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Versions: (draft-yang-alto-path-vector) 00 01
02 03 04 05 06 07 08 09 10 11
ALTO K. Gao
Internet-Draft Sichuan University
Intended status: Standards Track Y. Lee
Expires: 15 January 2021
S. Randriamasy
Nokia Bell Labs
Y.R. Yang
Yale University
J. Zhang
Tongji University
14 July 2020
ALTO Extension: Path Vector
draft-ietf-alto-path-vector-11
Abstract
This document is an extension to the base Application-Layer Traffic
Optimization protocol [RFC7285]. The current ALTO Cost Services only
allow applications to obtain cost values on an end-to-end path
defined by its source and destination. The present extension
provides abstracted information on particular network components or
elements traversed by a path between its source and destination.
Examples of such abstracted components are networks, data centers or
links. This is useful for applications whose performance is impacted
by particular network components they traverse or by their
properties. Applications having the choice among several connection
paths may use this information to select paths accordingly and
improve their performance. In particular, they may infer that
several paths share common links and prevent traffic bottlenecks by
avoiding such paths. This document introduces a new cost type called
Path Vector. A Path Vector is an array of entities that each
identifies an abstracted representation of a network part and that
are called Abstract Network Element (ANE). Each ANE is defined by a
set of properties. ANE properties are conveyed by an ALTO
information resource called "Property Map", that can be packed
together with the Path Vectors in a multipart response. They can
also be obtained via a separate ALTO request to a Property Map. An
ALTO Property Map is an extension to the ALTO protocol, that is
specified in another document entitled "Unified Properties for the
ALTO Protocol" [I-D.ietf-alto-unified-props-new].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on 15 January 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Requirements Languages . . . . . . . . . . . . . . . . . . . 6
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Design Requirements . . . . . . . . . . . . . . . . . . . 7
4.2. Recent Use Cases . . . . . . . . . . . . . . . . . . . . 9
4.2.1. Large-scale Data Analytics . . . . . . . . . . . . . 9
4.2.2. Context-aware Data Transfer . . . . . . . . . . . . . 10
4.2.3. CDN and Service Edge . . . . . . . . . . . . . . . . 10
5. Path Vector Extension: Overview . . . . . . . . . . . . . . . 10
5.1. Abstract Network Element . . . . . . . . . . . . . . . . 11
5.1.1. ANE Domain . . . . . . . . . . . . . . . . . . . . . 11
5.1.2. Ephemeral ANE and Persistent ANE . . . . . . . . . . 11
5.1.3. Property Filtering . . . . . . . . . . . . . . . . . 12
5.2. Path Vector Cost Type . . . . . . . . . . . . . . . . . . 12
5.3. Multipart Path Vector Response . . . . . . . . . . . . . 13
5.3.1. Identifying the Media Type of the Root Object . . . . 14
5.3.2. References to Part Messages . . . . . . . . . . . . . 14
5.3.3. Order of Part Messages . . . . . . . . . . . . . . . 15
6. Specification: Basic Data Types . . . . . . . . . . . . . . . 15
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6.1. ANE Name . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2. ANE Domain . . . . . . . . . . . . . . . . . . . . . . . 15
6.2.1. Entity Domain Type . . . . . . . . . . . . . . . . . 16
6.2.2. Entity Identifier Encoding . . . . . . . . . . . . . 16
6.2.3. Hierarchy and Inheritance . . . . . . . . . . . . . . 16
6.2.4. Media Type of Defining Resource . . . . . . . . . . . 16
6.3. ANE Property Name . . . . . . . . . . . . . . . . . . . . 16
6.4. Initial ANE Property Types . . . . . . . . . . . . . . . 16
6.4.1. New ANE Property Type: Maximum Reservable
Bandwidth . . . . . . . . . . . . . . . . . . . . . . 17
6.4.2. New ANE Property Type: Persistent Entity ID . . . . . 18
6.5. Path Vector Cost Type . . . . . . . . . . . . . . . . . . 18
6.5.1. Cost Metric: ane-path . . . . . . . . . . . . . . . . 18
6.5.2. Cost Mode: array . . . . . . . . . . . . . . . . . . 19
6.6. Part Resource ID . . . . . . . . . . . . . . . . . . . . 19
7. Specification: Service Extensions . . . . . . . . . . . . . . 19
7.1. Multipart Filtered Cost Map for Path Vector . . . . . . . 19
7.1.1. Media Type . . . . . . . . . . . . . . . . . . . . . 19
7.1.2. HTTP Method . . . . . . . . . . . . . . . . . . . . . 19
7.1.3. Accept Input Parameters . . . . . . . . . . . . . . . 20
7.1.4. Capabilities . . . . . . . . . . . . . . . . . . . . 21
7.1.5. Uses . . . . . . . . . . . . . . . . . . . . . . . . 21
7.1.6. Response . . . . . . . . . . . . . . . . . . . . . . 21
7.2. Multipart Endpoint Cost Service for Path Vector . . . . . 25
7.2.1. Media Type . . . . . . . . . . . . . . . . . . . . . 25
7.2.2. HTTP Method . . . . . . . . . . . . . . . . . . . . . 25
7.2.3. Accept Input Parameters . . . . . . . . . . . . . . . 25
7.2.4. Capabilities . . . . . . . . . . . . . . . . . . . . 26
7.2.5. Uses . . . . . . . . . . . . . . . . . . . . . . . . 26
7.2.6. Response . . . . . . . . . . . . . . . . . . . . . . 26
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 29
8.1. Example: Information Resource Directory . . . . . . . . . 29
8.2. Example: Multipart Filtered Cost Map . . . . . . . . . . 31
8.3. Example: Multipart Endpoint Cost Resource . . . . . . . . 32
8.4. Example: Incremental Updates . . . . . . . . . . . . . . 35
9. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 36
9.1. Compatibility with Legacy ALTO Clients/Servers . . . . . 36
9.2. Compatibility with Multi-Cost Extension . . . . . . . . . 36
9.3. Compatibility with Incremental Update . . . . . . . . . . 36
9.4. Compatibility with Cost Calendar . . . . . . . . . . . . 36
10. General Discussions . . . . . . . . . . . . . . . . . . . . . 37
10.1. Constraint Tests for General Cost Types . . . . . . . . 37
10.2. General Multipart Resources Query . . . . . . . . . . . 37
11. Security Considerations . . . . . . . . . . . . . . . . . . . 37
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38
12.1. ALTO Entity Domain Registry . . . . . . . . . . . . . . 38
12.2. ALTO Entity Property Type Registry . . . . . . . . . . . 39
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 40
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14. References . . . . . . . . . . . . . . . . . . . . . . . . . 40
14.1. Normative References . . . . . . . . . . . . . . . . . . 40
14.2. Informative References . . . . . . . . . . . . . . . . . 41
Appendix A. Changes since -10 . . . . . . . . . . . . . . . . . 42
Appendix B. Changes since -09 . . . . . . . . . . . . . . . . . 43
Appendix C. Changes since -08 . . . . . . . . . . . . . . . . . 43
Appendix D. Changes Since Version -06 . . . . . . . . . . . . . 43
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44
1. Introduction
Network performance metrics are crucial to the Quality of Experience
(QoE) of today's applications. The ALTO protocol allows Internet
Service Providers (ISPs) to provide guidance, such as topological
distance between different end hosts, to overlay applications. Thus,
the overlay applications can potentially improve the QoE by better
orchestrating their traffic to utilize the resources in the
underlying network infrastructure.
Existing ALTO Cost Map and Endpoint Cost Service provide only cost
information on an end-to-end path defined by its <source,
destination> endpoints: The base protocol [RFC7285] allows the
services to expose the topological distances of end-to-end paths,
while various extensions have been proposed to extend the capability
of these services, e.g., to express other performance metrics
[I-D.ietf-alto-performance-metrics], to query multiple costs
simultaneously [RFC8189], and to obtain the time-varying values
[I-D.ietf-alto-cost-calendar].
While the existing extensions are sufficient for many overlay
applications, however, the QoE of some overlay applications depends
not only on the cost information of end-to-end paths, but also on
some intermediate network components and their properties. For
example, job completion time, which is an important QoE metric for a
large-scale data analytics application, is impacted by shared
bottlenecks inside the carrier network.
Predicting such information can be very complex without the help of
the ISP [AAAI2019]. With proper guidance from the ISP, an overlay
application may be able to schedule its traffic for better QoE. In
the meantime, it may be helpful as well for ISPs if applications
could avoid using bottlenecks or challenging the network with poorly
scheduled traffic.
Despite the benefits, ISPs are not likely to expose details on their
network paths: first for the sake of confidentiality, second because
it may result in a huge volume and overhead, and last because it is
difficult for ISPs to figure out what information and what details an
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application needs. Likewise, applications do not necessarily need
all the network path details and are likely not able to understand
them.
