Network Working Group Muneyoshi Suzuki
INTERNET DRAFT NTT
Expires May 25, 1997 November 25, 1996
Architecture of the Resource Reservation Service
for the Commercial Internet
<draft-suzuki-res-resv-svc-arch-00.txt>
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Abstract
The purpose of this document is to clarify the architecture that
should be used for the resource reservation service for the
commercial Internet.
First, this document explains the basis of the tariff for current
telecommunication and Internet services. Then it clarifies problems
in the billing for Internet service, and describes how billing can be
improved by using the resource reservation setup protocol.
This document also studies technical and application models for a
commercial resource reservation service model, and clarifies an
architecture for the resource reservation setup protocol. Last, it
explains why ATM is an indispensable implementation technology for
the commercial resource reservation service, and investigates an
implementation method for a resource reservation setup protocol that
is based on ATM.
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1. Introduction
With the development of new multimedia applications, such as voice,
audio, picture, and video communication, the demands on the resource
reservation service are increasing, especially as Internet traffic
volume grows explosively due to these applications. Therefore,
tariff systems for Internet service have tended to adopt measured
rate billing, and the resource reservation setup protocol [2, 3] is
increasingly important as a method for implementing measured rate
billing.
The resource reservation setup protocol [1] must support billing if
it is to be applied to the commercial Internet, especially measured
rate billing between interconnected Internet Service Providers (ISPs)
is needed. And to investigate the implementation method of the
resource reservation setup protocol in the commercial Internet
environment is also needed.
The purpose of this document is to clarify the architecture that
should be used for the resource reservation service for the
commercial Internet. First, this document explains the basis of the
tariff for current telecommunication and Internet services. Then it
clarifies problems in the billing for Internet service, and describes
how billing can be improved by using the resource reservation setup
protocol.
This document also studies technical and application models for a
commercial resource reservation service model, and clarifies an
architecture for the resource reservation setup protocol. Last, it
explains why ATM is an indispensable implementation technology for
the commercial resource reservation service, and investigates an
implementation method for a resource reservation setup protocol that
is based on ATM.
Incidentally, it is essential to examine billing based on business
administration issues, not technical ones. For example, on a
telephone service, it technically makes sense to charge the caller
when the user being called is on another line. This is because,
telephone switches were in operation when they notified the caller
that the number he called was busy. However, such a billing policy
is contrary to the customs of business. Readers should note that the
billing problems and solutions discussed in this document are not
only based on the technical viewpoint.
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1.1 The Basis of the Tariff
Basic elements that determine the network tariff are distance,
bandwidth, time, and information volume. In many cases, the network
tariff reflects the link cost to some extent.
Note: In this document, distance means the distance between the
regions where users call from and to, not the actual length of the
physical links that connect users. In actual communication, a route
depends on network situations, so a charge based on the physical link
distance is inappropriate.
1.2 The Tariff in Telecommunication Services
Classifications of the basic styles of tariff systems in
telecommunication services and some examples are shown below. The
following classifications do not cover applied billing styles, for
example contents-based charging or premium charging such as the Dial
Q2 service of NTT, or the 900 telephone service.
o Flat-rate billing
- Leased line
In most cases, the tariff is based on distance and bandwidth.
- PVC-based frame relay and ATM
In most cases, the tariff is based on distance and bandwidth.
o Measured-rate billing
- Telephone
In most cases, the tariff is based on distance and time.
- Circuit switching
In most cases, the tariff is based on distance, bandwidth, and
time.
- SVC-based frame relay and ATM
In most cases, the tariff is based on distance, bandwidth, and
time, or information volume.
- X.25 packet switching
In most cases, the tariff is based on information volume.
Furthermore, measured rate billing is classified into calling- or
called-party billing. The basic charge style for telecommunication
service is calling-party billing.
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o Calling-party billing
- Usual telephone service
o Called-party billing
- The Free Dial service of NTT and the 800 telephone service.
Basically, telecommunication service is designed for connection-
oriented, point-to-point, and bidirectional communication. In the
case of measured-rate billing, usually the calling or the called
party pays the bidirectional communication charge. In the case of
called-party billing, a function that allows incoming calls to be
accepted or refused based on the calling-party address, or a function
that restricts the calling-party addresses that are permitted to use
called-party billing, is indispensable. This is because, the
communication charge that a called party is willing to accept is
usually limited.
