Internet Engineering Task Force                         Ken Carlberg
INTERNET DRAFT                                          G11
June 20, 2003

                   ETS Requirements for Stub Domains

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026 [1].

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   This document presents a list of requirements in support of Emergency
   Telecommunications Service (ETS) within a single adminsitrative stub
   domain. This document is an extension of the General Requirements of
   [2] and focuses on a more specific set of administrative constraints
   and scope.  Solutions to these requirements are not presented in this

1.  Introduction

   The objective of this document is to define a set of requirements
   that support ETS within a Stub Domain.  There have been a number of
   discussions in the IEPREP mailing list, as well as working group
   meetings, that have questioned the utility of a given mechanism to
   support ETS.  Many have advocated overprovisioning, while others have
   favored specific schemas to provide a quantifiable measure of
   service.  One constant in these discussions is that the

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   administrative control of the resources plays a significant role in
   the effectiveness of any proposed solution.  Specifically, if one
   administers a set of resources, a wide variety of approaches can be
   deployed upon that set.  However, once the approach crosses an
   administrative boundary, its effective comes into question, and at a
   minimum requires cooperation & trust from other authoritative
   domains.  To avoid this question, we constrain our scenario to the
   resources within a single stub domain.

   The following provides an explanation of some key terms used in this

   Resource:  A resource can be a viewed from the general level as IP
     nodes such as a router or host as well as the physical media
     (e.g., fiber) used to connect them.  A host can also be referred
     to in more specific terms as a client, server, or proxy.
     Resources can also be viewed more specifically in terms of the
     elements within a node (e.g., CPU, buffer, memory).  However,
     this document shall focus its attention at the node level.

   Domain:  This term has been used in many ways.  We constrain its
     usage in this document to the perspective of the network layer,
     and view it as being synonymous with an administrative domain.
     A domain may span large geographic regions and may consist of
     many types of physical subnetworks.

   Administrative Domain:  The collection of resources under the
     control of a single administrative authority.  This authority
     establishes the design and operation of a set of resources
     (i.e., the network).

   Transit Domain:  This is an administrative domain used to forward
     traffic from one domain to another.  An Internet Service Provider
     (ISP) is an example of a transit domain.

   Stub Domain:  This is an administrative domain that is either the
     source or the destination of a flow.  As a rule, it does not
     forward traffic that is destined for other domains.  The odd
     exception to this statement is the case of Mobile IP and its
     use of "dog-leg" routing to visiting hosts located in foreign
     networks.  An enterprise network is an example of a stub domain.

1.1  Previous Work

   A list of General Requirements for support of ETS is presented in
   [2].  The document articulates requirements when considering the
   broad case of supporting ETS over the Internet.  Since that document
   is not constrained to specific applications, adminsitrative

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   boundaries, or scenarios, the requirements contained within it tend
   to be quite general in their description and scope.  This follows the
   philosophy behind its inception in that the General Requirements are
   meant to be a baseline followed (if necessary) by more specific
   requirements that pertain to a more narrow scope.

   The requirements presented below in Section 3 are representative of
   the more narrow scope of a single adminstrative stub domain.  As in
   the case of [2], the requirements articulated in this document
   represent aspects to be taken into consideration when solutions are
   being designed, specified, and deployed.  Key words such as "MUST",
   "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
   interpreted as described in [3].

2.  Scope

   IETF standards that cover the resources within an adminstrative
   domain are within the scope of this document.  This includes
   gateways, routers, servers, etc., that are located and administered
   within the domain.  This document also does not restrict itself to a
   specific type of application such as Voice over IP.

   QoS mechanisms are also within the scope of this document.  These
   mechanisms may reside at the application, transport, or IP network
   layer.  While QoS mechanisms may exist at the link/physical layer,
   this document would only consider potential mappings of labels or
   code points.

2.1 Out of Scope:

   Resources owned or operated by other adminstrative authorities are
   outside the scope of this document.  One example are SIP servers that
   operate in other domains.  Another example are access links
   connecting the stub domain and its provider.  Controling only 1/2 of
   a link (the egress traffic from the stub) is considered insufficient
   for including inter-domain access links as a subject for this

   Author's Note: it may be worthwhile to revisit the issue of access
   links.  It is possible to constrain request eminating from the domain
   from an egress node (middle box or black box).

3. Requirements

   It must be understood that all of the following requirements pertain
   to mechanisms chosen by a domain's administrative authority to
   specifically support ETS.  If that authority chooses not to support

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   ETS or if these mechanisms exist within the domain exclusively for a
   different purpose, then the associated requirement does not apply.

