Specification of the Null Service Type
draft-ietf-issll-nullservice-00
The information below is for an old version of the document that is already published as an RFC.
Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 2997.
|
|
---|---|---|---|
Authors | Andrew H. Smith , Dr. Bruce S. Davie , Yoram Bernet | ||
Last updated | 2013-03-02 (Latest revision 1999-09-15) | ||
RFC stream | Internet Engineering Task Force (IETF) | ||
Intended RFC status | Proposed Standard | ||
Formats | |||
Additional resources | Mailing list discussion | ||
Stream | WG state | (None) | |
Document shepherd | (None) | ||
IESG | IESG state | Became RFC 2997 (Proposed Standard) | |
Consensus boilerplate | Unknown | ||
Telechat date | (None) | ||
Responsible AD | (None) | ||
Send notices to | (None) |
draft-ietf-issll-nullservice-00
Internet Draft Y. Bernet, Microsoft
Expires March 2000 A. Smith, Extreme Networks
draft-ietf-issll-nullservice-00.txt B. Davie, Cisco Systems
September, 1999
Specification of the Null Service Type
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
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-
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Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
1. Abstract
In the typical RSVP/Intserv model, applications request a specific
Intserv service type and quantify the resources required for that
service. For certain applications, the determination of service
parameters is best left to the discretion of the network
administrator. For example, ERP applications are often mission
critical and require some form of prioritized service, but cannot
readily specify their resource requirements. To serve such
applications, we introduce the notion of the 'Null Service'. The
Null Service allows applications to identify themselves to network
QoS policy agents, using RSVP signaling. However, it does not
require them to specify resource requirements. QoS policy agents in
the network respond by applying QoS policies appropriate for the
application (as determined by the network administrator). This mode
of RSVP usage is particularly applicable to networks that combine
differentiated service (diffserv) QoS mechanisms with RSVP signaling
[intdiff]. In this environment, QoS policy agents may direct the
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signaled application's traffic to a particular diffserv class of
service.
2. Motivation
Using standard RSVP/Intserv signaling, applications running on hosts
issue requests for network resources by communicating the following
information to network devices:
1. A requested service level (Guaranteed or Controlled Load).
2. The quantity of resources required at that service level.
3. Classification information by which the network can recognize
specific traffic (filterspec).
4. Policy/identity information indicating the user and/or the
application for which resources are required.
In response, standard RSVP aware network nodes choose to admit or
deny a resource request. The decision is based on the availability
of resources along the relevant path and on policies. Policies
define the resources that may be granted to specific users and/or
applications. When a resource request is admitted, network nodes
install classifiers that are used to recognize the admitted traffic
and policers that are used to assure that the traffic remains within
the limits of the resources requested.
The Guaranteed and Controlled Load Intserv services are not suitable
for certain applications that are unable to (or choose not
to)specify the resources they require from the network. Diffserv
services are better suited for this type of application. Nodes in a
diffserv network are typically provisioned to classify arriving
packets to some small number of behaviour aggregates (BAs)
[diffarch]. Traffic is handled on a per-BA basis. This provisioning
tends to be 'top-down' with respect to end-user traffic flows in the
sense that there is no signaling between hosts and the network.
Instead, the network administrator uses a combination of heuristics,
measurement and experience to provision the network devices to
handle aggregated traffic, with no deterministic knowledge of the
volume of traffic that will arrive at any specific node.
In applying diffserv mechanisms to manage application traffic,
network administrators are faced with two challenges:
1. Provisioning - network administrators need to anticipate the
volume of traffic likely to arrive at each network node for each
diffserv BA. If the volume of traffic arriving is likely to
exceed the capacity available for the BA claimed, the network
administrator has the choice of increasing the capacity for the
BA, reducing the volume of traffic claiming the BA, or
compromising service to all traffic arriving for the BA.
2. Classification - diffserv nodes classify traffic to user and/or
application, based on the diff-serv codepoint (DSCP) in each
packet's IP header or based on other fields in the packet's IP
header (source/destination address/port and protocol). The latter
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method of classification is referred to as MF classification.