Therefore, it is beneficial for both parties if an ALTO server
provides ALTO clients with an "abstract network state" that provides
the necessary details to applications, while hiding the network
complexity and confidential information. An "abstract network state"
is a selected set of abstract representations of intermediate network
components traversed by the paths between <source, destination> pairs
combined with properties of these components that are relevant to the
overlay applications' QoE. Both an application via its ALTO client
and the ISP via the ALTO server can achieve better confidentiality
and resource utilization by appropriately abstracting relevant path
components. The pressure on the server scalability can also be
reduced by abstracting components and their properties and combining
them in a single response.
This document extends [RFC7285] to allow an ALTO server convey
"abstract network state", for paths defined by their <source,
destination> pairs. To this end, it introduces a new cost type
called "Path Vector". A Path Vector is an array of identifiers of
so-called Abstract Network Element (ANE). An ANE represents an
abstract intermediate component traversed by a path. It can be
associated with various properties. The associations between ANEs
and their properties are encoded in an ALTO information resource
called Unified Property Map, which is specified in
[I-D.ietf-alto-unified-props-new].
For better confidentiality, this document aims to minimize
information exposure. In particular, this document enables and
recommends that first ANEs are constructed on demand, and second an
ANE is only associated with properties that are requested by an ALTO
client. A Path Vector response involved two ALTO Maps: the Cost Map
that contains the Path Vector results and the up-to-date Unified
Property Map that contains the properties requested for these ANEs.
To enforce consistency and improve server scalability, this document
uses the "multipart/related" message defined in [RFC2387] to return
the two maps in a single response.
The rest of the document are organized as follows. Section 3
introduces the extra terminologies that are used in this document.
Section 4 uses an illustrative example to introduce the additional
requirements of the ALTO framework, and discusses potential use
cases. Section 5 gives an overview of the protocol design.
Section 6 and Section 7 specify the Path Vector extension to the ALTO
IRD and the information resources, with some concrete examples
presented in Section 8. Section 9 discusses the backward
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compatibility with the base protocol and existing extensions.
Security and IANA considerations are discussed in Section 11 and
Section 12 respectively.
2. Requirements Languages
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
When the words appear in lower case, they are to be interpreted with
their natural language meanings.
3. Terminology
This document extends the ALTO base protocol [RFC7285] and the
Unified Property Map extension [I-D.ietf-alto-unified-props-new]. In
addition to the terms defined in these documents, this document also
uses the following additional terms:
* Abstract Network Element (ANE): An Abstract Network Element is a
representation of network components. It can be a link, a
middlebox, a virtualized network function (VNF), etc., or their
aggregations. An ANE can be constructed either statically in
advance or on demand based on the requested information. In a
response, each ANE is represented by a unique ANE Name. Note that
an ALTO client must not assume ANEs in different responses but
with the same ANE Name refer to the same network component(s).
* Path Vector: A Path Vector, or an ANE Path Vector, is a JSON array
of ANE Names. It conveys the information that the path between a
source and a destination traverses the ANEs in the same order as
they appear in the Path Vector.
* Path Vector resource: A Path Vector resource refers to an ALTO
resource which supports the extension defined in this document.
* Path Vector cost type: The Path Vector cost type is a special cost
type, which is specified in Section 6.5. When this cost type is
present in an IRD entry, it indicates that the information
resource is a Path Vector resource. When this cost type is
present in a Cost Map or an Endpoint Cost Map, it indicates each
cost value must be interpreted as a Path Vector.
* Path Vector request: A Path Vector request refers to the POST
message sent to an ALTO Path Vector resource.
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* Path Vector response: A Path Vector response refers to the
multipart/related message returned by a Path Vector resource.
4. Problem Statement
4.1. Design Requirements
This section gives an illustrative example of how an overlay
application can benefit from the Path Vector extension.
Assume that an application has control over a set of flows, which may
go through shared links or switches and share a bottleneck. The
application hopes to schedule the traffic among multiple flows to get
better performance. The capacity region information for those flows
will benefit the scheduling. However, existing cost maps can not
reveal such information.
Specifically, consider a network as shown in Figure 1. The network
has 7 switches (sw1 to sw7) forming a dumb-bell topology. Switches
sw1/sw3 provide access on one side, sw2/sw4 provide access on the
other side, and sw5-sw7 form the backbone. Endhosts eh1 to eh4 are
connected to access switches sw1 to sw4 respectively. Assume that
the bandwidth of link eh1 -> sw1 and link sw1 -> sw5 are 150 Mbps,
and the bandwidth of the rest links are 100 Mbps.
+------+
| |
--+ sw6 +--
/ | | \
PID1 +-----+ / +------+ \ +-----+ PID2
eh1__| |_ / \ ____| |__eh2
1.2.3.4 | sw1 | \ +--|---+ +---|--+ / | sw2 | 2.3.4.5
+-----+ \ | | | |/ +-----+
\_| sw5 +---------+ sw7 |
PID3 +-----+ / | | | |\ +-----+ PID4
eh3__| |__/ +------+ +------+ \____| |__eh4
3.4.5.6 | sw3 | | sw4 | 4.5.6.7
+-----+ +-----+
Figure 1: Raw Network Topology
The single-node ALTO topology abstraction of the network is shown in
Figure 2.
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+----------------------+
{eh1} | | {eh2}
PID1 | | PID2
+------+ +------+
| |
| |
{eh3} | | {eh4}
PID3 | | PID4
+------+ +------+
| |
+----------------------+
Figure 2: Base Single-Node Topology Abstraction
Consider an application overlay (e.g., a large-scale data analytics
system) which wants to optimize the total throughput of the traffic
among a set of end host <source, destination> pairs, say eh1 -> eh2
and eh1 -> eh4. The application can request a cost map providing
end-to-end available bandwidth, using "availbw" as cost-metric and
"numerical" as cost-mode.
The application will receive from the ALTO server that the bandwidth
of eh1 -> eh2 and eh1 -> eh4 are both 100 Mbps. But this information
is not enough to determine the optimal total throughput. Consider
the following two cases:
* Case 1: If eh1 -> eh2 uses the path eh1 -> sw1 -> sw5 -> sw6 ->
sw7 -> sw2 -> eh2 and eh1 -> eh4 uses path eh1 -> sw1 -> sw5 ->
sw7 -> sw4 -> eh4, then the application will obtain 150 Mbps at
most.
* Case 2: If eh1 -> eh2 uses the path eh1 -> sw1 -> sw5 -> sw7 ->
sw2 -> eh2 and eh1 -> eh4 uses the path eh1 -> sw1 -> sw5 -> sw7
-> sw4 -> eh4, then the application will obtain only 100 Mbps at
most.
To allow applications to distinguish the two aforementioned cases,
the network needs to provide more details. In particular:
* For eh1 -> eh2, the ALTO server must give more details which is
critical for the overlay application to distinguish between Case 1
and Case 2 and to compute the optimal total throughput
accordingly.
* The ALTO server must allow the client to distinguish the common
network components shared by eh1 -> eh2 and eh1 -> eh4, e.g., eh1
- sw1 and sw1 - sw5 in Case 1.
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* The ALTO server must give details on the properties of the network
components used by eh1 -> eh2 and eh1 -> eh4, e.g., the available
bandwidth between eh1 - sw1, sw1 - sw5, sw5 - sw7, sw5 - sw6, sw6
- sw7, sw7 - sw2, sw7 - sw4, sw2 - eh2, sw4 - eh4 in Case 1.
In general, we can conclude that to support the multiple flow
scheduling use case, the ALTO framework must be extended to satisfy
the following additional requirements:
AR1: An ALTO server must provide essential information on
intermediate network components on the path of a <source,
destination> pair that are critical to the QoE of the overlay
application.
AR2: An ALTO server must provide essential information on how the
paths of different <source, destination> pairs share a common
network component.
AR3: An ALTO server must provide essential information on the
properties associated to the network components.
The Path Vector extension defined in this document propose a solution
to provide these details.
4.2. Recent Use Cases
While the multiple flow scheduling problem is used to help identify
the additional requirements, the Path Vector extension can be applied
to a wide range of applications. This section highlights some real
use cases that are recently reported. See [I-D.bernstein-alto-topo]
for a more comprehensive survey of use cases where extended network
topology information is needed.
4.2.1. Large-scale Data Analytics
One potential use case of the Path Vector extension is for large-
scale data analytics such as [SENSE] and [LHC], where data of
Gigabytes, Terabytes and even Petabytes are transferred. For these
applications, the QoE is usually measured as the job completion time,
which is related to the completion time of the slowest data transfer.
