Dear authors of alto-path-vector and all,
After reviewing this draft, I have two comments:
1. To avoid confusion, I suggest replacing every network element (NE) by
network abstract element (ANE), since every network element in this draft
is "abstract" network element.
An alternative solution is to remove ANE. The network element is
"abstract" according to the definition in Wikipedia ("A network element
is usually defined as a manageable logical entity uniting one or more
physical devices."), which makes it redundant to emphasize "abstract" so
many times.
2. The title of section 4.4 should be "Query-specific Attribute", which
is the noun this section introduced. And the title of section 6.4 should
be "Filtered Cost Map Example" corresponding to section 5.8.
Here is a list of typos (comments are marked with ">>>"):
[Page 3]
5.8. Filtered Cost Map Extensions . . . . . . . . . . . . . . 12
5.8.1. Capabilities . . . . . . . . . . . . . . . . . . . . 12
5.8.2. Accept Input Parameters . . . . . . . . . . . . . . . 13
5.8.3. Propertymap . . . . . . . . . . . . . . . . . . . . . 14
5.8.4. Response . . . . . . . . . . . . . . . . . . . . . . 14
5.9. Endpoint Cost Service Extensions . . . . . . . . . . . . 14
5.9.1. Capabilities . . . . . . . . . . . . . . . . . . . . 15
5.9.2. Accept Input Parameters . . . . . . . . . . . . . . . 15
>>> Accept Input Parameters => Acceptable Input Parameters
[Page 3]
7. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 25
[Page 25]
7. Compatibility
>>> Compatibility => Compatibility Considerations/Compatibilities
[Page 4, 5]
The document is organized as follows. Section 3 gives an example of
flow scheduling to illustrate the need to introduce cost mode "path-
vector" and cost metric "ane". Section 4 gives an overview of the
path-vector extension. Section 5 specifies the new cost mode and
cost metric, new domain type, entity properties and protocol
extensions for (Filtered) Cost Maps and Endpoint Cost Services.
Section 6 presents several examples. Section 7 discusses the
compatibility issues with some other proposed ALTO extensions.
Section 8 discusses the time to live problem. Section 9 discusses
several design decisions. Section 10 and Section 11 discusses about
>>> discusses about => discusses
security and IANA Considerations.
2. Terminology
This document uses the following terms: Network Element, Network
Element Name, Network Element Property, Network Element Property Map
and Path Vector.
o Network Element (NE): A Network Element is an abstract network
element, which can be a link, a network switching device, or a set
of devices.
o Network Element Name (NEN): The id of a NE. It can be referenced
>>> a NE => an NE (which pronounced as [ɛn'iː])
by Cost Map, Filtered Cost Map, Endpoint Cost Service and Property
Map.
o Network Element Property (NEP): The property of a NE. It can be
the available bandwidth of a link, the delay or other available
properties.
[Page 10]
5.4.2. Domain-Specific Entity Addresses
The entity address of ane domain is encoded as a JSON string. The
string MUST be no more than 64 characters, and it MUST NOT contain
characters other than US-ASCII alphanumeric characters
(U+0030-U+0039, U+0041-U+005A, and U+0061-U+007A), the hyphen ('-',
U+002D), the colon (':', U+003A), the at sign ('@', code point
U+0040), the low line ('_', U+005F), or the '.' separator (U+002E).
The '.' separator is reserved for future use and MUST NOT be used
unless specifically indicated in this document, or an extension
>>> delete the comma before "or" (since there're only two items in a series)
document.
[Page 16]
6.1. Workflow
o Send the GET request for the whole Information Resource Directory.
o Look for the resource of the (Filtered) Cost Map/Endpoint Cost
Service which contains the path-vector cost type and get the
>>> get => gets
resource id of the property map.
[Page 20]
6.4. Multi-Cost Filtered Cost Map Example
The following example presents the request and response of "filtered-
multi-cost-map". In this example, the client is interested in the
path-vector and numerical routing cost information. The client uses
"or-constraints" but all the results satisfy the conditions. In
resposne, the extended "vtag" field is included in "meta" to provide
[Page 22]
6.5. Endpoint Cost Service Example
If the ALTO client expects the routing state information between
endpoints, it can also query the "default-endpoint-cost-map" resource
which supports path vector. In resposne, the extended "vtag" field
>>> resposne => response
[Page 23]
6.6. Network Element Property Map Example # 1
After the client send the query to the Multi-Cost Filtered Cost Map
"filtered-multi-cost-map" and get the response with query-id "query1"
(See Section 6.4). The client send request to the "ane-property-map-
[Page 24]
6.7. Network Element Property Map Example # 2
After the client send the query to the Endpoint Cost Service
"default-endpoint-cost-map" and get the response with query-id
"query2" (See Section 6.5). The client send request to the "ane-
>>> The client send => The client sends
[Page 27]
9.3. Snapshot and real-time update
As the suggested workflow mentioned in Section 6.1, the properties of
the abstract network elements are computed ahead of the query of
these properties. So the properties of abstract network elements are
likely to be snapshot rather than realt-time value when queried.
>>> (a) snapshot, (a) real-time value, realt-time => real-time
10. Security Considerations
We can identify multiple potential security issues. A main security
>>> A main => The main
issue is network privacy, as the path-vector information may reveal
more network internal structures than the more abstract single-node
abstraction. The network should consider protection mechanisms to
reduce information exposure, in particular, in settings where the
network and the application do not belong to the same trust domain.
On the other hand, in a setting of the same trust domain, a key
benefit of the path-vector abstraction is reduced information
transfer from the network to the application.
Best Regards,
Shenshen
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