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Internet Engineering Task Force                        Ken Carlberg
INTERNET DRAFT                                         G11
July, 2006


        A Framework for Supporting Emergency Telecommunications
          Services (ETS) Within a Single Administrative Domain
                <draft-ietf-ieprep-domain-frame-07.txt>


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Copyright Notice

   Copyright (C) The Internet Society (2006).


Abstract

   This document presents a framework discussing the role of various
   protocols and mechanisms that could be considered candidates for
   supporting Emergency Telecommunication Services (ETS) within a single
   administrative domain.  Comments about their potential usage as well
   as their current deployment are provided to the reader.  Specific
   solutions are not presented.






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1.  Introduction

   This document presents a framework for supporting Emergency Telecom-
   munications Services (ETS) within the scope of a single administra-
   tive domain.  This narrow scope provides a reference point for con-
   sidering protocols that could be deployed to support ETS.  [rfc4375]
   is a complimentary effort that articulates requirements for a single
   administrative domain and defines is as "collection of resources
   under the control of a single administrative authority".  We use this
   other effort as both a starting point and guide for this document.

   A different example of a framework document for ETS is [rfc4190],
   which focused on support for ETS within IP telephony.  In this case,
   the focal point was a particular application whose flows could span
   multiple autonomous domains.  Even though this document uses a some-
   what more constrained perspective than [rfc4190], we can still expect
   some measure of overlap in the areas that are discussed.


1.1.  Differences between Single and Inter-domain

   The progression of our work in the following sections is helped by
   stating some key differences between the single and inter-domain
   cases.  From a general perspective, one can start by observing the
   following

    a) Congruent with physical topology of resources, each domain
       is an authority zone and there is currently no scalable way
       to transfer authority between zones.
    b) Each authority zone is under separate management
    c) Authority zones are run by competitors, which acts as
       further deterrent to transferring authority.

   As a result of the initial statements in (a) through (c) above, addi-
   tional observations can be made that distinguish the single and
   inter-domain case, as stated in the following"

    d) Different policies might be implemented in different
       administrative domains.

    e) There is an absence of any practical method for ingress nodes of
       a transit domain to authenticate all of the IP network layer
       packets that have labels indicating a preference or importance.

    f) Given item (d) above, all current inter-domain QoS mechanisms
       at the network level generally create easily exploited and
       significantly painful DoS/DDoS attack vectors on the network.




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    g) A single administrative domain can deploy various mechanisms
       (e.g. Access Control Lists) into each and every edge device
       (e.g. ethernet switch or router) to ensure that only
       authorized end-users (or layer 2 interfaces) are able to emit
       frames/packets with non-default QoS labels into the network.
       This is not feasible in the inter-domain case because the
       inter-domain link contains aggregated flows.  In addition, the
       dissemination of Access Control Lists at the network level is
       not scalable in the inter-domain case.

    h) A single domain can deploy mechanisms into the edge devices to
       enforce its domain-wide policies -- without having to trust any
       3rd party to configure things correctly.  This is not possible
       in the inter-domain case.

   While the above is not an all-inclusive set of differences, it does
   provide some rationale why one may wish to focus efforts in the more
   constrained scenario of a single administrative domain.


2.  Common Practice: Provisioning

   The IEPREP working group, and mailing list, has had extensive discus-
   sions about over-provisioning.  Many of these exchanges have debated
   the need for QoS mechanisms versus over-provisioning of links.

   In reality, most IP network links are provisioned with a percentage
   of excess capacity beyond that of the average load.  The 'shared'
   resource model together with TCP's congestion avoidance algorithms
   helps compensate for those cases where spikes or bursts of traffic
   are experienced by the network.

   The thrust of the debate within the IEPREP working group is whether
   it is always better to over provision links to such a degree that
   spikes in load can still be supported with no loss due to congestion.
   Advocates of this position point to many ISPs in the U.S. that take
   this approach instead of using QoS mechanisms to honor agreements
   with their peers or customers.  These advocates point to cost effec-
   tiveness in comparison to complexity and security issues associated
   with other approaches.

