Internet Engineering Task Force E. Crawley, Editor
Internet Draft (Argon Networks)
draft-ietf-issll-atm-framework-02.txt L. Berger
(Fore Systems)
S. Berson
(ISI)
F. Baker
(Cisco Systems)
M. Borden
(Bay Networks)
J. Krawczyk
(ArrowPoint Communications)
February 9, 1998
A Framework for Integrated Services and RSVP over ATM
Status of this Memo
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Abstract
This document outlines the issues and framework related to providing IP
Integrated Services with RSVP over ATM. It provides an overall approach
to the problem(s) and related issues. These issues and problems are to
be addressed in further documents from the ISATM subgroup of the ISSLL
working group.
Editor's Note
This document is the merger of two previous documents, draft-ietf-
issll-atm-support-02.txt by Berger and Berson and draft-crawley-rsvp-
over-atm-00.txt by Baker, Berson, Borden, Crawley, and Krawczyk. The
former document has been split into this document and a set of
documents on RSVP over ATM implementation requirements and guidelines.
1. Introduction
The Internet currently has one class of service normally referred to as
"best effort." This service is typified by first-come, first-serve
scheduling at each hop in the network. Best effort service has worked
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well for electronic mail, World Wide Web (WWW) access, file transfer
(e.g. ftp), etc. For real-time traffic such as voice and video, the
current Internet has performed well only across unloaded portions of
the network. In order to provide quality real-time traffic, new
classes of service and a QoS signalling protocol are being introduced
in the Internet [1,6,7], while retaining the existing best effort
service. The QoS signalling protocol is RSVP [1], the Resource
7ReSerVation Protocol and the service models
One of the important features of ATM technology is the ability to
request a point-to-point Virtual Circuit (VC) with a specified Quality
of Service (QoS). An additional feature of ATM technology is the
ability to request point-to-multipoint VCs with a specified QoS.
Point-to-multipoint VCs allows leaf nodes to be added and removed from
the VC dynamically and so provides a mechanism for supporting IP
multicast. It is only natural that RSVP and the Internet Integrated
Services (IIS) model would like to utilize the QoS properties of any
underlying link layer including ATM, and this draft concentrates on
ATM.
Classical IP over ATM [10] has solved part of this problem, supporting
IP unicast best effort traffic over ATM. Classical IP over ATM is
based on a Logical IP Subnetwork (LIS), which is a separately
administered IP subnetwork. Hosts within an LIS communicate using the
ATM network, while hosts from different subnets communicate only by
going through an IP router (even though it may be possible to open a
direct VC between the two hosts over the ATM network). Classical IP
over ATM provides an Address Resolution Protocol (ATMARP) for ATM edge
devices to resolve IP addresses to native ATM addresses. For any pair
of IP/ATM edge devices (i.e. hosts or routers), a single VC is created
on demand and shared for all traffic between the two devices. A second
part of the RSVP and IIS over ATM problem, IP multicast, is being
solved with MARS [5], the Multicast Address Resolution Server.
MARS compliments ATMARP by allowing an IP address to resolve into a
list of native ATM addresses, rather than just a single address.
The ATM Forum's LAN Emulation (LANE) [17, 20] and Multiprotocol Over
ATM (MPOA) [18] also address the support of IP best effort traffic over
ATM through similar means.
A key remaining issue for IP in an ATM environment is the integration
of RSVP signalling and ATM signalling in support of the Internet
Integrated Services (IIS) model. There are two main areas involved in
supporting the IIS model, QoS translation and VC management. QoS
translation concerns mapping a QoS from the IIS model to a proper ATM
QoS, while VC management concentrates on how many VCs are needed and
which traffic flows are routed over which VCs.
1.1 Structure and Related Documents
This document provides a guide to the issues for IIS over ATM. It is
intended to frame the problems that are to be addressed in further
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documents. In this document, the modes and models for RSVP operation
over ATM will be discussed followed by a discussion of management of
ATM VCs for RSVP data and control. Lastly, the topic of encapsulations
will be discussed in relation to the models presented.
This document is part of a group of documents from the ISATM subgroup
of the ISSLL working group related to the operation of IntServ and RSVP
over ATM. [14] discusses the mapping of the IntServ models for
Controlled Load and Guaranteed Service to ATM. [15 and 16] discuss
detailed implementation requirements and guidelines for RSVP over ATM,
respectively. While these documents may not address all the issues
raised in this document, they should provide enough information for
development of solutions for IntServ and RSVP over ATM.
1.2 Terms
Several term used in this document are used in many contexts, often
with different meaning. These terms are used in this document with the
following meaning:
- Sender is used in this document to mean the ingress point to the ATM
network or "cloud".
- Receiver is used in this document to refer to the egress point from
the ATM network or "cloud".
- Reservation is used in this document to refer to an RSVP initiated
request for resources. RSVP initiates requests for resources based
on RESV message processing. RESV messages that simply refresh state
do not trigger resource requests. Resource requests may be made
based on RSVP sessions and RSVP reservation styles. RSVP styles
dictate whether the reserved resources are used by one sender or
shared by multiple senders. See [1] for details of each. Each new
request is referred to in this document as an RSVP reservation, or
simply reservation.
- Flow is used to refer to the data traffic associated with a
particular reservation. The specific meaning of flow is RSVP style
dependent. For shared style reservations, there is one flow per
session. For distinct style reservations, there is one flow per
sender (per session).
2. Issues Regarding the Operation of RSVP and IntServ over ATM
The issues related to RSVP and IntServ over ATM fall into several
general classes:
- How to make RSVP run over ATM now and in the future
- When to set up a virtual circuit (VC) for a specific Quality of
Service (QoS) related to RSVP
- How to map the IntServ models to ATM QoS models
- How to know that an ATM network is providing the QoS necessary for a
flow
- How to handle the many-to-many connectionless features of IP
multicast and RSVP in the one-to-many connection-oriented world of
ATM
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2.1 Modes/Models for RSVP and IntServ over ATM
[3] Discusses several different models for running IP over ATM
networks. [17, 18, and 20] also provide models for IP in ATM
environments. Any one of these models would work as long as the RSVP
control packets (IP protocol 46) and data packets can follow the same
IP path through the network. It is important that the RSVP PATH
messages follow the same IP path as the data such that appropriate PATH
state may be installed in the routers along the path. For an ATM
subnetwork, this means the ingress and egress points must be the same
in both directions for the RSVP control and data messages. Note that
the RSVP protocol does not require symmetric routing. The PATH state
installed by RSVP allows the RESV messages to "retrace" the hops that
the PATH message crossed. Within each of the models for IP over ATM,
there are decisions about using different types of data distribution in
ATM as well as different connection initiation. The following sections
look at some of the different ways QoS connections can be set up for
RSVP.
