RSVP Receiver Proxy October 1999
Network Working Group Silvano Gai
Internet Draft Dinesh Dutt
draft-sgai-rsvp-proxy-00.txt Nitsan Elfassy
Expiration Date: April 2000 Cisco Systems
Yoram Bernet
Microsoft
October 1999
RSVP Receiver Proxy
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
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Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1998). All Rights Reserved.
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RSVP Receiver Proxy October 1999
Abstract
RSVP has been extended in several directions [Policy], [Identity],
[DCLASS], [AggrRSVP], [DiffModel],[COPS-RSVP], These extensions have
broadened the applicability of RSVP characterizing it as a signaling
protocol usable outside the IntServ model.
With the addition of the "Null Service Type" [NullServ], RSVP is
being adopted also by mission critical applications that require some
form of prioritized service, but cannot readily specify their
resource requirements. These applications do not need to set-up a
reservation end-to-end, but only to signal to the network their
policy information [Policy], [Identity] and obtain in response an
applicable DSCP [DCLASS].
RSVP Receiver Proxy is an extension to the RSVP message processing
(not to the protocol itself), mainly designed to operate in
conjunction with the Null Service Type and with an extension of the
COPS for RSVP protocol [COPS-RSVP-EXT].
Table of contents
1. Introduction .....................................................3
2. An overview of RSVP Receiver Proxy ...............................5
3. Detailed description of the message processing ...................6
4. The role of the policy server ....................................8
4.1 Generation of the Resv message by the Receiver Proxy..........8
4.2 Communication With the Policy Server..........................9
4.3 Enhancements To Existing Infrastructure......................10
4.4 Processing of other RSVP messages............................10
5. RSVP With Null Service Type .....................................11
6. Security Considerations .........................................11
7. Intellectual Property Considerations ............................11
8. References ......................................................12
9. Author Information ..............................................14
10. Full Copyright Statement .......................................15
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1. Introduction
The IETF has come up with two architectures to support QoS in IP
networks. IntServ (Integrated Services [RFC1633], [RFC2210]) is an
architecture that provides the ability for applications to choose
among multiple, controlled levels of delivery service for their data
packets. It relies upon explicit signaling by applications to the
network for the desired QoS. These applications typically know their
traffic characteristics and have possibly strict latency
requirements. Such applications require so called "tight QoS" or
"quantitative QoS". RSVP is the protocol which can be used by
applications to signal their QoS requirements to the network.
Applications have to be modified to take advantage of the Integrated
Services. The receivers control the QoS given to the data stream.
DiffServ (Differentiated Services, [RFC2474], [RFC2475]) is another
IETF architecture for implementing scalable service differentiation
in the Internet. There is no explicit signaling protocol used in
DiffServ. The network is logically divided into edge devices and core
devices. The edge devices attempt to recognize data flows and assign
QoS based on this. They also assign a DSCP (DiffServ Code Point) in
the DS byte of the packets (the byte that used to be called the TOS
byte). Core devices use the DSCP to assign a QoS to the microflows.
Applications typically do not have to be modified to take advantage
of Differentiated Services. Receivers do not control the QoS given to
the data stream.
The recognition of data flows and the assignment of an appropriate
DSCP is a tricky task and often requires stateful inspection of flows
and symmetrical routing paths. Moreover, application recognition is
limited to the information present in the packet traversing the
network and in most current network devices is further limited to
what is in the IP/TCP/UDP headers. Application vendors desire to be
able to assign QoS to their packets based on both information that
may not be carried in the packet and information other than the
IP/TCP/UDP header fields. For example, a SAP print transaction may
require a different treatment than a SAP database update. Similarly,
if the user of the application is the CTO of the company, the
priority assigned to such packets maybe different from that assigned
to packets of the application being used by some other person in the
company.
For this reason RSVP has been proposed also for mission critical
applications (e.g. ERP) that require some form of prioritized
service, but cannot readily specify their resource requirements. The
ISSLL WG is discussing the specification of the Null Service Type as
a way to use RSVP with a broader range of applications [NullServ].