With the Path Vector extension, an ALTO client can identify
bottlenecks inside the network. Therefore, the overlay application
can make optimal traffic distribution or resource reservation (i.e.,
proportional to the size of the transferred data), leading to optimal
job completion time and network resource utilization.
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4.2.2. Context-aware Data Transfer
It is sometimes important to know how the capabilities of various
network components between two end hosts, especially in the mobile
environment. With the Path Vector extension, an ALTO client may
query the "network context" information, i.e., whether the two hosts
are connected to the access network through a wireless link or a
wire, and the capabilities of the access network. Thus, the client
may use different data transfer mechanisms, or even deploy different
5G User Plane Functions (UPF) [I-D.ietf-dmm-5g-uplane-analysis] to
optimize the data transfer.
4.2.3. CDN and Service Edge
A growing trend in today's applications is to bring storage and
computation closer to the end user for better QoE, such as Content
Delivery Network (CDN), AR/VR, and cloud gaming, as reported in
various recent documents ([I-D.contreras-alto-service-edge],
[I-D.huang-alto-mowie-for-network-aware-app], and
[I-D.yang-alto-deliver-functions-over-networks]).
With the Path Vector extension, an ALTO server can selectively reveal
the CDNs and service edges that reside along the paths between
different end hosts, together with their properties such as available
Service Level Agreement (SLA) plans. Otherwise, the ALTO client may
have to make multiple queries and potentially with the complete list
of CDNs and/or service edges. While both approaches offer the same
information, making multiple queries introduces larger delay and more
overhead on both the ALTO server and the ALTO client.
5. Path Vector Extension: Overview
This section gives a non-normative overview of the Path Vector
extension. It is assumed that readers are familiar with both the
base protocol [RFC7285] and the Unified Property Map extension
[I-D.ietf-alto-unified-props-new].
To satisfies the additional requirements, this extension:
1. introduces Abstract Network Element (ANE) as the abstraction of
intermediate network components,
2. extends the Cost Map and Endpoint Cost Service to convey the
intermediate network components traversed by the path of a
<source, destination> pair as Path Vectors,
3. uses the Unified Property Map to convey the association between
the intermediate network components and their properties.
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Thus, an ALTO client can learn about the intermediate network
components that are critical to the QoE of a <source, destination>
pair by investigating the corresponding Path Vector value (AR1),
identify common network components if an ANE appears in the Path
Vectors of multiple <source, destination> pairs (AR2), and retrieve
the properties of the network components by searching the Unified
Property Map (AR3).
5.1. Abstract Network Element
This extension introduces Abstract Network Element (ANE) as an
indirect and network-agnostic way to specify an aggregation of
intermediate network components between a source and a destination.
Specifically, an ANE is a string of type ANEName as specified in
Section 6.1 and its associated set of properties.
5.1.1. ANE Domain
In this extension, the associations between ANE and the properties
are conveyed in a Unified Property Map. Thus, they must follow the
mechanisms specified in the [I-D.ietf-alto-unified-props-new].
Specifically, this document defines a new entity domain called "ane"
as specified in Section 5.1.1 and defines two initial properties for
the "ane" domain.
5.1.2. Ephemeral ANE and Persistent ANE
For different requests, there can be different ways of grouping
network components and assigning ANEs. For example, an ALTO server
may define an ANE for each aggregated bottleneck link between the
sources and destinations specified in the request. As the aggregated
bottleneck links vary for different combinations of sources and
destinations, the ANEs are ephemeral and are no longer valid after
the request completes. Thus, the scope of ephemeral ANEs are limited
to the corresponding Path Vector response.
While ephemeral ANEs returned by a Path Vector response do not exist
beyond that response, some of them may represent entities that are
persistent and defined in a standalone Property Map. Indeed, it may
be useful for clients to occasionally query properties on persistent
entities, without caring about the path that traverses them.
Persistent entities have a persistent ID that is registered in a
Property Map, together with their properties.
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5.1.3. Property Filtering
Resource-constrained ALTO clients may benefit from the filtering of
Path Vector query results at the ALTO server, as an ALTO client may
only require a subset of the available properties.
Specifically, the available properties for a given resource are
announced in the Information Resource Directory as a new capability
called "ane-property-names". The selected properties are specified
in a filter called "ane-property-names" in the request body, and the
response must return and only return the selected properties for the
ANEs in the response.
The "ane-property-names" capability for Cost Map and for Endpoint
Cost Service are specified in Section 7.1.4 and Section 7.2.4
respectively. The "ane-property-names" filter for Cost Map and
Endpoint Cost Service are specified in Section 7.1.3 and
Section 7.2.3 accordingly.
5.2. Path Vector Cost Type
For an ALTO client to correctly interpret the Path Vector, this
extension specifies a new cost type called the Path Vector cost type,
which must be included both in the Information Resource Directory and
the ALTO Cost Map or Endpoint Cost Map so that an ALTO client can
correct interpret the cost values.
The Path Vector cost type must convey both the interpretation and
semantics in the "cost-mode" and "cost-metric" respectively.
Unfortunately, a single "cost-mode" value cannot fully specify the
interpretation of a Path Vector, which is a compound data type. For
example, in programming languages such as Java, a Path Vector will
have the type of JSONArray[ANEName].
Instead of extending the "type system" of ALTO, this document takes a
simple and backward compatible approach. Specifically, the "cost-
mode" of the Path Vector cost type is "array", which indicates the
value is a JSON array. Then, an ALTO client must check the value of
the "cost-metric". If the value is "ane-path", meaning the JSON
array should be further interpreted as a path of ANENames.
The Path Vector cost type is specified in Section 6.5.
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5.3. Multipart Path Vector Response
For a basic ALTO information resource, a response contains only one
type of ALTO resources, e.g., Network Map, Cost Map, or Property Map.
Thus, only one round of communication is required: An ALTO client
sends a request to an ALTO server, and the ALTO server returns a
response, as shown in Figure 3.
ALTO client ALTO server
|-------------- Request ---------------->|
|<------------- Response ----------------|
Figure 3: A Typical ALTO Request and Response
The Path Vector extension, on the other hand, involves two types of
information resources: Path Vectors conveyed in a Cost Map or an
Endpoint Cost Map, and ANE properties conveyed in a Unified Property
Map. Instead of two consecutive message exchanges, the Path Vector
extension enforces one round of communication. Specifically, the
Path Vector extension requires the ALTO client to include the source
and destination pairs and the requested ANE properties in a single
request, and encapsulates both Path Vectors and properties associated
with the ANEs in a single response, as shown in Figure 4.
ALTO client ALTO server
|------------- PV Request -------------->|
|<----- PV Response (Cost Map Part) -----|
|<--- PV Response (Property Map Part) ---|
Figure 4: The Path Vector Extension Request and Response
This design is based on the following considerations:
1. Since ANEs may be constructed on demand, and potentially based on
the requested properties (See Section 5.1 for more details). If
sources and destinations are not in the same request as the
properties, an ALTO server either cannot construct ANEs on-
demand, or must wait until both requests are received.
2. As ANEs may be constructed on demand, mappings of each ANE to its
underlying network devices and resources can be specific to the
request. In order to respond to the Property Map request
correctly, an ALTO server must store the mapping of each Path
Vector request until the client fully retrieves the property
information. The "stateful" behavior may substantially harm the
server scalability and potentially lead to Denial-of-Service
attacks.
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One approach to realize the one-round communication is to define a
new media type to contain both objects, but this violates modular
design. This document follows the standard-conforming usage of
"multipart/related" media type defined in [RFC2387] to elegantly
combine the objects. Path Vectors are encoded as a Cost Map or an
Endpoint Cost Map, and the Property Map is encoded as a Unified
Propert Map. They are encapsulated as parts of a multipart message.
The modular composition allows ALTO servers and clients to reuse the
data models of the existing information resources. Specifically,
this document addresses the following practical issues using
"multipart/related".
5.3.1. Identifying the Media Type of the Root Object
ALTO uses media type to indicate the type of an entry in the
Information Resource Directory (IRD) (e.g., "application/alto-
costmap+json" for Cost Map and "application/alto-endpointcost+json"
for Endpoint Cost Map). Simply putting "multipart/related" as the
media type, however, makes it impossible for an ALTO client to
identify the type of service provided by related entries.
To address this issue, this document uses the "type" parameter to
indicate the root object of a multipart/related message. For a Cost
Map resource, the "media-type" in the IRD entry must be "multipart/
related" with the parameter "type=application/alto-costmap+json"; for
an Endpoint Cost Service, the parameter must be "type=application/
alto-endpointcost+json".
5.3.2. References to Part Messages
The ALTO SSE extension (see [I-D.ietf-alto-incr-update-sse]) uses
"client-id" to demultiplex push updates. However, "client-id" is
provided for each request, which introduces ambiguity when applying
SSE to a Path Vector resource.
