home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Internet Info 1997 December
/
Internet_Info_CD-ROM_Walnut_Creek_December_1997.iso
/
drafts
/
draft_ietf_i
/
draft-ietf-issll-atm-imp-guide-00.txt
< prev
next >
Wrap
Text File
|
1997-03-25
|
37KB
|
942 lines
Internet Draft L. Berger
Expires: September 1997 FORE Systems
File: draft-ietf-issll-atm-imp-guide-00.txt
RSVP over ATM Implementation Guidelines
March 25, 1997
Status of Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
To learn the current status of any Internet-Draft, please check the
"1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net
(Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific
Rim).
Abstract
This note presents specific implementation guidelines for running
RSVP over ATM switched virtual circuits (SVCs). It presents
requirements and specific guidelines for running over today's ATM
networks. The general problem is discussed in [5]. Integrated
Services to ATM service mappings are covered in [7].
Author's Note
The postscript version of this document contains figures that are not
included in the text version, so it is best to use the postscript
version. Figures will be converted to ASCII in a future version.
Berger Expires: September 1997 [Page 1]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
Table of Contents
1. Introduction ........................................................3
1.1 Terms ...........................................................3
1.2 Assumptions .....................................................4
2. Multicast RSVP Session Support ......................................4
2.1 Data VC Management for Heterogeneous Sessions ...................5
2.2 Multicast End-Point Identification ..............................6
2.3 Multicast Data Distribution .....................................7
2.4 Receiver Transitions ............................................7
3. General RSVP Session Support ........................................8
3.1 RSVP Message VC Usage ...........................................8
3.2 VC Initiation ...................................................9
3.3 VC Teardown .....................................................10
3.4 Reservation to VC Mapping .......................................10
3.5 Dynamic QoS .....................................................11
3.6 Short-Cuts ......................................................12
3.7 Encapsulation ...................................................13
4. Security ............................................................13
5. Implementation Summary ..............................................13
5.1 Requirements ....................................................13
5.2 Baseline Requirements ...........................................14
6. Author's Address ....................................................15
Berger Expires: September 1997 [Page 2]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
1. Introduction
This note discusses running IP over ATM in an environment where SVCs
are used to support QoS flows and RSVP is used as the internet level
QoS signaling protocol. The general issues related to running RSVP[8]
over ATM have been covered in several papers including [5,4,6,11].
This document is intended as a companion to [5] and as a guide to
implementers. The reader should be familiar with[5]. This document
will define specific baseline requirements for implementations using
ATM UNI3.x and 4.0. Some stated requirements must be adhered to by
all RSVP over ATM implementations. Other stated requirements provide
a baseline set of functionality, while allowing for more
sophisticated approaches. We expect some vendors to additionally
provide some of the more sophisticated approaches described in [5],
and some networks to only make use of such approaches. The baseline
set of functionality is defined to ensure predictability and
interoperability between different implementations. We expect that
the baseline requirements may change in the future, and at such a
time this document will be replaced.
The rest of this section will define terms and assumptions used in
the document. Section 2 will cover implementation guidelines
specific to multicast sessions. Section 3 will cover implementation
guidelines common to all RSVP session. Section 5 will conclude with
a summary of stated requirements.
1.1 Terms
The terms "reservation" and "flow" are used in many contexts,
often with different meaning. These terms are used in this
document with the following meaning:
o 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 [8] for details of each. Each new request is
referred to in this document as an RSVP reservation, or
simply reservation.
o 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
Berger Expires: September 1997 [Page 3]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
one flow per sender (per session).
1.2 Assumptions
The following assumptions are made:
o RSVP We assume RSVP as the internet signalling protocol which
is described in [8]. The reader is assumed to be familiar
with [8].
o IPv4 and IPv6 RSVP support has been defined for both IPv4 and
IPv6. The guidelines in this document are intended to be
used to support RSVP with either IPv4 or IPv6. This document
does not require on version over the other.
o Best effort service model The current Internet only supports
best effort service. We assume that as additional components
of the Integrated Services model that best effort service
will continue to be a supported.
o ATM UNI 3.x and 4.0 We assume ATM service as defined by UNI
3.x and 4.0. ATM provides both point-to-point and point-to-
multipoint Virtual Circuits (VCs) with a specified Quality of
Service (QoS). ATM provides both Permanent Virtual Circuits
(PVCs) and Switched Virtual Circuits (SVCs). In the
Permanent Virtual Circuit (PVC) environment, PVCs are
typically used as point-to-point link replacements. So the
support issues are similar to point-to-point links. This
draft assumes that SVCs are used to support RSVP over ATM.