The current tendency in telecommunication-service tariff systems is
to change from measured-rate billing, which reflects link costs
accurately, to flat-rate billing, which simplifies the charging
system, and service tends to be provided by flat-rate billing inside
a single provider. The tariff for services between provider is
usually the sum of the individual providers charges. Flat-rate
billing, like that within a single provider, is not currently
realistic for services that cross providers.
1.3 Tariffs for Internet Service
Classifications of basic styles and examples of the tariff system for
Internet service are shown below.
o Flat-rate billing
- Internet access via leased line, PVC-based frame relay, or ATM
In most cases, the tariff is based on bandwidth.
o Measured-rate billing
- Dialup Internet access using a modem or N-ISDN
In most cases, the tariff is based on time.
- Internet access via leased line, PVC-based frame relay, or ATM
Some ISPs have adopted information-volume-based tariff systems.
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Note: Dialup access charges in this document do not include the basic
telephone fee.
Until now, the tariff system for Internet access has mainly been
flat-rate billing, because measured-rate billing is technically
difficult to implement. However, the development of new multimedia
applications, such as voice, audio, picture, and video communication,
has caused the traffic over the Internet to increase explosively.
The cost of using the public network service is lower than when using
a private network system, if users can share equipment and lines.
However, if the traffic from all its users is at a steady high rate,
the cost advantage of the public network service is lost. Therefore,
Internet service tariff systems, although they use leased line
access, tend to adopt information-volume-based tariff systems.
2. Billing in the Resource Reservation Service
2.1 Problems of Billing in Internet Service
Basically, the tariff system for Internet service seems similar to
that for telecommunication service. However, note that the tariff
system for Internet service based on the access method from the user
site to the ISP, is not based on the end-to-end communication method.
The Internet is a connection less and unreliable communication, and
some users are beginning to use it for multicast communication. But,
the telecommunication is basically a connection-oriented, point-to-
point, and bidirectional form of communication, so telecommunication
and Intrenet communication are essentially different in some ways.
Current Internet service does not allow billing based on end-to-end
user site distance. This is because the structure of the IP address
is flat, rather than a layered structure that contains information
about the provider and region. So information about distance for
billing purpose cannot be obtained from the IP address directly.
Note: In this document, an address means an identifier, such as a
class A, B, or C IP address, that uniquely distinguishes an end
point. It does not means a group identifier such as a class D
address.
For Internet service, billing based on bandwidth can be provided, but
only for the line bandwidth between the user site and the ISP; it is
not based on the end-to-end user or application bandwidth, such as
the bandwidth in telecommunication services.
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Current Internet service, except for the dialup access, does not
allow billing based on time because the IP is a connection less
communication, and timing information about the beginning and ending
of billing is too difficult to obtain.
Some current ISPs have adopted information-volume-based tariff
systems. However, this billing is based on the information volume of
IP packets that are sent to or received from the user site and the
ISP. Again, because the IP is a connection less and unreliable
communication, it is too difficult to provide billing based on the
information volume of IP packets that are actually used between end-
to-end users or applications.
It is not impossible to provide both user billing, and application
provider billing over the Internet when particular services are used.
These forms of billing are equivalent to calling- and called-party
billing in telecommunication service. However, obtaining the timing
information about the beginning and ending of application usage at
the IP layer is too difficult because the IP is a connection less
communication. To have billing based on usage time, the service
application responsible for the bill must identify the user and
monitor the usage. Also a billing process, where part of the billing
is transferred from the user to the service provider, must be
implemented. As a result, the billing system complexity is
increased.
2.2 Improved Billing Using the Resource Reservation Setup Protocol
As explained above, billing for current commercial Internet service
has many problems, but a resource reservation setup protocol may
solve these problems.
For example, the resource reservation setup protocol ensures the
availability of end-to-end network resources, so billing based on
bandwidth (FlowSpec) between user sites may be possible. Also, the
resource reservation setup protocol explicitly shows the resource
acquire and release timings, so billing based on time may be
feasible.
The resource reservation setup protocol also guarantees QoS based on
the FlowSpec, so billing based on the information volume that is
actually used between end-to-end users or applications may also be
feasible. Furthermore, there is a possibility that the billing for
each IP flow can be distributed to ether the sender or the receiver.
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However, the resource reservation setup protocol cannot solve the
problem of how billing can be based on distance because the flat
structure of the IP address does not change and it is still
impossible to obtain information about distance for billing from the
IP address directly even when the resource reservation setup protocol
is used.