To address this issue, an ALTO server must assign a unique identifier
to each part of the "multipart/related" response message. This
identifier, referred to as a Part Resource ID (See Section 6.6 for
details), must be present in the part message's "Resource-Id" header.
The MIME part header must also contain the "Content-Type" header,
whose value is the media type of the part (e.g., "application/alto-
costmap+json", "application/alto-endpointcost+json", or "application/
alto-propmap+json").
If an ALTO server provides incremental updates for this Path Vector
resource, it must generate incremental updates for each part
separately. The client-id must have the following format:
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pv-client-id '.' part-resource-id
where pv-client-id is the client-id assigned to the Path Vector
request, and part-resource-id is the "Resource-Id" header value of
the part. The media-type must match the "Content-Type" of the part.
The same problem applies to the part messages as well. The two parts
must contain a version tag, which SHOULD contain a unique Resource
ID. This document requires the resource-id in a Version Tag to have
the following format:
pv-resource-id '.' part-resource-id
where pv-resource-id is the resource ID of the Path Vector resource
in the IRD entry, and the part-resource-id has the same value as the
"Resource-Id" header of the part.
5.3.3. Order of Part Messages
According to [RFC2387], the Path Vector part, whose media type is the
same as the "type" parameter of the multipart response message, is
the root object. Thus, it is the element the application processes
first. Even though the "start" parameter allows it to be placed
anywhere in the part sequence, it is RECOMMENDED that the parts
arrive in the same order as they are processed, i.e., the Path Vector
part is always put as the first part, followed by the property map
part. It is also RECOMMENDED that when doing so, an ALTO server
SHOULD NOT set the "start" parameter, which implies the first part is
the root object.
6. Specification: Basic Data Types
6.1. ANE Name
An ANE Name is encoded as a JSON string with the same format as that
of the type PIDName (Section 10.1 of [RFC7285]).
The type ANEName is used in this document to indicate a string of
this format.
6.2. ANE Domain
The ANE domain associates property values with the Abstract Network
Elements in a Property Map. Accordingly, the ANE domain always
depends on a Property Map.
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6.2.1. Entity Domain Type
ane
6.2.2. Entity Identifier Encoding
The entity identifier of the "ane" domain has the same format as
defined in Section 5.1.3 in [I-D.ietf-alto-unified-props-new], and
the DomainTypeSpecificEntityID part has the same format as the
ANEName type.
6.2.3. Hierarchy and Inheritance
There is no hierarchy or inheritance for properties associated with
ANEs.
6.2.4. Media Type of Defining Resource
When resource specific domains are defined with entities of domain
type "ane", the defining resource for entity domain type "ane" MUST
be a Property Map. The media type of defining resources for the "ane"
domain is:
application/alto-propmap+json
Specifically, the defining resource of ephemeral ANEs is the Property
Map part of the multipart response. The defining resource of
persistent ANEs is the Property Map on which standalone queries for
properties of persistent ANEs are made.
6.3. ANE Property Name
An ANE Property Name is encoded as a JSON string with the same format
as that of Entity Property Name (Section 5.2.2 of
[I-D.ietf-alto-unified-props-new]).
6.4. Initial ANE Property Types
In this document, two initial ANE property types are specified, "max-
reservable-bandwidth" and "persistent-entity-id".
Note that the two property types defined in this document do not
depend on any information resource, so their ResourceID part must be
empty.
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----- L1
/
PID1 +---------------+ 10 Gbps +----------+ PID3
1.2.3.0/24+---+ +-----------+ +---------+ +---+3.4.5.0/24
| | MEC1 | | | |
| +-----------+ | +-----+ |
PID2 | | | +----------+
2.3.4.0/24+---+ | | NET3
| | | 15 Gbps
| | | \
+---------------+ | -------- L2
NET1 |
+---------------+
| +-----------+ | PID4
| | MEC2 | +---+4.5.6.0/24
| +-----------+ |
+---------------+
NET2
Figure 5: Examples of ANE Properties
In this document, Figure 5 is used to illustrate the use of the two
initial ANE property types. There are 3 sub-networks (NET1, NET2 and
NET3) and two interconnection links (L1 and L2). It is assumed that
each sub-network has sufficiently large bandwidth to be reserved.
6.4.1. New ANE Property Type: Maximum Reservable Bandwidth
Identifier: "max-reservable-bandwidth"
Intended Semantics: The maximum reservable bandwidth property stands
for the maximum bandwidth that can be reserved for all the traffic
that traverses an ANE. The value MUST be encoded as a non-
negative numerical cost value as defined in Section 6.1.2.1 of
[RFC7285] and the unit is bit per second. If this property is
requested but not present in an ANE, it MUST be interpreted as
that the ANE does not support bandwidth reservation.
Security Considerations: ALTO entity properties expose information
to ALTO clients. ALTO service providers should be made aware of
the security ramifications related to the exposure of an entity
property.
To illustrate the use of "max-reservable-bandwidth", consider the
network in Figure 5. An ALTO server can create an ANE for each
interconnection link, where the initial value for "max-reservable-
bandwidth" is the link capacity.
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6.4.2. New ANE Property Type: Persistent Entity ID
Identifier: "persistent-entity-id"
Intended Semantics: The persistent entity ID property is the entity
identifier of the persistent ANE associated with an ephemeral ANE.
The value of this property is encoded with the format defined in
Section 5.1.3 of [I-D.ietf-alto-unified-props-new]. In this
format, the entity ID combines:
* a defining information resource for the ANE on which a
"persistent-entity-id" is queried, which is the property map
defining the ANE as a persistent entity, together with the
properties
* the persistent name of the ANE in this property map
With this format, the client has all the needed information for
further standalone query properties on the persistent ANE.
Security Considerations: ALTO entity properties expose information
to ALTO clients. ALTO service providers should be made aware of
the security ramifications related to the exposure of an entity
property.
To illustrate the use of "persistent-entity-id", consider the network
in Figure 5. Assume the ALTO server has a Property Map resource
called "mec-props" that defines persistent ANEs "MEC1" and "MEC2"
that represent the corresponding mobile edge computing (MEC)
clusters. The "persistent-entity-id" of the ephemeral ANE that is
associated with MEC1 has the value "mec-props.ane:MEC1".
6.5. Path Vector Cost Type
This document defines a new cost type, which is referred to as the
"Path Vector" cost type. An ALTO server MUST offer this cost type if
it supports the Path Vector extension.
6.5.1. Cost Metric: ane-path
The cost metric "ane-path" indicates the value of such a cost type
conveys an array of ANE names, where each ANE name uniquely
represents an ANE traversed by traffic from a source to a
destination.
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6.5.2. Cost Mode: array
The cost mode "array" indicates that every cost value in a Cost Map
or an Endpoint Cost Map MUST be interpreted as a JSON array object.
Note that this cost mode only requires the cost value to be a JSON
array of JSONValue. However, an ALTO server that enables this
extension MUST return a JSON array of ANEName (Section 6.1) when the
cost metric is "ane-path".
6.6. Part Resource ID
A Part Resource ID is encoded as a JSON string with the same format
as that of the type ResourceID (Section 10.2 of [RFC7285]).
NOTE: Even though the client-id assigned to a Path Vector request and
the Part Resource ID may contain up to 64 characters by their own
definition, their concatenation (see Section 5.3.2) MUST also conform
to the same length constraint. The same requirement applies to the
resource ID of the Path Vector resource, too. Thus, it is
RECOMMENDED to limit the length of resource ID and client ID related
to a Path Vector resource to 31 characters.
7. Specification: Service Extensions
7.1. Multipart Filtered Cost Map for Path Vector
This document introduces a new ALTO resource called multipart
filtered cost map resource, which allows an ALTO server to provide
other ALTO resources associated to the cost map resource in the same
response.
7.1.1. Media Type
The media type of the multipart filtered cost map resource is
"multipart/related;type=application/alto-costmap+json".
7.1.2. HTTP Method
The multipart filtered cost map is requested using the HTTP POST
method.
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7.1.3. Accept Input Parameters
The input parameters of the multipart filtered cost map are supplied
in the body of an HTTP POST request. This document extends the input
parameters to a filtered cost map with a data format indicated by the
media type "application/alto-costmapfilter+json", which is a JSON
object of type PVReqFilteredCostMap, where:
object {
[EntityPropertyName ane-property-names<0..*>;]
} PVReqFilteredCostMap : ReqFilteredCostMap;
with fields:
ane-property-names: A list of properties that are associated with
the ANEs. Each property in this list MUST match one of the
supported ANE properties indicated in the resource's "ane-
property-names" capability. If the field is NOT present, it MUST
be interpreted as an empty list, indicating that the ALTO server
MUST NOT return any property in the Unified Property part.
