RSVP Applicability: Resource ReSerVation Protocol (RSVP) -- Version 1 Applicability Statement Some Guidelines on Deployment
Where RSVP can usefully be deployed, and the three problems to settle first.
Mankin, A., Ed., Baker, F., Braden, B., Bradner, S., O'Dell, M., Romanow, A., Weinrib, A., and L. Zhang, "Resource ReSerVation Protocol (RSVP) -- Version 1 Applicability Statement Some Guidelines on Deployment", RFC 2208, DOI 10.17487/RFC2208, September 1997, <https://www.rfc-editor.org/info/rfc2208>.
@misc{rfc2208,
series = {Request for Comments},
number = 2208,
howpublished = {RFC 2208},
publisher = {RFC Editor},
doi = {10.17487/RFC2208},
url = {https://www.rfc-editor.org/info/rfc2208},
author = {A. Mankin and F. Baker and B. Braden and S. Bradner and M. O'Dell and A. Romanow and A. Weinrib and L. Zhang},
title = {{Resource ReSerVation Protocol (RSVP) -- Version 1 Applicability Statement Some Guidelines on Deployment}},
pagetotal = 6,
year = 1997,
month = sep,
} RFC text
Contents
Network Working Group A. Mankin, Ed.
Request for Comments: 2208 USC/ISI
Category: Informational F. Baker
Cisco Systems
B. Braden
USC/ISI
S. Bradner
Harvard
M. O`Dell
UUNET Technologies
A. Romanow
Sun Microsystems
A. Weinrib
Intel Corporation
L. Zhang
UCLA
September 1997
Resource ReSerVation Protocol (RSVP)
Version 1 Applicability Statement
Some Guidelines on Deployment
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Abstract
This document describes the applicability of RSVP along with the
Integrated Services protocols and other components of resource
reservation and offers guidelines for deployment of resource
reservation at this time. This document accompanies the first
submission of RSVP and integrated services specifications onto the
Internet standards track.
1. Introduction
RSVP [RFC 2205] is a unicast and multicast signalling protocol,
designed to install and maintain reservation state information at
each router along the path of a stream of data. The state handled by
RSVP is defined by services [RFC 2211] and [RFC 2212] specified by
the Integrated Services WG. These services and RSVP are being
introduced to the IETF's standards track jointly. From henceforth,
the acronym RSVP on its own is used as a shorthand for the signalling
protocol combined with the integrated service specifications.
RSVP must be used in conjunction with several additional components,
described in Table 1.
Table 1 Additional Components of Resource Reservation
1. Message formats in which parameters for desired services can be
expressed. A proposed standard set of these formats is specified
in [RFC 2210].
2. Router and host mechanisms (e.g. packet classification and
scheduling, admission control algorithms) to implement one or
both of the models [RFC 2211] and [RFC 2212], which are also
in the standards track.
3. Message formats in which parameters for desired policies for
admission control and resource use can be expressed. A small
common subset of these formats for standards track is in the
RSVP WG's charter. The Policy objects in the RSVP Protocol
Specification are optional only at this time.
4. Diversely located mechanisms implementing desired admission
control policy functions, including authorization and other
security mechanisms.
In the presence of some form of each component in Table 1, RSVP-
enabled applications can achieve differentiated qualities of service
across IP networks. Networked multimedia applications, many of which
require (or will benefit from) a predictable end-user experience, are
likely to be initial users of RSVP-signalled services.
Because RSVP and the integrated services and other components listed
in Table 1 mark a significant change to the service model of IP
networks, RSVP has received considerable interest and press in
advance of its release as a standards track RFC. At present, many
vendors of operating systems and routers are incorporating RSVP and
integrated services into their products for near-future availability.
The goal of this applicability statement is to describe those uses of
the current RSVP specification that are known to be feasible, and to
identify areas of limitation and ongoing chartered work addressing
some of these limitations.
2. Issues Affecting Deployment of RSVP
Wide scale deployment of RSVP must be approached with care, as there
remains a number of outstanding issues that may affect the success of
deployment.
2.1. Scalability
The resource requirements (processing and storage) for running RSVP
on a router increase proportionally with the number of separate
sessions (i.e., RSVP reservations). Thus, supporting numerous small
reservations on a high-bandwidth link may easily overly tax the
routers and is inadvisable. Furthermore, implementing the packet
classification and scheduling capabilities currently used to provide
differentiated services for reserved flows may be very difficult for
some router products or on some of their high-speed interfaces (e.g.
OC-3 and above).
These scaling issues imply that it will generally not be appropriate
to deploy RSVP on high-bandwidth backbones at the present time.