2. Multicast RSVP Session Support
There are several aspects to running RSVP over ATM that are
particular to multicast sessions. These issues result from the
nature of ATM point-to-multipoint connections. This section
addresses multicast end-point identification, multicast data
distribution, multicast receiver transitions and next-hops requesting
different QoS values (heterogeneity) which includes the handling of
multicast best-effort receivers. Handling of best-effort receivers
is not strictly an RSVP issues, but needs to be addressed in any RSVP
over ATM implementation in order to maintain expected Internet
service. Implementation guidelines for issues related to all RSVP
sessions are covered in Section 3. Some of these guidelines cover
issues that have special interactions for multicast session, these
interactions are covered together with the more general issues.
Berger Expires: September 1997 [Page 4]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
2.1 Data VC Management for Heterogeneous Sessions
The issues relating to data VC management of heterogeneous
sessions are covered in detail in [5] and not repeated. In
summary, heterogeneity occurs when receivers request different
levels of QoS within a single session, and also when some
receivers do not request any QoS. Both types of heterogeneity are
shown in figure .
[Figure goes here]
Figure 1: Types of Multicast Receivers
[5] provided four models for dealing with heterogeneity: full
heterogeneity, limited heterogeneity, homogeneous, and modified
homogeneous models. No matter which model or combination of
models is used by an implementation, implementations must not
normally send more than one copy of a particular data packet to a
particular next-hop (ATM end-point). Some transient over
transmission is acceptable, but only during VC setup and
transition.
Implementations must also ensure that data traffic is sent to
best-effort receivers. Data traffic may be sent to best-effort
receivers via best-effort or QoS VCs as is appropriate for the
implemented model. In all cases, implementations must not create
VCs in such a way that data cannot be sent to best-effort
receivers. This includes the case of not being able to add a
best-effort receiver to a QoS VC, but does not include the case
where best-effort VCs cannot be setup. The failure to establish
best-effort VCs is considered to be a general IP over ATM failure
and is therefore beyond the scope of this document.
The key issue to be addressed by an implementation is providing
requested QoS downstream. One of or some combination of the
discussed models [5] may be used to provide requested QoS.
Unfortunately, none of the described models is the right answer
for all cases. For some networks, e.g. public WANs, it is likely
that the limited heterogeneous model or a hybrid limited-full
heterogeneous model will be desired. In other networks, e.g.
LANs, it is likely that a the modified homogeneous model will be
desired.
Since there is not one model that satisfies all cases,
implementations must implement one of either the limited
heterogeneity model or the modified homogeneous model.
Implementations should support both approaches and provide the
ability to select which method is actually used, but are not
Berger Expires: September 1997 [Page 5]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
required to do so. Implementations may also support heterogeneity
through some other mechanism, e.g., using multiple appropriately
sized VCs.
2.2 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 usually provide QoS end-points, but not best-effort end-
points.
There is even a case where RSVP next-hop information will not
provide the appropriate end-point. This occurs when the next-hop
is not RSVP capable, and RSVP is being automatically tunneled. 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 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 host case, MARS can 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, baseline RSVP over ATM implementations must only
establish RSVP-initiated VCs to RSVP capable end-points. It is
permissible to allow a user to override this behavior.
Berger Expires: September 1997 [Page 6]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
2.3 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. Figure shows
data flow for both modes of IP multicast data distribution. RSVP
over ATM solutions must ensure that IP multicast data is
distributed with appropriate QoS.
[Figure goes here]
Figure 2: IP Multicast Data Distribution Over ATM
Current multicast servers [1] do not support any mechanisms for
communicating QoS requirements to a multicast server. For this
reason, RSVP over ATM implementations must 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).
In the case of MARS[1], the selection of distribution modes is
administratively controlled. Therefore network administrators
that desire proper RSVP over ATM operation must appropriately
configure their network to support mesh mode distribution for
multicast groups that will be used in RSVP sessions.
2.4 Receiver Transitions
When setting up a point-to-multipoint VCs 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
would 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 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
Berger Expires: September 1997 [Page 7]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
cases: when establishing the first QoS VC, when establishing a VC
to support a QoS change, and 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 must not be sent on a new VCs until 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 must be
completed first, then the drop. This last behavior requires
receivers to be prepared to receive some duplicate packets at
times of QoS setup.
3. General RSVP Session Support
This section provides implementation guidelines that are common for
all (both unicast and multicast) RSVP sessions. The section covers
RSVP VC usage, QoS VC initiation, VC teardown, reservation to VC
Mapping, handling requested changes in QoS, short-cuts, and
encapsulation.
3.1 RSVP Message VC Usage
[5] covered the issues related to VC usage by RSVP messages. It
discussed several options including: mixed control and data,
single control VC per session, single control VC multiplexed
among sessions, and multiple VCs multiplexed among sessions. QoS
for control VCs was also discussed. Again that discussion is not
repeated, [5] should be reviewed for detailed information.
