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Internet Engineering Task Force                                         Authors
INTERNET DRAFT                                                     Ashish Mehra
                                                                   Dinesh Verma
                                                                    Renu Tewari
                                                               Tsipora Barzilai
                                                               Douglas Freimuth
                                                                   Mandis Beigi
                                                 IBM T J Watson Research Center
                                                                   14 July 2000

                Policy-Based Differentiated Services on AIX

    Status of Memo

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

       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 and may be updated, replaced, or obsoleted by
       other documents at any time.  It is inappropriate to use
       Internet-Drafts as reference material or to cite them other
       than as ``work in progress.''

       The list of current Internet-Drafts can be accessed at

       The list of Internet-Draft Shadow Directories can be
       accessed at http://www.ietf.org/shadow.html.

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       This draft presents a policy-based Differentiated
       Services [DSARCH] architecture that has been realized
       on the AIX operating system.  We briefly motivate the
       benefits of supporting DiffServ functions on servers using
       policy-based networking, and outline the requirements for
       DiffServ-enabled servers.  We then describe the policy-based
       DiffServ infrastructure we have developed for AIX.
       Experimental results using Web server workloads demonstrate
       the efficacy of the DiffServ mechanisms provided.  We also
       outline ongoing work in deploying diffserv-capable AIX
       servers on Internet2.

1.  Introduction

    The differentiated services (DiffServ) architecture and model
    [DSARCH, DSFRAME] provides the framework on which network operators
    can support different classes of service in a network.  In this
    framework, an access (or edge) device determines the class of
    service of data packets passing through it and modifies the Type of
    Service (TOS) byte of the IP header [DSHEAD]. Routers offer different
    classes of service in the network by supporting a variety of Per
    Hop Behaviors (PHBs)(e.g., Assured Forwarding [ASREF], Expedited
    Forwarding [EFREF]). In addition to standardizing service classes
    and their PHB's, a continued focus remains on exploring how various
    components within the framework can together meet the end-to-end
    quality of service requirements of network applications.  Towards
    that end, there have been proposals on the architecture of DiffServ
    access boxes [DIFFEDGE] as well as discussion of how differentiated
    services can inter-operate with integrated services and signaled
    quality of service (QoS) [DIFFEDGE] [RSVPDIFF].

           / Stub   \       /   Transit   \       /  Stub  \
          / Network  \     /    Network    \     /  Network \
   |---|        |        |---|   |---|          |---|   |---|        | |---|
   |Tx |-|        |ER1|---|BR1|          |BR2|---|ER2|        |-|Rx |
   |---|        |        |-- |   |---|          |---|   |---|        | |---|
          \          /     \                /     \          /
           \        /       \              /       \        /

                     Figure 1: Sample Network Configuration

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1.1 DiffServ Servers

    DiffServ deployment is typically perceived to be carried out as
    in Figure 1, which shows two stub networks connected together
    with a transit network.  The working assumption has been that the
    stub networks would support integrated services while the transit
    network(s) would support differentiated services.  We have considered
    a variety of deployment scenarios for IntServ and DiffServ [DSERVERS]
    and argued in favor of DiffServ functionality in the stub networks,
    especially on end hosts such as servers.  Recent developments have
    clearly highlighted the need for diffserv-capable servers.  Large
    multi-tiered Web sites frequently deploy frontend servers and devices
    to manage the flow of traffic into and out of the inner tiers.  With
    the successful deployment of content distribution networks and
    services, ``edge'' servers such as caching proxies are increasingly
    being placed at different points inside the network.  This is
    in addition to the existence of more traditional proxies, e.g.,
    application-level gateways/delays, SOCKS proxies, and voice call
    aggregation (H.323) proxies.

    More often than not, proxies reside at the boundary of two separate
    networks, which are likely to represent different DiffServ domains.
    In general, such proxy servers need to consistently manage the
    traffic flowing through by enforcing bandwidth controls, preserving
    TOS markings, or translating QoS requirements (e.g., re-marking) if
    necessary.  These developments strongly motivate the need to support
    the DiffServ architectural framework at end hosts - the sources and
    sinks of network connections.  The DiffServ support in Linux [LINUX]
    is an effort in that direction.