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Some of these applications have the requirement for the end-to-end
message processing of RSVP. Others simply need to signal to the
network their identity [Identity] and some additional policy
information [Policy] related to the flows and obtaining from the
network some decisions, e.g. the DSCP to be used [DCLASS].
RSVP Receiver Proxy is a proposal that mainly addresses this second
type of applications, i.e., applications that simply want to use RSVP
as a signaling protocol toward the network. For them, the end-to-end
nature of RSVP is not interesting and often is perceived as a
disadvantage, since it is characterized by a higher latency.
The RSVP Receiver Proxy:
o is an alternate way to process RSVP messages and policy information
in the switch/routers;
o it does not require any change to the RSVP protocol;
o it does require an extension to the COPS for RSVP protocol [COPS-
RSVP-EXT].
In general, "RSVP Proxy" should be symmetric, i.e., it may be useful
to have RSVP Sender Proxy as well as RSVP Receiver Proxy. This
document does not define RSVP Sender Proxy at this stage. If the
document is accepted by the IETF community, the RSVP Sender Proxy can
be added in the next version.
This document defines RSVP Receiver Proxy in association with the
Null Service Type, but nothing prevents using this feature also in
association with other service types, e.g. the Controlled Load
service.
The following section uses an example in which the Receiver Proxy
functionality is placed in the first hop switch/router. This is a
possibility, but it is not a requirement. While designing a network
the following trade-off should be considered:
o Proxying closer to the server reduces turn around time.
o Proxying further from the server enables additional downstream
network elements to benefit from the information carried in the
signaling messages, and to participate in the response.
o Proxying anywhere in the network enables the deployment of such
applications in which only the server is required to signal, but
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the client may remain unchanged.
The COPS-RSVP Extension [COPS-RSVP-EXT] should enable the network
administrator to decide how to make the tradeoffs described above.
2. An overview of RSVP Receiver Proxy
With RSVP Receiver Proxy a switch/router acts as a proxy for the
receiver, e.g. when it receives an RSVP Path message, it generates an
RSVP Resv message on behalf of the receiver.
The generation of the Resv message is done under policy control, the
switch/router may be programmed either to classify the packets
marking them with an appropriate DSCP or to use the DCLASS object
[DCLASS] to communicate the classification decision to the host.
The adoption of RSVP Receiver Proxy do not change the basic model of
RSVP, i.e.:
o the handling of data flows is unidirectional. If the application
data is strictly unidirectional it is sufficient to use RSVP only
in one direction. In the case of bidirectional data, running RSVP
only in one direction provides a certain performance benefit, but
to get the maximum performance benefit it is necessary to use RSVP
in both directions.
o The application on the host assumes the host model of RSVP,
including the extensions proposed in [DiffModel], [Policy],
[Identity], [NullServ].
o The message format and the message types are the same of RSVP,
including the DCLASS object previously proposed in [DCLASS] and the
Null Service Type [NullServ].
o The switch/router acts as a COPS client [COPS] in communicating
with the policy server, i.e. it uses RSVP client for COPS [COPS-
RSVP]. Certain extensions to COPS for RSVP are needed [COPS-RSVP-
EXT], see Section 4.
o The classification of traffic cannot be more granular than
microflow (the so called five-tuple) or in the case of IPSEC the
four-tuple that includes the Parameter Index, or SPI, in place of
the UDP/TCP-like ports [RFC2207].
o There is no special support for subflows (a set of packets inside a
microflow). Of course, an application may send different Path
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messages for the same flow at different times, thus providing a
support for subflows not overlapping in time.
3. Detailed description of the message processing
This sections details some of the message processing of a
switch/router acting as RSVP Receiver Proxy. The description is
mainly focused on the two fundamental messages in RSVP, i.e. the
Path Message and the Resv message. Other messages are discussed in
Section 4.4.
Figure 1 depicts a simple network topology (two hosts H1 & H2 and
intermediate routers, R1-R5) that will be used in the explanation.