   3.1 Label Mechanisms

   Application or transport layer label mechanisms used for ETS MUST be
   extensible such that they can support more than one label.  These
   mechanism MUST avoid a single off/on type of label (e.g., a single
   bit).  In addition, designers of such a mechanism MUST assume that
   there may be more than one set of ETS users.

   Network layer label mechanisms used for ETS SHOULD be extensible such
   that they can support more than one label.  We make this distinction
   in requirements because there may be fewer bits (a smaller field)
   available at the network layer than in the transport or application

   3.2  Proxies

   Proxies MAY set ETS labels on behalf of the source of a flow. This
   may involve removing labels that have been set by upstream node(s).

   3.3 QoS mechanisms

   Quality of Service (QoS) mechanisms, at either the network or
   application layer, SHOULD be used when networks cannot be
   overprovisioned to satisfy high bursts of traffic load.  Examples can
   involve bridging fiber networks to wireless subnetworks, or remote
   subnetworks connected over expensive bandwidth constrained wide area

   Note well. Over-provisioning is a normal cost-effective practice
   amongst network administrators/engineers.  The amount of
   overprovisioning can be a topic of debate.  More indepth discussion
   on this topic is presented in the companion Framework document of

   3.4  Users

   Any application layer label mechanisms used to support ETS MUST be
   capable of supporting both the set of ETS and non-ETS (presumably,
   normal) users.

   3.5  Policy

   Policy MUST be used to determine the percentage of resources of a
   mechanism used to support the various (ETS and non-ETS) users.  Under
   certain conditions, this percentage MAY reach 100% for a specific set

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   of users.  However, we recommend that this "all-or-nothing" approach
   be considered with great care.

   3.6  Discovery

   There should be a means of forwarding ETS labeled flows to those
   mechanisms within the domain used to support ETS.  Discovery MAY be
   used to determine where ETS labeled flows (either data or control)
   should be forwarded.

   3.8 MIB

   Management Information Bases (MIBs) SHOULD be defined for mechanisms
   specifically in place to support ETS.  These MIBs MAY include objects
   representing accounting, policy, authorization.

   3.7  <Security?>

   Author's note:  Is it enough to rely on the requirements previously
   stated in [2]?

   3.8  NAT/PAT

   Author's Note:  Should something be said here?

4.  Issues

   This section presents issues that arise in considering solutions for
   the requirements that have been defined for Stub Domains that support
   ETS.  This section does not specify solutions nor is it to be
   confused with requirements.  Subsequent documents that articulate a
   more specific set of requirements for a particular service may make a
   statement about the following issues.

4.1 Alternative Services

   The form of the service provided to ETS users and articulated in the
   form of policies may be realized in one of several forms.  Better
   than best effort is probably the service that most ETS users would
   expect when the communication system is stressed and overall quality
   has degraded.  However, the concept of best available service should
   also be considered under such conditions.  Further, a measure of
   degraded service may also be desirable to ensure a measure of
   communication versus none.  These services may be made available at
   the network or application layer.

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4.2 "Emergency"

   The ITU has migrated away from the term "emergency" and ETS because
   of legal ramifications within the U.K.  Apparantly, there is a legal
   expectation when the term "emergency" is used as a service.  Hence,
   the ITU is currently using the term Telecommunications for Disaster
   Relief (TDR).  Legal issues such as this are outside the scope of
   this document and the IETF.  However, to provide a bridge of
   understanding, the reader can assume that ETS within the IETF is
   synonymous with TDR in the ITU.

4.3 Redundancy

   The issue of making network fault tolerant is important and yet not
   one that can be easily articulated in terms of requirements.
   Redundancy in connectivity and nodes (be it routers or servers) is
   probably the most common approach taken by network adminstrators, and
   it can be assumed that stub domains will apply this approach in
   various degrees.

5. Security Considerations

   Security in terms of requirements is discussed section 3.

6. Acknowledgements

   Thanks to Ran Atkinson, James Polk, and Ian Brown for comments on an
   initial version of this draft.

7. References

   1  Bradner, S., "The Internet Standards Process -- Revision 3", BCP
      9, RFC 2026, October 1996.

   2  Carlberg, K., Atkinson, R., "General System Requirements for
      Emergency Telecommunications Service", Internet Draft,
      Work In Progress, September, 2002

   3  Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", RFC 2119, March 1997.

   4  Carlberg, K., "A Framework for Supporting ETS in Stub Domains",
      Internet Draft, Work in Progress, June 2003.

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8.  Author's Addresses

Ken Carlberg
Gower Street
London, WC1E 6BT
United Kingdom

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