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Versions: 00 01 02 03 RFC 2815

Internet Draft                                                 M. Seaman
Expires May 1999                                               3Com Corp.
draft-ietf-issll-is802-svc-mapping-03.txt                        A. Smith
Standards Track                                          Extreme Networks
                                                               E. Crawley
                                                           Argon Networks
                                                            J. Wroclawski
                                                                  MIT LCS
                                                            November 1998

            Integrated Service Mappings on IEEE 802 Networks


Status of this Memo

This document is an Internet Draft.  Internet Drafts are working
documents of the Internet Engineering Task Force (IETF), its Areas, and
its Working Groups. Note that other groups may also distribute working
documents as Internet Drafts.

Internet Drafts are draft documents valid for a maximum of six months.
Internet Drafts may be updated, replaced, or obsoleted by other
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To learn the current status of any Internet-Draft, please check the
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Directories on ftp.ietf.org (US East Coast), nic.nordu.net (Europe),
ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim).

This document is a product of the IS802 subgroup of the ISSLL working
group of the Internet Engineering Task Force.  Comments are solicited
and should be addressed to the working group's mailing list at
issll@mercury.lcs.mit.edu and/or the authors.

A revised version of this draft document will be submitted to the RFC
editor as a Proposed Standard for the Internet Community.  Discussion
and suggestions for improvement are requested.  This document will
expire before February 1999. Distribution of this draft is unlimited.

Copyright (C) The Internet Society (1998).  All Rights Reserved.








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Abstract

This document describes mappings of IETF Integrated Services over LANs
built from IEEE 802 network segments which may be interconnected by IEEE
802.1 MAC Bridges (switches) [1][2].  It describes parameter mappings
for supporting Controlled Load [6] and Guaranteed Service [7] using the
inherent capabilities of relevant IEEE 802 technologies and, in
particular, 802.1D-1998 queuing features in switches [2].

These mappings are one component of the Integrated Services over IEEE
802 LANs framework described in [5].



1.  Introduction

The IEEE 802.1 Interworking Task Group has developed a set of
enhancements to the basic MAC Service provided in Bridged Local Area
Networks (a.k.a. "switched LANs"). As a supplement to the original IEEE
MAC Bridges standard, IEEE 802.1D-1990 [1], the updated IEEE 802.1D-1998
[2] proposes differential traffic class queuing in switches and extends
the capabilities of Ethernet/802.3 media to carry a traffic class
indicator, or "user_priority" field, within data frames [8].

The availability of this differential traffic queuing, together with
additional mechanisms to provide admission control and signaling, allows
IEEE 802 networks to support a close approximation of the IETF-defined
Integrated Services capabilities [6][7]. This document describes methods
for mapping the service classes and parameters of the IETF model into
IEEE 802.1D network parameters.  A companion document [10] describes a
signaling protocol for use with these mappings.  It is recommended that
readers be familiar with the overall framework in which these mappings
and signaling protocol are expected to be used; this framework is
described fully in [5].

Within this document, Section 2 describes the method by which end
systems and routers bordering the IEEE Layer-2 cloud learn what traffic
class should be used for each data flow's packets.  Section 3 describes
the approach recommended to map IP-level traffic flows to IEEE traffic
classes within the Layer 2 network.  Section 4 describes the computation
of Characterization Parameters by the layer 2 network.  The remaining
sections discuss some particular issues with the use of the RSVP/SBM
signaling protocols, and describe the applicability of all of the above
to different layer 2 network topologies.






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2.  Flow Identification and Traffic Class Selection

One model for supporting integrated services over specific link layers
treats layer-2 devices very much as a special case of routers. In this
model, switches and other devices along the data path make packet
handling decisions based on the RSVP flow and filter specifications, and
use these specifications to classify the corresponding data packets. The
specifications could either be used directly, or could be used
indirectly by mapping each RSVP session onto a layer-2 construct such as
an ATM virtual circuit.

This approach is inappropriate for use in the IEEE 802 environment.
Filtering to the per-flow level becomes expensive with increasing switch
speed; devices with such filtering capabilities are likely to have a
very similar implementation complexity to IP routers, and may not make
use of simpler mechanisms such as 802.1D user priority.