   Proponents of QoS mechanisms argue that the relatively low cost of
   bandwidth enjoyed in the US (particularly, by large ISPs) is not
   necessarily available throughout the world.  Beyond the subject of
   cost, some domains are comprised of physical networks that support
   wide disparity in bandwidth capacity -- e.g., attachment points con-
   nected to high capacity fiber and lower capacity wireless links.




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   This document does not advocate one of these positions over the
   other.  The author does advocate that network
   administrators/operators should perform a cost analysis between over
   provisioning for spikes versus QoS mechanisms as applied within a
   domain and its access link to another domain (e.g., a customer and
   its ISP).  This analysis, in addition to examining policies and
   requirements of the administrative domain, should be the key to
   deciding how (or if) ETS should be supported within the domain.

   If the decision is to rely on over provisioning, then some of the
   following sections will have little to no bearing on how ETS is sup-
   ported within a domain.  The exception would be labeling mechanisms
   used to convey information to other communication architectures
   (e.g., SIP-to-SS7/ISUP gateways).


3.  Objective

   The primary objective is to provide a target measure of service
   within a domain for flows that have been labeled for ETS.  This level
   may be better than best effort, the best available service that the
   network (or parts thereof) can offer, or a specific percentage of
   resource set aside for ETS.  [rfc4375] presents a set of requirements
   in trying to achieve this objective.

   This framework document uses [rfc4375] as a reference point in dis-
   cussing existing areas of engineering work or protocols that can play
   a role in supporting ETS within a domain.  Discussion of these areas
   and protocols are not to be confused with expectations that they
   exist within a given domain.  Rather, the subjects discussed in Sec-
   tion 4 below are ones that are recognized as candidates that can
   exist and could be used to facilitate ETS users or data flows.



3.1.  Scenarios

   One of the topics of discussion that arises on the IEPREP mailing
   list, and the working group meetings, is the operating environment of
   the ETS user.  Many variations can be dreamed of with respect to
   underlying network technologies and applications.  Instead of getting
   lost in hundreds of potential scenarios, we attempt to abstract the
   limit the scenarios into two simple case examples.

     (a) A user in their home network attempts to use or leverage any
         ETS capability within the domain.

     (b) A user visits a foreign network and attempts to use or



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         leverage any ETS capability within the domain.

   We borrow the terms "home" and "foreign" network from that used in
   Mobile IP [rfc3344].  Case (a) is considered the normal and vastly
   most prevalent scenario in today's Internet.  Case (b) above may sim-
   ply be supported by the Dynamic Host Configuration Protocol (DHCP)
   [rfc2131], or a static set of addresses, that are assigned to 'visi-
   tors' of the network.  This effort is predominantly operational in
   nature and heavily reliant on the management and security policies of
   that network.

   A more ambitious way of supporting the mobile user is through the use
   of the Mobile IP (MIP) protocol.  In this case and at the IP level,
   foreign networks introduce the concept of triangle routing and the
   potential for multiple access points and service context within a
   subnetwork.  In addition, policy plays a critical role in dictating
   the measure of available services to the mobile user.

   The beaconing capability of MIP allows it to offer a measure of
   application transparent mobility as a mobile host (MH) moves from one
   subnetwork to another.  However, this feature may not be available in
   most domains.  In addition, its management requirements may
   discourage its widespread deployment and use.  Hence, users should
   probably not rely on its existence, but rather may want to expect a
   more simpler approach based on DHCP as described above.  The subject
   of mobile IP is discussed below in Section 4.


4.  Topic Areas

   The topic areas presented below are not presented in any particular
   order or along any specific layering model.  They represent capabili-
   ties that may be found within an administrative domain.  Many are
   topics of on-going work within the IETF.

   It must be stressed that readers of this document should not expect
   any of the following to exist within a domain for ETS users.  In many
   cases, while some of the following areas have been standardized and
   in wide use for several years, others have seen very limited deploy-
   ment.