Example: Consider the network in Figure 1. If an ALTO client wants
to query the "max-reservable-bandwidth" between PID1 and PID2, it can
submit the following request.
POST /costmap/pv HTTP/1.1
Host: alto.example.com
Accept: multipart/related;type=application/alto-costmap+json,
application/alto-error+json
Content-Length: [TBD]
Content-Type: application/alto-costmapfilter+json
{
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
},
"pids": {
"srcs": [ "PID1" ],
"dsts": [ "PID2" ]
},
"ane-property-names": [ "max-reservable-bandwidth" ]
}
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7.1.4. Capabilities
The multipart filtered cost map resource extends the capabilities
defined in Section 11.3.2.4 of [RFC7285]. The capabilities are
defined by a JSON object of type PVFilteredCostMapCapabilities:
object {
[EntityPropertyName ane-property-names<0..*>;]
} PVFilteredCostMapCapabilities : FilteredCostMapCapabilities;
with fields:
cost-type-names: The "cost-type-names" field MUST only include the
Path Vector cost type, unless explicitly documented by a future
extension. This also implies that the Path Vector cost type MUST
be defined in the "cost-types" of the Information Resource
Directory's "meta" field.
cost-constraints: If the "cost-type-names" field includes the Path
Vector cost type, "cost-constraints" field MUST be "false" or not
present unless specifically instructed by a future document.
testable-cost-type-names: If the "cost-type-names" field includes
the Path Vector cost type, the Path Vector cost type MUST NOT be
included in the "testable-cost-type-names" field unless
specifically instructed by a future document.
ane-property-names: Defines a list of ANE properties that can be
returned. If the field is NOT present, it MUST be interpreted as
an empty list, indicating the ALTO server cannot provide any ANE
property.
7.1.5. Uses
This member MUST include the resource ID of the network map based on
which the PIDs are defined. If this resource supports "persistent-
entity-id", it MUST also include the defining resources of persistent
ANEs that may appear in the response.
7.1.6. Response
The response MUST indicate an error, using ALTO protocol error
handling, as defined in Section 8.5 of [RFC7285], if the request does
no.
The "Content-Type" header of the response MUST be "multipart/related"
as defined by [RFC2387] with the following parameters:
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type: The type parameter MUST be "application/alto-costmap+json".
Note that [RFC2387] permits both parameters with and without the
double quotes.
start: The start parameter is as defined in [RFC2387]. If present,
it MUST have the same value as the "Resource-Id" header of the
Path Vector part.
boundary: The boundary parameter is as defined in [RFC2387].
The body of the response consists of two parts:
* The Path Vector part MUST include "Resource-Id" and "Content-Type"
in its header. The value of "Resource-Id" MUST has the format of
a Part Resource ID. The "Content-Type" MUST be "application/alto-
costmap+json".
The body of the Path Vector part MUST be a JSON object with the
same format as defined in Section 11.2.3.6 of [RFC7285]. The JSON
object MUST include the "vtag" field in the "meta" field, which
provides the version tag of the returned cost map. The resource
ID of the version tag MUST follow the format in Section 5.3.2.
The "meta" field MUST also include the "dependent-vtags" field,
whose value is a single-element array to indicate the version tag
of the network map used, where the network map is specified in the
"uses" attribute of the multipart filtered cost map resource in
IRD.
* The Unified Property Map part MUST also include "Resource-Id" and
"Content-Type" in its header. The value of "Resource-Id" has the
format of a Part Resource ID. The "Content-Type" MUST be
"application/alto-propmap+json".
The body of the Unified Property Map part MUST be a JSON object
with the same format as defined in Section 4.6 of
[I-D.ietf-alto-unified-props-new]. The JSON object MUST include
the "dependent-vtags" field in the "meta" field. The value of the
"dependent-vtags" field MUST be an array of VersionTag objects as
defined by Section 10.3 of [RFC7285]. The "vtag" of the Path
Vector part MUST be included in the "dependent-vtags". If
"persistent-entity-id" is requested, the version tags of the
dependent resources that may expose the entities in the response
MUST also be included. The PropertyMapData has one member for
each ANEName that appears in the Path Vector part, which is an
entity identifier belonging to the self-defined entity domain as
defined in Section 5.1.2.3 of [I-D.ietf-alto-unified-props-new].
The EntityProps has one member for each property requested by an
ALTO client if applicable.
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If the "start" parameter is not present, the Path Vector part MUST be
the first part in the multipart response.
Example: Consider the network in Figure 1. The response of the
example request in Section 7.1.3 is as follows, where "ANE1"
represents the aggregation of all the switches in the network.
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HTTP/1.1 200 OK
Content-Length: [TBD]
Content-Type: multipart/related; boundary=example-1;
type=application/alto-costmap+json
--example-1
Resource-Id: costmap
Content-Type: application/alto-costmap+json
{
"meta": {
"vtag": {
"resource-id": "filtered-cost-map-pv.costmap",
"tag": "d827f484cb66ce6df6b5077cb8562b0a"
},
"dependent-vtags": [
{
"resource-id": "my-default-networkmap",
"tag": "75ed013b3cb58f896e839582504f6228"
}
],
"cost-type": { "cost-mode": "array", "cost-metric": "ane-path" }
},
"cost-map": {
"PID1": { "PID2": ["ANE1"] }
}
}
--example-1
Resource-Id: propmap
Content-Type: application/alto-propmap+json
{
"meta": {
"dependent-vtags": [
{
"resource-id": "filtered-cost-map-pv.costmap",
"tag": "d827f484cb66ce6df6b5077cb8562b0a"
}
]
},
"property-map": {
".ane:ANE1": { "max-reservable-bandwidth": 100000000 }
}
}
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7.2. Multipart Endpoint Cost Service for Path Vector
This document introduces a new ALTO resource called multipart
endpoint cost resource, which allows an ALTO server to provide other
ALTO resources associated to the endpoint cost resource in the same
response.
7.2.1. Media Type
The media type of the multipart endpoint cost resource is
"multipart/related;type=application/alto-endpointcost+json".
7.2.2. HTTP Method
The multipart endpoint cost resource is requested using the HTTP POST
method.
7.2.3. Accept Input Parameters
The input parameters of the multipart endpoint cost resource are
supplied in the body of an HTTP POST request. This document extends
the input parameters to an endpoint cost map with a data format
indicated by the media type "application/alto-
endpointcostparams+json", which is a JSON object of type
PVEndpointCostParams, where
object {
[EntityPropertyName ane-property-names<0..*>;]
} PVReqEndpointcost : ReqEndpointcost;
with fields:
ane-property-names: This document defines the "ane-property-names"
in PVReqEndpointcost as the same as in PVReqFilteredCostMap. See
Section 7.1.3.
Example: Consider the network in Figure 1. If an ALTO client wants
to query the "max-reservable-bandwidth" between eh1 and eh2, it can
submit the following request.
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POST /ecs/pv HTTP/1.1
Host: alto.example.com
Accept: multipart/related;type=application/alto-endpointcost+json,
application/alto-error+json
Content-Length: [TBD]
Content-Type: application/alto-endpointcostparams+json
{
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
},
"endpoints": {
"srcs": [ "ipv4:1.2.3.4" ],
"dsts": [ "ipv4:2.3.4.5" ]
},
"ane-property-names": [ "max-reservable-bandwidth" ]
}
7.2.4. Capabilities
The capabilities of the multipart endpoint cost resource are defined
by a JSON object of type PVEndpointcostCapabilities, which is defined
as the same as PVFilteredCostMapCapabilities. See Section 7.1.4.
7.2.5. Uses
If this resource supports "persistent-entity-id", it MUST also
include the defining resources of persistent ANEs that may appear in
the response.
7.2.6. Response
The response MUST indicate an error, using ALTO protocol error
handling, as defined in Section 8.5 of [RFC7285], if the request is
invalid.
The "Content-Type" header of the response MUST be "multipart/related"
as defined by [RFC7285] with the following parameters:
type: The type parameter MUST be "application/alto-
endpointcost+json".
start: The start parameter is as defined in Section 7.1.6.
boundary: The boundary parameter is as defined in [RFC2387].
The body consists of two parts:
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* The Path Vector part MUST include "Resource-Id" and "Content-Type"
in its header. The value of "Resource-Id" MUST has the format of
a Part Resource ID. The "Content-Type" MUST be "application/alto-
endpointcost+json".
The body of the Path Vector part MUST be a JSON object with the
same format as defined in Section 11.5.1.6 of [RFC7285]. The JSON
object MUST include the "vtag" field in the "meta" field, which
provides the version tag of the returned endpoint cost map. The
resource ID of the version tag MUST follow the format in
Section 5.3.2.