1.2 Policy-Based Networking

    As networking equipment becomes more complex in an effort to provide
    more complex QoS features, it is necessary to standardize the
    network configuration parameters used to establish a network policy.
    In the absence of such standards, it is generally not possible
    for networking equipment from different vendors to interoperate
    successfully, making realization of end-to-end QoS extremely
    difficult.  Policy-based networking has grown out of the efforts of
    the Directory Enabled Networking (DEN) Ad Hoc working group [DEN]
    operating under the auspices of the Desktop Management Task Force
    (DMTF). The DMTF is an organization with much broader concerns of
    configuration and resources far beyond the network.

    Policy-based networking enables administration of network policies
    from a centralized policy server, thus reducing some of the
    complexity surrounding network policy configuration for QoS. The

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    underlying model behind network policies, along with an annotated
    list of the terminology, is discussed in [POLICY]. A policy schema
    for QoS being considered by the IETF's policy working group is
    described in [SCHEMA]. We are concerned only with policy-based
    networking to the extent it can be used to define and manage policies
    that influence QoS.

    In this draft we present a policy-based differentiated services
    architecture that has been implemented on the AIX operating system.
    This architecture satisfies the requirements outlined in [DSERVERS]
    and leverages policy-based networking to enable provisioning of
    DiffServ services via platform-independent, high-level policies.  The
    goal of this Internet Draft is to describe the current support for
    Differentiated Services on AIX. We first summarize key requirements
    for provisioning of DiffServ functions on servers.  We then present
    the policy-based architecture that provides DiffServ services
    to QoS-unaware (e.g., standard/existing) as well as QoS aware
    applications.  The components constituting the architecture are
    described next.  We report experimental results demonstrating the
    efficacy of the underlying DiffServ mechanisms and outline an ongoing
    effort to deploy diffserv-capable AIX servers on the Internet2

2.  Policy-Based DiffServ Architecture

    We have realized a policy-based architecture for Differentiated
    Services on AIX. Our choice of such an architecture is motivated by
    the need to satisfy a number of essential requirements [DSERVERS].
    We briefly describe these requirements before presenting the

2.1 Requirements

    An architecture for diffserv enabled servers must satisfy the
    following requirements:

      - It should allow standard/existing networked applications (that
        are QoS unaware) to be classified into a PHB other than best

        Many existing networked applications, e.g.  databases,
        transaction services, CICS, MQSeries, SAP etc., and middleware
        technologies (e.g., Java RMI, CORBA IIOP, HTTP) have been
        designed to run over best effort networks.  For a staged
        deployment of DiffServ, these applications should not have to be
        modified to take advantage of the different classes of service.

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        Thus, an architecture for diffserv servers must support the
        ability to be application-unaware.

      - It should allow classification at different granularities.

        The differentiated services architecture is based on classifying
        5-tuples (the source and destination IP addresses, the source
        and destination port numbers, and the protocol) or 6-tuples (if
        we include the incoming DS field) into an outgoing DS field at
        each access router.  While classification at this granularity is
        sufficient to meet may needs, classification should be possible
        at the granularity of an application, or the identity of a user.

      - It should allow policy decisions to be applied uniformly across
        existing applications as well as new applications that signal the
        desired service level.  A similar policy enforcement should occur
        for applications that use a signaled interface (e.g.  RAPI) to
        signal their performance needs.

        Since both types of applications would require access to the same
        network resources, they should be controlled and administered by
        the same policy information.

      - It should allow differentiated service support to coexist with
        secure communications using IP-sec or SSL.

        Secure communications using IP-sec or SSL is a reality in current
        Internet communications.  Since IP-sec encrypts transport layer
        headers, the differentiated services architecture must perform
        its encryption functions prior to the IP-sec functions.  SSL
        offers no hindrances as long as classification is based solely on
        contents of transport and network layer headers.

      - It should allow functions needed in order to conform with the
        rate requirements enforced by network layer SLSs.

        The end-host must not violate the terms of the contracts
        negotiated with the network provider.  It must put into place
        appropriate mechanisms to ensure that applications comply with
        network level SLSs.