The Integrated Services over IEEE 802 LANs framework [5] and this
document use an "aggregated flow" approach based on use of layer 2
traffic classes. In this model, each arriving flow is assigned to one of
the available layer-2 classes, and traverses the 802 cloud in this
class.  Traffic flows requiring similar service are grouped together
into a single class, while the system's admission control and class
selection rules ensure that the service requirements for flows in each
of the classes are met.  In many situations this is a viable
intermediate point between no QoS control and full router-type
integrated services. The approach can work effectively even with
switches implementing only the simplest differential traffic
classification capability specified in the 802.1D model.  In the
aggregated flow model, traffic arriving at the boundary of a layer-2
cloud is tagged by the boundary device (end host or border router) with
an appropriate traffic class, represented as an 802.1D "user_priority"
value. Two fundamental questions are "who determines the correspondence
between IP-level traffic flows and link-level classes?" and  "how is
this correspondence conveyed to the boundary devices that must mark the
data frames?"

One approach to answering these questions would be for the meanings of
the classes to be universally defined. This document would then
standardise the meanings of a set of classes; e.g. 1 = best effort, 2 =
100 ms peak delay target, 3 = 10 ms peak delay target, 4 = 1 ms peak
delay target, etc. The meanings of these universally defined classes
could then be encoded directly in end stations, and the flow-to-class
mappings computed directly in these devices.






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This universal definition approach would be simple to implement, but is
too rigid to map the wide range of possible user requirements onto the
limited number of available 802.1D classes. The model described in [5]
uses a more flexible mapping: clients ask "the network" which
user_priority traffic class to use for a given traffic flow, as
categorised by its flow-spec and layer-2 endpoints. The network provides
a value back to the requester that is appropriate considering the
current network topology, load conditions, other admitted flows, etc.
The task of configuring switches with this mapping (e.g. through network
management, a switch-switch protocol or via some network-wide QoS-
mapping directory service) is an order of magnitude less complex than
performing the same function in end stations. Also, when new services
(or other network reconfigurations) are added to such a network, the
network elements will typically be the ones to be upgraded with new
queuing algorithms etc. and can be provided with new mappings at this
time.

In this model, when a new session or "flow" requiring QoS support is
created, a client must ask "the network" which traffic class (IEEE 802
user_priority) to use for a given traffic flow, so that it can label the
packets of the flow as it places them into the network. A
request/response protocol is needed between client and network to return
this information. The request can be piggy-backed onto an admission
control request and the response can be piggy-backed onto an admission
control acknowledgment. This "one pass" assignment has the benefit of
completing the admission control transaction in a timely way and
reducing the exposure to changing conditions that could occur if clients
cached the knowledge for extensive periods. A set of extensions to the
RSVP protocol for communicating this information have been defined[10].

The network (i.e. the first network element encountered downstream from
the client) must then answer the following questions:

1. Which of the available traffic classes would be appropriate for this
flow?
    In general, a newly arriving flow might be assigned to a number of
    classes. For example, if 10ms of delay is acceptable, the flow could
    potentially be assigned to either a 10ms delay class or a 1ms delay
    class. This packing problem is quite difficult to solve if the
    target parameters of the classes are allowed to change dynamically
    as flows arrive and depart.  It is quite simple if the target
    parameters of each class is held fixed, and the class table is
    simply searched to find a class appropriate for the arriving flow.
    This document adopts the latter approach.






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2. Of the appropriate traffic classes, which if any have enough capacity
available to accept the new flow?
    This is the admission control problem. It is necessary to compare
    the level of traffic currently assigned to each class with the
    available level of network resources (bandwidth, buffers, etc), to
    ensure that adding the new flow to the class will not cause the
    class's performance to go below its target values. This problem is
    compounded because in a priority queuing system adding traffic to a
    higher-priority class can affect the performance of lower-priority
    classes. The admission control algorithm for a system using the
    default 802 priority behavior must be reasonably sophisticated to
    provide acceptable results.

If an acceptable class is found, the network returns the chosen
user_priority value to the client.