Baseline RSVP over ATM implementations must send RSVP control
(messages) over the best effort data path, see figure . It is
permissible to allow a user to override this behavior. The stated
approach minimizes VC requirements since the best effort data path
will need to exist in order for RSVP sessions to be established
and in order for RSVP reservations to be initiated. The specific
best effort paths that will be used by RSVP are: for unicast, the
Berger Expires: September 1997 [Page 8]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
same VC used to reach the unicast destination; and for multicast,
the same VC that is used for best effort traffic destined to the
IP multicast group. Note that for multicast there may be another
best effort VC that is used to carry session data traffic, i.e.,
for data that is both in the multicast group and matching a
sessions protocol and port.
[Figure goes here]
Figure 3: RSVP Control Message VC Usage
The disadvantage of this approach is that best effort VCs may not
provide the reliability that RSVP needs. However the best-effort
path is expected to satisfy RSVP reliability requirements in most
networks. Especially since RSVP allows for a certain amount of
packet loss without any loss of state synchronization.
3.2 VC Initiation
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
sub-net sender.
For data flows, this means that sub-net senders must establish all
QoS VCs and the sub-net receiver must be able to accept incoming
QoS VCs. 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. All RSVP over ATM approaches that have
VCs initiated and controlled by the sub-net senders will
interoperate. Figure shows this model of data flow VC
initiation.
[Figure goes here]
Figure 4: Data Flow VC Initiation
Baseline RSVP over ATM implementations are prohibited from sending
data on a RSVP initiated QoS VC in the backwards direction. There
are two reasons. The first is that use of the backwards data path
requires the VC initiator to appropriate set backwards QoS
parameters. The second is that backwards data paths are not
available with point-to-multipoint VCs, so backwards data paths
Berger Expires: September 1997 [Page 9]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
could only be used to support unicast RSVP reservations. Since
reverse path usage is a special case that cannot be used to
support multicast flows and such use for unicast requires some
undefined out of band communication, implementations must not send
data on QoS VCs in the backwards direction.
3.3 VC Teardown
Normally data VCs are torndown based on inactivity timers. This
mechanism is used since IP is connectionless and there is
therefore no way to know when a VC is no longer needed. Since
RSVP provides explicit mechanisms (messages and timeouts) to
determine when an associated data VC is no longer needed, the
traditional VC timeout mechanisms is not needed. Data VCs set up
to support RSVP controlled flows should only be released at the
direction of RSVP. Such 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[12],
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[13] states that inactivity timers must not be
used at the VC receiver.
In RSVP over ATM implementations, the configurable inactivity
timer mentioned in [12] must be set to "infinite" for VCs
initiated at the request of RSVP. 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 [13],
RSVP over ATM implementations must not use an inactivity timer to
clear any received connection.
3.4 Reservation to VC Mapping
As discussed in [5], data associated with multiple RSVP sessions
could be sent using the same shared VCs. Implementation of such
"aggregation" models is still a matter for research. Therefore,
baseline RSVP over ATM implementations must use independent VCs
for each RSVP session. Implementations may also support
aggregation approaches. Use of such approaches must be at the
discretion of the user.
Berger Expires: September 1997 [Page 10]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
3.5 Dynamic QoS
As stated in [5], there is a mismatch in the service provided by
RSVP and that provided by ATM UNI3.x and 4.0. RSVP allows
modifications to QoS parameters at any time, while ATM does not
support any modifications to QoS parameters after VC setup. See
[5] for more detail.
The baseline 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
only then is the old VC 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. Implementations may also limit number of
changes processed in a time period per [5].
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.
Berger Expires: September 1997 [Page 11]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
3.6 Short-Cuts
Short-cuts [10] 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 sub-nets. The ability for short-
cuts and RSVP to interoperate has been raised as a general
question. The 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, which is shown in figure , PATH and RESV messages
following different paths.
[Figure goes here]
Figure 5: Asymmetric RSVP Message Forwarding With ATM Short-Cuts
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. Baseline RSVP
over ATM implementations should 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.
Berger Expires: September 1997 [Page 12]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
3.7 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. There are multiple encapsulation
options for running IP over ATM, for example RFC 1483[9] and
LANE[2]. There is also other encapsulation options, such as
MPOA[3].
Baseline RSVP over ATM implementations must use a consistent
encapsulation scheme for all IP over ATM packets. This includes
RSVP packets and associated IP data packets. So, encapsulation
used on QoS data VCs and related control VCs must be the same as
used by best-effort VCs.
4. Security
The same considerations stated in [8] and [12] apply to this
document. There are no additional security issues raised in this
document.