This method of classification may be unreliable and imposes a
management burden.
By using RSVP signaling, the management of application traffic in
diffserv networks can be significantly facilitated. (Note that
RSVP/diffserv interoperability has been discussed previously in the
context of the Guaranteed and Controlled Load Intserv services. This
draft focuses on RSVP/diffserv interoperability in the context of
the Null Service.
3. Operational Overview
In the proposed mechanism, the RSVP sender offers the new service
type, 'Null Service Type' in the ADSPEC that is included with the
PATH message. A new Tspec corresponding to the new service type is
added to the SENDER_TSPEC. In addition, the RSVP sender will
typically include with the PATH message policy objects identifying
the user, application and sub application ID [identity,
application].
(Note that at this time, the new Tspec is defined only to carry the
maximum packet size parameter (M), for the purpose of avoiding
fragmentation. No other parameters are defined.)
Network nodes receiving these PATH messages interpret the service
type to indicate that the application is requesting no specific
service type or quantifiable resources. Instead, network nodes
manage the traffic flow based on the requesting user, the requesting
application and the type of application sub-flow.
This mechanism offers significant advantages over a pure diffserv
network. At the very least, it informs each network node which would
be affected by the traffic flow (and which is interested in
intercepting the signaling) of:
1. The demand for resources in terms of number of flows of a
particular type traversing the node.
2. The binding between classification information and user,
application and sub-application.
This information is particularly useful to policy enforcement points
and policy decision points (PEPs and PDPs). The network
administrator can configure these elements of the policy management
system to apply appropriate policy based on the identity of the
user, the application and the specific sub application ID.
PEPs and PDPs may be configured to return an RSVP RESV message to
the sender. The returned RESV message may include a DCLASS object
[dclass]. The DCLASS object instructs the sender to mark packets on
the corresponding flow with a specific DSCP (or set of DSCPs). This
mechanism allows PEP/PDPs to affect the volume of traffic arriving
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at a node for any given BA. It enables the PEP/PDP to do so based on
sophisticated policies.
3.1 Operational Notes
3.1.1 Scalability Issues
In any network in which per-flow signaling is used, it is wise to
consider scalability concerns. The Null Service encourages signaling
for a broader set of applications than that which would otherwise be
signaled for. However, RSVP signaling does not, in general, generate
a significant amount of traffic relative to the actual data traffic
associated with the session. In addition, the Null Service does not
encourage every application to signal. It should be used by
applications that are considered mission critical or needing QoS
management by network administrators.
Perhaps of more concern is the impact on processing resources at
network nodes that process the signaling messages. When considering
this issue, it's important to point out that it is not necessary to
process the signaling messages at each network node. In fact, the
combination of RSVP signaling with diff-serv networks may afford
significant benefits even when the RSVP messages are processed only
at certain key nodes (such as boundaries between network domains,
first-hop routers, PEPs or any subset of these). Individual nodes
should be enabled or disabled for RSVP processing at the discretion
of the network administrator. See [intdiff] for a discussion of the
impact of RSVP signaling on diff-serv networks.
In any case, per-flow state is not necessarily required, even in
nodes that apply per-flow processing.
3.1.2 Policy Enforcement in Legacy Networks
Network nodes that adhere to the RSVP spec should transparently pass
signaling messages for the Null Service. As such, it is possible to
introduce a small number of PEPs that are enabled for Null Service
into a legacy network and to realize the benefits described in this
draft.
3.1.3 Combining Existing Intserv Services with the Null Service
This draft does not preclude applications from offering both a
quantitative Intserv service (Guaranteed or Controlled Load)and the
Null Service, at the same time. An example of such an application
would be a telephony application that benefits from the Guaranteed
Service but is able to adapt to a less strict service. By
advertising its support for both, the application enables network
policy to decide which service type to provide.
4. Signaling Details
4.1 ADSPEC Generation
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The RSVP sender constructs an initial RSVP ADSPEC object specifying
the Null Service Type. Since there are no service specific
parameters associated with this service type, the associated ADSPEC
fragment is empty and contains only the header word. Network nodes
may or may not supply valid values for bandwidth and latency general
parameters. As such, they may use the unknown values defined in
[RFC2216].