2.1.1 UNI 3.x and 4.0
In the User Network Interface (UNI) 3.0 and 3.1 specifications [8,9]
and 4.0 specification, both permanent and switched virtual circuits
(PVC and SVC) may be established with a specified service category
(CBR, VBR, and UBR for UNI 3.x and VBR-rt and ABR for 4.0) and specific
traffic descriptors in point-to-point and point-to-multipoint
configurations. Additional QoS parameters are not available in UNI 3.x
and those that are available are vendor-specific. Consequently, the
level of QoS control available in standard UNI 3.x networks is somewhat
limited. However, using these building blocks, it is possible to use
RSVP and the IntServ models. ATM 4.0 with the Traffic Management (TM)
4.0 specification [21] allows much greater control of QoS. [14]
provides the details of mapping the IntServ models to UNI 3.x and 4.0
service categories and traffic parameters.
2.1.1.1 Permanent Virtual Circuits (PVCs)
PVCs emulate dedicated point-to-point lines in a network, so the
operation of RSVP can be identical to the operation over any point-to-
point network. The QoS of the PVC must be consistent and equivalent to
the type of traffic and service model used. The devices on either end
of the PVC have to provide traffic control services in order to
multiplex multiple flows over the same PVC. With PVCs, there is no
issue of when or how long it takes to set up VCs, since they are made
in advance but the resources of the PVC are limited to what has been
pre-allocated. PVCs that are not fully utilized can tie up ATM network
resources that could be used for SVCs.
An additional issue for using PVCs is one of network engineering.
Frequently, multiple PVCs are set up such that if all the PVCs were
running at full capacity, the link would be over-subscribed. This
frequently used "statistical multiplexing gain" makes providing IIS
over PVCs very difficult and unreliable. Any application of IIS over
PVCs has to be assured that the PVCs are able to receive all the
requested QoS.
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2.1.1.2 Switched Virtual Circuits (SVCs)
SVCs allow paths in the ATM network to be set up "on demand". This
allows flexibility in the use of RSVP over ATM along with some
complexity. Parallel VCs can be set up to allow best-effort and better
service class paths through the network, as shown in Figure 1. The
cost and time to set up SVCs can impact their use. For example, it may
be better to initially route QoS traffic over existing VCs until a SVC
with the desired QoS can be set up for the flow. Scaling issues can
come into play if a single RSVP flow is used per VC, as will be
discussed in Section 4.3.1.1. The number of VCs in any ATM device may
also be limited so the number of RSVP flows that can be supported by a
device can be strictly limited to the number of VCs available, if we
assume one flow per VC. Section 4 discusses the topic of VC management
for RSVP in greater detail.
Data Flow ==========>
+-----+
| | --------------> +----+
| Src | --------------> | R1 |
| *| --------------> +----+
+-----+ QoS VCs
/\
||
VC ||
Initiator
Figure 1: Data Flow VC Initiation
While RSVP is receiver oriented, ATM is sender oriented. This might
seem like a problem but the sender or ingress point receives RSVP RESV
messages and can determine whether a new VC has to be set up to the
destination or egress point.
2.1.1.3 Point to MultiPoint
In order to provide QoS for IP multicast, an important feature of RSVP,
data flows must be distributed to multiple destinations from a given
source. Point-to-multipoint VCs provide such a mechanism. It is
important to map the actions of IP multicasting and RSVP (e.g. IGMP
JOIN/LEAVE and RSVP RESV/RESV TEAR) to add party and drop party
functions for ATM. Point-to-multipoint VCs as defined in UNI 3.x and
UNI 4.0 have a single service class for all destinations. This is
contrary to the RSVP "heterogeneous receiver" concept. It is possible
to set up a different VC to each receiver requesting a different QoS,
as shown in Figure 2. This again can run into scaling and resource
problems when managing multiple VCs on the same interface to different
destinations.
+----+
+------> | R1 |
| +----+
|
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| +----+
+-----+ -----+ +--> | R2 |
| | ---------+ +----+ Receiver Request
Types:
| Src | ----> QoS 1 and QoS
2
| | .........+ +----+ ....> Best-Effort
+-----+ .....+ +..> | R3 |
: +----+
/\ :
|| : +----+
|| +......> | R4 |
|| +----+
Single
IP Mulicast
Group
Figure 2: Types of Multicast Receivers
RSVP sends messages both up and down the multicast distribution tree.
In the case of a large ATM cloud, this could result in a RSVP message
implosion at an ATM ingress point with many receivers.
ATM 4.0 expands on the point-to-multipoint VCs by adding a Leaf
Initiated Join (LIJ) capability. LIJ allows an ATM end point to join
into an existing point-to-multipoint VC without necessarily contacting
the source of the VC. This can reduce the burden on the ATM source
point for setting up new branches and more closely matches the
receiver-based model of RSVP and IP multicast. However, many of the
same scaling issues exist and the new branches added to a point-to-
multipoint VC must use the same QoS as existing branches.
2.1.1.4 Multicast Servers
IP-over-ATM has the concept of a multicast server or reflector that can
accept cells from multiple senders and send them via a point-to-
multipoint VC to a set of receivers. This moves the VC scaling issues
noted previously for point-to-multipoint VCs to the multicast server.
Additionally, the multicast server will need to know how to interpret
RSVP packets or receive instruction from another node so it will be
able to provide VCs of the appropriate QoS for the RSVP flows.
2.1.2 Hop-by-Hop vs. Short Cut
If the ATM "cloud" is made up a number of logical IP subnets (LISs),
then it is possible to use "short cuts" from a node on one LIS directly
to a node on another LIS, avoiding router hops between the LISs. NHRP
[4], is one mechanism for determining the ATM address of the egress
point on the ATM network given a destination IP address. It is a topic
for further study to determine if significant benefit is achieved from
short cut routes vs. the extra state required.
2.1.3 Future Models
ATM is constantly evolving. If we assume that RSVP and IntServ
applications are going to be wide-spread, it makes sense to consider
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changes to ATM that would improve the operation of RSVP and IntServ
over ATM. Similarly, the RSVP protocol and IntServ models will
continue to evolve and changes that affect them should also be
considered. The following are a few ideas that have been discussed
that would make the integration of the IntServ models and RSVP easier
or more complete. They are presented here to encourage continued
development and discussion of ideas that can help aid in the
integration of RSVP, IntServ, and ATM.
2.1.3.1 Heterogeneous Point-to-MultiPoint
The IntServ models and RSVP support the idea of "heterogeneous
receivers"; e.g., not all receivers of a particular multicast flow are
required to ask for the same QoS from the network, as shown in Figure
2.
The most important scenario that can utilize this feature occurs when
some receivers in an RSVP session ask for a specific QoS while others
receive the flow with a best-effort service. In some cases where there
are multiple senders on a shared-reservation flow (e.g., an audio
conference), an individual receiver only needs to reserve enough
resources to receive one sender at a time. However, other receivers
may elect to reserve more resources, perhaps to allow for some amount
of "over-speaking" or in order to record the conference (post
processing during playback can separate the senders by their source
addresses).