      - It must coexist with the support for integrated services in the

        Integrated Services and Differentiated Services offer a
        complementary set of QoS features, which may each be most
        appropriate to meet a different set of application requirements.
        Both methods should coexist in the end-host.

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2.2 Architecture Overview

    The DiffServ architecture on AIX enables server-based implementation
    of the core differentiated services requirements.  Figure 2 shows
    the main components of the architecture that consists of the Policy
    Agent, the QoS Manager and the DiffServ API.

    One of the key features of the architecture is that it supports
    policy based networking that can enable different vendors to
    inter-operate easily.  With policy-based controls there is no need
    to modify existing applications, thereby, making application-unaware
    DiffServ support a reality.  Most other implementations require the
    applications to request for a particular traffic profile.

    The policy agent resides at the user-level and provides policy
    management while interfacing with the kernel-resident QoS Manager.
    It provides support for adding, deleting, and modifying policies
    that can either be defined by a local configuration file or
    can be retrieved from a centralized repository using LDAP. A
    policy specification consist of multiple rules and parameters
    including permissions (accept, deny), rate control parameters
    for the in-profile traffic, TOS marking values for in-profile and
    out-of-profile traffic, etc.  A policy schema to describe policies in
    a standardized fashion has been defined in [POLICY]; the AIX policy
    agent conforms to these schema definitions.  Along with the policy
    agent there exists command line support for applications or system
    administrators to directly set up rules, filters and classes.

    The QoS Manager is a kernel-based module that implements the core
    DiffServ functionality.  The two main functions of the QoS Manager
    are classification and traffic conditioning.  The classifier
    determines the class a packet or connection belongs to based on its
    network 5-tuple and the instantiated filter specification.  The
    traffic conditioning support includes packet marking, policing with
    drop or mark and traffic shaping based on the flow specification.
    The QoS Manager interacts with the transport layer of the stack to
    control the flow of outgoing traffic.

    The interactions between the user level agents and the kernel-based
    QoS manager happens via different types of control messages over
    special control sockets.  The messages include adding, deleting, and
    modifying traffic conditioning rules and filters.

    For applications that are aware of DiffServ specifications, there is
    also a supported DiffServ API to communicate with the policy agent in
    order to set up the rules.  Refer to [DSERVERS] for details.

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    The following section provides the implementation details on each of
    the components of the architecture, focusing on the Policy Agent and
    the QoS Manager.

   +------------+ +--------------+    ~  +--------+ Policy-Based Ctrl ~
   | QoS unaware| | QoS aware    |    ~  |Command |                   ~
   |Application | | Application  |    ~  |Line    |   +---------+     ~
   +------------+ +--------------+    ~  +--------+   |Policy   |     ~
           |       |     | control    ~       |       |Data Base|     ~
           | data  |     | path       ~  +-------+    | (LDAP)  |     ~
           |/ path\|  +------------+  ~  |       |<-->+---------+     ~
           |       |  |DiffServ API|<-~->|Policy |    +---------+---+ ~
           |       |  +------------+  ~  |Agent  |<-->|Local        | ~
           |       |                  ~  +-------+    |Configuration| ~
           |       |                  ~       |       +-------------+ ~
           |       |                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           |       |                          |
     |                  socket layer                              |
                  |                           |
                  |                           |
                +----------------+            |
                |Transport Layer |           +--------------------+
                | TCP / UDP      |<--------->|  QoS Manager       |
                +----------------+           |                    |
                  |                          | Rules - flow spec  |
                  |                          |         filter spec|
                +---------------+            | Actions-Marking    |
                |  IP           |            |         Policing   |
                +---------------+            |         Shaping    |
                  |                          +--------------------+

       Figure 2. Architecture of DiffServ Enabled Server

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3.  Architectural Components

3.1 Policy Database and System Agent

    The policy agent is a user level daemon provides policy management
    support by translating QoS policies and interfacing with the
    QoS kernel extension to install, modify, and delete policy
    rules.  Policy rules may be defined in a local configuration file
    (/etc/policyd.conf), retrieved from a central policy database server
    using LDAP [LDAP], or created via command line programs (see Figure

3.1.1 QoS Policy

    The IETF's policy working group is attempting to define a QoS
    schema in which QoS policy can be succinctly described such that
    the various QoS policy parameters have a standardized definition so
    that networking equipment supporting QoS functions can interoperate
    effectively and deterministically.  We use the QoS schema proposed
    and described in [SCHEMA] to represent QoS policies.