Looking forward, the operators of such backbones will probably not
choose to naively implement RSVP for each separate stream. Rather,
techniques are being developed that will, at the "edge" of the
backbone, aggregate together the streams that require special
treatment. Within the backbone, various less costly approaches would
then be used to set aside resources for the aggregate as a whole, as
a way of meeting end-to-end requirements of individual flows.
In the near term, various vendors are likely to use diverse
approaches to the aggregation of reservations. There is not
currently chartered work in the IETF for development of standards in
this space. A BOF, Future Directions of Differential Services, on
April 7, 1997, at the Memphis IETF, is to consider the IETF's next
steps on this, among other issues. Public documentation of
aggregation techniques and experience is encouraged.
2.2. Security Considerations
The RSVP WG submission for Proposed Standard includes two security-
related documents [Baker96, RFC 2207]. [Baker96] addresses denial and
hijacking or theft of service attacks. [RFC 2207] addresses RSVP
mechanisms for data flows that themselves use IPSEC.
The first document is proposed to protect against spoofed reservation
requests arriving at RSVP routers; such requests might be used to
obtain service to unauthorized parties or to lock up network
resources in a denial of service attack. Modified and spoofed
reservation requests are detected by use of hop-by-hop MD5 checksums
(in an Integrity Object) between RSVP neighbor routers. As
described, RSVP hop-by-hop authentication assumes that key management
and distribution for routers is resolved and deployed. Until an
effective key infrastructure is in place, manually keyed session
integrity might be used. In addition, [Baker96] may be updated with
RFC 2085.
That RSVP needs an effective key infrastructure among routers is not
unique to RSVP: it is widely acknowledged that there are numerous
denial of service attacks on the routing infrastructure (quite
independent of RSVP) that will only be resolved by deployment of a
key infrastructure.
Theft of service risks will require the user to deploy with caution.
An elementary precaution is to configure management logging of new
and changed filter specifications in RSVP-enabled infrastructure,
e.g. the newFlow trap [RFC 2206].
The Integrity object defined by [Baker96] may also play a role in
policy control, as will be described in 2.3.
The second security-related document provides a mechanism for
carrying flows in which the transport and user octets have been
encrypted (RFC 1827). Although such encryption is highly beneficial
to certain applications, it is not relevant to the functional
security of RSVP or reservations.
The following section on Policy Control includes additional
discussion of RSVP authorization security.
2.3. Policy Control
Policy control addresses the issue of who can, or cannot, make
reservations once a reservation protocol can be used to set up
unequal services.
Currently, the RSVP specification defines a mechanism for
transporting policy information along with reservations. However,
the specification does not define policies themselves. At present,
vendors have stated that they will use the RSVP-defined mechanism to
implement proprietary policies.
The RSVP WG is chartered to specify a simple standardized policy
object and complete simple mechanisms for session use of the
Integrity object in the near future. This applicability statement
may be updated at the completion of the WG's charter.
Before any decision to deploy RSVP, it would be wise to ensure that
the policy control available from a vendor is adequate for the
intended usage. In addition to the lack of documented policy
mechanisms in any of the policy areas (such as access control,
authorization, and accounting), the community has little experience
with describing, setting and controlling policies that limit Internet
service. Therefore it is likely that vendor solutions will be
revised often, particularly before the IETF has developed any policy
specification.
3. Recommendations
Given the current form of the RSVP specifications, multimedia
applications to be run within an intranet are likely to be the first
to benefit from RSVP. SNA/DLSW is another "application" considered
likely to benefit. Within the single or small number of related
administrative domains of an intranet, scalability, security and
access policy will be more manageable than in the global Internet,
and risk will be more controllable. Use of RSVP and supporting
components for small numbers of flows within a single Internet
Service Provider is similar to an intranet use.
Current experience with RSVP has been collected only from test runs
in limited testbeds and intranet deployment. We recommend that
people begin to use RSVP in production intranet or limited ISP
environments (as mentioned above), in which benefits can be realized
without having to resolve some of the issues described in Section 2.
To quote RFC 2026 about the use of Proposed Standard technology:
Implementors should treat Proposed Standards as immature
specifications. It is desirable to implement them in order to gain
experience and to validate, test, and clarify the specification.
However, since the content of Proposed Standards may be changed if
problems are found or better solutions are identified, deploying
implementations of such standards into a disruption-sensitive
environment is not recommended.
General issues of scalability, security and policy control as
outlined in Section 2 are the subjects of active research and
development, as are a number of topics beyond this applicability
statement, such as third-party setup of either reservations or
differentiated service.
