Re: [tcmtf] Improved version (v8) of the TCM-TF charter draft

"Reinaldo Penno (repenno)" <repenno@cisco.com> Wed, 20 November 2013 18:41 UTC

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From: "Reinaldo Penno (repenno)" <repenno@cisco.com>
To: "jsaldana@unizar.es" <jsaldana@unizar.es>, "tcmtf@ietf.org" <tcmtf@ietf.org>, "tsv-area@ietf.org" <tsv-area@ietf.org>
Thread-Topic: [tcmtf] Improved version (v8) of the TCM-TF charter draft
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Date: Wed, 20 Nov 2013 18:40:48 +0000
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Cc: Martin Stiemerling <mls.ietf@googlemail.com>, 'Spencer Dawkins' <spencerdawkins.ietf@gmail.com>
Subject: Re: [tcmtf] Improved version (v8) of the TCM-TF charter draft
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Hi,

Some comments:

* Put somewhere more explicitly the problem statement. If we are doing
this to save bandwidth, then I suggest saying so in one bullet instead of
being lost inside a huge paragraph.
* Number 5: "So the first objective of this group². Then number 6 "As a
first objective, a document..². There are two first objectives with
different descriptions. Are these the same document or different documents?
* "The document will present a list of available traffic classification
methods which can be used for identification of the service or application
to which a particular flow belongs². My first reaction would be to not try
to list available classification methods since it will get into
implementation details. And what if traffic is e2e encrypted? Given the
whole surveillance thing should we we can expect this to happen? How would
you know a flow is candidate or suitable for compression?
* I wonder if some of the possible scenarios really apply. It seems we are
throwing everything to see what sticks.  Example: Journalist covering the
a cycling competition do not need write their report real time. And if
they need to do a interview, it seems to be working well right now, HD and
everything. 
* "- an agreement between two network operators could allow them to
compress a number of flows they are exchanging between a pair of Internet
Routers². Not sure compressing flows between peering routers is a good
use-case. 


On 11/20/13, 3:13 AM, "Jose Saldana" <jsaldana@unizar.es>; wrote:

>TCM-TF charter draft v8
>
>Description of Working Group
>
>1. In the last years we are witnessing the raise of new real-time services
>that use the Internet for the delivery of interactive multimedia
>applications: VoIP, videoconferencing, telemedicine, video vigilance,
>online
>gaming, etc. Due to the need of interactivity, many of these services use
>small packets (some tens of bytes), since they have to send frequent
>updates
>between the extremes of the communication. In addition, some other
>services
>also send small packets, but they are not delay-sensitive (e.g., instant
>messaging, m2m packets sending collected data in sensor networks using
>wireless or satellite scenarios). For both the delay-sensitive and
>delay-insensitive applications, their small data payloads incur
>significant
>overhead, and it becomes even higher when IPv6 is used, since the basic
>IPv6
>header is twice the size of the IPv4 one.
>
>2. The efficiency cannot be increased by the inclusion of a higher number
>of
>samples in a single packet, since this would harm the delay requirements
>of
>the service. But there exist some scenarios in which a number of flows
>share
>the same path. In this case, packets belonging to different flows can be
>grouped together, adding a small multiplexing delay as a counterpart of
>bandwidth saving. This delay will have to be maintained under some
>threshold
>in order to grant the delay requirements. Some examples of the scenarios
>where grouping packets is possible are:
>
>- aggregation networks of a network operator;
>- an end-to-end tunnel between appliances located in two different offices
>of the same company;
>- the access connection of an Internet Café including a high number of
>VoIP/gaming flows;
>- an agreement between two network operators could allow them to compress
>a
>number of flows they are exchanging between a pair of Internet Routers;
>- a wireless Internet connection shared by a number of people in a place
>with low Internet penetration
>- a community network, in which a number of people in the same
>geographical
>place share their connections in a cooperative way
>- a satellite connection used for collecting the data of a high number of
>sensors.
>- a satellite connection used for providing connectivity in a
>non-connected
>area during a short period of time (e.g. journalists covering the arrival
>of
>a mountain stage of a cycling competition).
>- an air-to-ground connection providing Internet connectivity to the
>passengers of an aircraft, multiplexing a number of simultaneous VoIP
>flows.
>The same can be applied between a cruise ship and a satellite.
>
>3. VoIP using RTP is a clear example of a real-time service using small
>packets with high overhead. In order to improve efficiency, RFC4170
>(TCRTP)
>defined a method for grouping packets when a number of flows share a path,
>considering three different layers: header compression by means of ECRTP;
>multiplexing by means of PPPMux; tunneling by means of L2TPv3.
>
>4. However, in the last years, emerging real-time services which do not
>use
>UDP/RTP have become popular: some of them use UDP. In addition, new header
>compression methods have been defined (ROHC). So there is a need of
>widening
>the scope of RFC4170 in order to consider not only UDP/RTP but also other
>protocols. The same structure of three layers will be considered:
>
>- Header compression: Taking into account that real-time applications use
>different headers (RTP/UDP, UDP), different protocols can be used: no
>compression, ECRTP, IPHC and ROHC.
>- Multiplexing: If a number of flows share a path between an origin and a
>destination, a TCM-optimizer (called TCM-ingress optimizer) can build a
>bigger multiplexed packet in which a number of payloads share a common
>header. Another TCM-optimizer (called TCM-egress optimizer) is then
>necessary at the end of the common path, so as to rebuild the packets as
>they were originally sent. PPPMux will be the main option. Other ones are
>not discarded.
>- Tunneling will be used to send the multiplexed packets end-to-end. The
>options in this layer are L2TP, GRE and MPLS.
>
>5. So the first objective of this group is to specify the protocol stack
>for
>tunneling, compressing and multiplexing traffic flows (TCM-TF). Since
>standard protocols are being used at each layer, the signaling methods of
>those protocols will be used. Interactions with the Working Groups and
>Areas
>in which these protocols are developed can be expected. However, the
>development of new compressing, multiplexing or tunneling protocols is not
>an objective of this Working Group. In addition, since the current RFC
>4170
>would be considered as one of the options, this RFC could be obsoleted.
>
>6. As a first objective, a document (TCM-TF - reference model) will define
>the different options which can be used at each layer. Specific problems
>caused by the interaction between layers will have to be issued, and
>suitable extensions may have to be added to the involved protocols.
>
>7. If a pair of ingress/egress optimizers want to establish a TCM-TF
>session, they have first to use a mechanism to negotiate which concrete
>option would they use in each layer: header compression, multiplexing and
>tunneling. This will depend on the protocols that each extreme implements
>at
>each level, and in the scenario. So another document (TCM-TF - negotiation
>protocol) will include:
>
>- a mechanism to setup/release a TCM-TF session between an ingress and an
>egress-optimizer, also including:
>- a negotiation mechanism to decide the options to use at each layer
>(header
>compression, multiplexing and tunneling) between an ingress and an
>egress-optimizer, 
>
>8. As a counterpart of the bandwidth saving, TCM-TF may add some delay and
>jitter. This is not a problem for the services which are not sensitive to
>delay. However, regarding delay-sensitive services, the Working Group will
>also develop a document (TCM-TF - recommendations) with useful
>recommendations in order to decide which packet flows can or can not be
>multiplexed and how. The document will present a list of available traffic
>classification methods which can be used for identification of the service
>or application to which a particular flow belongs, as well as
>recommendations of the maximum delay and jitter to be added depending of
>the
>identified service or application. The eventual impact of multiplexing on
>protocol dynamics (e.g. the loss of a multiplexed packet, MTU-related
>issues) will also have to be addressed.
>
>9. The working group may identify additional deliverables that are
>necessary/useful, e.g., a mechanism for a TCM-ingress optimizer to
>discover
>an egress optimizer, and vice versa. The working group would re-charter to
>add them before working on them.
>
>10. In addition, specific uses of TCM-TF, such as in wireless and
>satellite
>scenarios, could be considered, and it might be studied whether
>modifications or extensions are required on the protocol. The working
>group
>would re-charter to work on those modifications/extensions.
>
>11. Interactions with other Working Groups can be expected, since TCM-TF
>uses already defined protocols for compression, multiplexing and tunneling
>(ROHC, PPPMux, MPLS, GRE, L2TP).
>
>
>Goals and Milestones
>
>Specification of TCM-TF  reference model.
>
>Specification of TCM-TF negotiation protocol.
>
>Specification of TCM-TF recommendations of using existing traffic
>classification methods, maximum delay and jitter to add, depending on the
>service.
>
>
>Current version of Document (TCM-TF - reference model):
>https://datatracker.ietf.org/doc/draft-saldana-tsvwg-tcmtf/
>
>Current version of Document (TCM-TF - recommendations):
>http://datatracker.ietf.org/doc/draft-suznjevic-tsvwg-mtd-tcmtf/
>
>
>
>Best regards,
>
>Jose 
>
>
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