* The Unified Property Map part MUST also include "Resource-Id" and
"Content-Type" in its header. The value of "Resource-Id" MUST has
the format of a Part Resource ID. The "Content-Type" MUST be
"application/alto-propmap+json".
The body of the Unified Property Map part MUST be a JSON object
with the same format as defined in Section 4.6 of
[I-D.ietf-alto-unified-props-new]. The JSON object MUST include
the "dependent-vtags" field in the "meta" field. The value of the
"dependent-vtags" field MUST be an array of VersionTag objects as
defined by Section 10.3 of [RFC7285]. The "vtag" of the Path
Vector part MUST be included in the "dependent-vtags". If
"persistent-entity-id" is requested, the version tags of the
dependent resources that may expose the entities in the response
MUST also be included. The PropertyMapData has one member for
each ANEName that appears in the Path Vector part, which is an
entity identifier belonging to the self-defined entity domain as
defined in Section 5.1.2.3 of [I-D.ietf-alto-unified-props-new].
The EntityProps has one member for each property requested by the
ALTO client if applicable.
If the "start" parameter is not present, the Path Vector part MUST be
the first part in the multipart response.
Example: Consider the network in Figure 1. The response of the
example request in Section 7.2.3 is as follows.
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HTTP/1.1 200 OK
Content-Length: [TBD]
Content-Type: multipart/related; boundary=example-1;
type=application/alto-endpointcost+json
--example-1
Resource-Id: ecs
Content-Type: application/alto-endpointcost+json
{
"meta": {
"vtag": {
"resource-id": "ecs-pv.costmap",
"tag": "d827f484cb66ce6df6b5077cb8562b0a"
},
"dependent-vtags": [
{
"resource-id": "my-default-networkmap",
"tag": "75ed013b3cb58f896e839582504f6228"
}
],
"cost-type": { "cost-mode": "array", "cost-metric": "ane-path" }
},
"cost-map": {
"ipv4:1.2.3.4": { "ipv4:2.3.4.5": ["ANE1"] }
}
}
--example-1
Resource-Id: propmap
Content-Type: application/alto-propmap+json
{
"meta": {
"dependent-vtags": [
{
"resource-id": "ecs-pv.costmap",
"tag": "d827f484cb66ce6df6b5077cb8562b0a"
}
]
},
"property-map": {
".ane:ANE1": { "max-reservable-bandwidth": 100000000 }
}
}
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8. Examples
This section lists some examples of Path Vector queries and the
corresponding responses. Some long lines are truncated for better
readability.
8.1. Example: Information Resource Directory
To give a comprehensive example of the Path Vector extension, we
consider the network in Figure 5. The example ALTO server provides
the following information resources:
* "my-default-networkmap": A Network Map resource which contains the
PIDs in the network.
* "filtered-cost-map-pv": A Multipart Filtered Cost Map resource for
Path Vector, which exposes the "max-reservable-bandwidth" property
for the PIDs in "my-default-networkmap".
* "ane-props": A filtered Unified Property resource that exposes the
information for persistent ANEs in the network.
* "endpoint-cost-pv": A Multipart Endpoint Cost Service for Path
Vector, which exposes the "max-reservable-bandwidth" and the
"persistent-entity-id" properties.
* "update-pv": An Update Stream service, which provides the
incremental update service for the "endpoint-cost-pv" service.
Below is the Information Resource Directory of the example ALTO
server. To enable the Path Vector extension, the "path-vector" cost
type (Section 6.5) is defined in the "cost-types" of the "meta"
field, and is included in the "cost-type-names" of resources
"filetered-cost-map-pv" and "endpoint-cost-pv".
{
"meta": {
"cost-types": {
"path-vector": {
"cost-mode": "array",
"cost-metric": "ane-path"
}
}
},
"resources": {
"my-default-networkmap": {
"uri" : "https://alto.example.com/networkmap",
"media-type" : "application/alto-networkmap+json"
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},
"filtered-cost-map-pv": {
"uri": "https://alto.example.com/costmap/pv",
"media-type": "multipart/related;
type=application/alto-costmap+json",
"accepts": "application/alto-costmapfilter+json",
"capabilities": {
"cost-type-names": [ "path-vector" ],
"ane-property-names": [ "max-reservable-bandwidth" ]
},
"uses": [ "my-default-networkmap" ]
},
"ane-props": {
"uri": "https://alto.example.com/ane-props",
"media-type": "application/alto-propmap+json",
"accepts": "application/alto-propmapparams+json",
"capabilities": {
"mappings": {
".ane": [ "cpu" ]
}
}
},
"endpoint-cost-pv": {
"uri": "https://alto.exmaple.com/endpointcost/pv",
"media-type": "multipart/related;
type=application/alto-endpointcost+json",
"accepts": "application/alto-endpointcostparams+json",
"capabilities": {
"cost-type-names": [ "path-vector" ],
"ane-property-names": [
"max-reservable-bandwidth", "persistent-entity-id"
]
},
"uses": [ "ane-props" ]
},
"update-pv": {
"uri": "https://alto.example.com/updates/pv",
"media-type": "text/event-stream",
"uses": [ "endpoint-cost-pv" ],
"accepts": "application/alto-updatestreamparams+json",
"capabilities": {
"support-stream-control": true
}
}
}
}
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8.2. Example: Multipart Filtered Cost Map
The following examples demonstrate the request to the "filtered-cost-
map-pv" resource and the corresponding response.
The request uses the "path-vector" cost type in the "cost-type"
field. The "ane-property-names" field is missing, indicating that
the client only requests for the Path Vector but not the ANE
properties.
The response consists of two parts. The first part returns the array
of ANEName for each source and destination pair. There are two ANEs,
where "L1" represents the interconnection link L1, and "L2"
represents the interconnection link L2.
The second part returns an empty Property Map. Note that the ANE
entries are omitted since they have no properties (See Section 3.1 of
[I-D.ietf-alto-unified-props-new]).
POST /costmap/pv HTTP/1.1
Host: alto.example.com
Accept: multipart/related;type=application/alto-costmap+json,
application/alto-error+json
Content-Length: [TBD]
Content-Type: application/alto-costmapfilter+json
{
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
},
"pids": {
"srcs": [ "PID1" ],
"dsts": [ "PID3", "PID4" ]
}
}
HTTP/1.1 200 OK
Content-Length: [TBD]
Content-Type: multipart/related; boundary=boundary;
type=application/alto-costmap+json
--boundary
Resource-Id: costmap
Content-Type: application/alto-costmap+json
{
"meta": {
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"vtag": {
"resource-id": "filtered-cost-map-pv.costmap",
"tag": "d827f484cb66ce6df6b5077cb8562b0a"
},
"dependent-vtags": [
{
"resource-id": "my-default-networkmap",
"tag": "75ed013b3cb58f896e839582504f6228"
}
],
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
}
},
"cost-map": {
"PID1": {
"PID3": [ "L1" ],
"PID4": [ "L1", "L2" ]
}
}
}
--boundary
Resource-Id: propmap
Content-Type: application/alto-propmap+json
{
"meta": {
"dependent-vtags": [
{
"resource-id": "filtered-cost-map-pv.costmap",
"tag": "d827f484cb66ce6df6b5077cb8562b0a"
}
]
},
"property-map": {
}
}
8.3. Example: Multipart Endpoint Cost Resource
The following examples demonstrate the request to the "endpoint-cost-
pv" resource and the corresponding response.
The request uses the path vector cost type in the "cost-type" field,
and queries the Maximum Reservable Bandwidth ANE property and the
Persistent Entity property.
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The response consists of two parts. The first part returns the array
of ANEName for each valid source and destination pair, where "NET1"
represent sub-network NET1, and "AGGR" is the aggregation of L1 and
NET3.
The second part returns the requested properties of ANEs. Since NET1
has sufficient bandwidth, it sets the "max-reservable-bandwidth" to a
sufficiently large number. It also represents a persistent ANE
defined in the "ane-props" resource, identified by "ane-
props.ane:datacenter1". The aggregated "max-reservable-bandwidth" of
ane:AGGR is constrained by the link capacity of L1. The "persistent-
entity-id" property is omitted as both L1 and NET3 do not represent
any persistent entity.