The ADSPEC is added to the RSVP PATH message created at the sender.
4.2 RSVP SENDER_TSPEC Object
An additional Tspec is defined to correspond to the Null Service. If
only the Null Service is offered in the ADSPEC, then this is the
only Tspec included in the SENDER_TSPEC object. If guaranteed or
controlled load services are also offered in the ADSPEC, then the
new Tspec is appended following the standard Intserv token-bucket
Tspec [RFC2210].
4.3 RSVP FLOWSPEC Object
Receivers may respond to PATH messages by generating an RSVP RESV
message including a FLOWSPEC object. The FLOWSPEC object should
specify that it is requesting the Null Service. It is possible that,
in the future, a specific Rspec may be defined to correspond to the
new service type.
5. Detailed Message Formats
5.1 Standard ADSPEC Format
A standard RSVP ADSPEC object is described in [RFC2210]. It includes
a message header and a default general parameters fragment.
Following the default general parameters fragment are fragments for
each supported service type.
5.2 ADSPEC for Null Service Type
The Null Service ADSPEC includes the message header and the default
general parameters fragment, followed by a single fragment denoting
the Null Service. The new fragment introduced for the Null Service
is formatted as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6 (a) |x| Reserved | 0 (b) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
a - indicates Null Service (6).
x - is the break-bit.
b - indicates zero words in addition to the header.
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A complete ADSPEC supporting only the Null Service is illustrated
below:
31 24 23 16 15 8 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1 | 0 (a) | Reserved | Msg length รป1 (b) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2 | 1 (c) |x| Reserved | 8 (d) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3 | 4 (e) | (f) | 1 (g) |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4 | IS hop cnt (32-bit unsigned) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5 | 6 (h) | (i) | 1 (j) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6 | Path b/w estimate (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7 | 8 (k) | (l) | 1 (m) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8 | Minimum path latency (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
9 | 10 (n) | (o) | 1 (p) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
10 | Composed MTU (32-bit unsigned) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
11 | 6 (q) |x| Reserved | 0 (r) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Word 1: Message Header:
(a) - Message header and version number
(b) - Message length - 10 words not including header
Words 2-10: Default general characterization parameters
(c) - Per-Service header, service number 1 (Default General
Parameters)
(x) - Global Break bit (NON_IS_HOP general parameter 2)
(d) - Length of General Parameters data block (8 words)
(e) - Parameter ID, parameter 4 (NUMBER_OF_IS_HOPS general
parameter)
(f) - Parameter 4 flag byte
(g) - Parameter 4 length, 1 word not including header
(h) - Parameter ID, parameter 6 (AVAILABLE_PATH_BANDWIDTH general
parameter)
(i) - Parameter 6 flag byte
(j) - Parameter 6 length, 1 word not including header
(k) - Parameter ID, parameter 8 (MINIMUM_PATH_LATENCY general
parameter)
(l) - Parameter 8 flag byte
(m) - Parameter 8 length, 1 word not including header
(n) - Parameter ID, parameter 10 (PATH_MTU general parameter)
(o) - Parameter 10 flag byte
(p) - Parameter 10 length, 1 word not including header
Word 11: Null Service parameters
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(q) - Per-Service header, service number 6 (Null)
(x) - Break bit for Null Service
(r) - Length (0) of per-service data not including header word.
Note that the standard rules for parsing ADSPEC service fragments
ensure that the ADSPEC will not be rejected by legacy network
elements. Specifically, these rules state that a network element
encountering a per-service data header which it does not understand
should set bit 23 (the break-bit) to indicate that the service is
not supported and should use the length field from the header to
skip over the rest of the fragment.
Also note that it is likely that it will not be possible for hosts
or network nodes to generate meaningful values for words 5 and/or 7
(bandwidth estimates and path latency), due to the nature of the
service. In this case, the unknown values from [RFC2216] should be
used.
