proposed definitions 1 
and 2.

Drop the definition of
round trip propagation time:

frame check sequence (FCS) : is a field.  Go with definition #3, except 
change "remainder" to result.  Both are correct, with remainder being more 
correct, but a bit arcane for some readers.

flow control:
Use Definition 2 which does not presuppose how flow control will be done.

Backpressure:  and throttle:
Change opposing ring, to opposing ringlet, to maintain consistency.

congestion management
Change "This" to "The set of procedures"
"This" does not refer to anything!

uncorrelated jitter:
Drop this definition.  It has nothing to do with the jitter that we are 
interested in for 802.17.

wander::
I wonder what the definition of wander is.  

burstiness:
Change "Data" to "Stations"
Even better, burstiness is the uneven flow of data across a link or links, or 
the uneven flow of data from a station.

For completeness change 
delivered out-of-sequence frames [ITU I.)33.1 A.16 (modified)] A frame (Ft) 
arriving at a destination station after a fame Ft+1, Ft+2, Ft+3…., Fn in a 
sequence of frames F1, F2, F3, …. , Fn sent from a source station.
    To
delivered out-of-sequence frames [ITU I.)33.1 A.16 (modified)] A frame (Ft) 
arriving at a destination station after a fame Ft+1, Ft+2, Ft+3…., Fn, or 
before fame Ft-1, Ft-2, Ft-3…., Ft-n, in a sequence of frames F1, F2, F3, …. 
, Fn sent from a source station.

repeat [802.5-1998 1.3.50] The action of receiving a bit stream (for example, 
frame, token, or fill) and placing it on the medium. Stations repeating the 
bit stream may copy it into a buffer or modify control bits as appropriate.>
Delete the parenthetical "(for example, frame, token, or fill)" as this does 
not apply to 802.17.

spatial reuse
The definitions are not specific and need help.  Here is a general one for 
spatial reuse.

spatial reuse A term referring to the capability of a ringlet to 
simultaneously carry two or more data streams that are limited to 
non-overlapping portions of the ringlet. 

I need to better understand what global and local spatial reuse are.