3. Model of a Commercial Resource Reservation Service
3.1 Technical Model of the Resource Reservation Service
This subsection looks at unreliable, unidirectional, and tree
structured multicast architecture as a technical model for a resource
reservation service. For the time being, the QoS to all receivers is
assumed to be the same. The following section examines heterogeneous
QoS and filter spec.
+---+
| S |
+---+
+-----------------/---\-----------------+
| a / \ b |
| / \ |
| / ISP-A /\ |
| / / \ |
| / c / \ d |
+-----------/--------/------\-----------+
+---+ +-------+ +---+
|R1 | |router | |R2 |
+---+ +-------+ +---+
+-----------------/---\-----------------+
| e / \ f |
| / \ |
| / ISP-B /\ |
| / / \ |
| / g / \ h |
+-----------/--------/------\-----------+
+---+ +---+ +---+
|R3 | |R4 | |R5 |
+---+ +---+ +---+
Fig. 3.1: Resource Reservation Service Model.
As shown in Fig. 3.1, ISP-A and ISP-B are interconnected, a sender S
and receivers R1 and R2 belong to ISP-A, and receivers R3, R4, and R5
belong to ISP-B. This subsection studies the receiver billing and
the sender billing resource reservation service with this model.
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3.1.1 Receiver billing
When the resource reservation service is provided under receiver
billing, the problem is how to bill for the shared links, such as b,
c, and f. The shared link cost must be distributed and billed to
receivers based on some rule.
One solution inside a single ISP is to adopt a tariff system that
does not depend on how the links shared between receivers. Billing
that is based on the cost of the links that make up the multicast
tree is equivalent to billing based on distance. Therefore, billing
that does not depend on the link sharing approach is equivalent to
billing that is not based on distance. This means the billing can be
based on bandwidth (FlowSpec), time, and information volume.
For example, if an interconnected destination ISP is regarded as a
receiver, ISP-A bills to R1, R2 and ISP-B, and ISP-B bills to R3, R4,
and R5 [1]. The billing from ISP-A to ISP-B is distributed based on
some rule, and is added to the base charge in ISP-B. If a large
number of users join the multicast and the statistical tendency of
network utilization is known, it is possible to provide this type of
tariff system, although it does not accurately reflect communication
costs.
Another solution is to distribute the shared link cost among the
receivers that share the link. For example, the cost of link b would
be shared by R2, R3, R4 and R5. This method does reflect accurate
communication costs. However, in practice it is difficult to
implement the billing system since the complexity of computing the
cost of the shared link, located near a sender like b, is increased
because the receiver can dynamically join and leave the multicast
tree.
Therefore, in the case of receiver billing, if many users join the
multicast and the statistical tendency of network utilization is
known, billing based on bandwidth (FlowSpec), time, and information
volume can be provided.
3.1.2 Sender billing
When the resource reservation service is provided under the sender
billing, the problem due to the shared link is avoided, because there
is no need to distribute the shared link cost. In the above model,
the sender would be billed for the link costs from a to h.
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Therefore, with sender billing, billing based on accurate link costs
can be provided. Billing based on the link cost is equivalent to
billing based on distance. However, information about distance for
billing cannot be obtained from the IP address directly. Therefore,
a database that can extract information about distance from the
destination IP address is needed to enable billing based on the link
cost.
This is also true for receiver billing: if a number of users join the
multicast and the statistical tendency of network utilization is
known, it is possible to provide billing based on bandwidth
(FlowSpec), time, and information volume. That is, the sender pays
for the billing to R1, R2, and ISP-B in ISP-A, and to R3, R4, and R5
in ISP-B.
Therefore, with sender billing, if a database is implemented that can
extract information about distance for billing from the destination
IP address, it will be possible to provide billing based on distance,
bandwidth (FlowSpec), time, and information volume. And if many
users join the multicast and the statistical tendency of network
utilization is known, it will also be possible to provide billing
based on bandwidth (FlowSpec), time, and information volume.
3.2 Application Model for the Resource Reservation Service
This subsection examines the following multimedia applications to
develop an application model for the resource reservation service.
o Broadcast-type application model
o Advertisement-type application model
o Conference-type application model
Methods of implementing the application model using the technical
model described in the previous subsection are also examined.