Note that the client may be an end station, a router at the edge of the
layer 2 network, or a first switch acting as a proxy for a device that
does not participate in these protocols for whatever reason. Note also
that a device e.g. a server or router may choose to implement both the
"client" as well as the "network" portion of this model so that it can
select its own user_priority values. Such an implementation would
generally be discouraged unless the device has a close tie-in with the
network topology and resource allocation policies. It may, however, work
acceptably in cases where there is known over-provisioning of resources.


3.  Choosing a flow's IEEE 802 user_priority class

This section describes the method by which IP-level flows are mapped
into appropriate IEEE user_priority classes. The IP-level services
considered are Best Effort, Controlled Load, and Guaranteed Service.

The major issue is that admission control requests and application
requirements are specified in terms of a multidimensional vector of
parameters e.g. bandwidth, delay, jitter, service class.  This
multidimensional space must be mapped onto a set of traffic classes
whose default behaviour in L2 switches is unidimensional (i.e. strict
priority default queuing). This priority queuing alone can provide only
relative ordering between traffic classes. It can neither enforce an
absolute (quantifiable) delay bound for a traffic class, nor can it
discriminate amongst Int-Serv flows within the aggregate in a traffic
class. Therefore, it cannot provide the absolute control of packet loss
and delay required for individual Int-Serv flows.






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To provide absolute control of loss and delay three things must occur:

 (1)   The amount of bandwidth available to the QoS-controlled flows
       must be known, and the number of flows admitted to the network
       (allowed to use the bandwidth) must be limited.

 (2)   A traffic scheduling mechanism is needed to give preferential
       service to flows with lower delay targets.

 (3)   Some mechanism must ensure that best-effort flows and QoS
       controlled flows that are exceeding their Tspecs do not damage
       the quality of service delivered to in-Tspec QoS controlled
       flows. This mechanism could be part of the traffic scheduler, or
       it could be a separate policing mechanism.

For IEEE 802 networks, the first function (admission control) is
provided by a Subnet Bandwidth Manager, as discussed below. We use the
link-level user_priority mechanism at each switch and bridge to
implement the second function (preferential service to flows with lower
delay targets). Because a simple priority scheduler cannot provide
policing (function three), policing for IEEE networks is generally
implemented at the edge of the network by a layer-3 device. When this
policing is performed only at the edges of the network it is of
necessity approximate. This issue is discussed further in [5].


3.1.  Context of admission control and delay bounds

As described above, it is the combination of priority-based scheduling
and admission control that creates quantified delay bounds. Thus, any
attempt to quantify the delay bounds expected by a given traffic class
has to made in the context of the admission control elements. Section 6
of the framework [5] provides for two different models of admission
control - centralized or distributed Bandwidth Allocators.

It is important to note that in this approach it is the admission
control algorithm that determines which of the Int-Serv services is
being offered. Given a set of priority classes with delay targets, a
relatively simple admission control algorithm can place flows into
classes so that the bandwidth and delay behavior experienced by each
flow corresponds to the requirements of the Controlled-Load service, but
cannot offer the higher assurance of the Guaranteed service. To offer
the Guaranteed service, the admission control algorithm must be much
more stringent in its allocation of resources, and must also compute the
C and D error terms required of this service.





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A delay bound can only be realized at the admission control element
itself so any delay numbers attached to a traffic class represent the
delay that a single element can allow for.  That element may represent a
whole L2 domain or just a single L2 segment.

With either admission control model, the delay bound has no scope
outside of a L2 domain. The only requirement is that it be understood by
all Bandwidth Allocators in the L2 domain and, for example, be exported
as C and D terms to L3 devices implementing the Guaranteed Service.
Thus, the end-to-end delay experienced by a flow can only be
characterized by summing along the path using the usual RSVP mechanisms.


3.2.  Default service mappings

Table 1 presents the default mapping from delay targets to IEEE 802.1
user_priority classes. However, these mappings must be viewed as
defaults, and must be changeable.

In order to simplify the task of changing mappings, this mapping table
is held by *switches* (and routers if desired) but generally not by end-
station hosts.  It is a read-write table. The values proposed below are
defaults and can be overridden by management control so long as all
switches agree to some extent (the required level of agreement requires
further analysis).

