Internet Engineering Task Force Ken Carlberg
INTERNET DRAFT G11
December 28, 2003
A Framework for Supporting ETS
Within a Single Administrative Domain
<draft-ietf-ieprep-domain-frame-00.txt>
Status of this Memo
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Abstract
This document presents a framework discussing the role of various
protocols and mechanisms that could be considered candidates for
supporting 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.
1. Introduction
This document presents a framework for supporting Emergency
Telecommunications Service (ETS) within the scope of a single
administrative domain. This narrow scope provides a reference point
for considering protocols that could be deployed to support ETS. [2]
is a complimentary effort that articulates requirements for a single
administrative domain. 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 [3], which
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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. Eventhough this document uses a
somewhat more constrained perspective than [3], 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, which are articulated in the following:
a) Different policies might be implemented in different
administrative domains.
b) There is an absence of any practical method for authenticating
all of the network layer packets that have labels indicating a
preference or importance at ingress nodes to other
administrative domains (e.g. on the uplink into an ISP).
c) Given item (b) above, all current inter-domain QoS mechanisms
at the network level create easily exploited and significantly
painful DoS/DDoS attack vectors on the network.
d) 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 feasable 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.
e) A single domain can deploy mechanisms into the edge devices to
enforce its domain-wide policies -- without having to trust any
3rd part 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 extentive
discussions about over-provisioning. Many of these exchanges have
debated the need for QoS mechanisms versus over-provisioning of
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links.
In reality, nearly all IP network links are over-provisioned with
excess capacity for 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
links should be over provisioned 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 effectiveness in
comparison to complexity and security issues associated with other
approaches.
This document does not advocate one position over the other. The
author does take the position that network adminstrators/operators
should perform a cost analysis between over provisioning for spikes
versus QoS mechanisms. 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 stub
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
supported within a stub 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 stub domain for flows that have been labeled for ETS. This
level may be better than best effort, or it may be the best available
service that the network (or parts thereof) can offer. [2] presents
a set of requirements in trying to achieve this objective.
This framework document uses [2] as a reference point in discussing
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 Section 4
below are ones that are recognized as candidates that can exist and
could be used to facilitate ETS users or data flows.
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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 the HOME network attempts to use or leverage any
ETS capability within the stub domain.
(b) A user visits a FOREIGN network and attempts to use or
leverage any ETS capability within the stub domain.
We borrow the terms "home" and "foreign" network from that used in
Mobile IP [4]. Case (a) is considered the normal and vastly most
prevalent scenario in today's Internet. Case (b) above may simply be
supported by the Dynamic Host Configuration Protocol (DHCP) [5], or a
static set of addresses, that are assigned to 'visitors' of the
network. This effort is predominantly operational in nature and
heavily reliant on the management and security policies of that stub
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 criticial 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 existance, 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
capabilities 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
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any of the following to exist within a for ETS users. In many cases,
while some of the following areas have been standardized for several
years, many have seen very limited deployment.
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 is an intra-domain routing protocol that produces Labeled
Switched Paths (LSP) through a network [6]. When traffic reaches the
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.
[7] is an RFC describing how MPLS can 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 subsections, this three bit field
can be mapped to fields in several other protocols.
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
complimented 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 capability that spanned networks and
administrative domains [8]. Currently, RSVP has not been widely
deployed, and the limited deployment so far has been mostly
constrained to boundaries within a domain. Early deployments of RSVP
ran into unanticipated scaling issues; it is not entirely clear how
scalable an RSVP approach would be across the Internet. Also,
currently many network products do not support RSVP for anything
beyond simple MPLS signalling.
[9] is one example of how RSVP has evolved to compliment efforts that
are scoped to operate within a domain. In this case, extentions to
RSVP are defined that allow it to establish intra-domain Labled
Switched Paths (LSP) in Multi-Protocol Labeled Switching (MPLS).
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[10] specifies extentions to RSVP so that it can support generic
policy based admission control. This standard goes beyond the
support of the POLICY_DATA object stipulated in [9], by defining the
means of control and enforcement of access and usage policies. While
the standard does not advocate a particular policy architecture, the
IETF has defined one that can compliment [10] -- we 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
classification being a tuple of 1 or more fields. 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 stub 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
network and transport layers. This means that application layer
labels will mostly likely be ignored by routers/switches. Thus,
endpoints (which may be a server or proxy) that intend to add RSVP
support for ETS should map application layer ETS labels to labels at
the network or transport layer.