In order to prevent denial-of-service attacks via reservations, the
service models do not allow the service elements to simply drop non-
conforming packets. For example, Controlled Load service model [7]
assigns non-conformant packets to best-effort status (which may result
in packet drops if there is congestion).
Emulating these behaviors over an ATM network is problematic and needs
to be studied. If a single maximum QoS is used over a point-to-
multipoint VC, resources could be wasted if cells are sent over certain
links where the reassembled packets will eventually be dropped. In
addition, the "maximum QoS" may actually cause a degradation in service
to the best-effort branches.
The term "variegated VC" has been coined to describe a point-to-
multipoint VC that allows a different QoS on each branch. This approach
seems to match the spirit of the Integrated Service and RSVP models,
but some thought has to be put into the cell drop strategy when
traversing from a "bigger" branch to a "smaller" one. The "best-effort
for non-conforming packets" behavior must also be retained. Early
Packet Discard (EPD) schemes must be used so that all the cells for a
given packet can be discarded at the same time rather than discarding
only a few cells from several packets making all the packets useless to
the receivers.
2.1.3.2 Lightweight Signalling
Q.2931 signalling is very complete and carries with it a significant
burden for signalling in all possible public and private connections.
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It might be worth investigating a lighter weight signalling mechanism
for faster connection setup in private networks.
2.1.3.3 QoS Renegotiation
Another change that would help RSVP over ATM is the ability to request
a different QoS for an active VC. This would eliminate the need to
setup and tear down VCs as the QoS changed. RSVP allows receivers to
change their reservations and senders to change their traffic
descriptors dynamically. This, along with the merging of reservations,
can create a situation where the QoS needs of a VC can change.
Allowing changes to the QoS of an existing VC would allow these
features to work without creating a new VC. In the ITU-T ATM
specifications [24,25], some cell rates can be renegotiated or changed.
Specifically, the Peak Cell Rate (PCR) of an existing VC can be changed
and, in some cases, QoS parameters may be renegotiated during the call
setup phase. It is unclear if this is sufficient for the QoS
renegotiation needs of the IntServ models.
2.1.3.4 Group Addressing
The model of one-to-many communications provided by point-to-multipoint
VCs does not really match the many-to-many communications provided by
IP multicasting. A scaleable mapping from IP multicast addresses to an
ATM "group address" can address this problem.
2.1.3.5 Label Switching
The MultiProtocol Label Switching (MPLS) working group is discussing
methods for optimizing the use of ATM and other switched networks for
IP by encapsulating the data with a header that is used by the interior
switches to achieve faster forwarding lookups. [22] discusses a
framework for this work. It is unclear how this work will affect
IntServ and RSVP over label switched networks but there may be some
interactions.
2.1.4 QoS Routing
RSVP is explicitly not a routing protocol. However, since it conveys
QoS information, it may prove to be a valuable input to a routing
protocol that can make path determinations based on QoS and network
load information. In other words, instead of asking for just the IP
next hop for a given destination address, it might be worthwhile for
RSVP to provide information on the QoS needs of the flow if routing has
the ability to use this information in order to determine a route.
Other forms of QoS routing have existed in the past such as using the
IP TOS and Precedence bits to select a path through the network. Some
have discussed using these same bits to select one of a set of parallel
ATM VCs as a form of QoS routing. ATM routing has also considered the
problem of QoS routing through the Private Network-to-Network Interface
(PNNI) [26] routing protocol for routing ATM VCs on a path that can
support their needs. The work in this area is just starting and there
are numerous issues to consider. [23], as part of the work of the QoSR
working group frame the issues for QoS Routing in the Internet.
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2.2 Reliance on Unicast and Multicast Routing
RSVP was designed to support both unicast and IP multicast
applications. This means that RSVP needs to work closely with
multicast and unicast routing. Unicast routing over ATM has been
addressed [10] and [11]. MARS [5] provides multicast address
resolution for IP over ATM networks, an important part of the solution
for multicast but still relies on multicast routing protocols to
connect multicast senders and receivers on different subnets.
2.3 Aggregation of Flows
Some of the scaling issues noted in previous sections can be addressed
by aggregating several RSVP flows over a single VC if the destinations
of the VC match for all the flows being aggregated. However, this
causes considerable complexity in the management of VCs and in the
scheduling of packets within each VC at the root point of the VC. Note
that the rescheduling of flows within a VC is not possible in the
switches in the core of the ATM network. Virtual Paths (VPs) can be
used for aggregating multiple VCs. This topic is discussed in greater
detail as it applies to multicast data distribution in section 4.2.3.4
2.4 Mapping QoS Parameters
The mapping of QoS parameters from the IntServ models to the ATM
service classes is an important issue in making RSVP and IntServ work
over ATM. [14] addresses these issues very completely for the
Controlled Load and Guaranteed Service models. An additional issue is
that while some guidelines can be developed for mapping the parameters
of a given service model to the traffic descriptors of an ATM traffic
class, implementation variables, policy, and cost factors can make
strict mapping problematic. So, a set of workable mappings that can be
applied to different network requirements and scenarios is needed as
long as the mappings can satisfy the needs of the service model(s).
2.5 Directly Connected ATM Hosts
It is obvious that the needs of hosts that are directly connected to
ATM networks must be considered for RSVP and IntServ over ATM.
Functionality for RSVP over ATM must not assume that an ATM host has
all the functionality of a router, but such things as MARS and NHRP
clients would be worthwhile features. A host must managed VCs just
like any other ATM sender or receiver as described later in section 4.
2.6 Accounting and Policy Issues
Since RSVP and IntServ create classes of preferential service, some
form of administrative control and/or cost allocation is needed to
control access. There are certain types of policies specific to ATM
and IP over ATM that need to be studied to determine how they
interoperate with the IP and IntServ policies being developed. Typical
IP policies would be that only certain users are allowed to make
reservations. This policy would translate well to IP over ATM due to
the similarity to the mechanisms used for Call Admission Control (CAC).
There may be a need for policies specific to IP over ATM. For example,
since signalling costs in ATM are high relative to IP, an IP over ATM
specific policy might restrict the ability to change the prevailing QoS
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in a VC. If VCs are relatively scarce, there also might be specific
accounting costs in creating a new VC. The work so far has been
preliminary, and much work remains to be done. The policy mechanisms
outlined in [12] and [13] provide the basic mechanisms for implementing
policies for RSVP and IntServ over any media, not just ATM.
3. Framework for IntServ and RSVP over ATM
Now that we have defined some of the issues for IntServ and RSVP over
ATM, we can formulate a framework for solutions. The problem breaks
down to two very distinct areas; the mapping of IntServ models to ATM
service categories and QoS parameters and the operation of RSVP over
ATM.