In future networks this mapping table might be adjusted dynamically and
without human intervention. It is possible that some form of network-
wide lookup service could be implemented that serviced requests from
clients e.g. traffic_class = getQoSbyName("H.323 video") and notified
switches of what traffic categories they were likely to encounter and
how to allocate those requests into traffic classes. Alternatively, the
network's admission control mechanisms might directly adjust the mapping
table to maximize the utilization of network resources. Such mechanisms
are for further study.

The delay bounds numbers proposed in Table 1 are for per-Bandwidth
Allocator element delay targets and are derived from a subjective
analysis of the needs of typical delay-sensitive applications e.g.
voice, video. See Annex H of [2] for further discussion of the selection
of these values. Although these values appear to address the needs of
current video and voice technology, it should be noted that there is no
requirement to adhere to these values and no dependence of IEEE 802.1 on
these values.






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         user_priority  Service

              0         Default, assumed to be Best Effort
              1         reserved, "less than" Best Effort
              2         reserved
              3         reserved
              4         Delay Sensitive, no bound
              5         Delay Sensitive, 100ms bound
              6         Delay Sensitive, 10ms bound
              7         Network Control

          Table 1 - Example user_priority to service mappings

    Note: These mappings are believed to be useful defaults but further
    implementation and usage experience is required. The mappings may be
    refined in future editions of this document.

With this example set of mappings, delay-sensitive, admission controlled
traffic flows are mapped to user_priority values in ascending order of
their delay bound requirement. Note that the bounds are targets only -
see [5] for a discussion of the effects of other non-conformant flows on
delay bounds of other flows. Only by applying admission control to
higher-priority classes can any promises be made to lower-priority
classes.

This set of mappings also leaves several classes as reserved for future
definition.

    Note: this mapping does not dictate what mechanisms or algorithms a
    network element (e.g. an Ethernet switch) must perform to implement
    these mappings: this is an implementation choice and does not matter
    so long as the requirements for the particular service model are
    met.

    Note: these mappings apply primarily to networks constructed from
    devices that implement the priority-scheduling behavior defined as
    the default in 802.1D. Some devices may implement more complex
    scheduling behaviors not based only on priority. In that
    circumstance these mappings might still be used, but other, more
    specialized mappings may be more appropriate.









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3.3.  Discussion

The recommendation of classes 4, 5 and 6 for Delay Sensitive, Admission
Controlled flows is somewhat arbitrary; any classes with priorities
greater than that assigned to Best Effort can be used. Those proposed
here have the advantage that, for transit through 802.1D switches with
only two-level strict priority queuing, all delay-sensitive traffic gets
"high priority" treatment (the 802.1D default split is 0-3 and 4-7 for a
device with 2 queues).

The choice of the delay bound targets is tuned to an average expected
application mix, and might be retuned by a network manager facing a
widely different mix of user needs. The choice is potentially very
significant: wise choice can lead to a much more efficient allocation of
resources as well as greater (though still not very good) isolation
between flows.

Placing Network Control traffic at class 7 is necessary to protect
important traffic such as route updates and network management.
Unfortunately, placing this traffic higher in the user_priority ordering
causes it to have a direct effect on the ability of devices to provide
assurances to QoS controlled application traffic. Therefore, an estimate
of the amount of Network Control traffic must be made by any device that
is performing admission control (e.g. SBMs). This would be in terms of
the parameters that are normally taken into account by the admission
control algorithm. This estimate should be used in the admission control
decisions for the lower classes (the estimate is likely to be a
configuration parameter of SBMs).

A traffic class such as class 1 for "less than best effort" might be
useful for devices that wish to dynamically "penalty tag" all of the
data of flows that are presently exceeding their allocation or Tspec.
This provides a way to isolate flows that are exceeding their service
limits from flows that are not, to avoid reducing the QoS delivered to
flows that are within their contract. Data from such tagged flows might
also be preferentially discarded by an overloaded downstream device.

A somewhat simpler approach would be to tag only the portion of a flow's
packets that actually exceed the Tspec at any given instant as low
priority. However, it is often considered to be a bad idea to treat
flows in this way as it will likely cause significant re-ordering of the
flow's packets, which is not desirable. Note that the default 802.1D
treatment of user_priorities 1 and 2 is "less than" the default class 0.