POST /endpointcost/pv HTTP/1.1
Host: alto.example.com
Accept: multipart/related;
type=application/alto-endpointcost+json,
application/alto-error+json
Content-Length: [TBD]
Content-Type: application/alto-endpointcostparams+json
{
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
},
"endpoints": {
"srcs": [ "ipv4:1.2.3.4", "ipv4:2.3.4.5" ],
"dsts": [ "ipv4:3.4.5.6" ]
},
"ane-property-names": [
"max-reservable-bandwidth",
"persistent-entity-id"
]
}
HTTP/1.1 200 OK
Content-Length: [TBD]
Content-Type: multipart/related; boundary=boundary;
type=application/alto-endpointcost+json
--boundary
Resource-Id: ecs
Content-Type: application/alto-endpointcost+json
{
"meta": {
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"vtags": {
"resource-id": "endpoint-cost-pv.ecs",
"tag": "bb6bb72eafe8f9bdc4f335c7ed3b10822a391cef"
},
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
}
},
"endpoint-cost-map": {
"ipv4:1.2.3.4": {
"ipv4:3.4.5.6": [ "NET1", "AGGR" ]
},
"ipv4:2.3.4.5": {
"ipv4:3.4.5.6": [ "NET1", "AGGR" ]
}
}
}
--boundary
Resource-Id: propmap
Content-Type: application/alto-propmap+json
{
"meta": {
"dependent-vtags": [
{
"resource-id": "endpoint-cost-pv.ecs",
"tag": "bb6bb72eafe8f9bdc4f335c7ed3b10822a391cef"
},
{
"resource-id": "ane-props",
"tag": "bf3c8c1819d2421c9a95a9d02af557a3"
}
]
},
"property-map": {
".ane:NET1": {
"max-reservable-bandwidth": 50000000000,
"persistent-entity-id": "ane-props.ane:datacenter1",
},
".ane:AGGR": {
"max-reservable-bandwidth": 10000000000
}
}
}
After the client obtains "ane-props.ane:datacenter1", it can query
the "ane-props" resource to get the properties of the persistent ANE.
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8.4. Example: Incremental Updates
In this example, an ALTO client subscribes to the incremental update
for the multipart endpoint cost resource "endpoint-cost-pv".
POST /updates/pv HTTP/1.1
Host: alto.example.com
Accept: text/event-stream
Content-Type: application/alto-updatestreamparams+json
Content-Length: [TBD]
{
"add": {
"ecspvsub1": {
"resource-id": "endpoint-cost-pv",
"input": <ecs-input>
}
}
}
Based on the server-side process defined in
[I-D.ietf-alto-incr-update-sse], the ALTO server will send the
"control-uri" first using Server-Sent Event (SSE), followed by the
full response of the multipart message.
HTTP/1.1 200 OK
Connection: keep-alive
Content-Type: text/event-stream
event: application/alto-updatestreamcontrol+json
data: {"control-uri": "https://alto.example.com/updates/streams/123"}
event: multipart/related;boundary=boundary;
type=application/alto-endpointcost+json,ecspvsub1
data: --boundary
data: Resource-ID: ecsmap
data: Content-Type: application/alto-endpointcost+json
data:
data: <endpoint-cost-map-entry>
data: --boundary
data: Resource-ID: propmap
data: Content-Type: application/alto-propmap+json
data:
data: <property-map-entry>
data: --boundary--
When the contents change, the ALTO server will publish the updates
for each node in this tree separately.
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event: application/merge-patch+json, ecspvsub1.ecsmap
data: <Merge patch for endpoint-cost-map-update>
event: application/merge-patch+json, ecspvsub1.propmap
data: <Merge patch for property-map-update>
9. Compatibility
9.1. Compatibility with Legacy ALTO Clients/Servers
The multipart filtered cost map resource and the multipart endpoint
cost resource has no backward compatibility issue with legacy ALTO
clients and servers. Although these two types of resources reuse the
media types defined in the base ALTO protocol for the accept input
parameters, they have different media types for responses. If the
ALTO server provides these two types of resources, but the ALTO
client does not support them, the ALTO client will ignore the
resources without conducting any incompatibility.
9.2. Compatibility with Multi-Cost Extension
This document does not specify how to integrate the Path Vector cost
type with the multi-cost extension [RFC8189]. While it is not
RECOMMENDED to put the Path Vector cost type with other cost types in
a single query, there is no compatible issue.
9.3. Compatibility with Incremental Update
The extension specified in this document is not compatible with the
original incremental update extension
[I-D.ietf-alto-incr-update-sse]. A legacy ALTO client cannot
recognize the compound client-id, and a legacy ALTO server may use
the same client-id for updates of both parts.
ALTO clients and servers must follow the specifications given in this
document to ensure compatibility with the incremental update
extension.
9.4. Compatibility with Cost Calendar
The extension specified in this document is compatible with the Cost
Calendar extension [I-D.ietf-alto-cost-calendar]. When used together
with the Cost Calendar extension, the cost value between a source and
a destination is an array of path vectors, where the k-th path vector
refers to the abstract network paths traversed in the k-th time
interval by traffic from the source to the destination.
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When used with time-varying properties, e.g., maximum reservable
bandwidth (maxresbw), a property of a single entity may also have
different values in different time intervals. In this case, an ANE
with different property values must be considered as different ANEs.
The two extensions combined together can provide the historical
network correlation information for a set of source and destination
pairs. A network broker or client may use this information to derive
other resource requirements such as Time-Block-Maximum Bandwidth,
Bandwidth-Sliding-Window, and Time-Bandwidth-Product (TBP) (See
[SENSE] for details).
10. General Discussions
10.1. Constraint Tests for General Cost Types
The constraint test is a simple approach to query the data. It
allows users to filter the query result by specifying some boolean
tests. This approach is already used in the ALTO protocol.
[RFC7285] and [RFC8189] allow ALTO clients to specify the
"constraints" and "or-constraints" tests to better filter the result.
However, the current syntax can only be used to test scalar cost
types, and cannot easily express constraints on complex cost types,
e.g., the Path Vector cost type defined in this document.
In practice, developing a language for general-purpose boolean tests
can be complex and is likely to be a duplicated work. Thus, it is
worth looking into the direction of integrating existing well-
developed query languages, e.g., XQuery and JSONiq, or their subset
with ALTO.
Filtering the Path Vector results or developing a more sophisticated
filtering mechanism is beyond the scope of this document.
10.2. General Multipart Resources Query
Querying multiple ALTO information resources continuously may be a
general requirement. And the coming issues like inefficiency and
inconsistency are also general. There is no standard solving these
issues yet. So we need some approach to make the ALTO client request
the compound ALTO information resources in a single query.
11. Security Considerations
This document is an extension of the base ALTO protocol, so the
Security Considerations [RFC7285] of the base ALTO protocol fully
apply when this extension is provided by an ALTO server.
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The Path Vector extension requires additional considerations on two
security considerations discussed in the base protocol:
confidentiality of ALTO information (Section 15.3 of [RFC7285]) and
availability of ALTO service (Section 15.5 of [RFC7285]).
For confidentiality of ALTO information, a network operator should be
aware of that this extension may introduce a new risk: the Path
Vector information may make network attacks easier. For example, as
the Path Vector information may reveal more fine-grained internal
network structures than the base protocol, an ALTO client may detect
the bottleneck link and start a distributed denial-of-service (DDoS)
attack involving minimal flows to conduct the in-network congestion.
To mitigate this risk, the ALTO server should consider protection
mechanisms to reduce information exposure or obfuscate the real
information, in particular, in settings where the network and the
application do not belong to the same trust domain. But the
implementation of Path Vector extension involving reduction or
obfuscation should guarantee the requested properties are still
accurate.
For availability of ALTO service, an ALTO server should be cognizant
that using Path Vector extension might have a new risk: frequent
requesting for path vectors might conduct intolerable increment of
the server-side storage and break the ALTO server. It is known that
the computation of Path Vectors is unlikely to be cacheable, in that
the results will depend on the particular requests (e.g., where the
flows are distributed). Hence, the service providing Path Vectors
may become an entry point for denial-of-service attacks on the
availability of an ALTO server. To avoid this risk, authenticity and
authorization of this ALTO service may need to be better protected.
12. IANA Considerations
12.1. ALTO Entity Domain Registry
This document registers a new entry to the ALTO Domain Entity
Registry, as instructed by Section 12.2 of
[I-D.ietf-alto-unified-props-new]. The new entry is as shown below
in Table 1.
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+------------+----------------+-------------+-------------------+
| Identifier | Entity Address | Hierarchy & | Media Type of |
| | Encoding | Inheritance | Defining Resource |
+============+================+=============+===================+
| ane | See | None | application/alto- |
| | Section 6.2.2 | | propmap+json |
+------------+----------------+-------------+-------------------+
Table 1: ALTO Entity Domain
Identifier: See Section 6.2.1.
Entity Identifier Encoding: See Section 6.2.2.
Hierarchy: None
Inheritance: None
Media Type of Defining Resource: See Section 6.2.4.
Security Considerations: In some usage scenarios, ANE addresses
carried in ALTO Protocol messages may reveal information about an
ALTO client or an ALTO service provider. Applications and ALTO
service providers using addresses of ANEs will be made aware of
how (or if) the addressing scheme relates to private information
and network proximity, in further iterations of this document.
