By the way, below are the links to some documents that are mentioned in the
previous email.
[1] https://tools.ietf.org/html/rfc8895
RFC 8895: Application-Layer Traffic Optimization (ALTO) Incremental Updates
Using Server-Sent Events (SSE)
[2] https://tools.ietf.org/html/rfc7540
RFC 7540: Hypertext Transfer Protocol Version 2 (HTTP/2)
[3]
https://www.etsi.org/deliver/etsi_gs/ZSM/001_099/002/01.01.01_60/gs_ZSM002v010101p.pdf
ETSI ZSM Architecture (See B.4 and B.5 for pub-sub in ZSM)
[4]
https://docs.opendaylight.org/projects/controller/en/latest/dev-guide.html#messaging-patterns
OpenDaylight MD-SAL
[5] https://kubemq.io/
KubeMQ: the native message broker for Kubernetes
[2]
-----Original Messages-----
From:kai...@scu.edu.cn
Sent Time:2021-03-03 21:39:30 (Wednesday)
To: "Qin Wu" <bill...@huawei.com>
Cc: "alto-cha...@ietf.org" <alto-cha...@ietf.org>, "alto-...@ietf.org"
<alto-...@ietf.org>, "IETF ALTO" <alto@ietf.org>
Subject: Re: [alto] ALTO Draft ReCharter WG review
Dear all,
Below are some comments on the 2nd item in the recharter text.
As far as I know, the ALTO incremental update extension (RFC 8895) already
provides a mechanism to enable the "pub-sub" of ALTO information, using
Server-Sent Events (SSE). I see there are multiple directions indicated by the
new charter item:
1. Decouple the "pub-sub" protocol with the underlying mechanism.
Besides SSE, other mechanisms can also be used to realize the "pub-sub" of ALTO
information, such as HTTP/2, HTTP/3 or the methods mentioned in the charter
text. Thus, a direct extension is to define the abstract format of control
messages and data messages (i.e., WHAT information should be provided but not
HOW), and allow different underlying protocols to use protocol-specific
encodings.
For example, SSE encodes the metadata (e.g., content-type and stream id) and
the content of an event using "event:" and "data:" prefixes at the beginning of
each line, and uses empty lines to indicate the end of a message, while HTTP/2
(RFC 7540) may encode the metadata and the content of an event using
PUSH_PROMISE/HEADERS and DATA frame .
I think this requirement may help integrating ALTO in network management
platforms (such as OpenDaylight, Kubernetes, and ETSI ZSM*) which design their
own pub-sub systems for reasons such as consistency or ease of development. It
would be great if there is an interest in this direction from
companies/organizations.
* The integration fabric of ETSI ZSM provides pub-sub support but ZSM also
allows services to use their own pub-sub mechanisms.
2. Enable more fine-grained control of pub-sub.
In RFC 8895, there are two types of commands which only defines WHAT
information to subscribe:
- add: Make one or more new requests to receive the incremental updates.
- remove: Terminate the subscription of one or more previously-made requests.
In the meantime, the updates will be continuously sent to the client whenever a
server sees fit.
The charter text proposes to enable ALTO clients to request and receive "a
diverse types (such as event-triggered/sporadic, continuous), continuous,
customized feed of publisher-generated information". It seems to me that the
new extension wants to allow clients to specify not only WHAT information to be
subscribed but also WHEN/HOW the information should be delivered (e.g., Notify
me the latest value every 5 second.).
Personally I find both directions to be interesting and useful. It would be
great if they can be supported by real use cases.
Just my two cents.
Best,
Kai
-----Original Messages-----
From:"Qin Wu" <bill...@huawei.com>
Sent Time:2021-02-22 21:50:44 (Monday)
To: "IETF ALTO" <alto@ietf.org>
Cc: "alto-cha...@ietf.org" <alto-cha...@ietf.org>, "alto-...@ietf.org"
<alto-...@ietf.org>
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)
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