3.2.1 Broadcast-type application model
We assume that the broadcast-type application model has the following
features.
o The application provider broadcasts to receivers using the
multicast, and, in practice, the application is open to the public.
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o Many receivers subscribe to the broadcast, and the statistical
tendency of network utilization is known.
o Joining the multicast tree is initiated from the receiver.
o The receiver pays the full amount billed.
o The billing is based on information volume or bandwidth (FlowSpec)
and time, and not on distance.
Features of this model correspond to receiver billing in the
technical model, so it is appropriate for this model to be supported
by it. Therefore, receiver billing based on bandwidth (FlowSpec) and
time, or information volume can be provided.
3.2.2 Advertisement-type application model
We assume that the advertisement-type application model has the
following features.
o The application provider advertises to receivers using the
multicast, and, in practice, the application is open to the public.
o Many receivers subscribe to the advertisement, and the statistical
tendency of network utilization is known.
o Joining the multicast tree is initiated from the receiver side.
o The application provider pays the full amount billed.
o A function that restricts the region in which the receiver is
permitted to join, or a function that decides whether to accept or
refuse the joining request based on the IP address of the receiver
or based on the tariff to be billed, is indispensable. This is
because the communication charge that is acceptable to an
application provider is usually limited.
Features of this model roughly correspond to sender billing in the
technical model, so it is appropriate for this model to be supported
by it. But this model needs a function that restricts the region in
which the receiver is permitted to join, or a function that decides
whether to accept or refuse the joining request based on the IP
address of the receiver or based on the tariff to be billed.
If the region that the receiver is permitted to join is simply
restricted by the ISP boundary, the model can be implemented by
restricting the IP flow forwarding between ISPs.
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But if the decision to accept or refuse the joining request is based
on the IP address of the receiver or based on the tariff to be
billed, a database that can extract information about permission or
distance for billing from the destination IP address is needed. In
the resource reservation setup protocol, a procedure that supports
this kind of processing is also needed.
However, if this procedure is processed only by the sender, and the
number of receivers significantly increases, saturation of the sender
protocol processing may occur. Therefore, an intermediate node is
needed inside the multicast tree, and this intermediate node will
decide whether to accept or refuse the joining request.
Therefore, in the advertisement-type application model, if the region
that the receiver is permitted to join is simply restricted by the
ISP boundary, it is appropriate for this model to be supported by the
sender billing in the technical model. Thus, sender billing based on
bandwidth (FlowSpec) and time, or information volume, can be
provided.
If the decision to accept or refuse the joining request is based on
the IP address of the receiver or based on the tariff to be billed,
in addition to the sender billing in the technical model, a database,
that can extract information about permission or distance for billing
from the destination IP address is needed. In the resource
reservation setup protocol, a procedure that supports this process is
also needed. In this case, it can be provided by sender billing
based on distance, bandwidth (FlowSpec) and time, or information
volume.
3.2.3 Conference-type application model.
We assume that the conference-type application model has the
following features.
o The conference is held by a small number of participants.
o The statistical tendency of network utilization in the conference
depends on each conference style and the tendency is hard to
estimate.
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o Joining the conference is initiated by each participant. That is
- Joining the multicast tree from an existing participant or
receiving information from the conference server is initiated by
the receiver.
- Construction of the multicast tree for existing participants or
information sent to the conference server is initiated by the
sender.
o Management of conference participants is indispensable. A function
that can decide to accept or refuse a participation request based
on the IP address of the potential participant, or a similar
function is needed.
To avoid establishing an unreasonably expensive tariff for short
distance communications, this model needs billing based on accurate
link costs, because the tendency of network utilization is hard to
estimate.
Therefore, in this model, in addition to the sender billing from the
technical model, a database that can extract information about
permission and distance for billing from the destination IP address
is needed. In the resource reservation setup protocol, a procedure
that supports this process is also needed. In this case, it can be
provided by sender billing based on distance, bandwidth (FlowSpec)
and time, or information volume.
3.3 Architecture of the Resource Reservation Setup Protocol
A combination of the billing side and the reserve initiating side in
the resource reservation setup protocol based on the above studies is
shown in Table 3.1.
Table 3.1: Combination of Billing and Reserve Initiating Sides.