4.1.  MPLS

   Multi-Protocol Label Switching (MPLS) is generally the first protocol
   that comes to mind when the subject of traffic engineering is brought
   up.  MPLS signaling produces Labeled Switched Paths (LSP) through a
   network of Label Switch Routers [rfc3031].  When traffic reaches the



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   ingress boundary of an MPLS domain (which may or may not be congruent
   with an administrative domain), the packets are classified, labeled,
   scheduled, and forwarded along an LSP.

   [rfc3270] is a Request For Comment (RFC) describing how MPLS can be
   used to support Differentiated Services.  The RFC discusses the use
   of the 3 bit EXP (experimental) field to convey the Per Hop Behavior
   (PHB) to be applied to the packet.  As we shall see in later subsec-
   tions, this three bit field can be mapped to fields in several other
   proto- cols.

   The inherent feature of classification, scheduling, and labeling are
   viewed as symbiotic and therefore many times it is integrated with
   other protocols and architectures.  Examples of this include RSVP and
   Differentiated Services.  Below, we discuss several instances where a
   given protocol specification or mechanism has been known to be com-
   plimented with MPLS.  This includes the potential labels that may be
   associated with ETS.  However, we stress that MPLS is only one of
   several approaches to support traffic engineering.  In addition, the
   complexity of the MPLS protocol and architecture may make it suited
   for only large domains.


4.2.  RSVP

   The original design of RSVP, together with the Integrated Services
   model, was one of an end-to-end signaling capability to set up a path
   of reserved resources that spanned networks and administrative
   domains [rfc2205].  Currently, RSVP has not been widely deployed by
   network administrators for QoS across domains.  Today's limited
   deployment by network administrators so far has been mostly con-
   strained to boundaries within a domain, and commonly in conjunction
   with MPLS signaling.  Early deployments of RSVP ran into unantici-
   pated scaling issues; it is not entirely clear how scalable an RSVP
   approach would be across the Internet.

   [rfc3209] is one example of how RSVP has evolved to compliment
   efforts that are scoped to operate within a domain.  In this case,
   extensions to RSVP are defined that allow it to establish intra-
   domain Labeled Switched Paths (LSP) in Multi-Protocol Labeled Switch-
   ing (MPLS).

   [rfc2750] specifies extensions to RSVP so that it can support generic
   policy based admission control.  This standard goes beyond the sup-
   port of the POLICY_DATA object stipulated in [rfc3209], by defining
   the means of control and enforcement of access and usage policies.
   While the standard does not advocate a particular policy architec-
   ture, the IETF has defined one that can compliment [rfc2750] -- we



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   expand on this in subsection 4.3 below.


4.2.1.  Relation to ETS

   The ability to reserve resources correlates to an ability to provide
   preferential service for specifically classified traffic -- the clas-
   sification being a tuple of 1 or more fields which may or may not
   include an ETS specific label.  In cases where a tuple includes a
   label that has been defined for ETS usage, the reservation helps
   ensure that an emergency related flow will be forwarded towards its
   destination.  Within the scope of this document, this means that RSVP
   would be used to facilitate the forwarding of traffic within a
   domain.

   We note that this places an importance on defining a label and an
   associated field that can be set and/or examined by RSVP capable
   nodes.

   Another important observation is that major vendor routers currently
   constrain their examination of fields for classification to the net-
   work and transport layers.  This means that application layer labels
   will mostly likely be ignored by routers/switches.


4.3.  Policy

   The Common Open Policy Service (COPS) protocol [rfc2748] was defined
   to provide policy control over QoS signaling protocols, such as RSVP.
   COPS is based on a query/response model in which Policy Enforcement
   Points (PEPs) interact with Policy Decision Points (i.e., policy
   servers) to exchange policy information.  COPs provides application
   level security and can operate over IPSEC or TLS.  COPS is also
   stateful protocol that also supports a push model.  This means that
   servers can download new policies, or alter existing ones to known
   clients.

   [rfc2749] articulates the usage of COPS with RSVP.  This document
   specifies COPS client types, context objects, and decision objects.
   Thus, when an RSVP reservation is received by a PEP, the PEP decides
   whether to accept or reject it based on policy.  This policy informa-
   tion can be stored a priori to the reception of the RSVP PATH mes-
   sage, or it can be retrieved in an on-demand basis.  A similar course
   of action could be applied in cases where ETS labeled control flows
   are received by the PEP.  This of course would require an associated
   (and new) set of documents that first articulates types of ETS sig-
   naling and then specifies its usage with COPS.