Mapping IntServ models to ATM service categories and QoS parameters is
a matter of determining which categories can support the goals of the
service models and matching up the parameters and variables between the
IntServ description and the ATM description(s). Since ATM has such a
wide variety of service categories and parameters, more than one ATM
service category should be able to support each of the two IntServ
models. This will provide a good bit of flexibility in configuration
and deployment. [14] examines this topic completely.
The operation of RSVP over ATM requires careful management of VCs in
order to match the dynamics of the RSVP protocol. VCs need to be
managed for both the RSVP QoS data and the RSVP signalling messages.
The remainder of this document will discuss several approaches to
managing VCs for RSVP and [15] and [16] discuss their application for
implementations in term of interoperability requirement and
implementation guidelines.
4. RSVP VC Management
This section provides more detail on the issues related to the
management of SVCs for RSVP and IntServ.
4.1 VC Initiation
As discussed in section 2.1.1.2, there is an apparent mismatch between
RSVP and ATM. Specifically, RSVP control is receiver oriented and ATM
control is sender oriented. This initially may seem like a major
issue, but really is not. While RSVP reservation (RESV) requests are
generated at the receiver, actual allocation of resources takes place
at the subnet sender. For data flows, this means that subnet senders
will establish all QoS VCs and the subnet receiver must be able to
accept incoming QoS VCs, as illustrated in Figure 1. These
restrictions are consistent with RSVP version 1 processing rules and
allow senders to use different flow to VC mappings and even different
QoS renegotiation techniques without interoperability problems.
The use of the reverse path provided by point-to-point VCs by receivers
is for further study. There are two related issues. The first is that
use of the reverse path requires the VC initiator to set appropriate
reverse path QoS parameters. The second issue is that reverse paths are
not available with point-to-multipoint VCs, so reverse paths could only
be used to support unicast RSVP reservations.
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4.2 Data VC Management
Any RSVP over ATM implementation must map RSVP and RSVP associated data
flows to ATM Virtual Circuits (VCs). LAN Emulation [17], Classical IP
[10] and, more recently, NHRP [4] discuss mapping IP traffic onto ATM
SVCs, but they only cover a single QoS class, i.e., best effort
traffic. When QoS is introduced, VC mapping must be revisited. For RSVP
controlled QoS flows, one issue is VCs to use for QoS data flows.
In the Classic IP over ATM and current NHRP models, a single point-to-
point VC is used for all traffic between two ATM attached hosts
(routers and end-stations). It is likely that such a single VC will
not be adequate or optimal when supporting data flows with multiple QoS
types. RSVP's basic purpose is to install support for flows with
multiple QoS types, so it is essential for any RSVP over ATM solution
to address VC usage for QoS data flows, as shown in Figure 1.
RSVP reservation styles must also be taken into account in any VC usage
strategy.
This section describes issues and methods for management of VCs
associated with QoS data flows. When establishing and maintaining VCs,
the subnet sender will need to deal with several complicating factors
including multiple QoS reservations, requests for QoS changes, ATM
short-cuts, and several multicast specific issues. The multicast
specific issues result from the nature of ATM connections. The key
multicast related issues are heterogeneity, data distribution, receiver
transitions, and end-point identification.
4.2.1 Reservation to VC Mapping
There are various approaches available for mapping reservations on to
VCs. A distinguishing attribute of all approaches is how reservations
are combined on to individual VCs. When mapping reservations on to
VCs, individual VCs can be used to support a single reservation, or
reservation can be combined with others on to "aggregate" VCs. In the
first case, each reservation will be supported by one or more VCs.
Multicast reservation requests may translate into the setup of multiple
VCs as is described in more detail in section 4.2.2. Unicast
reservation requests will always translate into the setup of a single
QoS VC. In both cases, each VC will only carry data associated with a
single reservation. The greatest benefit if this approach is ease of
implementation, but it comes at the cost of increased (VC) setup time
and the consumption of greater number of VC and associated resources.
When multiple reservations are combined onto a single VC, it is
referred to as the "aggregation" model. With this model, large VCs
could be set up between IP routers and hosts in an ATM network. These
VCs could be managed much like IP Integrated Service (IIS) point-to-
point links (e.g. T-1, DS-3) are managed now. Traffic from multiple
sources over multiple RSVP sessions might be multiplexed on the same
VC. This approach has a number of advantages. First, there is
typically no signalling latency as VCs would be in existence when the
traffic started flowing, so no time is wasted in setting up VCs.
Second, the heterogeneity problem (section 4.2.2) in full over ATM has
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been reduced to a solved problem. Finally, the dynamic QoS problem
(section 4.2.7) for ATM has also been reduced to a solved problem.
The aggregation model can be used with point-to-point and point-to-
multipoint VCs. The problem with the aggregation model is that the
choice of what QoS to use for the VCs may be difficult, without
knowledge of the likely reservation types and sizes but is made easier
since the VCs can be changed as needed.
4.2.2 Unicast Data VC Management
Unicast data VC management is much simpler than multicast data VC
management but there are still some similar issues. If one considers
unicast to be a devolved case of multicast, then implementing the
multicast solutions will cover unicast. However, some may want to
consider unicast-only implementations. In these situations, the choice
of using a single flow per VC or aggregation of flows onto a single VC
remains but the problem of heterogeneity discussed in the following
section is removed.
4.2.3 Multicast Heterogeneity
As mentioned in section 2.1.3.1 and shown in figure 2, multicast
heterogeneity occurs when receivers request different qualities of
service within a single session. This means that the amount of
requested resources differs on a per next hop basis. A related type of
heterogeneity occurs due to best-effort receivers. In any IP multicast
group, it is possible that some receivers will request QoS (via RSVP)
and some receivers will not. In shared media networks, like Ethernet,
receivers that have not requested resources can typically be given
identical service to those that have without complications. This is
not the case with ATM. In ATM networks, any additional end-points of a
VC must be explicitly added. There may be costs associated with adding
the best-effort receiver, and there might not be adequate resources.
An RSVP over ATM solution will need to support heterogeneous receivers
even though ATM does not currently provide such support directly.
RSVP heterogeneity is supported over ATM in the way RSVP reservations
are mapped into ATM VCs. There are four alternative approaches this
mapping. There are multiple models for supporting RSVP heterogeneity
over ATM. Section 4.2.3.1 examines the multiple VCs per RSVP
reservation (or full heterogeneity) model where a single reservation
can be forwarded onto several VCs each with a different QoS. Section
4.2.3.2 presents a limited heterogeneity model where exactly one QoS VC
is used along with a best effort VC. Section 4.2.3.3 examines the VC
per RSVP reservation (or homogeneous) model, where each RSVP
reservation is mapped to a single ATM VC. Section 4.2.3.4 describes
the aggregation model allowing aggregation of multiple RSVP
reservations into a single VC.