4.3 Policy
The Common Open Policy Service (COPS) protocol [11] 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.
[12] 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
information can be stored a priori to the reception of the RSVP PATH
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message, 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 signaling and then specifies its usage with COPS.
A complimentary document to the COPS protocols is [13], which
describes the use of COPS for policy provisioning.
As a side note, the current lack in deployment of RSVP in network
products has also played at least an indirect role in the subsequent
lack of implementations & deployment of COPS. [14] is an additional
source for recent thoughts on this subject.
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.
4.4.1 802.1
The IEEE 802.1q standard defined a tag appended to a Media Access
Controller (MAC) frame for support of layer 2 Virtual Local Area
Networks (VLAN). This tag has two parts: a VLAN identifier (12 bits)
and a Prioritiation 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 [15]. It consists 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
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 reserved for ETS traffic.
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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 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 [16]. Cable
subnetworks 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
specification. Another change was the ability to perform packet
fragmentation of large packets so that Priority marked packets (i.e.,
packets marked with non-best effort labels) can be multiplexed
inbetween 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
experienced 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
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addition of active queue management like Random Early Detection could
provide simple mechanisms for dealing with bursty traffic
contributing 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
considered flat and non-congruent with unicast routing. Efforts like
the Multicast Source Discovery Protocol [17] together with the
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 [18]. 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 stub domains has gained more
acceptance as an additional network service. This support is further
enhanced by corresponding support by physical networks.
4.5.1 IP Layer
The value of IP multicast is its efficient use of resources in
sending 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 naturally compliment the push-to-talk feature of land mobile
radio networks (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,
certain vendors and providers are offering push-to-talk service to
the general public in addition to First Responders. Some of these
systems are operated over IP networks, or are interfaced with IP
networks 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 stub 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 establishement and teardown.
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The seamless integration of these talk groups with multicast group
addresses is a feature that has not been discussed in open forums.
4.5.2 802.1d
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.
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
networks). 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
benefit. 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 benefitial compared
to relying on statically configured information.
The Service Location Protocol (SLP) [19] is designed to provide
information about the existance, 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
authority. This model follows the scope of this framework document.
Anycasting [20] is another means of discovering nodes that support a
given service. Interdomain anycast addresses, propagated by BGP,
have been used by one of the root servers for a while. [21] covers
the topic of anycast addresses for IPv6. Unlike SLP,
users/applications must know the anycast address associated with the
target service. The tradeoffs between this approach and SLP is
outside the scope of this framework document.
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4.7 Mobility
The mobile user extends the scenario of how an ETS user operates
within a domain. While the ownership of the mobile host may be
different from other nodes in the same domain, the management of that
node in terms of policies and administration is still defined by the
foreign network (i.e., stub domain) that it is attached to.
4.7.1 Mobile IP
Currently within the IETF, the subject of mobility is addressed in
several ways. The oldest and most mature area involves mobile hosts
and its support based on the Mobile IP protocol [RFC3344]. In this
case, mobility is kept transparent from the upper layers and its
support is focused at the network layer.
The Mobile IP protocol (MIP) and architecture addresses the
fundamental characteristics of a ETS user migrating to a foreign
network and attempting to contact other users. One can also make an
arguement that the percieved needs of an ETS user, e.g., labeling
traffic to distinguish it from other flows can also be acheived
independent of the MIP. A potential exception to this position is
the "busy" bit that can be set during the initial registration of the
Mobile Host (MH) to the Foreign Network. If the bit is tied to a
maximum number of simultaneous number of MHs, then it may be of
interest to specify an extension that distinguishes an ETS capable MH
from other MHs. Local policy would determine the course of action to
be taken.
4.7.2 Other Areas of Mobility
As of the publication of this document, there are other working
groups within the IETF that are involved in mobility. The Mobile
Ad-Hoc Networking (MANET) working group has focused on the case in
which all nodes, routers and hosts, can move in relation to each
other. The output of this group has been in the form of experimental
protocols, and so the subject area may be considered too immature in
considering how it and the various protocols can play a role in
supporting ETS.