    As currently defined, a policy (or policy rule) consists of two
    components, a policy condition  and a policy action.  The mechanisms
    enforcing the policy are in the form:  if policy condition  then
    policy action.  The policy condition component is essentially a
    traffic classifier (see section ).  The policy action specifies
    the permissions and restrictions that apply to the packets matched
    by the policy condition.  A policy action contains specifications:
    permission (accept or deny), token bucket parameters defining
    in-profile traffic, TOS byte value for in-profile traffic, and TOS
    byte value for out-of-profile traffic.  Refer to [SCHEMA] for more
    details on policy rules.

3.1.2 Policy Configuration

    A policy expressed in the configuration file has two primary
    statements, ServiceCategories and ServicePolicyRule, that contain the
    attributes to express the diffserv policy.  The ServiceCategories
    statement specifies the type of service that a flow of IP packets
    should receive as they traverse the network.  The ServicePolicyRule
    statement specifies the characteristics of IP packets that are
    used to match to a corresponding service category, and receive the
    specified class of service.  The policy agent can also be configured
    to translate diffserv policies from an LDAP database.  The Policy
    Agent periodically updates policies from the configuration file or an
    LDAP server.

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    Policies can also be input from the command line via system commands.
    The AIX QoS implementation provides several system commands to manage
    and monitor policies [AIXDOC]. These commands ease the burden of
    managing policies for the QoS administrator and provide a way to
    monitor the amount of traffic matched with each installed policy.
    The available system commands for policy management are briefly
    described below.

     1. Add Policy:  The qosadd command adds the specified
        ServiceCategory or PolicyRule entry to the default policy
        configuration file /etc/policyd.conf and installs the changes in
        the QoS Manager kernel.  The qosadd command communicates with
        the Policy Agent and specifies the action to add a policy.  The
        flags on the qosadd command are passed in to the Policy Agent
        to specify the QoS attributes for the policy.  The Policy Agent
        writes the appropriate policy out to the configuration file
        and then copies the new policy into the QoS Manager kernel for

     2. Remove Policy:  The qosremove command removes the specified
        ServiceCategory or PolicyRule entry from the configuration file
        and removes the entry in the QoS Manager kernel.  The qosremove
        command communicates with the Policy Agent and specifies
        the action to remove a policy.  The flags on the qosremove
        command are passed in to the Policy Agent to specify the QoS
        ServiceCategory or PolicyRule to remove.  The policy is removed
        from the configuration file and then the Policy Agent makes a
        call to remove the policy from the QoS Manager kernel.

     3. Modify Policy:  The qosmod command modifies the specified
        ServiceCategory or PolicyRule entry in the configuration file
        and installs the changes in the QoS Manager kernel.  The qosmod
        command communicates with the Policy Agent and specifies the
        action to modify a policy.  The flags on the qosmod command are
        passed into the Policy Agent to specify which ServiceCategory or
        PolicyRule to modify and to specify the attributes to modify.
        The Policy Agent modifies the configuration file and the makes
        a call to the QoS Manager kernel to modify the appropriate
        installed policies.

     4. List Policy:  The qoslist command lists the specified
        ServiceCategory or PolicyRule.  The command will list all
        ServiceCategories or PolicyRules if none are specified.  The
        qoslist command communicates with the Policy Agent and specifies
        the action to list a policy or list all policies.  The flags
        on the qoslist command are used to specify the ServiceCategory
        or PolicyRule to list.  The Policy Agent queries the list of
        installed policies and creates the appropriate output.