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   A complimentary document to the COPS protocols is COPS Usage for Pol-
   icy Provisioning (COPS-PR) [rfc3084].

   As a side note, the current lack in deployment by network administra-
   tors of RSVP has also played at least an indirect role in the subse-
   quent lack of implementation & deployment of COPS-PR.  [rfc3535] is
   an output from the IAB Network Management Workshop in which the topic
   of COPS and its current state of deployment was discussed.  At the
   time of that workshop in 2002, COPS-PR was considered a
   technology/architecture that did not fully meet the needs of network
   operators.  It should also be noted that at the 60'th IETF meeting
   held in San Diego in 2004, COPS was discussed as a candidate protocol
   that should be declared as historic because of its lack of use and
   concerns about its design.  In the future, an altered design of COPS
   may emerge that addresses the concern of operators, but speculation
   of that or other possibilities is beyond the scope of this document.


4.4.  Subnetwork Technologies

   This is a generalization of work that is considered "under" IP and
   for the most part outside of the IETF standards body.  We discuss
   some specific topics here because there is a relationship between
   them and IP in the sense that each physical network interacts at its
   edge with IP.


4.4.1.  IEEE 802.1 VLANs

   The IEEE 802.1q standard defined a tag appended to a Media Access
   Controller (MAC) frame for support of layer 2 Virtual Local Area Net-
   works (VLAN).  This tag has two parts: a VLAN identifier (12 bits)
   and a Prioritization field of three bits.  A subsequent standard,
   IEEE 802.1p, later incorporated into a revision of IEEE 802.1d,
   defined the Prioritization field of this new tag [iso15802].  It con-
   sists of eight levels of priority, with the highest priority being a
   value of 7.  Vendors may choose a queue per priority codepoint, or
   aggregate several codepoints to a single queue.

   The three bit Prioritization field can be easily mapped to the old
   ToS field of the upper layer IP header.  In turn, these bits can also
   be mapped to a subset of differentiated code points.  Bits in the IP
   header that could be used to support ETS (e.g., specific Diff-Serv
   code points) can in turn be mapped to the Prioritization bits of
   802.1p.  This mapping could be accomplished in a one-to-one manner
   between the 802.1p field and the IP ToS bits, or in an aggregate
   manner if one considers the entire Diff-Serv field in the IP header.
   In either case, because of the scarcity of bits, ETS users should



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   expect that their traffic will be combined or aggregated with the
   same level of priority as some other types of "important" traffic.
   In other words, given the existing 3 bit Priority Field for 802.1p,
   there will not be an exclusive bit value reserved for ETS traffic.

   Certain vendors are currently providing mappings between 802.1p field
   and the ToS bits.  This is in addition to integrating the signaling
   of RSVP with the low level inband signaling offered in the Priority
   field of 802.1p.

   It is important to note that the 802.1p standard does not specify the
   correlation of a layer 2 codepoint to a physical network bandwidth
   reservation.  Instead, this standard provides what has been termed as
   "best effort QoS".  The value of the 802.1p Priority code points is
   realized at the edges: either as the MAC payload is passed to upper
   layers (like IP), or bridged to other physical networks like Frame
   Relay.  Either of these actions help provide an intra-domain wide
   propagation of a labeled flow for both layer 2 and layer 3 flows.



4.4.2.  IEEE 802.11e QoS

   The 802.11e standard is a proposed enhancement that specifies mechan-
   isms to provide QoS to the 802.11 family of protocols for wireless
   LANs.

   Previously, 802.11 had two modes of operation.  One was Distributed
   Coordination Function (DCF) , which is based on the classic collision
   detection schema of "listen before sending".  A second optional mode
   is the Point Coordination Function (PCF).  The modes splits access
   time into contention-free and contention-active periods -- transmit-
   ting data during the former.