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4.  Computation of integrated services characterization parameters by
IEEE 802 devices

The integrated service model requires that each network element that
supports integrated services compute and make available certain
"characterization parameters" describing the element's behavior. These
parameters may be either generally applicable or specific to a
particular QoS control service.  These parameters may be computed by
calculation, measurement, or estimation. When a network element cannot
compute its own parameters (for example, a simple link), we assume that
the device sending onto or receiving data from the link will compute the
link's parameters as well as it's own.  The accuracy of calculation of
these parameters may not be very critical; in some cases loose estimates
are all that is required to provide a useful service. This is important
in the IEEE 802 case, where it will be virtually impossible to compute
parameters accurately for certain topologies and switch technologies.
Indeed, it is an assumption of the use of this model by relatively
simple switches (see [5] for a discussion of the different types of
switch functionality that might be expected) that they merely provide
values to describe the device and admit flows conservatively.  The
discussion below presents a general outline for the computation of these
parameters, and points out some cases where the parameters must be
computed accurately. Further specification of how to export these
parameters is for further study.


4.1.  General characterization parameters

There are some general parameters [9] that a device will need to use
and/or supply for all service types:

  * Ingress link

  * Egress links and their MTUs, framing overheads and minimum packet
    sizes (see media-specific information presented above).

  * Available path bandwidth: updated hop-by-hop by any device along the
    path of the flow.

  * Minimum latency

Of these parameters, the MTU and minimum packet size information must be
reported accurately. Also, the "break bits" must be set correctly, both
the overall bit that indicates the existence of QoS control support and
the individual bits that specify support for a particular scheduling





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service. The available bandwidth should be reported as accurately as
possible, but very loose estimates are acceptable. The minimum latency
parameter should be determined and reported as accurately as possible if
the element offers Guaranteed service, but may be loosely estimated or
reported as zero if the element offers only Controlled-Load service.


4.2.  Parameters to implement Guaranteed Service

A network element supporting the Guaranteed Service must be able to
determine the following parameters [7]:

  * Constant delay bound through this device (in addition to any value
    provided by "minimum latency" above) and up to the receiver at the
    next network element for the packets of this flow if it were to be
    admitted.  This includes any access latency bound to the outgoing
    link as well as propagation delay across that link. This value is
    advertised as the 'C' parameter of the Guaranteed Service.

  * Rate-proportional delay bound through this device and up to the
    receiver at the next network element for the packets of this flow if
    it were to be admitted.  This value is advertised as the 'D'
    parameter of the Guaranteed Service.

  * Receive resources that would need to be associated with this flow
    (e.g. buffering, bandwidth) if it were to be admitted and not suffer
    packet loss if it kept within its supplied Tspec/Rspec. These values
    are used by the admission control algorithm to decide whether a new
    flow can be accepted by the device.

  * Transmit resources that would need to be associated with this flow
    (e.g. buffering, bandwidth, constant- and rate-proportional delay
    bounds) if it were to be admitted. These values are used by the
    admission control algorithm to decide whether a new flow can be
    accepted by the device.

The exported characterization parameters for this service should be
reported as accurately as possible. If estimations or approximations are
used, they should err in whatever direction causes the user to receive
better performance than requested. For example, the C and D error terms
should overestimate delay, rather than underestimate it.









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4.3.  Parameters to implement Controlled Load

A network element implementing the Controlled Load service must be able
to determine the following [6]:

  * Receive resources that would need to be associated with this flow
    (e.g. buffering) if it were to be admitted. These values are used by
    the admission control algorithm to decide whether a new flow can be
    accepted by the device.

  * Transmit resources that would need to be associated with this flow
    (e.g. buffering) if it were to be admitted. These values are used by
    the admission control algorithm to decide whether a new flow can be
    accepted by the device.

The Controlled Load service does not export any service-specific
characterization parameters. Internal resource allocation estimates
should ensure that the service quality remains high when considering the
statistical aggregation of Controlled Load flows into 802 traffic
classes.


4.4.  Parameters to implement Best Effort

For a network element that implements only best effort service there are
no explicit parameters that need to be characterized. Note that an
integrated services aware network element that implements only best
effort service will set the "break bit" described in [11].