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     5. Display Policy Statistics:  The qosstat command displays
        information about the installed QoS policies.  The qosstat
        command communicates directly with the QoS Manager kernel to
        query the structures that maintain the QoS statistics.  The
        structures in the QoS Manager kernel are updated dynamically
        upon the completion of each QoS action.  Information such as
        the filter specification, flow class and data statistics are

3.1.3 Priorities for Overlapping Policies

    The Policy agent contains a priority queue used for the installation
    of policies in the QoS Manager kernel.  This functionality is
    important since the QoS Manager permits installation of overlapping
    policies.  The priority queue in the Policy Agent can be utilized to
    determine the matching priority in the event of overlapping policies.
    The ServicePolicyRules statement in the policy definition allows the
    specification of the PolicyRulePriority attribute to set the priority
    of matching in the overlapping case.

3.2 QoS Manager Kernel Extension

    The QoS Manager is a kernel module that implements the basic QoS
    mechanisms that can be used to deliver a particular quality of
    service to an IP flow or flow aggregate.  It is used to realize both
    the IntServ and DiffServ models for QoS on AIX.

    The QoS Manager is defined as a new protocol module in the networking
    subsystem, with a protocol switch table entry to represent the
    various functions it exports to other modules.  Applications access
    the QoS Manager from user space by exchanging control messages over
    special control sockets, which are distinct from data sockets.  A
    similar paradigm is used for passing routing information in 4.4
    BSD. We modified the socket and transport layers to invoke the
    classification and policy enforcement functions exported by the QoS
    Manager before sending out packets.  These functions are briefly
    discussed next.

3.2.1 Classification

    The QoS Manager currently classifies data sockets based on the five
    tuple <source IP address, source port number, destination IP address,
    destination port number, protocol type>.  In general, it can also
    classify data sockets based on other information available only at
    hosts, e.g., user id, group id, and application.  Each installed

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    policy maintains a list of data sockets that match the filter
    associated with the policy.  This list is updated during connection
    establishment/teardown as well as policy creation/deletion.

3.2.2 Policy Enforcement

    Policies are enforced using traffic conditioning mechanisms that
    actively regulate the flow of out-bound packets.  The QoS Manager
    implements several traffic conditioning mechanisms:  marking,
    policing, dropping, and shaping.


    Policing monitors a specific flow to determine if it conforms to
    the traffic profile given by its token bucket specification.  QoS
    Manager supports a token bucket specification with two parameters:
    the average rate and the burst size.  Precisely what should be done
    with both in-and out-of-profile traffic is governed by policy.  For
    example, out-of-profile packets could be dropped immediately, delayed
    until they conform (shaped), or delivered at a lower quality of


    Dropping is the simplest form of traffic conditioning where
    non-compliant packets are discarded.


    Shaping involves holding back out-of-profile packets until they
    conform to the specified traffic profile.  QoS Manager implements
    shaping by either witholding packets in the socket send buffers (for
    TCP) or blocking the kernel (or application) thread shepherding the
    packet (for UDP). Applications sending data on non-blocking sockets
    are returned an error for out-of-profile traffic.  To continue
    transmitting out-of-profile packets when they become compliant, QoS
    Manager relies upon a system shaping timer and other triggers (such
    as ACKs).  The granularity of the shaping timer is configurable at
    user level, which allows it to be tuned for correct and efficient
    traffic shaping.  QoS Manager provides max-min fairness between
    traffic originating on the different data sockets associated with
    (i.e., controlled by) a given policy.

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    Marking, which involves setting the TOS bits in the IP header for
    each outgoing packet, is implemented by updating the TOS byte in the
    protocol control block associated with a data socket.  Each transport
    protocol automatically copies the newly generated marking to the
    outgoing packet's header.  When combined with policing, in-profile
    packets are marked with one DS codepoint while out-of-profile packets
    are marked with another, as specified in the policy.

4.  Experimental Results

    The goal of these experimental results is to demonstrate the efficacy
    of policy enforcement using the AIX diffserv architecture.  The
    experiments determine if the traffic conditioning techniques used
    result in delivering the specified classes of service.