+---------------+---------------+---------------+
| Application | Billing Side |Initiating Side|
+===============+===============+===============+
| Broadcast | Receiver | Receiver |
+---------------+---------------+---------------+
| Advertisement | Sender | Receiver |
+---------------+---------------+---------------+
| Conference | Sender |Sender,Receiver|
+---------------+---------------+---------------+
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In addition to supporting all combinations of the billing side and
the reserve initiating side shown above, the commercial resource
reservation service must satisfy the following requirements for
sender billing.
o A function is needed that restricts the region that a receiver is
permitted to join, or that decides whether to accept or refuse the
joining request based on the receiver IP address and/or on the
tariff to be billed.
o If the application is open to the public, an intermediate node that
decides whether to accept or refuse the joining request is needed
inside the multicast tree.
A resource reservation setup protocol that satisfies these
requirements can be achieved with the following sender initiation
architecture.
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o The basis of the resource reservation setup protocol is sender
initiation. That is, as shown in Fig. 3.2, the sender explicitly
designates the receiver address, sends a resource reservation setup
message (SETUP), and constructs the multicast tree.
+---+
+--------| S |--------+
| +---+ |
+--------|--------/-|-\--------|--------+
| | / | \ | |
| | / | \ | |
| SETUP / SETUP /\ SETUP |
| | / | / \ | |
| | / | / \ | |
+--------|--/------ | ------\--|--------+
+-V-+ +---V---+ +-V-+
|R1 | | | |R2 |
+---+ |router | +---+
+------| |------+
| +-------+ |
+--------|--------/-|-\--------|--------+
| | / | \ | |
| | / | \ | |
| SETUP / SETUP /\ SETUP |
| | / | / \ | |
| | / | / \ | |
+--------|--/------ | ------\--|--------+
+-V-+ +-V-+ +-V-+
|R3 | |R4 | |R5 |
+---+ +---+ +---+
Fig. 3.2: Sender Initiation.
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o In the case of receiver initiation, as shown in Fig. 3.3, the
receiver explicitly sends the joining request message (JOIN), and
if the sender accepts it, the sender sends a resource reservation
setup message to the receiver.
+---+
| S |
+A--+
+-----------------/|-|\-----------------+
| / | | \ |
| / | | \ |
| JOIN| |SETUP |
| / | | / \ |
| / | |/ \ |
+-----------/------|-|------\-----------+
+---+ +----V--+ +---+
|R1 | | | |R2 |
+---+ |router | +---+
+-------> |
| +---- +-------+
+-------|-|-------/---\-----------------+
| | | / \ |
| | | / \ |
| JOIN| |SETUP /\ |
| | | / / \ |
| | | / / \ |
+-------|-|-/--------/------\-----------+
+--V+ +---+ +---+
|R3 | |R4 | |R5 |
+---+ +---+ +---+
Fig. 3.3: Receiver Initiation.
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o However, if the application is open to the public, as shown in Fig.
3.4, the intermediate node inside the multicast tree that decides
whether to accept or refuse the joining request, may send a
resource reservation setup message as a response to the joining
request message.
+---+
| S |
+---+
+-----------------/---\-----------------+
| / \ |
| / \ |
| / /\ |
| / / \ |
| / / \ |
+-----------/--------/------\-----------+
+---+ +-------+ +---+
|R1 | | | |R2 |
+---+ | node | +---+
+-------> |
| +---- +-------+
+-------|-|-------/---\-----------------+
| | | / \ |
| | | / \ |
| JOIN| |SETUP /\ |
| | | / / \ |
| | | / / \ |
+-------|-|-/--------/------\-----------+
+--V+ +---+ +---+
|R3 | |R4 | |R5 |
+---+ +---+ +---+
Fig. 3.4: Intermediate Node.
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4. Implementation Method of the Resource Reservation Setup Protocol
4.1 Datalink Media for the Commercial Resource Reservation Service
The resource reservation setup protocol can designate the end-to-end
resource to be reserved, but the datalink layer actually has
responsibility for reservation and QoS control. Current datalink
media that can control QoS are ATM, PPP over SDH/SONET with packet
scheduler, serial line with packet scheduler, IEEE 802.9 isoEthernet,
IEEE 802.12 100VG-Any LAN, and Ethernet/Token Ring with IEEE 802.1p.
The I/O channel media are IEEE 1394 and Universal Serial Bus. Inside
the user site, these media may be used.
However, every node in the commercial resource reservation service
backbone will have to handle between 1,000 and 10,000 IP flows
initiated by users. To handle such a large volume of IP flow, the IP
flow must be processed by hardware on a high-speed line interface
such as SDH/SONET.