4.2.3.1 Full Heterogeneity Model
RSVP supports heterogeneous QoS, meaning that different receivers of
the same multicast group can request a different QoS. But importantly,
some receivers might have no reservation at all and want to receive the
traffic on a best effort service basis. The IP model allows receivers
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to join a multicast group at any time on a best effort basis, and it is
important that ATM as part of the Internet continue to provide this
service. We define the "full heterogeneity" model as providing a
separate VC for each distinct QoS for a multicast session including
best effort and one or more qualities of service.
Note that while full heterogeneity gives users exactly what they
request, it requires more resources of the network than other possible
approaches. The exact amount of bandwidth used for duplicate traffic
depends on the network topology and group membership.
4.2.3.2 Limited Heterogeneity Model
We define the "limited heterogeneity" model as the case where the
receivers of a multicast session are limited to use either best effort
service or a single alternate quality of service. The alternate QoS
can be chosen either by higher level protocols or by dynamic
renegotiation of QoS as described below.
In order to support limited heterogeneity, each ATM edge device
participating in a session would need at most two VCs. One VC would be
a point-to-multipoint best effort service VC and would serve all best
effort service IP destinations for this RSVP session.
The other VC would be a point to multipoint VC with QoS and would serve
all IP destinations for this RSVP session that have an RSVP reservation
established.
As with full heterogeneity, a disadvantage of the limited heterogeneity
scheme is that each packet will need to be duplicated at the network
layer and one copy sent into each of the 2 VCs. Again, the exact
amount of excess traffic will depend on the network topology and group
membership. If any of the existing QoS VC end-points cannot upgrade to
the new QoS, then the new reservation fails though the resources exist
for the new receiver.
4.2.3.3 Homogeneous and Modified Homogeneous Models
We define the "homogeneous" model as the case where all receivers of a
multicast session use a single quality of service VC. Best-effort
receivers also use the single RSVP triggered QoS VC. The single VC can
be a point-to-point or point-to-multipoint as appropriate. The QoS VC
is sized to provide the maximum resources requested by all RSVP next-
hops.
This model matches the way the current RSVP specification addresses
heterogeneous requests. The current processing rules and traffic
control interface describe a model where the largest requested
reservation for a specific outgoing interface is used in resource
allocation, and traffic is transmitted at the higher rate to all next-
hops. This approach would be the simplest method for RSVP over ATM
implementations.
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While this approach is simple to implement, providing better than best-
effort service may actually be the opposite of what the user desires.
There may be charges incurred or resources that are wrongfully
allocated. There are two specific problems. The first problem is that
a user making a small or no reservation would share a QoS VC resources
without making (and perhaps paying for) an RSVP reservation. The second
problem is that a receiver may not receive any data. This may occur
when there is insufficient resources to add a receiver. The rejected
user would not be added to the single VC and it would not even receive
traffic on a best effort basis.
Not sending data traffic to best-effort receivers because of another
receiver's RSVP request is clearly unacceptable. The previously
described limited heterogeneous model ensures that data is always sent
to both QoS and best-effort receivers, but it does so by requiring
replication of data at the sender in all cases. It is possible to
extend the homogeneous model to both ensure that data is always sent to
best-effort receivers and also to avoid replication in the normal case.
This extension is to add special handling for the case where a best-
effort receiver cannot be added to the QoS VC. In this case, a best
effort VC can be established to any receivers that could not be added
to the QoS VC. Only in this special error case would senders be
required to replicate data. We define this approach as the "modified
homogeneous" model.
4.2.3.4 Aggregation
The last scheme is the multiple RSVP reservations per VC (or
aggregation) model. With this model, large VCs could be set up between
IP routers and hosts in an ATM network. These VCs could be managed much
like IP Integrated Service (IIS) point-to-point links (e.g. T-1, DS-3)
are managed now. Traffic from multiple sources over multiple RSVP
sessions might be multiplexed on the same VC. This approach has a
number of advantages. First, there is typically no signalling latency
as VCs would be in existence when the traffic started flowing, so no
time is wasted in setting up VCs. Second, the heterogeneity problem
in full over ATM has been reduced to a solved problem. Finally, the
dynamic QoS problem for ATM has also been reduced to a solved problem.
This approach can be used with point-to-point and point-to-multipoint
VCs. The problem with the aggregation approach is that the choice of
what QoS to use for which of the VCs is difficult, but is made easier
if the VCs can be changed as needed.
4.2.4 Multicast End-Point Identification
Implementations must be able to identify ATM end-points participating
in an IP multicast group. The ATM end-points will be IP multicast
receivers and/or next-hops. Both QoS and best-effort end-points must
be identified. RSVP next-hop information will provide QoS end-points,
but not best-effort end-points. Another issue is identifying end-points
of multicast traffic handled by non-RSVP capable next-hops. In this
case a PATH message travels through a non-RSVP egress router on the way
to the next hop RSVP node. When the next hop RSVP node sends a RESV
message it may arrive at the source over a different route than what
the data is using. The source will get the RESV message, but will not
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know which egress router needs the QoS. For unicast sessions, there is
no problem since the ATM end-point will be the IP next-hop router.
Unfortunately, multicast routing may not be able to uniquely identify
the IP next-hop router. So it is possible that a multicast end-point
can not be identified.
In the most common case, MARS will be used to identify all end-points
of a multicast group. In the router to router case, a multicast
routing protocol may provide all next-hops for a particular multicast
group. In either case, RSVP over ATM implementations must obtain a
full list of end-points, both QoS and non-QoS, using the appropriate
mechanisms. The full list can be compared against the RSVP identified
end-points to determine the list of best-effort receivers. There is no
straightforward solution to uniquely identifying end-points of
multicast traffic handled by non-RSVP next hops. The preferred
solution is to use multicast routing protocols that support unique end-
point identification. In cases where such routing protocols are
unavailable, all IP routers that will be used to support RSVP over ATM
should support RSVP. To ensure proper behavior, implementations
should, by default, only establish RSVP-initiated VCs to RSVP capable
end-points.
4.2.5 Multicast Data Distribution
Two models are planned for IP multicast data distribution over ATM. In
one model, senders establish point-to-multipoint VCs to all ATM
attached destinations, and data is then sent over these VCs. This
model is often called "multicast mesh" or "VC mesh" mode distribution.
In the second model, senders send data over point-to-point VCs to a
central point and the central point relays the data onto point-to-
multipoint VCs that have been established to all receivers of the IP
multicast group. This model is often referred to as "multicast server"
mode distribution. RSVP over ATM solutions must ensure that IP
multicast data is distributed with appropriate QoS.
In the Classical IP context, multicast server support is provided via
MARS [5]. MARS does not currently provide a way to communicate QoS
requirements to a MARS multicast server. Therefore, RSVP over ATM
implementations must, by default, support "mesh-mode" distribution for
RSVP controlled multicast flows. When using multicast servers that do
not support QoS requests, a sender must set the service, not global,
break bit(s).