   The 802.11e standard enhances DCF by adding support for eight dif-
   ferent traffic categories or classifications.  Each higher category
   waits a little less time than the next lower one before it sends its
   data.

   In the case of PCF, a Hybrid Coordination Function has been added
   that polls stations during contention-free time slots and grants them
   a specific start time and maximum duration for transmission.  This
   second mode is more complex than enhanced DCF, but the QoS can be
   more finely tuned to offer specific bandwidth control and jitter.  It
   must be noted that neither enhancement offers a guarantee of service.






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4.4.3.  Cable Networks

   The Data Over Cable Service Interface Specification (DOCSIS) is a
   standard used to facilitate the communication and interaction of the
   cable subnetwork with upper layer IP networks [docsis].  Cable sub-
   networks tend to be asynchronous in terms of data load capacity:
   typically, 27M downstream, and anywhere from 320kb to 10M upstream
   (i.e., in the direction of the user towards the Internet).

   The evolution of the DOCSIS specification, from 1.0 to 1.1, brought
   about changes to support a service other than best effort.  One of
   the changes was indirectly added when the 802.1D protocol added the
   Priority field, which was incorporated within the DOCSIS 1.1 specifi-
   cation.  Another change was the ability to perform packet fragmenta-
   tion of large packets so that Priority marked packets (i.e., packets
   marked with non-best effort labels) can be multiplexed in between the
   fragmented larger packet.

   Its important to note that the DOCSIS specifications do not specify
   how vendors implement classification, policing, and scheduling of
   traffic.  Hence, operators must rely on mechanisms in Cable Modem
   Termination Systems (CMTS) and edge routers to leverage indirectly or
   directly the added specifications of DOCSIS 1.1.  As in the case of
   802.1p, ETS labeled traffic would most likely be aggregated with
   other types of traffic, which implies that an exclusive bit (or set
   of bits) will not be reserved for ETS users.  Policies and other
   managed configurations will determine the form of the service experi-
   enced by ETS labeled traffic.

   Traffic engineering and management of ETS labeled flows, including
   its classification and scheduling at the edges of the DOCSIS cloud,
   could be accomplished in several ways.  A simple schema could be
   based on non-FIFO queuing mechanisms like class based queuing,
   weighted fair queuing (or combinations and derivations thereof).  The
   addition of active queue management like Random Early Detection could
   provide simple mechanisms for dealing with bursty traffic contribut-
   ing to congestion.  A more elaborate scheme for traffic engineering
   would include the use of MPLS.  However, the complexity of MPLS
   should be taken into consideration before its deployment in networks.


4.5.  Multicast

   Network layer multicast has existed for quite a few years.  Efforts
   such as the Mbone have provided a form of tunneled multicast that
   spans domains, but the routing hierarchy of the Mbone can be con-
   sidered flat and non-congruent with unicast routing.  Efforts like
   the Multicast Source Discovery Protocol [rfc3618] together with the



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   Protocol Independent Multicast Sparse Mode (PIM-SM) have been used by
   a small subset of Internet Service Providers to provide form of
   inter-domain multicast [rfc2362].  However, network layer multicast
   has for the most part not been accepted as a common production level
   service by a vast majority of ISPs.

   In contrast, intra-domain multicast in domains has gained more accep-
   tance as an additional network service.  Multicast can produce denial
   of service attacks using the any sender model, with the problem made
   more acute with flood & prune algorithms. Source specific multicast
   [rfc3569], together with access control lists of who is allowed to be
   a sender, reduces the potential and scope of such attacks.


4.5.1.  IP Layer

   The value of IP multicast is its efficient use of resources in send-
   ing the same datagram to multiple receivers.  An extensive discussion
   on the strengths and concerns about multicast is outside the scope of
   this document.  However, one can argue that multicast can very natur-
   ally compliment the push-to-talk feature of land mobile radio net-
   works (LMR).

