Re: [alto] ALTO Draft ReCharter WG review - extensible set of policy attributes

Qin Wu <> Thu, 11 March 2021 08:32 UTC

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From: Qin Wu <>
To: "Randriamasy, Sabine (Nokia - FR/Paris-Saclay)" <>, IETF ALTO <>
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Thread-Topic: ALTO Draft ReCharter WG review - extensible set of policy attributes
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Subject: Re: [alto] ALTO Draft ReCharter WG review - extensible set of policy attributes
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Hi, Sabine:
发件人: Randriamasy, Sabine (Nokia - FR/Paris-Saclay) []
发送时间: 2021年3月11日 1:55
收件人: Qin Wu <>; IETF ALTO <>
主题: RE: ALTO Draft ReCharter WG review - extensible set of policy attributes

Hello ALTO WG,

Regarding the proposed work item on “Protocol extensions to support a richer and extensible set of policy attributes in ALTO information update request and response” (GPE for short) , I would like to add the following:

This work item can be useful, among others, to allow a UE getting cellular network KPIs from an ALTO Server, to figure out for example whether the cell is congested, or which cell to choose.

An ALTO Server cannot provide real-time information. With the proposed extensions, it can indicate a number of real-time network parameters against which ALTO cost values can be modulated.

[Qin]: Yes, the current ALTO server can only provide non-real time or near real time information, performance metrics work allows ALTO server expose performance data. If ALTO protocol is extended to support pub sub mechanism,
Providing real time information will not be an issue.

But I agree in many cases, providing real time information is not necessary, e.g., cloud gaming use case provided Tencent and china mobile, their case is different from your proposed case, they will use cloud gaming server as ALTO client to get needed information.

These parameters are received by UEs directly from the network and not from ALTO. The UE receives an array of ALTO cell KPI values that each depend on the value of a parameter. The UE can pick the  ALTO value corresponding to the value of the real-time parameter received from the network. Thus, the UE modulates the received ALTO values in real-time.

[Qin]: your case is UE centric solution, UE gets network KPI from ALTO server and get real time parameter from another data source in the Network, what is not clear is how real time parameter is correlated with Network KPI information within UE.
Also the interface between UE and RAN is not in the scope of ALTO work, I think.

This use-case is illustrated in the slides presented at the previous IETF 109 ALTO WG meeting, see (1), slide 4. A preliminary design with example IRD and ALTO request and response can be found in slides 7 and 8.

Any feedback is more than welcome,

From: alto <<>> On Behalf Of Qin Wu
Sent: Monday, February 22, 2021 2:51 PM
To: IETF ALTO <<>>
Subject: [alto] ALTO Draft ReCharter WG review

Hi, :
We have requested one hour session for ALTO WG meeting in the upcoming IETF 110, which is arranged on Friday, March 12, 14:30-15:30(UTC).
The goal is to boil down ALTO recharter and have consensus on charter contents in IETF 110.
To get this goal, an updated inline draft charter text for ALTO has just been posted to this list,

This charter has received a couple of rounds of informal review from WG members, chairs and our Ads from brief to deep thorough, 5 new chartered items have been listed.
We would like to solicit feedback on these new chartered items and your use case, deployment, idea corresponding to these new chartered items.
Sharing your past deployment story will also be appreciated.

The ALTO working group was established in 2008 to devise a request/response protocol to allow a host to benefit from a server that is more cognizant of the network infrastructure than the host is.

The working group has developed an HTTP-based protocol and recent work has reported large-scale deployment of ALTO based solutions supporting applications such as content distribution networks (CDN).

ALTO is now proposed as a component for cloud-based interactive applications, large-scale data analytics, multi-cloud SD-WAN deployment, and distributed
computing. In all these cases, exposing network information such as abstract topologies and network function deployment location helps applications.

To support these emerging uses, extensions are needed, and additional functional and architectural features need to be considered as follows:

o Protocol extensions to support a richer and extensible set of policy attributes in ALTO information update request and response. Such policy attributes may indicate information dependency (e.g., ALTO path-cost/QoS properties with dependency on real-time network  indications), optimization criteria (e.g., lowest latency/throughput network performance objective), and constraints (e.g., relaxation bound of optimization criteria, domain or network node to be traversed, diversity and redundancy of paths).

o Protocol extensions for facilitating operational automation tasks and improving transport efficiency. In particular, extensions to provide "pub/sub" mechanisms to allow the client to request and receive a diverse types (such as event-triggered/sporadic, continuous), continuous, customized feed of publisher-generated information. Efforts developed in other working groups such as MQTT Publish / Subscribe Architecture, WebSub, Subscription to YANG Notifications will be considered, and issues such as scalability (e.g., using unicast or broadcast/multicast, and periodicity of object updates) should be considered.

o The working group will investigate the configuration, management, and operation of ALTO systems and may develop suitable data models.

o Extensions to ALTO services to support multi-domain settings. ALTO is currently specified for a single ALTO server in a single administrative domain, but a network may consist of
multiple domains and the potential information sources may not be limited to a certain domain. The working group will investigate extending the ALTO framework to (1) specify multi-ALTO-server protocol flow and usage guidelines when an ALTO service involves network paths spanning multiple domains with multiple ALTO servers, and (2) extend or introduce ALTO
services allowing east-west interfaces for multiple ALTO server integration and collaboration. The specifications and extensions should use existing services whenever possible. The specifications and extensions should consider realistic complexities including incremental deployment, dynamicity, and security issues such as access control, authorization (e.g., an ALTO server provides information for a network that the server has no authorization), and privacy protection in multi-domain settings.

o The working group will update RFC 7971 to provide operational considerations for recent protocol extensions (e.g., cost calendar, unified properties, and path vector) and new extensions that the WG develops. New considerations will include decisions about the set of information resources (e.g., what metrics to use), notification of changes either in proactive or reactive mode (e.g., pull the backend, or trigger just-in-time measurements), aggregation/processing of the collected information  (e.g., compute information and network information )according to the clients’ requests, and integration with new transport mechanisms (e.g., HTTP/2 and HTTP/3).

When the WG considers standardizing information that the ALTO server could provide, the following criteria are important
to ensure real feasibility:

- Can the ALTO server realistically provide (measure or derive) that information?

- Is it information that the ALTO client cannot find easily some other way?

- Is the distribution of the information allowed by the operator of the network? Does the exposure of the information introduce privacy and information leakage concerns?

Issues related to the specific content exchanged in systems that make use of ALTO are excluded from the WG's scope, as is the issue of dealing with enforcing the legality of the content. The WG will also not propose standards on how congestion is signaled, remediated, or avoided.

-Qin Wu (on behalf of chairs)