4.2.6 Receiver Transitions
When setting up a point-to-multipoint VCs for multicast RSVP sessions,
there will be a time when some receivers have been added to a QoS VC
and some have not. During such transition times it is possible to
start sending data on the newly established VC. The issue is when to
start send data on the new VC. If data is sent both on the new VC and
the old VC, then data will be delivered with proper QoS to some
receivers and with the old QoS to all receivers. This means the QoS
receivers can get duplicate data. If data is sent just on the new QoS
VC, the receivers that have not yet been added will lose information.
So, the issue comes down to whether to send to both the old and new
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VCs, or to send to just one of the VCs. In one case duplicate
information will be received, in the other some information may not be
received.
This issue needs to be considered for three cases:
- When establishing the first QoS VC
- When establishing a VC to support a QoS change
- When adding a new end-point to an already established QoS VC
The first two cases are very similar. It both, it is possible to send
data on the partially completed new VC, and the issue of duplicate
versus lost information is the same. The last case is when an end-point
must be added to an existing QoS VC. In this case the end-point must
be both added to the QoS VC and dropped from a best-effort VC. The
issue is which to do first. If the add is first requested, then the
end-point may get duplicate information. If the drop is requested
first, then the end-point may loose information.
In order to ensure predictable behavior and delivery of data to all
receivers, data can only be sent on a new VCs once all parties have
been added. This will ensure that all data is only delivered once to
all receivers. This approach does not quite apply for the last case.
In the last case, the add operation should be completed first, then the
drop operation. This means that receivers must be prepared to receive
some duplicate packets at times of QoS setup.
4.2.7 Dynamic QoS
RSVP provides dynamic quality of service (QoS) in that the resources
that are requested may change at any time. There are several common
reasons for a change of reservation QoS.
1. An existing receiver can request a new larger (or smaller) QoS.
2. A sender may change its traffic specification (TSpec), which can
trigger a change in the reservation requests of the receivers.
3. A new sender can start sending to a multicast group with a larger
traffic specification than existing senders, triggering larger
reservations.
4. A new receiver can make a reservation that is larger than existing
reservations.
If the limited heterogeneity model is being used and the merge node for
the larger reservation is an ATM edge device, a new larger reservation
must be set up across the ATM network. Since ATM service, as currently
defined in UNI 3.x and UNI 4.0, does not allow renegotiating the QoS of
a VC, dynamically changing the reservation means creating a new VC with
the new QoS, and tearing down an established VC. Tearing down a VC and
setting up a new VC in ATM are complex operations that involve a non-
trivial amount of processing time, and may have a substantial latency.
There are several options for dealing with this mismatch in service. A
specific approach will need to be a part of any RSVP over ATM solution.
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The default method for supporting changes in RSVP reservations is to
attempt to replace an existing VC with a new appropriately sized VC.
During setup of the replacement VC, the old VC must be left in place
unmodified. The old VC is left unmodified to minimize interruption of
QoS data delivery. Once the replacement VC is established, data
transmission is shifted to the new VC, and the old VC is then closed.
If setup of the replacement VC fails, then the old QoS VC should
continue to be used. When the new reservation is greater than the old
reservation, the reservation request should be answered with an error.
When the new reservation is less than the old reservation, the request
should be treated as if the modification was successful. While leaving
the larger allocation in place is suboptimal, it maximizes delivery of
service to the user. Implementations should retry replacing the too
large VC after some appropriate elapsed time.
One additional issue is that only one QoS change can be processed at
one time per reservation. If the (RSVP) requested QoS is changed while
the first replacement VC is still being setup, then the replacement VC
is released and the whole VC replacement process is restarted. To limit
the number of changes and to avoid excessive signalling load,
implementations may limit the number of changes that will be processed
in a given period. One implementation approach would have each ATM
edge device configured with a time parameter T (which can change over
time) that gives the minimum amount of time the edge device will wait
between successive changes of the QoS of a particular VC. Thus if the
QoS of a VC is changed at time t, all messages that would change the
QoS of that VC that arrive before time t+T would be queued. If several
messages changing the QoS of a VC arrive during the interval, redundant
messages can be discarded. At time t+T, the remaining change(s) of QoS,
if any, can be executed. This timer approach would apply more generally
to any network structure, and might be worthwhile to incorporate into
RSVP.
The sequence of events for a single VC would be
- Wait if timer is active
- Establish VC with new QoS
- Remap data traffic to new VC
- Tear down old VC
- Activate timer
There is an interesting interaction between heterogeneous reservations
and dynamic QoS. In the case where a RESV message is received from a
new next-hop and the requested resources are larger than any existing
reservation, both dynamic QoS and heterogeneity need to be addressed. A
key issue is whether to first add the new next-hop or to change to the
new QoS. This is a fairly straight forward special case. Since the
older, smaller reservation does not support the new next-hop, the
dynamic QoS process should be initiated first. Since the new QoS is
only needed by the new next-hop, it should be the first end-point of
the new VC. This way signalling is minimized when the setup to the new
next-hop fails.
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4.2.8 Short-Cuts
Short-cuts [4] allow ATM attached routers and hosts to directly
establish point-to-point VCs across LIS boundaries, i.e., the VC end-
points are on different IP subnets. The ability for short-cuts and
RSVP to interoperate has been raised as a general question. An area of
concern is the ability to handle asymmetric short-cuts. Specifically
how RSVP can handle the case where a downstream short-cut may not have
a matching upstream short-cut. In this case, PATH and RESV messages
following different paths.
Examination of RSVP shows that the protocol already includes mechanisms
that will support short-cuts. The mechanism is the same one used to
support RESV messages arriving at the wrong router and the wrong
interface. The key aspect of this mechanism is RSVP only processing
messages that arrive at the proper interface and RSVP forwarding of
messages that arrive on the wrong interface. The proper interface is
indicated in the NHOP object of the message. So, existing RSVP
mechanisms will support asymmetric short-cuts. The short-cut model of
VC establishment still poses several issues when running with RSVP. The
major issues are dealing with established best-effort short-cuts, when
to establish short-cuts, and QoS only short-cuts. These issues will
need to be addressed by RSVP implementations.
The key issue to be addressed by any RSVP over ATM solution is when to
establish a short-cut for a QoS data flow. The default behavior is to
simply follow best-effort traffic. When a short-cut has been
established for best-effort traffic to a destination or next-hop, that
same end-point should be used when setting up RSVP triggered VCs for
QoS traffic to the same destination or next-hop. This will happen
naturally when PATH messages are forwarded over the best-effort short-
cut. Note that in this approach when best-effort short-cuts are never
established, RSVP triggered QoS short-cuts will also never be
established. More study is expected in this area.
4.2.9 VC Teardown
RSVP can identify from either explicit messages or timeouts when a data
VC is no longer needed. Therefore, data VCs set up to support RSVP
controlled flows should only be released at the direction of RSVP. VCs
must not be timed out due to inactivity by either the VC initiator or
the VC receiver. This conflicts with VCs timing out as described in
RFC 1755 [11], section 3.4 on VC Teardown. RFC 1755 recommends tearing
down a VC that is inactive for a certain length of time. Twenty minutes
is recommended. This timeout is typically implemented at both the VC
initiator and the VC receiver. Although, section 3.1 of the update to
RFC 1755 [11] states that inactivity timers must not be used at the VC
receiver.