5. Implementation Summary
This section provides a summary of previously stated requirements.
5.1 Requirements
All RSVP over ATM UNI 3.0 and 4.0 implementations must conform to
the following:
o Heterogeneity
Implementations must not, in the normal case, send more than
one copy of a particular data packet to a particular next-hop
(ATM end-point).
Implementations must ensure that data traffic is sent to
best-effort receivers.
o Multicast Data Distribution
When using multicast servers that do not support QoS
requests, a sender must set the service, not global, break
bit(s).
o Receiver Transitions
While creating new VCs, senders must either send on only the
old VC or on both the old and the new VCs.
o VC Initiation
Berger Expires: September 1997 [Page 13]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
All RSVP triggered QoS VCs must be established by the sub-net
senders.
VC receivers must be able to accept incoming QoS VCs.
o VC Teardown
VC initiators must not tear down RSVP initiated VCs due to
inactivity.
VC receivers must not tear down any incoming VCs due to
inactivity.
5.2 Baseline Requirements
Baseline requirements define a minimum set of functionality that
must be provided by implementations. Implementations may also
provide additional functionality that may be configured to
override the baseline behavior. Which behavior is selected is a
policy issue for network providers. We expect some networks to
only make use of baseline functionality and others to only make
use of additional functionality.
o Heterogeneity
Either limited heterogeneity model or the modified
homogeneous model must be supported for handling
heterogeneity.
Implementations should support both approaches and provide
the ability to select which method is actually used, but are
not required to do so.
o Multicast End-Point Identification
Implementations must only establish RSVP-initiated VCs to
RSVP capable end-points.
o Multicast Data Distribution
Implementations must support "mesh-mode" distribution for
RSVP controlled multicast flows. In the case of MARS,
distribution mode is administratively controlled. So this
requirement can only be implemented by network
administrators.
o RSVP Control VC Management
Implementations must send RSVP control (messages) over the
best effort data path.
o Reservation to VC Mapping
Implementations must use a single VC to support each RSVP
reservation.
Berger Expires: September 1997 [Page 14]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
o Dynamic QoS
Implementations must support RSVP requested changes in
reservations by attempting 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.
o Short-Cuts
Implementations should establish QoS short-cut whenever a
best-effort short-cut is in use to a particular destination
or next-hop. This means that when best-effort short-cuts are
never established, RSVP triggered short-cuts also should not
be established.
o Encapsulation
Implementations must encapsulate data sent on QoS VCs with
the same encapsulation as is used on best-effort VCs.
6. Author's Address
Lou Berger
FORE Systems
6905 Rockledge Drive
Suite 800
Bethesda, MD 20817
Phone: +1 301 571 2534
EMail: lberger@fore.com
REFERENCES
[1] Armitage, G., "Support for Multicast over UNI 3.0/3.1 based ATM
Networks," Internet Draft, February 1996.
[2] The ATM Forum, "LAN Emulation Over ATM Specification", Version 1.0.
[3] The ATM Forum, "MPOA Baseline Version 1", 95-0824r9, September 1996.
[4] Berson, S., "`Classical' RSVP and IP over ATM," INET '96, July 1996.
[5] Berson, S., Berger, L., "IP Integrated Services with RSVP over ATM,"
Internet Draft, March 1997.
[6] Borden, M., Crawley, E., Krawczyk, J, Baker, F., and Berson, S.,
"Issues for RSVP and Integrated Services over ATM," Internet Draft,
February 1996.
[7] Borden, M., and Garrett, M., "Interoperation of Controlled-Load and
Berger Expires: September 1997 [Page 15]
Internet Draft RSVP over ATM Implementation Guidelines March 1996
Guaranteed-Service with ATM," Internet Draft, June 1996.
[8] Braden, R., Zhang, L., Berson, S., Herzog, S., and Jamin, S.,
"Resource ReSerVation Protocol (RSVP) -- Version 1 Functional
Specification," Internet Draft, November 1996.
[9] Heinanen, J., "Multiprotocol Encapsulation over ATM Adaptation Layer
5," RFC 1483.
[10] Luciani, J., Katz, D., Piscitello, D., Cole, B., "NBMA Next Hop
Resolution Protocol (NHRP)," Internet Draft, June 1996.
[11] Onvural, R., Srinivasan, V., "A Framework for Supporting RSVP Flows
Over ATM Networks," Internet Draft, March 1996.
[12] Perez, M., Liaw, F., Grossman, D., Mankin, A., Hoffman, E., and
Malis, A., "ATM Signalling Support for IP over ATM," RFC 1755.
[13] Perez, M., Mankin, A. "ATM Signalling Support for IP over ATM -
UNI 4.0 Update" Internet Draft, November 1996.
Berger Expires: September 1997 [Page 16]