The SDH/SONET hierarchy is defined as being a four times rate, 155M,
622M, 2.4G, and 10G bps. However, in an actual network, there is a
strong possibility that a 622 Mbps line cannot handle all of the
traffic, but there is no demand for a 2.4 Gbps line speed. In the
commercial WAN environment, the intermediate-speed link, which is not
supported by SDH/SONET, is provided by the ATM connection on the
SDH/SONET. So, the use of ATM enables economical networks that can
meet the traffic demand. After all, if, and only if, PPP over
SDH/SONET is implemented by hardware, there is a possibility that
speeds equivalent to ATM speeds can be attained over SDH/SONET, but
economically this is entirely inappropriate for commercial network
service.
If SVC ATM is used as the datalink media of the resource reservation
service, it may be possible to solve the problem that prevents
billing based on distance without needing a database, that can
extract information about distance for billing from the destination
IP address. In this case, the E.164/NSAP, which are layered
structure addresses and which contain information about provider and
region, can be used.
Therefore, ATM is an indispensable implementation technology for the
commercial resource reservation service, and there is no room for any
other selection. The remainder of this section examines an
implementation method of the resource reservation setup protocol
based on ATM.
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4.2 Mapping of ATM VC and IP Flow
An IP flow and an ATM VC must be mapped one-to-one, and must not
aggregate multiple IP flows to single ATM VC, because ATM itself has
the traffic control function. It is only wasteful to control both
the ATM-layer and the IP-layer traffic, and has no effect other than
to raise equipment cost and increase processing overhead.
An IP flow also must not be divided among multiple ATM VCs.
Synchronization between multiple ATM VCs to the same destination is
not guaranteed. Therefore, synchronized information would be needed
between ATM VCs, and this causes unnecessary overhead, decreases the
reliability of the IP flow, and wastes network resources.
4.3 Dynamic QoS Changes
The need to change QoS in an ATM system is a serious problem. Part
of the ITU-T SCS2 signaling protocol, Q.2963.1 specifies a procedure
to change the peak rate, but this is not sufficient as a procedure to
change QoS. Also, signaling procedures in ATM Forum UNI 3.1/4.0 do
not support QoS changes. ITU-T traffic control recommendation I.371
and ATM Forum UNI 3.1/4.0 do not specify traffic behavior during QoS
changing. The only possibility is ABT, which is defined in I.371 and
supports QoS changes initiated by F5 OAM. Unfortunately, the current
ABT supports point-to-point connection only.
Therefore, current ATM standards cannot support QoS changes in
practice. There is a possibility that QoS changes can be supported
in the resource reservation service by releasing old ATM connections
and establishing new ones, but this method causes the following
problems.
o Network overload may be caused by call processing.
o Since call processing is closely related to ATM billing, the
billing system complexity is increased.
o New calls are not always successfully established.
It is also feasible to establish new ATM connections and then release
old ones, but this method causes the following problems.
o The current ATM NIC for WS/PC does not support a large number of
QoS VCs.
o Although it is only temporary, old and new VCs exist
simultaneously, which increases the complexity of the billing
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system.
o New calls are not always successfully established. Especially,
there is a possibility that only part of point-to-multipoint call
will be reestablished successfully. This increases the complexity
of exception processing.
Therefore, QoS changes by signaling are impractical under current ATM
standards, but should be supported after ATM standards specify it.
ITU-T SG11 and SG13 and ATM Forum SIG SWG and TM SWG should specify a
procedure for dynamic QoS changes and traffic behavior during QoS
changing. Additional research on point-to-multipoint ABT is also
needed.
4.4 Heterogeneous QoS
Heterogeneous QoS, which not always the same at each receivers, is
not supported by ATM point-to-multipoint connection. Originally, the
concept of heterogeneous QoS was introduced to support hierarchical
coded IP flow. But as described in [6], it should be supported by a
presentation layer, and it is not responsible for the network and
transport layers. In single-node operation, IP packet discarding
based on contents is needed to support an IP flow that has
heterogeneous QoS. But the network and transport layer cannot
support such processing.
When multiple receivers require different QoS, it does not make sense
to establish a point-to-multipoint VC based on the largest QoS
request.