    The test setup is chosen to represent how this implementation
    might be used in an enterprise LAN. The AIX 5.0 (beta version) QoS
    implementation is configured on an RS/6000 4-way SMP, with 166 MHz
    processors and a total physical memory of 512 MB. The server runs
    the publicly available Apache Web Server 3.1 with the appropriate
    diffserv policies configured by the policy agent.  Client workload
    is generated by the publicly available Webstone 2.5 benchmark.
    There are four Webstone clients, each running on a RS/6000 200 MHz
    uniprocessor with 128 MB physical memory.  The four clients are
    attached to a 100Mbps Ethernet switch with a 1 Gbps uplink to the
    server.  Each Webstone client repeatedly makes 100 concurrent HTTP
    requests for a 100 KB file.

    The following traffic conditioning techniques are exercised during
    the experiments.

      - Marking is performed standalone to simply mark the IP TOS byte
        of each packet with a DS codepoint for further processing in
        external network routers.

      - Policing is performed with marking so that the in-profile packets
        are marked with a DS codepoint to receive the desired class of
        service using the IP TOS field.  The out-of-profile packets are
        left unmarked.  The token bucket parameters of burst size and
        average rate are expressed in the policy to determine the traffic

      - Shaping is performed with marking to only transmit in-profile
        packets.  The out-of-profile packets are held back until they are
        compliant with the traffic profile expressed in the QoS policy.

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        The shaping timer value is configurable via the no (network
        option) system command and is set at 10 milliseconds.

    For the policing and shaping experiments the token bucket burst size
    is set to 60 KB.

     Action       |  M      P      P       P      S      S      S
     Rate         | None 64Kbps 1.5Mpbs 45Mpbs 64Kbps 1.5Mbps 45Mbps
Thruput (total)   | 137  130      130    130   0.064   1.44   45.09
Thrhput (in-prof.)|      0.064    1.5    45    0.064   1.44   45.09

M: Marking only
P: Policing with marking
S: Shaping with marking

Table 1: Throughput (Mbps) of Webstone Clients with Different QoS Policies

    Table 1 shows the total throughput observed by Webstone clients for
    different traffic conditioning policies.  The values presented are
    the total and in-profile throughput for:  (i) marking only with no
    rate control, (ii) policing with 3 different bandwidth values, and
    (iii) shaping at 3 different values.  The total throughput achieved
    with policing is slightly less than that of marking only due to
    the additional overhead of policing checks in the data path.  The
    in-profile throughput conforms to the specified value.

    Table 2 shows the commands for marking and policing.  In case I,
    line 1 sets up marking with a DSCP value 00001000.  The second line
    specifies that the policy applies to TCP traffic with source IP
    address and source port 80.  In case II, line 1 sets up a
    policing rule for 63 kbps with a burst size of 469 kb.

I. Policy for marking only:

qosadd -s 64k -t 00001000 service
qosadd -s 64k -r 64k-policy -n 6 -A -P 80 policy

II. Policy for policing and marking:

qosadd -s 64k -t 00001000 -b 469 -m 63 service
qosadd -s 64k -r 64k-policy -n 6 -A -P 80 policy

Table 2: AIX commands for setting up  marking and policing rules

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5.  Deployment

    We are collaborating with the International Center for Advanced
    Internet Research (ICAIR) to deploy the AIX policy-based diffserv
    functionality within the context of the I2DVN and QBONE projects
    of Internet2 [ICAIR]. The goal is to study network-intensive
    applications by performing end-to-end QoS experiments over a network
    providing differentiated services.  The end points exist at the ICAIR
    Center at Northwestern University and IBM Hawthorne, NY. Once the
    Internet2 connections are configured for the end points, experiments
    will be conducted across the Abilene network connecting the IBM
    Hawthorne site and the ICAIR center.

    The initial application is a streaming video application called
    VideoCharger installed on an RS/6000 SMP at each end-point.  QoS
    policies are defined on an LDAP server at each end-point, and
    retrieved by the AIX Policy Agent for installation in the QoS
    Manager.  Tests have been performed to assure proper interaction
    between the video application and the QoS Manager so that packets
    are properly marked with the desired DS codepoint.  The application
    scenario being considered is one in which medium bandwidth video (1.5
    Mbps MPEG-1) will be generated in unicast mode from a VideoCharger
    server to VideoCharger clients and to a special measurement client.
    The measurement client will be used to measure the latency and
    throughput between the server and clients.  Those statistics will
    then be compared with the traffic profile expressed in the QoS

6.  Security Considerations

    We have highlighted a number of security considerations for servers
    supporting differentiated services in an earlier draft [DSERVERS].