   Push-to-talk is a form of group communication where every user in the
   "talk group" can participate in the same conversation.  LMR is the
   type of network used by First Responders (e.g., police, fireman, and
   medical personnel) that are involved in emergencies.  Currently, cer-
   tain vendors and providers are offering push-to-talk service to the
   general public in addition to First Responders.  Some of these sys-
   tems are operated over IP networks, or are interfaced with IP net-
   works to extend the set of users that can communicate with each
   other.  We can consider at least a subset of these systems as either
   closed IP networks, or domains, since they do not act as transits to
   other parts of the Internet.

   The potential integration of LMR talk groups with IP multicast is an
   open issue.  LMR talk groups are established in a static manner with
   man-in-the-loop participation in their establishment and teardown.
   The seamless integration of these talk groups with multicast group
   addresses is a feature that has not been discussed in open forums.


4.5.2.  IEEE 802.1d MAC Bridges

   The IEEE 802.1d standard specifies fields and capabilities for a
   number of features.  In subsection 4.3.2 above, we discussed its use
   for defining a Prioritization field.  The 802.1d standard also covers
   the topic of filtering MAC layer multicast frames.



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   One of the concerns about multicast are broadcast storms that can
   arise and generate a denial of service against other users/nodes.
   Some administrators purposely filter out multicast frames in cases
   where the subnetwork resource is relatively small (e.g., 802.11 net-
   works).  Operational considerations with respect to ETS may wish to
   consider doing this in an as-needed basis based on the conditions of
   the network against the perceived need for multicast.  In cases where
   filtering out multicast can be activated dynamically, COPS may be a
   good means of providing consistent domain-wide policy control.


4.6.  Discovery

   If a service is being offered to explicitly support ETS, then it
   would seem reasonable that discovery of the service may be of bene-
   fit.  For example, if a domain has a subset of servers that recognize
   ETS labeled traffic, then dynamic discovery of where these servers
   are (or even if they exist) would be more beneficial compared to
   relying on statically configured information.

   The Service Location Protocol (SLP) [rfc2608] is designed to provide
   information about the existence, location, and configuration of
   networked services.  In many cases, the name of the host supporting
   the desired service is needed to be known a priori in order for users
   to access it.  SLP eliminates this requirement by using a descriptive
   model that identifies the service.  Based on this description, SLP
   then resolves the network address of the service and returns this
   information to the requester.  An interesting design element of SLP
   is that it assumes that the protocol is run over a collection of
   nodes that are under the control of a single administrative author-
   ity.  This model follows the scope of this framework document.  How-
   ever, the scope of SLP may be better suited for parts of an enter-
   prise network versus an entire domain.

   Anycasting [rfc1546] is another means of discovering nodes that sup-
   port a given service.  Interdomain anycast addresses, propagated by
   BGP, represent anycast in a wide scope and have been used by multiple
   root servers for a while.  Anycast can also be realized in a more
   constrained and limited scope (i.e., solely within a domain or sub-
   net), and as in the case of multicast may not be supported.

   [rfc3513] covers the topic of anycast addresses for IPv6.  Unlike
   SLP, users/applications must know the anycast address associated with
   the target service.  In addition, responses to multiple requests to
   the anycast address may come from different servers.  Lack of
   response (not due to connectivity problems) correlates to the
   discovery that a target service is not available.  Detailed tradeoffs
   between this approach and SLP is outside the scope of this framework



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   document.

   The Dynamic Delegation Discovery System is used to implement a bind-
   ing of strings to data, in order to support dynamically configured
   delegation systems [rfc3401].  The DDDS functions by mapping some
   unique string to data stored within a DDDS Database by iteratively
   applying string transformation rules until a terminal condition is
   reached.  The potential then exists where a client could specify a
   set of known tags (e.g., RetrieveMail:Pop3) which would
   identify/discover the appropriate server with which it can communi-
   cate.



4.7.  Differentiated Services (Diff-Serv)

   There are a number of examples where Diff-Serv [rfc2274] has been
   deployed strictly within a domain, with no extension of service to
   neighboring domains.  Various reasons exist for Diff-Serv not being
   widely deployed in an inter-domain context, including ones rooted in
   the complexity and problems in supporting the security requirements
   for Diff-Serv code points.  An extensive discussion on Diff-Serv
   deployment is outside the scope of this document.

