Tunneling Compressed Multiplexed Traffic Flows (TCM-TF) charter draft v11

Description of Working Group 

1. RFC4170 (TCRTP) defines a method for grouping packets when a number of
UDP/RTP VoIP flows share a common path, considering three different layers:
ECRTP header compression; PPPMux multiplexing; L2TPv3 tunneling. TCRTP
optimizes the traffic, increasing the bandwidth efficiency of VoIP and reduces
the amount of packets per second at the same time.

2. However, in the last years, emerging real-time services which use bare UDP
instead of UDP/RTP have become popular. Due to the need of interactivity, many
of these services use small packets (some tens of bytes). Some other services
also send small packets, but they are not delay-sensitive (e.g., instant
messaging, m2m packets in sensor networks). In addition, a significant effort
has been devoted to the deployment of new header compression methods with
improved robustness (ROHC).

3. So there is a need of replacing RFC4170 with an extended solution able to
optimize these new flows, also using improved compression methods. The same
structure of three layers will be considered:

    * Header compression: different protocols can be used: no compression,
      ECRTP, IPHC and ROHC.

    * Multiplexing: PPPMux will be the option.

    * Tunneling: the options in this layer are L2TP, GRE and MPLS.

4. New scenarios where bandwidth savings are desirable have been identified,
in addition to those considered in RFC4170. In these scenarios, there are
moments or places where network capacity gets scarce, so allocating more
bandwidth is a possible solution, but it implies a recurring cost. However,
the inclusion of a pair of boxes able to optimize the traffic when/where
required is a one-time investment. These scenarios can be classified into:

    * Multidomain, the TCMT-TF tunnel goes all the way from one network edge
      to another, and can therefore cross several domains.
    * Single Domain, TCM-TF is only activated inside an ISP, from the edge to
      border inside the network operator.
    * Private Solutions. TCM-TF is used to connect private networks
      geographically apart (e.g. corporation headquarters and subsidiaries), 
      without the ISP being aware or having to manage those flows.
    * Mixed Scenarios, any combination of the above.

5. A first document (TCM-TF - reference model) will define the different
options which can be used at each layer. It will include a detailed
specification of the scenarios of interest. 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. The impact on other protocols will
also be studied. 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
would be obsoleted.

6. Since standard protocols are being considered at each layer, the signaling
methods of those protocols will be used. Thus, interactions with the Working
Groups and Areas in which these protocols are developed can be expected.
Taking into account that different options will be considered when a pair of
TCM-TF optimizers want to establish a session, they will have first to
negotiate which concrete option would they use in each layer. 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.

7. 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.

8. 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.

9. 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

1. Specification of TCM-TF reference model and the scenarios of interest, to
obsolete RFC4170 (current version at 
https://datatracker.ietf.org/doc/draft-saldana-tsvwg-tcmtf/)

2. Specification of TCM-TF negotiation protocol.

3. Specification of TCM-TF recommendations of using existing traffic
classification methods, maximum delay and jitter to add, depending on the
service (current version at 
http://datatracker.ietf.org/doc/draft-suznjevic-tsvwg-mtd-tcmtf/)