4. References
[Baker96] Baker, F., "RSVP Cryptographic Authentication", Work in
Progress.
[RFC 2206], Baker, F. and J. Krawczyk, "RSVP Management Information
Base", RFC 2206, September 1997.
[RFC 2207] Berger, L. and T. O'Malley, "RSVP Extensions for IPSEC
Data Flows", RFC 2207, September 1997.
[RFC 2211] Wroclawski, J., "Specification of Controlled-Load
Network Element Service", RFC 2211, September 1997.
[RFC 2212] Shenker, S., C. Partridge and R. Guerin, "Specification
of Guaranteed Quality of Service", RFC 2212, September 1997.
[RFC 2205] Braden, R. Ed. et al, "Resource ReserVation Protocol
-- Version 1 Functional Specification", RFC 2205,
September 1997.
[RFC 2210] Wroclawski, J., "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997.
5. Authors' Addresses
Fred Baker Abel Weinrib
Cisco Systems Intel Corporation
Phone: 408-526-4257 Phone: 503-264-8972
EMail: fred@cisco.com EMail: aweinrib@ibeam.intel.com
Bob Braden
USC/ISI Lixia Zhang
4676 Admiralty Way UCLA Computer Science Department
Marina Del Rey, CA 90292 4531G Boelter Hall
Phone: 310-822-1511 Los Angeles, CA 90095-1596 USA
EMail: braden@isi.edu Phone: 310-825-2695
EMail: lixia@cs.ucla.edu
Scott Bradner Allyn Romanow
Harvard University Sun Microsystems
Phone: 617-495-3864 Phone: 415-786-5179
EMail: sob@harvard.edu EMail: allyn@eng.sun.com
Michael O'Dell Allison Mankin
UUNET Technologies mankin@east.isi.edu
Phone: 703-206-5471
EMail: mo@uu.net
ISO Plain Language
On this page
§1Introduction and the Components RSVP Needs
RSVP is a unicast and multicast signalling protocol, designed to install and maintain reservation state information at each router along the path of a stream of data. The state handled by RSVP is defined by services specified by the Integrated Services Working Group. Those services and RSVP are being introduced to the IETF standards track jointly, and from then on the acronym RSVP on its own is used as a shorthand for the signalling protocol combined with the integrated service specifications.
RSVP must be used in conjunction with several additional components. There are message formats in which parameters for desired services can be expressed, specified in a proposed standard set. There are router and host mechanisms, such as packet classification and scheduling and admission control algorithms, to implement one or both of the service models. There are message formats in which parameters for desired policies for admission control and resource use can be expressed, and the Policy objects in the RSVP protocol specification are optional at this time. And there are diversely located mechanisms implementing desired admission control policy functions, including authorization and other security mechanisms.
In the presence of some form of each of these components, RSVP-enabled applications can achieve differentiated qualities of service across IP networks. Networked multimedia applications, many of which require or will benefit from a predictable end-user experience, are likely to be the initial users of RSVP-signalled services. Because RSVP and the integrated services mark a significant change to the service model of IP networks, RSVP has received considerable interest and press in advance of its release as a standards track RFC, and at the time of writing many vendors of operating systems and routers are incorporating RSVP and integrated services into their products for near-future availability. The goal of the applicability statement is to describe those uses of the current specification that are known to be feasible, and to identify areas of limitation and ongoing chartered work addressing some of these limitations.
RSVP on its own only says what is wanted. The routers still have to be built to act on the request, and someone has to decide who is allowed to make it.
- Service parametersMessage formats in which parameters for desired services can be expressed.
- Router and host mechanismsPacket classification and scheduling, and admission control algorithms, to implement the service models.
- Policy parametersMessage formats in which parameters for desired policies for admission control and resource use can be expressed.
- Policy enforcementDiversely located mechanisms implementing admission control policy, including authorization and other security mechanisms.
§2.1Scalability
The resource requirements, in processing and storage, for running RSVP on a router increase proportionally with the number of separate sessions, that is, RSVP reservations. Supporting numerous small reservations on a high-bandwidth link may therefore easily overtax the routers, and is inadvisable. Implementing the packet classification and scheduling capabilities currently used to provide differentiated services for reserved flows may also be very difficult for some router products, or on some of their high-speed interfaces such as OC-3 and above.