The Network Mobile (NEMO) working group has just recently been formed
to address the issues that arise when entire networks move in
relation to each other. This effort can currently be considered too
immature for supporting ETS.
The Context Transfer, Handoff Candidate Discovery, and Dormant Mode
Host Alerting (SEAMOBY) working group is another relatively new
working group in the area of mobile communications. It too is
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probably too immature at this time to be determined if specific
aspects could (or even should) be added to supprt ETS. However, the
subject area of context transfer is an important one and it has the
potential to constructively support ETS.
4.8 Differentiated Service (Diff-Serv)
There are a number of examples where Diff-Serv [22] 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.
[23] presents common examples of various codepoints used for well
known applications. The document does not recommend these
associations as being standard or fixed. Rather, the examples in
[23] 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
mechansisms, 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. Leading Edge
Author's note-1: Are there topics that should be discussed here that
talk about going beyond the basic areas covered in Section 4? And if
so, what are they?
Author's Note-2: Should an additional discussion be presented on how
various levels of service can be provided. Discussions on the IEPREP
list have raised the notion of "gold, silver, bronze service". But
is this something that can actually be quantified? Or is this
distinction something that should just be left to the administrator.
The authors have their doubts as to how well this can be done within
the context of an informational RFC.
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6. Security Considerations
To Be Done.
7. Acknowledgements
Thanks to Ran Atkinson for comments and suggestions on the initial
version of this draft.
8. References
1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
2 Carlberg, K., Atkinson, R., "Requirements for Supporting ETS in
Stub Domains", Internet Draft, Work In Progress, June 2003
3 Carlberg, K,. et. al, "Framework for Supporting ETS in IP
Telephony", Internet Draft, Work In Progress, June, 2003
4 Perkins, C., "IP Mobility Support for IPv4", RFC 3344, August
2002
5 Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997
6 Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label
Switching Architecture", RFC 3031, January 2001.
7 Le Faucheur, F., et al, "MPLS Support of Differentiated Services",
RFC 3270, May 2002
8 Braden, R., et al, "Resource Reservation Protocol (RSVP) Version
1 Functional Specification", RFC 2205, September 1997
9 Awduche, D., "RSVP-TE: Extensions to RSVP for LSP Tunnels",
RFC 3209, December 2001
10 Herzog, S., "RSVP Extensions for Policy Control", RFC 2750,
January 2000
11 Durham, D., et al, "The COPS (Common Open Policy Service)
Protocol", RFC 2748, January 2000.
12 Herzog, S., et al, "COPS Usage for RSVP", RFC 2749, January
2000
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13 Chan, K., et al, "COPS Usage for Policy Provisioning (COPS-PR)",
RFC 3084, March 2001
14 Schoenwaelder, J., "Overview of the 2002 IAB Network Management
Workshop", RFC 3535, May 2003
15 "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"
16 "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.
17 Meyer, D., Fenner, B., "Multicast Source Discovery Protocol
(MSDP)", RFC 3618, October 2003
18 Estrin, D., et al, "Protocol Independent Multicast-Sparse Mode
(PIM-SM): Protocol Specification", RFC 2362, June 1998
19 Guttman, C., et al, "Service Location Protocol, Version 2",
RFC 2608, June 1999.
20 Partridge, C., et al, "Host Anycasting Service", RFC 1546,
November 1993
21 Hinden, R., Deering, S., "Internet Protocol Version 6 (IPv6)
Addressing Architecture", RFC 3513, April 2003
22 Nichols, K., et al, "Definition of the Differentiated Services
Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474,
December 1998.
23 Baker, F., "Recommended Packet Marking Policy", Internet Draft,
Work In Progress, July 2002.
8. Author's Addresses
Ken Carlberg
G11
Gower Street
London, WC1E 6BT
United Kingdom
Carlberg Expires June 28, 2004 [Page 14]
Internet Draft ETS Single Domain Framework December 28, 2003
carlberg@g11.org.uk
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Carlberg Expires June 28, 2004 [Page 15]