   [Baker] presents common examples of various codepoints used for well
   known applications.  The document does not recommend these associa-
   tions as being standard or fixed.  Rather, the examples in [Baker]
   provide a reference point for known deployments that can act as a
   guide for other network administrators.

   An arguement can be made that Diff-Serv, with its existing code point
   specifications of Assured Forwarding (AF) and Expedited Forwarding
   (EF), goes beyond what could be needed to support ETS within a
   domain.  By this we mean that the complexity in terms of maintenance
   and support of AF or EF may exceed or cause undue burden on the
   management resources of a domain.  Given this possibility, users or
   network administrators may wish to determine if various queuing
   mechanisms, like class based weighted fair queuing, is sufficient to
   support ETS flows through a domain.  Note, as we stated earlier in
   section 2, over provisioning is another option to consider.  We
   assume that if the reader is considering something like Diff-Serv,
   then it has been determined that over provisioning is not a viable
   option given their individual needs or capabilities.


5.  Security Considerations

   Services used to offer better or best available service for a



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   particular set of users (in the case of this document, ETS users) are
   prime targets for security attacks, or simple misuse.  Hence,
   administrators that choose to incorporate additional
   protocols/services to support ETS are strongly encouraged to consider
   new policies to address the added potential of security attacks.
   These policies, and any additional security measures, should be con-
   sidered independent of any mechanisms or equipment that restricts
   access to the administrative domain.

   Determining how authorization is accomplished is open issue.  Many
   times the choice is a function of the service that is deployed.  One
   example is source addresses in an access list permitting senders to
   the multicast group (as described in section 4.5).  Within a single
   domain environment, cases can be found where network administrators
   tend to find this approach acceptable.  However, other services may
   require more stringent measures that employ detailed credentials, and
   possibly multiple levels of access and authentication.  Ease of use,
   deployment, scalability, and susceptability to security breach all
   play a role in determining authorization schemas.  The potential is
   that accomplishing this for only a single domain may be easier than
   at the inter-domain scope if only in terms of scalability and trust.


6.  Summary Comments

   This document has presented a number of protocols and complimentary
   technologies that can be used to support ETS users.  Their selection
   is dictated by the fact that all or significant portions of the pro-
   tocols can be operated and controlled within a single administrative
   domain.  It is this reason why other protocols like those under
   current development in the Next Steps in Signaling (NSIS) working
   group have not be discussed.

   By listing a variety of efforts in this document, we avoid taking on
   the role of "king maker" and at the same time indirectly point out
   that a variety of solutions exist in support of ETS.  These solutions
   may involve QoS, traffic engineering, or simply portection against
   detrimental conditions (e.g., spikes in traffic load).  Again, the
   choice is up to the reader.


7.  Acknowledgements

   Thanks to Ran Atkinson, Scott Bradner, Jon Peterson, and Kimberly
   King for comments and suggestions on this draft.






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8.  IANA Considerations

   This document has no considerations for IANA


9.  References

9.1.  Normative Reference

   [rfc4375] Carlberg, K., "Requirements for Supporting Emergency
             Telecommunications Services in Single Domains",
             RFC 4375, January 2006


9.2.  Informative References

   [baker] Baker, F., et. al., "Configuration Guidelines for
           DiffServ Service Classes", Internet Draft,
           draft-ietf-tsvwg-diffserv-service-classes-02, Work In
           Progress, Feb 2006

   [docsis] "Data-Over-Cable Service Interface Specifications: Cable
            Modem to Customer Premise Equipment Interface
            Specification SP-CMCI-I07-020301", DOCSIS, March 2002,
            http://www.cablemodem.com.