    The authors would like to acknowledge the helpful comments and
    suggestions of the following individuals:  Brian Carpenter, Edward
    Ellesson, Ray Jennings, Dilip Kandlur, Arvind Krishna, and Ken White.


    [AFREF] J Heinanen et. al., `` Assured Forwarding PHB Group'',
         Internet Draft draft-ietf-diffserv-af-04.txt, January 1999, Work
         in progress.

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    [EFREF] V. Jacobson et. al, ``An Expedited Forwarding PHB'', Internet
         Draft draft-ietf-diffserv-phb-ef-01.txt, November 1998, Work in

    [DIFFEDGE]  Y. Bernet, D. Durham and F. Reichmeyer, ``Requirements
         of Diff-Serv Boundary Routers'', Internet Draft
         draft-bernet-diffedge-01.txt, November 1998, Work in

    [DSARCH]  S. Blake, et. al. "An Architecture for Differentiated
         Services", Internet RFC 2475, December 1998.

    [DSFRAME]  Y. Bernet, J. Binder, S. Blake, et. al. " A
         Framework for Differentiated Services", Internet Draft
         <draft-ietf-diffserv-framework-01.txt>, November 1998, Work in

    [DSHEAD]  K. Nichols et. al., "Definition of the Differentiated
         Services Field (DS Byte) in the IPv4 and IPv6 Headers", Internet
         RFC 2474, December 1998.

    [POLICY]  J. Strassner and E. Ellesson, ``Policy Framework Core
         Information Model'', IETF Draft draft-ietf-policy-core-schema-00.txt,
         November 1998, Work in progress.

    [RSVPDIFF]  Y. Bernet, R. Yavatkar et. al., ``A Framework for
         use of RSVP with DiffServ Networks'', Internet Draft
         draft-ietf-diffserv-rsvp-01.txt, November 1998, Work in

    [DSERVERS]  A. Mehra et. al., ``Architectural Considerations for
         DiffServ Servers'', Internet Draft draft-mehra-diffserv-servers-01.txt,
         February 1999, Work in progress.

    [LDAP] M. Wahl et. al, ``Lightweight Directory Access Protocol(v3)'',
         Internet RFC 2251, December 1997.

    [LINUX] Werner Almesberger et. al, ``Differentiated Services on
         Linux'', Internet Draft draft-almesberger-wajhak-diffserv-linux-01.txt,
         June 1999, Work in progress.

    [ICAIR] Brian Carpenter et. al, ``Experiments with Differentiated
         Services at ICAIR'', Internet2 Workshop Presentation
         http://sss.advanced.org/meetings/houston2000, February 2000.

    [AIXDOC]  IBM Publications Austin, TX, ``AIX Version 5.0 System
         Management Guide:Communications and Networks'', IBM Publication

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         Future Release.

    [SCHEMA]  R. Rajan et. al, ``Schema for Differentiated Services
         and Integrated Services in Networks'', Internet Draft
         draft-rajan-policy-qosschema-00.txt, October 1998, Work in

    [DEN] S. Judd and J. Strassner, ``Directory Enabled Networks
         - Information Model and Base Schema'', Draft v3.0c5 DEN
         Specifications, September 1998.

Authors' Address

Ashish Mehra               Phone: (914) 784-7628
Dinesh Verma               Phone: (914) 784-7466
Renu  Tewari               Phone: (914) 784-7154
Tsipora Barzilai           Phone: (914) 697-8326
Douglas Freimuth           Phone: (914) 784-6221
Mandis Beigi               Phone: (914) 784-3277
IBM T. J. Watson Research Center
P.O. Box 704
Yorktown Heights, NY 10598
Email: mehraa,dverma,tewarir,tsipora,freimuth,mandis@watson.ibm.com

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