Path Message ----->
<----- Resv Message
+-----+ +-----+
| PS1 | | PS1 |
+-----+ +-----+
/ | \ / |
/ | \ / |
/ | \ / |
+----+ +----+ +----+ +----+ +----+ +----+ +----+
| H1 |---| R1 |---| R2 |---| R3 |---| R4 |---| R5 |---| H2 |
+----+ +----+ +----+ +----+ +----+ +----+ +----+
H1 ----> R1 ----> R2 ----> R3 ----> R4 ----> R5 ----> H2 (Regular
| RSVP
v case)
H1 <---- R1 <---- R2 <---- R3 <---- R4 <---- R5 ----> H2
H1 ----> R1
| (RSVP Receiver Proxy)
v
H1 <---- R1
Hx: Host x
Ry: Router y
PSz: Policy Server z
Figure 1: Possible Message Forwarding Behaviors in RSVP
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Immediately below the network, the normal RSVP message processing is
reported. The Path message goes hop-by-hop from H1 to H2. The Resv
message uses the reverse path of the Path message and goes from H2 to
H1. The interaction between the network devices and the policy
servers is the one specified by COPS for RSVP ([COPS], [COPS-RSVP]).
With RSVP Receiver Proxy the propagation of the RSVP Path message is
terminated in the router acting as a proxy. Any router in the network
may act as RSVP Receiver Proxy, but it is a good design guideline to
place the proxy functionality as close as possible to the sender. In
our case R1 acts as a proxy for H2 under the control of a policy
server.
For example, an application on H1 uses RSVP to signal parameters upon
which to base the decision to assign the QoS for a microflow. The
example assumes that the information needs to be used only by the
edge network device and it is not required to propagate this further
down the network
A possible sequence of steps consists of:
o The application on H1 indicates to the RSVP subsystem that it is a
sender and specifies its traffic characteristics. It may specify
additional parameters.
o This causes the RSVP subsystem on H1 to start transmitting RSVP
Path messages in accordance with normal RSVP/SBM rules.
o The first hop switch/router (R1) receives this message and it
communicates with the policy server for a decision on how to treat
the Path message. It copies all the relevant information contained
in the Path message to the policy server.
o The policy server communicates a decision to R1 to not forward the
Path message, but instead to originate and send a Resv message to
H1. H1 data traffic gets assigned the right DSCP by the
switch/router as per the policy communicated by the policy server.
The Resv message may also specify to the host the DSCP and shaping
information to be associated with the microflow using the DCLASS
object [DCLASS].
o On receiving the Resv message, H1 may start marking correctly the
data traffic accordingly to the DSCP received in the Resv message.
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4. The role of the policy server
To implement both RSVP and RSVP Receiver Proxy the policy server
needs to specify a set of decisions [COPS-RSVP-EXT] which is extended
compared to COPS-RSVP [COPS-RSVP]. If the decision is to accept the
Path message, the decision message must specify how the network
device behaves with respect to each of the following:
o Forwarding of the Path message;
o Originating a RSVP Resv message;
o Processing and possibly Forwarding a RSVP Resv message.
The decision may also possibly include the QoS specification to be
associated with the flow identified in the Path message. This
specification consists of a DSCP and possibly a TSPEC (as specified
by RSVP [RFC2210]) for policing the traffic.
4.1 Generation of the Resv message by the Receiver Proxy
It maybe required that the network device originate a Resv message.
This is a proxy Resv message in the sense that it is being generated
by the network device and not by the actual receiver(s) identified in
the RSVP Path message. The format of a Resv message is as follows
(see [RFC2205] for details):
<Resv Message> ::= <Common Header> [ <INTEGRITY> ]
<SESSION> <RSVP HOP> <TIME_VALUES><DCLASS>
[ <RESV_CONFIRM> ] [ <SCOPE> ] [ <POLICY_DATA>... ]
<STYLE> <flow descriptor list>
o The network device puts its IP address and L2 address in the source
IP and source mac-address fields. Since Resv messages follow Path
messages, this would constitute a valid Resv message.
o The SESSION object can be copied from the Path message.
o The RSVP HOP object can be filled in with the IP address of the
switch/router generating this Resv message.