These scaling issues imply that it will generally not be appropriate to deploy RSVP on high-bandwidth backbones at the present time. Looking forward, the operators of such backbones will probably not choose to implement RSVP naively for each separate stream. Rather, techniques are being developed that will, at the edge of the backbone, aggregate together the streams that require special treatment, and within the backbone various less costly approaches would then be used to set aside resources for the aggregate as a whole, as a way of meeting the end-to-end requirements of individual flows. In the near term, various vendors are likely to use diverse approaches to the aggregation of reservations, and there is not currently chartered work in the IETF for the development of standards in this space. A BOF on Future Directions of Differential Services, on April 7, 1997 at the Memphis IETF, was to consider the IETF's next steps on this among other issues, and public documentation of aggregation techniques and experience is encouraged.
Every reservation costs the router memory and processing, so a backbone carrying thousands of streams would drown in them. The likely answer is to treat a group of streams as one reservation at the edge of the network.
§2.2Security Considerations
The RSVP working group's submission for Proposed Standard includes two security-related documents. One addresses denial of service and hijacking or theft of service attacks. The other addresses RSVP mechanisms for data flows that themselves use IP security.
The first document is proposed to protect against spoofed reservation requests arriving at RSVP routers, which might be used to obtain service for unauthorized parties or to lock up network resources in a denial of service attack. Modified and spoofed reservation requests are detected by the use of hop-by-hop MD5 checksums, in an Integrity Object, between RSVP neighbour routers. RSVP hop-by-hop authentication assumes that key management and distribution for routers is resolved and deployed, and until an effective key infrastructure is in place, manually keyed session integrity might be used.
That RSVP needs an effective key infrastructure among routers is not unique to RSVP: it is widely acknowledged that there are numerous denial of service attacks on the routing infrastructure, quite independent of RSVP, that will only be resolved by deployment of a key infrastructure. Theft of service risks will require the user to deploy with caution, and an elementary precaution is to configure management logging of new and changed filter specifications in RSVP-enabled infrastructure, for example the newFlow trap. The second security-related document provides a mechanism for carrying flows in which the transport and user octets have been encrypted. Although such encryption is highly beneficial to certain applications, it is not relevant to the functional security of RSVP or reservations.
Because a reservation request is just a message, someone could forge one and take bandwidth that is not theirs. The protection is a checksum between neighbouring routers, which in turn needs a way to manage keys.
§2.3Policy Control
Policy control addresses the issue of who can, and who cannot, make reservations, once a reservation protocol can be used to set up unequal services. The RSVP specification defines a mechanism for transporting policy information along with reservations, but it does not define the policies themselves, and vendors have stated that they will use the RSVP-defined mechanism to implement proprietary policies.
The RSVP working group is chartered to specify a simple standardized policy object and complete simple mechanisms for session use of the Integrity object in the near future, and this applicability statement may be updated at the completion of that charter. Before any decision to deploy RSVP, it would be wise to ensure that the policy control available from a vendor is adequate for the intended usage. In addition to the lack of documented policy mechanisms in any of the policy areas, such as access control, authorization and accounting, the community has little experience with describing, setting and controlling policies that limit Internet service. It is therefore likely that vendor solutions will be revised often, particularly before the IETF has developed any policy specification.
RSVP can carry a rule about who may reserve what, but the rule itself is left to the operator, and each vendor was expected to invent its own. That is the part most likely to change.
§3Recommendations
Given the current form of the RSVP specifications, multimedia applications to be run within an intranet are likely to be the first to benefit from RSVP, and SNA/DLSW is another application considered likely to benefit. Within the single or small number of related administrative domains of an intranet, scalability, security and access policy will be more manageable than in the global Internet, and risk will be more controllable. Use of RSVP and supporting components for small numbers of flows within a single Internet service provider is similar to an intranet use.
Current experience with RSVP has been collected only from test runs in limited testbeds and intranet deployment, so the memo recommends that people begin to use RSVP in production intranet or limited ISP environments, where benefits can be realized without having to resolve some of the issues described earlier. It quotes RFC 2026 on the use of Proposed Standard technology: implementors should treat Proposed Standards as immature specifications, and it is desirable to implement them in order to gain experience and to validate, test and clarify the specification, but since the content of Proposed Standards may be changed if problems are found or better solutions are identified, deploying implementations of such standards into a disruption-sensitive environment is not recommended.
General issues of scalability, security and policy control are the subjects of active research and development, as are a number of topics beyond this applicability statement, such as third-party setup of either reservations or differentiated service.
Start small, on a network you control, with a handful of flows. Try it to learn, not to run a service that matters.
| Environment | What the memo says |
|---|---|
| Within an intranet | Likely to be the first to benefit, with multimedia applications |
| One service provider, few flows | Similar to an intranet use |
| High-bandwidth backbones | Generally not appropriate at the present time |
| The global Internet | Scalability, security and access policy are harder to manage |