5.  Merging of RSVP/SBM objects

Where reservations that use the SBM protocol's TCLASS object [10] need
to be merged, an algorithm needs to be defined that is consistent with
the mappings to individual user_priority values in use in the Layer-2
cloud.  A merged reservation must receive at least as good a service as
the best of the component reservations.

There is no single merging rule that can prevent all of the following
side-effects:


  * If a merger were to demote the existing branch of the flow into a
    higher-delay traffic class then this is a denial of service to the
    existing flow which would likely receive worse service than before.





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  * If a merger were to promote the existing branch of the flow into a
    new, lower-delay, traffic class, this might then suffer either
    admission control failures or may cost more in some sense than the
    already-admitted flow. This can also be considered as a denial-of-
    service attack.

  * Promotion of the new branch may lead to rejection of the request
    because it has been re-assigned to a traffic class that has not
    enough resources to accommodate it.

Therefore, such a merger is declared to be illegal and the usual SBM
admission control failure rules are applied. Traffic class selection is
performed based on the TSpec information. When the first RESV for a flow
arrives, a traffic class is chosen based on the request, an SBM TCLASS
object is inserted into the message and admission control for that
traffic class is done by the SBM. Reservation succeeds or fails as
usual.

When a second RESV for the same flow arrives at a different egress point
of the Layer-2 cloud the process starts to repeat. Eventually the SBM-
augmented RESV may hit a switch with an existing reservation in place
for the flow i.e. an L2 branch point for the flow. If so, the traffic
class chosen for the second reservation is checked against the first. If
they are the same, the RESV requests are merged and passed on towards
the sender(s).

If the second TCLASS would have been different, an RSVP/SBM ResvErr
error is returned to the Layer-3 device that launched the second RESV
request into the Layer-2 cloud. This device will then pass on the
ResvErr to the original requester according to RSVP rules.



6.  Applicability of these service mappings

Switches using layer-2-only standards (e.g. 802.1D-1990, 802.1D-1998)
need to inter-operate with routers and layer-3 switches. Wide deployment
of such 802.1D-1998 switches will occur in a number of roles in the
network: "desktop switches" provide dedicated 10/100 Mbps links to end
stations and high speed core switches often act as central campus
switching points for layer-3 devices. Layer-2 devices will have to
operate in all of the following scenarios:

  * every device along a network path is layer-3 capable and intrusive
    into the full data stream





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  * only the edge devices are pure layer-2

  * every alternate device lacks layer-3 functionality

  * most devices lack layer-3 functionality except for some key control
    points such as router firewalls, for example.

    Where int-serv flows pass through equipment which does not support
    Integrated Services or 802.1D traffic management and which places
    all packets through the same queuing and overload-dropping paths, it
    is obvious that some of a flow's desired service parameters become
    more difficult to support. In particular, the two integrated service
    classes studied here, Controlled Load and Guaranteed Service, both
    assume that flows will be policed and kept "insulated" from
    misbehaving other flows or from best effort traffic during their
    passage through the network. This cannot be done within an IEEE 802
    network using devices with the default user_priority function; in
    this case policing must be approximated at the network edges.

    In addition, in order to provide a Guaranteed Service, *all*
    switching elements along the path must participate in special
    treatment for packets in such flows: where there is a "break" in
    guaranteed service, all bets are off. Thus, a network path that
    includes even a single switch transmitting onto a shared or half-
    duplex LAN segment is unlikely to be able to provide a very good
    approximation to Guaranteed Service. For Controlled Load service,
    the requirements on the switches and link types are less stringent
    although it is still necessary to provide differential queueing and
    buffering in switches for CL flows over best effort in order to
    approximate CL service. Note that users receive indication of such
    breaks in the path through the "break bits" described in [11]. These
    bits must be correctly set when IEEE 802 devices that cannot provide
    a specific service exist in a network.

    Other approaches might be to pass more information between switches
    about the capabilities of their neighbours and to route around non-
    QoS-capable switches: such methods are for further study. And of
    course the easiest solution of all is to upgrade links and switches
    to higher capacities.