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o The TIME_VALUES object contains the refresh period. See below.
o The STYLE object is set to Wildcard Filter (WF) style indicating
that the reservation is to be shared and that the sender is
wildcarded. Associated with a WF style is a FLOWSPEC object which
is encoded as specified in [RFC2210] or [NullServ].
o The SCOPE and RESV_CONFIRM objects need not be included in the Resv
message.
o The POLICY_DATA objects will be as returned by the policy server.
o The Resv message may also contain the new DCLASS object is
contained in the COPS decision message. The DCLASS object specifies
the DSCP to be associated with the microflow for which the Path
message was received.
o The Resv messages need to be originated and sent for each of the
periodically-received Path messages.
4.2 Communication With the Policy Server
When a network device establishes the connection with the policy
server, it sends a COPS Client-Open message for the RSVP client. It
should indicate in this message whether the network device is capable
of supporting only the base RSVP message processing or also the
Receiver Proxy message processing. It can do this with in a
capability list (that can accommodate also future extensions). To
deal with existing clients, if the policy server does not receive a
capability list, it should assume that it is communicating with a
legacy RSVP client. The capability list can be included as part of
the ClientSI object passed in the Client-Open message [COPS-RSVP-
EXT].
On receiving a RSVP Path message, the network device sends a COPS REQ
message to the policy server. This message will be the standard REQ
message sent on receiving a RSVP Path message.
The DEC message returned by the policy server for this REQ message
must contain the information needed to take the decisions listed in
Section 4.
The DEC message SHOULD also contain a list of DSCP [DCLASS].
The DEC message may also contain bandwidth information to be
associated with the microflow: communicating Shaping/limiting
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parameters to the network is a powerful Policy Management tool for
the PDP/LPDP both for Qualitative and Quantitative services. This
topic needs further study.
The network device must also be able to determine if a Path message
is a refresh or a new one. It must communicate with the policy server
only for new Path messages or for updated ones.
In the absence of a policy server or if the connection to the policy
server is not up, the operation of RSVP Receiver Proxy depends on
policy configuration local to the network device. For example, the
network device may have a local configuration that specifies:
o do not accept new flows;
o honor existing flows until they time-out.
4.3 Enhancements To Existing Infrastructure
o COPS for RSVP will have to be enhanced to support the new format
for RSVP REQ and DEC message as stated in [COPS-RSVP-EXT].
o When SBM is in use, it is possible that a device which does not
support RSVP Receiver Proxy becomes the DSBM on the first-hop
segment. This can be prevented by the network administrator by
configuring the appropriate priority on the device with RSVP
Receiver Proxy support.
4.4 Processing of other RSVP messages
This section details the processing of the protocol messages in RSVP
other than Path and Resv. Only the differences in the processing from
classical RSVP is specified.
o PathTear message is honored and is forwarded or not similar to a
Path message. The policy server is not contacted on receiving a
PathTear message. This is consistent with the existing behavior of
COPS for RSVP[RSVP-COPS].
o PathErr messages are treated as in normal RSVP.
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5. RSVP With Null Service Type
RSVP protocol can be represented as consisting of two parts: a
message processing part and a resource allocation & resource
enforcement part. The following are the minimal requirements for a
network device to support RSVP Null Service Type:
o The network device MUST implement the message processing part of
the RSVP protocol. This includes the ability to receive and
interpret a raw IP packet or UDP-based RSVP packet.
o If the network device is a L2 device, it SHOULD implement SBM.
o The network device SHOULD know how to talk to a policy server using
COPS. Specifically, the network device SHOULD be able to talk to
COPS as a RSVP client using the extensions defined in [COPS-RSVP-
EXT].
o The node SHOULD keep the RSVP state so that the following Path
refresh won't cause a repetitive Path handling.
o The network device SHOULD be able to generate a Resv message
periodically in a coherent way with the RSVP soft state
maintenance.
o In the absence of a connection to the policy server, this network
device depends on policy configuration local to the network device
(see Section 4.2).
6. Security Considerations
RSVP messages contain an INTEGRITY object which authenticates the
originating node and is also used to verify the contents of the
message. Moreover the RSVP message SHOULD contain an IDENTITY object
that SHOULD be authenticated. If the policy server does not implement
any security mechanisms, it SHOULD use a clear text version of the
user identity.
7. Intellectual Property Considerations
The IETF is being notified of intellectual property rights claimed in
regard to some or all of the specification contained in this
document. For more information consult the online list of claimed
rights.