   [iso15802] "Information technology - Telecommunications and
             information exchange between systems - Local and
             metropolitan area networks - Common specifications -
             Part 3: Media Access Control (MAC) Bridges:  Revision.
             This is a revision of ISO/IEC 10038: 1993, 802.1j-1992
             and 802.6k-1992. It incorporates P802.11c, P802.1p
             and P802.12e."  ISO/IEC 15802-3:1998"

   [rfc1546] Partridge, C., et al, "Host Anycasting Service", RFC
             1546, November 1993

   [rfc2131] Droms, R., "Dynamic Host Configuration Protocol",
             RFC 2131, March 1997

   [rfc2205] Braden, R., et al, "Resource Reservation Protocol (RSVP)
             Version 1 Functional Specification", RFC 2205, Sept 1997

   [rfc2362] Estrin, D., et al, "Protocol Independent Multicast-Sparse
             Mode (PIM-SM): Protocol Specification", RFC 2362, June
             1998

   [rfc2474] Nichols, K., et al, "Definition of the Differentiated



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             Services Field (DS Field) in the IPv4 and IPv6 Headers",
             RFC 2474, December 1998.

   [rfc2608] Guttman, C., et al, "Service Location Protocol, Version
             2", RFC 2608, June 1999.

   [rfc2748] Durham, D., et al, "The COPS (Common Open Policy
             Service) Protocol", RFC 2748, January 2000.

   [rfc2749] Herzog, S., et al, "COPS Usage for RSVP", RFC 2749,
             January 2000

   [rfc2750] Herzog, S., "RSVP Extensions for Policy Control",
             RFC 2750, January 2000

   [rfc3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
             Label Switching Architecture", RFC 3031, January 2001.

   [rfc3270] Le Faucheur, F., et al, "MPLS Support of Differentiated
             Services", RFC 3270, May 2002

   [rfc3209] Awduche, D., "RSVP-TE: Extensions to RSVP for LSP
             Tunnels", RFC 3209, December 2001

   [rfc3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
             August 2002

   [rfc3084] Chan, K., et al, "COPS Usage for Policy Provisioning
            (COPS-PR)", RFC 3084, March 2001

   [rfc3401] Mealling, M., "Dynamic Delegation Discovery System
             (DDDS) Part One: The Comprehensive DDDS", RFC 3401
             Oct 2002

   [rfc3513] Hinden, R., Deering, S., "Internet Protocol Version 6
             (IPv6) Addressing Architecture", RFC 3513, April 2003

   [rfc3535] Schoenwaelder, J., "Overview of the 2002 IAB Network
             Management Workshop", RFC 3535, May 2003

   [rfc3569] Bhattacharyya, S., "An Overview of Source-Specific
             Multicast (SSM)", RFC 3569, July, 2003

   [rfc3618] Meyer, D., Fenner, B., "Multicast Source Discovery
             Protocol (MSDP)", RFC 3618, October 2003

   [rfc4190] Carlberg, K,. et. al, "Framework for Supporting ETS in
             IP Telephony", RFC 4190, IETF, November 2005.



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                           Table of Contents



1. Introduction ...................................................    2
1.1  Differences between Single and Inter-domain ..................    2
2. Common Practice: Provisioning ..................................    3
3. Objective ......................................................    4
3.1 Scenarios .....................................................    4
4. Topic Areas ....................................................    5
4.1 MPLS ..........................................................    5
4.2 RSVP ..........................................................    6
4.2.1 Relation to ETS .............................................    7
4.3 Policy ........................................................    7
4.4 Subnetwork Technologies .......................................    8
4.4.1  IEEE 802.1 VLANs ...........................................    8
4.4.2  IEEE 802.11e QoS ...........................................    9
4.4.3  Cable Networks .............................................   10
4.5 Multicast .....................................................   10
4.5.1  IP Layer ...................................................   11
4.5.2  IEEE 802.1d MAC Bridges ....................................   11
4.6 Discovery .....................................................   12
4.7 Differentiated Services (Diff-Serv) ...........................   13
5.  Security Considerations .......................................   13
6.  Summary Comments ..............................................   14
7. Acknowledgements ...............................................   14
8. IANA Considerations ............................................   15
9. References .....................................................   15
9.1 Normative Reference ...........................................   15
9.2 Informative References ........................................   15

10.  Author's Address

   Ken Carlberg
   G11
   123a Versailles Circle
   Baltimore, MD
   USA
   carlberg@g11.org.uk


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