12.2. ALTO Entity Property Type Registry
Two initial entries are registered to the ALTO Domain "ane" in the
"ALTO Entity Property Type Registry", as instructed by Section 12.3
of [I-D.ietf-alto-unified-props-new]. The two new entries are shown
below in Table 2.
+--------------------------+--------------------+
| Identifier | Intended Semantics |
+==========================+====================+
| max-reservable-bandwidth | See Section 6.4.1 |
+--------------------------+--------------------+
| persistent-entity-id | See Section 6.4.2 |
+--------------------------+--------------------+
Table 2: Initial Entries for ane Domain in
the ALTO Entity Property Types Registry
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13. Acknowledgments
The authors would like to thank discussions with Andreas Voellmy,
Erran Li, Haibin Song, Haizhou Du, Jiayuan Hu, Qiao Xiang, Tianyuan
Liu, Xiao Shi, Xin Wang, and Yan Luo. The authors thank Greg
Bernstein (Grotto Networks), Dawn Chen (Tongji University), Wendy
Roome, and Michael Scharf for their contributions to earlier drafts.
14. References
14.1. Normative References
[I-D.ietf-alto-cost-calendar]
Randriamasy, S., Yang, Y., WU, Q., Lingli, D., and N.
Schwan, "Application-Layer Traffic Optimization (ALTO)
Cost Calendar", Work in Progress, Internet-Draft, draft-
ietf-alto-cost-calendar-21, 17 March 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-alto-cost-
calendar-21.txt>.
[I-D.ietf-alto-incr-update-sse]
Roome, W. and Y. Yang, "ALTO Incremental Updates Using
Server-Sent Events (SSE)", Work in Progress, Internet-
Draft, draft-ietf-alto-incr-update-sse-22, 20 March 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-alto-incr-
update-sse-22.txt>.
[I-D.ietf-alto-performance-metrics]
WU, Q., Yang, Y., Lee, Y., Dhody, D., Randriamasy, S., and
L. Contreras, "ALTO Performance Cost Metrics", Work in
Progress, Internet-Draft, draft-ietf-alto-performance-
metrics-11, 12 June 2020, <http://www.ietf.org/internet-
drafts/draft-ietf-alto-performance-metrics-11.txt>.
[I-D.ietf-alto-unified-props-new]
Roome, W., Randriamasy, S., Yang, Y., Zhang, J., and K.
Gao, "Unified Properties for the ALTO Protocol", Work in
Progress, Internet-Draft, draft-ietf-alto-unified-props-
new-11, 9 March 2020, <http://www.ietf.org/internet-
drafts/draft-ietf-alto-unified-props-new-11.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2387] Levinson, E., "The MIME Multipart/Related Content-type",
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RFC 2387, DOI 10.17487/RFC2387, August 1998,
<https://www.rfc-editor.org/info/rfc2387>.
[RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S.,
Previdi, S., Roome, W., Shalunov, S., and R. Woundy,
"Application-Layer Traffic Optimization (ALTO) Protocol",
RFC 7285, DOI 10.17487/RFC7285, September 2014,
<https://www.rfc-editor.org/info/rfc7285>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost
Application-Layer Traffic Optimization (ALTO)", RFC 8189,
DOI 10.17487/RFC8189, October 2017,
<https://www.rfc-editor.org/info/rfc8189>.
14.2. Informative References
[AAAI2019] Xiang, Q., Yu, H., Aspnes, J., Le, F., Kong, L., and Y.R.
Yang, "Optimizing in the dark: Learning an optimal
solution through a simple request interface", Proceedings
of the AAAI Conference on Artificial Intelligence 33,
1674-1681 , 2019.
[I-D.bernstein-alto-topo]
Bernstein, G., Yang, Y., and Y. Lee, "ALTO Topology
Service: Uses Cases, Requirements, and Framework", Work in
Progress, Internet-Draft, draft-bernstein-alto-topo-00, 21
October 2013, <http://www.ietf.org/internet-drafts/draft-
bernstein-alto-topo-00.txt>.
[I-D.contreras-alto-service-edge]
Contreras, L., Perez, D., and C. Rothenberg, "Use of ALTO
for Determining Service Edge", Work in Progress, Internet-
Draft, draft-contreras-alto-service-edge-00, 4 November
2019, <http://www.ietf.org/internet-drafts/draft-
contreras-alto-service-edge-00.txt>.
[I-D.huang-alto-mowie-for-network-aware-app]
Huang, W., Zhang, Y., Yang, R., Xiong, C., Lei, Y., Han,
Y., and G. Li, "MoWIE for Network Aware Application", Work
in Progress, Internet-Draft, draft-huang-alto-mowie-for-
network-aware-app-00, 9 March 2020, <http://www.ietf.org/
internet-drafts/draft-huang-alto-mowie-for-network-aware-
app-00.txt>.
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[I-D.ietf-dmm-5g-uplane-analysis]
Homma, S., Miyasaka, T., Matsushima, S., and D. Voyer,
"User Plane Protocol and Architectural Analysis on 3GPP 5G
System", Work in Progress, Internet-Draft, draft-ietf-dmm-
5g-uplane-analysis-03, 3 November 2019,
<http://www.ietf.org/internet-drafts/draft-ietf-dmm-5g-
uplane-analysis-03.txt>.
[I-D.yang-alto-deliver-functions-over-networks]
Yang, S., Cui, L., Xu, M., Yang, Y., and R. Huang,
"Delivering Functions over Networks: Traffic and
Performance Optimization for Edge Computing using ALTO",
Work in Progress, Internet-Draft, draft-yang-alto-deliver-
functions-over-networks-01, 13 July 2020,
<http://www.ietf.org/internet-drafts/draft-yang-alto-
deliver-functions-over-networks-01.txt>.
[LHC] "CERN - LHC", 2019, <https://atlas.cern/tags/lhc>.
[SENSE] "Services - SENSE", 2019, <http://sense.es.net/services>.
[TON2019] Gao, K., Xiang, Q., Wang, X., Yang, Y.R., and J. Bi, "An
objective-driven on-demand network abstraction for
adaptive applications", IEEE/ACM Transactions on
Networking (TON) Vol 27, no. 2 (2019): 805-818., 2019.
Appendix A. Changes since -10
Revision -11
* replaces "part" with "components" in the abstract;
* identifies additional requirements (AR) derived from the flow
scheduling example, and introduces how the extension addresses the
additional requirements
* fixes the inconsistent use of "start" parameter in multipart
responses;
* specifies explicitly how to handle "cost-constraints";
* uses the latest IANA registration mechanism defined in
[I-D.ietf-alto-unified-props-new];
* renames "persistent-entities" to "persistent-entity-id";
* makes "application/alto-propmap+json" as the media type of
defining resources for the "ane" domain;
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* updates the examples;
* adds the discussion on ephemeral and persistent ANEs.
Appendix B. Changes since -09
Revision -10
* revises the introduction which
- extends the scope where the PV extension can be applied beyond
the "path correlation" information
* brings back the capacity region use case to better illustrate the
problem
* revises the overview to explain and defend the concepts and
decision choices
* fixes inconsistent terms, typos
Appendix C. Changes since -08
This revision
* fixes a few spelling errors
* emphasizes that abstract network elements can be generated on
demand in both introduction and motivating use cases
Appendix D. Changes Since Version -06
* We emphasize the importance of the path vector extension in two
aspects:
1. It expands the problem space that can be solved by ALTO, from
preferences of network paths to correlations of network paths.
2. It is motivated by new usage scenarios from both application's
and network's perspectives.
* More use cases are included, in addition to the original capacity
region use case.
* We add more discussions to fully explore the design space of the
path vector extension and justify our design decisions, including
the concept of abstract network element, cost type (reverted to
-05), newer capabilities and the multipart message.
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* Fix the incremental update process to be compatible with SSE -16
draft, which uses client-id instead of resource-id to demultiplex
updates.
* Register an additional ANE property (i.e., persistent-entities) to
cover all use cases mentioned in the draft.
Authors' Addresses
Kai Gao
China
610000
Chengdu
No.24 South Section 1, Yihuan Road
Sichuan University
Email: kaigao@scu.edu.cn
Young Lee
Sabine Randriamasy
Nokia Bell Labs
Route de Villejust
91460 Nozay
France
Email: sabine.randriamasy@nokia-bell-labs.com
Yang Richard Yang
Yale University
51 Prospect Street
New Haven, CT
United States of America
Email: yry@cs.yale.edu
Jingxuan Jensen Zhang
China
201804
Shanghai
4800 Caoan Road
Tongji University
Email: jingxuan.n.zhang@gmail.com
Gao, et al. Expires 15 January 2021 [Page 44]
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