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8. References
[COPS] Boyle, J., Cohen, R., Durham, D., Herzog, S., Raja, R.,
Sastry, A., "The COPS (Common Open Policy Service)
Protocol", IETF <draft-ietf-rap-cops-07.txt>, August
1999.
[RFC1633] R. Braden, D. Clark, S. Shenker, "Integrated Services in
the Internet Architecture: an Overview," June 1994.
[RFC2205] Braden, R., Zhang, L., Berson, S., Herzog, S., and Jamin,
S., "Resource Reservation Protocol (RSVP) Version 1
Functional Specification", IETF RFC 2205, Proposed
Standard, September 1997.
[RFC2210] J. Wroclawski, "The Use of RSVP with IETF Integrated
Services," September 1997.
[RFC2474] K. Nichols, S. Blake, F. Baker, D. Black, "Definition of
the Differentiated Services Field (DS Field) in the IPv4
and IPv6 Headers," December 1998.
[RFC2475] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, W.
Weiss, "An Architecture for Differentiated Service," RFC
2475, December 1998.
[COPS-RSVP] Jim Boyle, Ron Cohen, David Durham, Shai Herzog, Raju
Rajan, Arun Sastry, "COPS usage for RSVP," <draft-ietf-
rap-cops-rsvp-05.txt>, June 14, 1999
[COPS-RSVP-EXT] Nitsan Elfassy, Dinesh Dutt, "COPS Extensions for
RSVP Receiver Proxy Support"," <draft-nitsan-cops-rsvp-
proxy-00.txt>, October 1999.
[Policy] Shai Herzog, "RSVP Extensions for Policy Control,"
Internet Draft., < draft-ietf-rap-rsvp-ext-06.txt>, April
1999.
[DiffModel] Y. Bernet, A. Smith, S. Blake, "A Conceptual Model for
Diffserv Routers," Internet Draft, <draft-ietf-diffserv-
model-00.txt>, June 1999.
[Identity] Satyendra Yadav, Raj Yavatkar, Ramesh Pabbati, Peter
Ford, Tim Moore, Shai Herzog, "Identity Representation
for RSVP," Internet-Draft <draft-ietf-rap-rsvp-identity-
05.txt>, September 1999.
Gai, Dutt, Elfassy, Bernet [Page 12]
RSVP Receiver Proxy October 1999
[AggrRSVP] Fred Baker, Carol Iturralde, Francois Le Faucheur, Bruce
Davie, "Aggregation of RSVP for IP4 and IP6
Reservations," <draft-ietf-issll-rsvp-aggr-00.txt>,
September 1999
[DCLASS] Bernet, Y., "Usage and Format of the DCLASS Object With
RSVP Signaling," <draft-ietf-issll-dclass-00.txt >,
August 1999.
[NullServ] Yoram Bernet, Andrew Smith, B. Davie, "Specification of
the Null Service Type," <draft-ietf-issll-nullservice-
00.txt>, September 1999
[RSVPDIFF] Bernet, R. Yavatkar, P. Ford, F. Baker, L. Zhang, M.
Speer, B. Braden, B. Davie, J. Wroclawski, E. Felstaine,
"Integrated Services Operation Over Diffserv Networks,"
<draft-ietf-issll-diffserv-rsvp-03.txt>, September 1999
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9. Author Information
Silvano Gai
Cisco Systems, Inc.
170 Tasman Dr.
San Jose, CA 95134-1706
Phone: (408) 527-2690
email: sgai@cisco.com
Dinesh Dutt
Cisco Systems, Inc.
170 Tasman Dr.
San Jose, CA 95134-1706
Phone: (408) 527-0955
email: ddutt@cisco.com
Nitsan Elfassy
Cisco Systems, Inc.
Cisco Systems, Inc.
170 Tasman Dr.
San Jose, CA 95134-1706
Phone: +972 9 970 0066
email: nitsan@cisco.com
Bernet, Yoram
Microsoft
One Microsoft Way,
Redmond, WA 98052
Phone: (425) 936-9568
Email: yoramb@microsoft.com
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10. Full Copyright Statement
Copyright (C) The Internet Society (1997). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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