5.3 SENDER_TSPEC Object Format
The following Tspec is defined to correspond to the Null Service:
31 24 23 16 15 8 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1 | 6 (a) |0| Reserved | 2 (b) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2 | 128 (c) | 0 (d) | 1 (e) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Word 1: Service header
(a) - Service number 6 (Null Service)
(b) - Length of per-service data, 2 words not including per-service
header
Word 2-3: Parameter
(c) - Parameter ID, parameter 128 (Null Service TSpec)
(d) - Parameter 128 flags (none set)
(e) - Parameter 128 length, 1 words not including parameter header
Note that the illustration above does not include the standard RSVP
SENDER_TSPEC object header, nor does it include the sub-object
header (which indicates the message format version number and
length), defined in RFC 2205 and RFC 2210, respectively.
In the case that only the Null Service is advertised in the ADSPEC,
the Tspec above would be appended immediately after the SENDER_TSPEC
object header and sub-object header. In the case that additional
service types are advertised, requiring the token bucket specific
Tspec defined in RFC2210, the Tspec above would be appended
following the token bucket Tspec, which would in turn follow the
object header and sub-object header.
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5.4 FLOWSPEC Object Format
The format of an RSVP FLOWSPEC object originating at a receiver
requesting the Null Service is shown below. The value of 6 in the
per-service header (field (c), below) indicates that Null Service is
being requested.
31 24 23 16 15 8 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1 | 0 (a) | reserved | 3 (b) |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2 | 6 (c) |0| Reserved | 2 (d) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3 | 128 (e) | 0 (f) | 1 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(a) - Message format version number (0)
(b) - Overall length 3 words not including header)
(c) - Service header, service number 6 (Null)
(d) - Length of data, 2 words not including per-service header
(e) - Parameter ID, parameter 128 (Null Service TSpec)
(f) - Parameter 128 flags (none set)
(g) - Parameter 128 length, 1 words not including parameter header
5.5 DCLASS Object Format
DCLASS objects may be included in RESV messages. For details
regarding the DCLASS object format, see [dclass].
6. Security Considerations
The message formatting and usage rules described in this note raise
no new security issues beyond standard RSVP.
9. References
[RFC2205] Braden, B., et al., "Resource Reservation Protocol (RSVP)
- Version 1 Functional Specification", RFC 2205, September 1997.
[RFC2216] Shenker, S., and Wroclawski, J., "Network Element QoS
Control Service Specification Template", RFC 2216, September 1997.
[RFC2210] Wroclawski, J., "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997.
[intdiff] Bernet, Y., Yavatkar, R., Ford, P., Baker, F., Zhang, L.,
Nichols, K., Speer, M., Braden, B., Davie, B., "Integrated Services
Operation over Diffserv Networks", Internet Draft, June 1999.
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[diffarch] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
Weiss, W., "An Architecture for Differentiated Services", RFC 2475,
December 1998.
[identity] Yadav, S., Yavatkar, R., Pabbati, R., Ford, P., Moore,
T., Herzog, S., "Identity Representation for RSVP", Internet Draft,
February 1999.
[application] Bernet, Y., "Application and Sub Application Identity
Policy Objects for Use with RSVP", Internet Draft, February 1999.
[dclass] Bernet, Y., "Usage and Format of the DCLASS Object with
RSVP Signaling", Internet Draft, June 1999.
10. Acknowledgments
We thank Fred Baker, Dinesh Dutt, Nitsan Elfassy, John Schnizlein,
Ramesh Pabbati and Sanjay Kaniyar for their comments on this draft.
11. Author's Addresses
Yoram Bernet
Microsoft
One Microsoft Way
Redmond, WA 98052
(425) 936-9568
Yoramb@microsoft.com
Andrew Smith
Extreme Networks
3585 Monroe St.
Santa Clara CA 95051
USA
+1 (408) 579 2821
andrew@extremenetworks.com
Bruce Davie
Cisco Systems
250 Apollo Drive
Chelmsford, MA 01824
(978)-244-8000
bsd@cisco.com
Bernet expires March, 2000 9