Hi, all
Notice that Jordi was asking for volunteers to review ALTO WG documents, I
tried to spend some time reviewing this ALTO new transport document and my
comments are following.
Note that some of my questions/comments may be due to my not fully
understanding of this document(sorry!)...
Sec.1 Introduction
Specifically, this document specifies the
following:
* Extensions to the ALTO Protocol to create, update, or remove an
incrementally changing network information resource.
So I thought that the ALTO client can request to create and delete a TIPS view,
and also query the content of the TIPS or receive push updates. But I am not
sure how the ALTO protocol could be extended to allow the client to update that
view. I thought ALTO is a network information exposure protocol, the capability
to update a network information resource sounds surprising to me.
Sec.2.1 Transport Requirements
s/direct/directly
Sec.2.2 TIPS Terminology
* In the definition of Updates graph, the authors mention that:
A static network information resource (e.g., Cost Map,
Network Map) may need only a single updates graph. A dynamic
network information resource (e.g., Filtered Cost Map) may create
an updates graph (within a new TIPS view) for each unique filter
request.
How to understand cost map and network map as static network information
resource? I don't see the 7285 making that distinction, I think the cost map
information could be dynamically changing. Maybe you mean something else I
failed to get, but I don't think there exists static network information
resource on a time span.
* The definition of snapshot/incremental update is a full/partial
replacement of resource contained within an updates graph, but the word
"replacement" sounds quite strange to me. Why it is a replacement? Could you
clarify a little bit more? Or maybe you want to use generation/creation?
* The definition for ID#i-#j:
Denotes the update item (op, data) on a specific edge in the
updates graph to transition from version at node i to version at
node j, where i and j are the respective sequence numbers of the
nodes the edge connects.
What's the abbreviation for op, operation? I don't see this field in the
ALTO message. The update item is defined as either a snapshot or incremental
update, I don't know how this is related to (op,data).
* The text below Information Resource Directory(IRD)
Figure 4 shows an example illustrating the TIPS abstraction. Each
ALTO client (Client 1, Client 2, or Client 3) maintains a single HTTP
connection with the ALTO server.
s/Figure 4/Figure 1? Also note that you described this figure as the TIPS
abstraction, but the figure 1 title is "ALTO Transport Information".
* Regarding Figure 1, I found that description of information resource
#2 is lost, is this intentional? Maybe add some description for resource #2 to
communicate the intent? Or simply remove it and rename resource#3 to resource#2.
* Note that you also refer to network Map as static resource here, see
my similar comments above.
* Above Figure 1: tvi/ug = incremental updates graph associated with tsi
s/tsi/tvi?
Sec.3.1 Basic Data Model of Updates Graph
* Mandatory incremental updates and optional incremental updates are
mentioned in the explanation of Figure 2, but I never see this defined, so what
is mandatory/optional incremental updates? What is the difference between
mandatory and optional ones? Maybe point to some reference here, or clarify in
the document.
Sec.3.2 Resource Location Schema
* I guess I don't really understand what is a location schema. Maybe
add a reference or more text for clarity.
* At the very beginning of this section:
To access each individual update in an updates graph, consider the
model represented as a "virtual" file system (adjacency list)...
In my opinion, it is not a real file system. The file system is a tree
structure, each non-root node has and only has one parent, but in figure 3, for
example, node 103 has both 0 and 102 as parents node, fine for a directed
acyclic graph, but not a file structure. Maybe I am wrong, but please check
that.
* It is not easy to understand your figure 3. At first I was struggling
to understand what the indentation means for each number, and what the shortcut
means. Then I've got some understanding which I am not sure is correct. Maybe
you want to add more explanation for this figure.
Sec.3.3 Updates Graph Modification Invariants
* Sorry, but I guess I still don't understand what the title means,
what is the modification invariant?
* You mentioned in the last paragraph that a server might compact a
resource's update graph to save space, and [105,106] are valid set for server
to save. But then what if a client requests content from 101 to 105? Doesn't
this mean that resource state prior to 105 is no longer reachable for clients?
Sec.6.3 Open Example
* The client sends a request to ALTO server, how its username and
password is reflected on the request? It is the Authorization field? Maybe
mention it more explicit like that: The user name and password are combined in
the format of user:password and encoded using Base64 in the Authorization
field. Otherwise I would rather not even mention this authorization thing.
Sec. 7.2.1. Server Processing "Error" Conditions
* For 429 error code: s/ "Re-Try After" headers/ "Retry After" headers/
(remove hyphen)
Sec7.4 New Next Edge Recommendation
* s/recieve/receive/
Appendix B
* last bullet: s/Section Section/Section/ (remove a "Section")
Best Regards,
Qiufang Ma
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