When this timeout occurs for an RSVP initiated VC, a valid VC with QoS
will be torn down unexpectedly. While this behavior is acceptable for
best-effort traffic, it is important that RSVP controlled VCs not be
torn down. If there is no choice about the VC being torn down, the
RSVP daemon must be notified, so a reservation failure message can be
sent.
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For VCs initiated at the request of RSVP, the configurable inactivity
timer mentioned in [11] must be set to "infinite". Setting the
inactivity timer value at the VC initiator should not be problematic
since the proper value can be relayed internally at the originator.
Setting the inactivity timer at the VC receiver is more difficult, and
would require some mechanism to signal that an incoming VC was RSVP
initiated. To avoid this complexity and to conform to [11]
implementations must not use an inactivity timer to clear received
connections.
4.3 RSVP Control Management
One last important issue is providing a data path for the RSVP messages
themselves. There are two main types of messages in RSVP, PATH and
RESV. PATH messages are sent to unicast or multicast addresses, while
RESV messages are sent only to unicast addresses. Other RSVP messages
1
are handled similar to either PATH or RESV . So ATM VCs used for RSVP
signalling messages need to provide both unicast and multicast
functionality. There are several different approaches for how to assign
VCs to use for RSVP signalling messages.
The main approaches are:
- use same VC as data
- single VC per session
- single point-to-multipoint VC multiplexed among sessions
- multiple point-to-point VCs multiplexed among sessions
There are several different issues that affect the choice of how to
assign VCs for RSVP signalling. One issue is the number of additional
VCs needed for RSVP signalling. Related to this issue is the degree of
multiplexing on the RSVP VCs. In general more multiplexing means fewer
VCs. An additional issue is the latency in dynamically setting up new
RSVP signalling VCs. A final issue is complexity of implementation. The
remainder of this section discusses the issues and tradeoffs among
these different approaches and suggests guidelines for when to use
which alternative.
4.3.1 Mixed data and control traffic
In this scheme RSVP signalling messages are sent on the same VCs as is
the data traffic. The main advantage of this scheme is that no
additional VCs are needed beyond what is needed for the data traffic.
An additional advantage is that there is no ATM signalling latency for
PATH messages (which follow the same routing as the data messages).
However there can be a major problem when data traffic on a VC is
nonconforming. With nonconforming traffic, RSVP signalling messages may
be dropped. While RSVP is resilient to a moderate level of dropped
messages, excessive drops would lead to repeated tearing down and re-
establishing of QoS VCs, a very undesirable behavior for ATM. Due to
these problems, this may not be a good choice for providing RSVP
signalling messages, even though the number of VCs needed for this
scheme is minimized. One variation of this scheme is to use the best
1
This can be slightly more complicated for RERR messages
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effort data path for signalling traffic. In this scheme, there is no
issue with nonconforming traffic, but there is an issue with congestion
in the ATM network. RSVP provides some resiliency to message loss due
to congestion, but RSVP control messages should be offered a preferred
class of service. A related variation of this scheme that is hopeful
but requires further study is to have a packet scheduling algorithm
(before entering the ATM network) that gives priority to the RSVP
signalling traffic. This can be difficult to do at the IP layer.
4.3.1.1 Single RSVP VC per RSVP Reservation
In this scheme, there is a parallel RSVP signalling VC for each RSVP
reservation. This scheme results in twice the number of VCs, but means
that RSVP signalling messages have the advantage of a separate VC. This
separate VC means that RSVP signalling messages have their own traffic
contract and compliant signalling messages are not subject to dropping
due to other noncompliant traffic (such as can happen with the scheme
in section 4.3.1). The advantage of this scheme is its simplicity -
whenever a data VC is created, a separate RSVP signalling VC is
created. The disadvantage of the extra VC is that extra ATM signalling
needs to be done. Additionally, this scheme requires twice the minimum
number of VCs and also additional latency, but is quite simple.
4.3.1.2 Multiplexed point-to-multipoint RSVP VCs
In this scheme, there is a single point-to-multipoint RSVP signalling
VC for each unique ingress router and unique set of egress routers.
This scheme allows multiplexing of RSVP signalling traffic that shares
the same ingress router and the same egress routers. This can save on
the number of VCs, by multiplexing, but there are problems when the
destinations of the multiplexed point-to-multipoint VCs are changing.
Several alternatives exist in these cases, that have applicability in
different situations. First, when the egress routers change, the
ingress router can check if it already has a point-to-multipoint RSVP
signalling VC for the new list of egress routers. If the RSVP
signalling VC already exists, then the RSVP signalling traffic can be
switched to this existing VC. If no such VC exists, one approach would
be to create a new VC with the new list of egress routers. Other
approaches include modifying the existing VC to add an egress router or
using a separate new VC for the new egress routers. When a destination
drops out of a group, an alternative would be to keep sending to the
existing VC even though some traffic is wasted. The number of VCs used
in this scheme is a function of traffic patterns across the ATM
network, but is always less than the number used with the Single RSVP
VC per data VC. In addition, existing best effort data VCs could be
used for RSVP signalling. Reusing best effort VCs saves on the number
of VCs at the cost of higher probability of RSVP signalling packet
loss. One possible place where this scheme will work well is in the
core of the network where there is the most opportunity to take
advantage of the savings due to multiplexing. The exact savings depend
on the patterns of traffic and the topology of the ATM network.
4.3.1.3 Multiplexed point-to-point RSVP VCs
In this scheme, multiple point-to-point RSVP signalling VCs are used
for a single point-to-multipoint data VC. This scheme allows
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multiplexing of RSVP signalling traffic but requires the same traffic
to be sent on each of several VCs. This scheme is quite flexible and
allows a large amount of multiplexing.
Since point-to-point VCs can set up a reverse channel at the same time
as setting up the forward channel, this scheme could save substantially
on signalling cost. In addition, signalling traffic could share
existing best effort VCs. Sharing existing best effort VCs reduces the
total number of VCs needed, but might cause signalling traffic drops if
there is congestion in the ATM network. This point-to-point scheme
would work well in the core of the network where there is much
opportunity for multiplexing. Also in the core of the network, RSVP VCs
can stay permanently established either as Permanent Virtual Circuits
(PVCs) or as long lived Switched Virtual Circuits (SVCs). The number
of VCs in this scheme will depend on traffic patterns, but in the core
of a network would be approximately n(n-1)/2 where n is the number of
IP nodes in the network. In the core of the network, this will
typically be small compared to the total number of VCs.