However a point-to-multipoint VC is established based on the maximum
QoS, when a receiver that requests a larger QoS joins the multicast
tree, or when the receiver that requested the largest QoS leaves the
tree, and the QoS of the VC must be changed. However, current ATM
standards cannot support such QoS changes.
Also it does not have any advantage in terms of the tariff. The
billing for a resource reservation service may be based on the QoS
acquired in the ATM layer, which may be larger than the QoS requested
in the IP layer. Therefore, to use the QoS from the ATM layer is
obviously better for the IP flow.
As explained above, current ATM standards cannot support
heterogeneous QoS, and it does not offer any advantage in terms of
tariff.
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4.5 Filter Spec
ATM does not support a function, that merges information from various
VCs, such as filter spec. It should also be supported by a
presentation layer, and is not responsible for the network and
transport layers.
5. Conclusions
This document clarified the followings in terms of an architecture
for the resource reservation setup protocol.
o The basis of the resource reservation setup protocol is sender
initiation. That is, the sender explicitly designates the receiver
address, sends a resource reservation setup message and constructs
a multicast tree.
o In the case of receiver initiation, the receiver explicitly sends a
joining request message; if the sender accepts it, the sender sends
a resource reservation setup message to the receiver.
o However, if the application is open to the public, an intermediate
node inside the multicast tree decides whether to accept or refuse
the joining request, and may send a resource reservation setup
message as a response to the joining request message.
ATM is an indispensable implementation technology for the commercial
resource reservation service, and the following were clarified in
terms of an implementation method of the resource reservation setup
protocol based on ATM.
o An IP flow and an ATM VC must be mapped one-to-one.
o In practice, current ATM standards cannot support dynamic QoS
changes. Such changes should be supported after the ATM standard
specifies it.
o Current ATM standards cannot support heterogeneous QoS, which also
does not have any advantage in terms of tariff. The hierarchical
coded IP flow should be supported by the presentation layer.
o Filter spec should be supported by the presentation layer.
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Finally, if the billing policies of ISPs are fundamentally different
from each other in the commercial resource reservation service, it
will be difficult to achieve smooth interconnection. Therefore, the
author believes that ISPs need to conclude agreements or to clarify
recommendations concerning minimum common billing policies for the
resource reservation service, especially on the definition of
distance for billing purpose.
6. Security Considerations
Security considerations are not discussed in this document.
References
[1] S. Herzog, "Accounting and Access Control Policies for
Resource Reservation Protocols," Internet Draft, June 1996,
<draft-ietf-rsvp-policy-arch-00.ps>.
[2] R. Braden Ed., "Resource ReSerVation Protocol (RSVP)-Version 1
Functional Specification," Internet Draft, October 1996, <draft-
ietf-rsvp-spec-14.ps>.
[3] L. Delgrossi and L. Berger, Ed., "Internet Stream Protocol
Version 2 (ST2) Protocol Specification - Version ST2+," RFC 1819,
August 1995.
[4] S. Berson and L. Berger, "IP Integrated Services with RSVP
over ATM," Internet Draft, September 1996, <draft-ietf-issll-atm-
support-01.ps>.
[5] M. Borden and M. Garrett, "Interoperation of Controlled-Load
and Guaranteed-Service with ATM," Internet Draft, September 1996,
<draft-issll-intserv-atm-mapping-01.txt>.
[6] K. Sebayashi and H. Uose, "ATM Multicast Communications Method
with Receiver-initiated QoS Guarantee," Global Information
Infrastructure Evolution, ISBN 90-5199-290-4, IOS Press, 1996.
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Acknowledgments
This document is based on my discussions with many colleagues at
NTT. I would like to specially thank Hiroshi Ishikawa, Sadahiko
Kanou, Masaru Nishi, Satoshi Takamatsu, and Hideaki Arai of the
NTT Network Strategy Planning Dept., and also Hisao Uose of the
NTT Multimedia Networks Labs. for their valuable comments.
Also section 4 of this document is based on various discussions
during NTT Multimedia Joint Project with NACSIS. I would like to
thank Prof. Shoichiro Asano of National Center for Science
Information Systems for his invaluable advice in this area.
Author's Address
Muneyoshi Suzuki
NTT Multimedia Networks Laboratories
3-9-11, Midori-cho
Musashino-shi, Tokyo 180, Japan
Phone: +81-422-59-2119
Fax: +81-422-59-3203
EMail: suzuki@nal.ecl.net
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