7.  References








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[1]  "MAC Bridges", ISO/IEC 10038, ANSI/IEEE Std 802.1D-1993

[2]  "Information technology - Telecommunications and information
     exchange between systems - Local and metropolitan area networks -
     Common specifications - Part 3: Media Access Control (MAC) Bridges:
     Revision (Incorporating IEEE P802.1p: Traffic Class Expediting and
     Dynamic Multicast Filtering", ISO/IEC Final CD 15802-3 IEEE
     P802.1D/D16, March 1998

[3]  Clark, D. et al. "Integrated Services in the Internet Architecture:
     an Overview" RFC1633, June 1994

[4]  Braden, R., L. Zhang, S. Berson, S. Herzog, S. Jamin, "Resource
     Reservation Protocol (RSVP) - Version 1 Functional Specification",
     RFC 2205, September 1997

[5]  Ghanwani, A., Pace, W., Srinivasan, V., Smith, A., Seaman, M., "A
     Framework for Providing Integrated Services Over Shared and
     Switched LAN Technologies", Internet Draft, May 1998 <draft-ietf-
     issll-is802-framework-05>

[6]  Wroclawski, J., "Specification of the Controlled-Load Network
     Element Service", RFC 2211, September 1997

[7]  Schenker, S., Partridge, C., Guerin, R., "Specification of
     Guaranteed Quality of Service", RFC 2212 September 1997

[8]  "IEEE Standards for Local and Metropolitan Area Networks:  for
     Virtual Bridged Local Area Networks", July 1998, IEEE Draft
     Standard P802.1Q/D11

[9]  Shenker, S., Wroclawski, J., "General Characterization Parameters
     for Integrated Service Network Elements", RFC 2215, September 1997

[10] Yavatkar, R., Hoffman, D., Bernet, Y., Baker, F., Speer, M., "SBM
     (Subnet Bandwidth Manager): A Protocol for Admission Control over
     IEEE 802-style Networks", Internet Draft, March 1998 <draft-ietf-
     issll-sbm-06>

[11] Wroclawski, J., "The use of RSVP with IETF Integrated Services",
     RFC 2210, September 1997.









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8.  Security Considerations

Any use of QoS requires examination of security considerations because
it leaves the possibility open for denial of service or theft of service
attacks. This document introduces no new security issues on top of those
discussed in the companion ISSLL documents [5] and [10].  Any use of
these service mappings assumes that all requests for service are
authenticated appropriately.


9.  Acknowledgments

This document draws heavily on the work of the ISSLL WG of the IETF and
the IEEE P802.1 Interworking Task Group.


10.  Authors' addresses

     Mick Seaman
     3Com Corp.
     5400 Bayfront Plaza
     Santa Clara CA 95052-8145
     USA
     +1 (408) 764 5000
     mick_seaman@3com.com

     Andrew Smith
     Extreme Networks
     10460 Bandley Drive
     Cupertino CA 95014
     USA
     +1 (408) 863 2821
     andrew@extremenetworks.com

     Eric Crawley
     Argon Networks
     25 Porter Rd.
     Littleton MA 01460
     USA
     +1 (508) 486 0665
     esc@argon.com

     John Wroclawski
     MIT Laboratory for Computer Science
     545 Technology Sq.





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     Cambridge, MA  02139
     USA
     +1 (617) 253 7885
     jtw@lcs.mit.edu


Table of Contents

1 Introduction ....................................................    2
2 Flow Identification and Traffic Class Selection .................    3
3 Choosing a flow's IEEE 802 user_priority class ..................    5
3.1 Context of admission control and delay bounds .................    6
3.2 Default service mappings ......................................    7
3.3 Discussion ....................................................    9
4 Computation of integrated services characterization parameters
     by IEEE 802 devices ..........................................   10
4.1 General characterization parameters ...........................   10
4.2 Parameters to implement Guaranteed Service ....................   11
4.3 Parameters to implement Controlled Load .......................   12
4.4 Parameters to implement Best Effort ...........................   12
5 Merging of RSVP/SBM objects .....................................   12
6 Applicability of these service mappings .........................   13
7 References ......................................................   14
8 Security Considerations .........................................   16
9 Acknowledgments .................................................   16
10 Authors' addresses .............................................   16
























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