4.3.2 QoS for RSVP VCs
There is an issue of what QoS, if any, to assign to the RSVP signalling
VCs. For other RSVP VC schemes, a QoS (possibly best effort) will be
needed. What QoS to use partially depends on the expected level of
multiplexing that is being done on the VCs, and the expected
reliability of best effort VCs. Since RSVP signalling is infrequent
(typically every 30 seconds), only a relatively small QoS should be
needed. This is important since using a larger QoS risks the VC setup
being rejected for lack of resources. Falling back to best effort when
a QoS call is rejected is possible, but if the ATM net is congested,
there will likely be problems with RSVP packet loss on the best effort
VC also. Additional experimentation is needed in this area.
5. Encapsulation
Since RSVP is a signalling protocol used to control flows of IP data
packets, encapsulation for both RSVP packets and associated IP data
packets must be defined. The methods for transmitting IP packets over
ATM (Classical IP over ATM[10], LANE[17], and MPOA[18]) are all based
on the encapsulations defined in RFC1483 [19]. RFC1483 specifies two
encapsulations, LLC Encapsulation and VC-based multiplexing. The
former allows multiple protocols to be encapsulated over the same VC
and the latter requires different VCs for different protocols.
For the purposes of RSVP over ATM, any encapsulation can be used as
long as the VCs are managed in accordance to the methods outlined in
Section 4. Obviously, running multiple protocol data streams over the
same VC with LLC encapsulation can cause the same problems as running
multiple flows over the same VC.
While none of the transmission methods directly address the issue of
QoS, RFC1755 [11] does suggest some common values for VC setup for
best-effort traffic. [14] discusses the relationship of the RFC1755
setup parameters and those needed to support IntServ flows in greater
detail.
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6. Security Considerations
The same considerations stated in [1] and [11] apply to this document.
There are no additional security issues raised in this document.
7. References
[1] R. Braden, L. Zhang, S. Berson, S. Herzog, S. Jamin. Resource
ReSerVation Protocol (RSVP) -- Version 1 Functional Specification
RFC 2209, September 1997.
[2] M. Borden, E. Crawley, B. Davie, S. Batsell. Integration of Real-
time Services in an IP-ATM Network Architecture. Request for
Comments (Informational) RFC 1821, August 1995.
[3] R. Cole, D. Shur, C. Villamizar. IP over ATM: A Framework Document.
Request for Comments (Informational), RFC 1932, April 1996.
[4] D. Katz, D. Piscitello, B. Cole, J. Luciani. NBMA Next Hop
Resolution Protocol (NHRP). Internet Draft, draft-ietf-rolc-nhrp-
12.txt, October 1997.
[5] G. Armitage, Support for Multicast over UNI 3.0/3.1 based ATM
Networks. RFC 2022. November 1996.
[6] S. Shenker, C. Partridge. Specification of Guaranteed Quality of
Service. RFC 2212, September 1997.
[7] J. Wroclawski. Specification of the Controlled-Load Network Element
Service. RFC 2211, September 1997.
[8] ATM Forum. ATM User-Network Interface Specification Version 3.0.
Prentice Hall, September 1993
[9] ATM Forum. ATM User Network Interface (UNI) Specification Version
3.1. Prentice Hall, June 1995.
[10]M. Laubach, Classical IP and ARP over ATM. Request for Comments
(Proposed Standard) RFC1577, January 1994.
[11]M. Perez, A. Mankin, E. Hoffman, G. Grossman, A. Malis, ATM
Signalling Support for IP over ATM, Request for Comments (Proposed
Standard) RFC1755, February 1995.
[12]S. Herzog. RSVP Extensions for Policy Control. Internet Draft,
draft-ietf-rsvp-policy-ext-02.txt, April 1997.
[13]S. Herzog. Local Policy Modules (LPM): Policy Control for RSVP,
Internet Draft, draft-ietf-rsvp-policy-lpm-01.txt, November 1996.
[14]M. Borden, M. Garrett. Interoperation of Controlled-Load and
Guaranteed Service with ATM, Internet Draft, draft-ietf-issll-atm-
mapping-03.txt, August 1997.
[15]L. Berger. RSVP over ATM Implementation Requirements. Internet
Draft, draft-ietf-issll-atm-imp-req-00.txt, July 1997.
[16]L. Berger. RSVP over ATM Implementation Guidelines. Internet Draft,
draft-ietf-issll-atm-imp-guide-01.txt, July 1997.
[17]ATM Forum Technical Committee. LAN Emulation over ATM, Version 1.0
Specification, af-lane-0021.000, January 1995.
[18]ATM Forum Technical Committee. Baseline Text for MPOA, af-95-
0824r9, September 1996.
[19]J. Heinanen. Multiprotocol Encapsulation over ATM Adaptation Layer
5, RFC 1483, July 1993.
[20]ATM Forum Technical Committee. LAN Emulation over ATM Version 2 -
LUNI Specification, December 1996.
[21]ATM Forum Technical Committee. Traffic Management Specification
v4.0, af-tm-0056.000, April 1996.
Expires August 1998 Page 22
Internet Draft Framework for IntServ and RSVP over ATMFebruary 1998
[22]R. Callon, et al. A Framework for Multiprotocol Label Switching,
Internet Draft, draft-ietf-mpls-framework-01.txt, July 1997.
[23]B. Rajagopalan, R. Nair, H. Sandick, E. Crawley. A Framework for
QoS-based Routing in the Internet, Internet Draft, draft-ietf-qosr-
framework-01.txt, July 1997.
[24]ITU-T. Digital Subscriber Signaling System No. 2-Connection
modification: Peak cell rate modification by the connection owner,
ITU-T Recommendation Q.2963.1, July 1996.
[25]ITU-T. Digital Subscriber Signaling System No. 2-Connection
characteristics negotiation during call/connection establishment
phase, ITU-T Recommendation Q.2962, July 1996.
[26]ATM Forum Technical Committee. Private Network-Network Interface
Specification v1.0 (PNNI), March 1996
8. Author's Address
Eric S. Crawley
Argon Networks
25 Porter Road
Littleton, Ma 01460
+1 978 486-0665
esc@argon.com
Lou Berger
FORE Systems
6905 Rockledge Drive
Suite 800
Bethesda, MD 20817
+1 301 571-2534
lberger@fore.com
Steven Berson
USC Information Sciences Institute
4676 Admiralty Way
Marina del Rey, CA 90292
+1 310 822-1511
berson@isi.edu
Fred Baker
Cisco Systems
519 Lado Drive
Santa Barbara, California 93111
+1 805 681-0115
fred@cisco.com
Marty Borden
Bay Networks
125 Nagog Park
Acton, MA 01720
mborden@baynetworks.com
+1 978 266-1011
Expires August 1998 Page 23
Internet Draft Framework for IntServ and RSVP over ATMFebruary 1998
John J. Krawczyk
ArrowPoint Communications
235 Littleton Road
Westford, Massachusetts 01886
+1 978 692-5875
jj@arrowpoint.com
Expires August 1998 Page 24
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