One document matched: draft-polk-tsvwg-intserv-multiple-tspec-04.txt
Differences from draft-polk-tsvwg-intserv-multiple-tspec-03.txt
TSVWG WG James Polk
Internet-Draft Subha Dhesikan
Expires: Jan 12, 2011 Cisco Systems
Intended Status: Standards Track (PS) July 12, 2010
Updates: RFC 2205, 2210, 4495 (if published as an RFC)
Integrated Services (IntServ) Extension to Allow Signaling of Multiple
Traffic Specifications and Multiple Flow Specifications in RSVPv1
draft-polk-tsvwg-intserv-multiple-tspec-04
Abstract
This document defines extensions to Integrated Services (IntServ)
allowing multiple traffic specifications and multiple flow
specifications to be conveyed in the same Resource Reservation
Protocol (RSVPv1) reservation message exchange. This ability helps
optimize an agreeable bandwidth through a network between endpoints
in a single round trip.
Legal
This documents and the information contained therein are provided on
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FOR A PARTICULAR PURPOSE.
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This Internet-Draft will expire on January 12, 2011.
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Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
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warranty as described in the BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview of the Proposal for including multiple TSPECs and
FLOWSPECs . . . . . . . . . . . . 6
3. Multi_TSPEC and MULTI_FLOWSPEC Solution . . . . . . . . . . . 8
3.1 New MULTI_TSPEC and MULTI-RSPEC Parameters . . . . . . . 9
3.2 Multiple TSPEC in a PATH Message . . . . . . . . . . . . 9
3.3 Multiple FLOWSPEC for Controlled Load Service . . . . . . 12
3.4 Multiple FLOWSPEC for Guaranteed Service . . . . . . . . 14
4. Rules of Usage . . . . . . . . . . . . . . . . . . . . . . . 17
4.1 Backward Compatibility . . . . . . . . . . . . . . . . . 17
4.2 Applies to Only a Single Session . . . . . . . . . . . . 17
4.3 No Special Error Handling for PATH Message . . . . . . . 18
4.4 Preference Order to be Maintained . . . . . . . . . . . 18
4.5 Bandwidth Reduction in Downstream Routers . . . . . . . 18
4.6 Merging Rules . . . . . . . . . . . . . . . . . . . . . 19
4.7 Other Considerations . . . . . . . . . . . . . . . . . . 20
4.8 Known Open Issues . . . . . . . . . . . . . . . . . . . . 20
5. Security considerations . . . . . . . . . . . . . . . . . . . 20
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 21
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 21
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1. Normative References . . . . . . . . . . . . . . . . . 21
8.2. Informative References . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 22
Appendix A. Alternatives for Sending Multiple TSPECs. . . . . 22
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC 2119].
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1. Introduction
This document defines how Integrated Services (IntServ) [RFC2210]
includes multiple traffic specifications and multiple flow
specifications in the same Resource Reservation Protocol (RSVPv1)
[RFC2205] message. This ability helps optimize an agreeable
bandwidth through a network between endpoints in a single round
trip.
There is a separation of function between RSVP and IntServ, in
which RSVP does not define the internal objects to establish
controlled load or guarantee services. These are generally left to
be opaque in RSVP. At the same time, IntServ does not require
that RSVP be the only reservation protocol for transporting both
the controlled load or guaranteed service objects - but RSVP does
often carry the objects anyway. This makes the two independent -
yet related in usage, but are also frequently talked about as if
they are one and the same. They are not.
The 'traffic specification' contains the traffic characteristics of
a sender's data flow and is a required object in a PATH message. The
TSPEC object is defined in RFC 2210 to convey the traffic
specification from the sender and is opaque to RSVP. The ADSPEC
object - for 'advertising specification' - is used to gather
information along the downstream data path to aid the receiver in
the computation of QoS properties of this data path. The ADSPEC is
also opaque to RSVP and is defined in RFC 2210. Both of these
IntServ objects are part of the Sender Descriptor [RFC2205].
Once the Sender Descriptor is received at its destination node,
after having traveled through the network of routers, the
SENDER_TSPEC information is matched with the information gathered in
the ADSPEC, if present, about the data path. Together, these two
objects help the receiver build its flow specification (encoded in
the FLOWSPEC object) for the RESV message. The RESV message
establishes the reservation through the network of routers on the
data path established by the PATH message. If the ADSPEC is not
present in the Sender_Descriptor, it cannot aid the receiver in
building the flow specification.
The SENDER_TSPEC is not changed in transit between endpoints (i.e.,
there are no bandwidth request adjustments along the way). However,
the ADSPEC is changed, based on the conditions experienced through
the network (i.e., bandwidth availability within each router) as the
RSVP message travels hop-by-hop.
Today, real-time applications have evolved such that they are able
to dynamically adapt to available bandwidth, not only by dropping
and adding layers, but also by reducing frame rates and resolution.
It is therefore limiting to have a single bandwidth request in
Integrated Services, and by extension, RSVP.
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With only one traffic specification in a PATH message and only one
flow specification in a RESV message (with some styles of
reservations a RESV message may actually contain multiple flow
specifications, but then there is only one per sender), applications
will either have to give up altogether on session establishment in
case of failure of the reservation establishment for the highest
"bandwidth or will have to resort to multiple successive RSVP
signaling attempts in a trial-and-error manner until they finally
establish the reservation a lower "bandwidth". These multiple
signaling round-trip would affect the session establishment time and
in turn would negatively impact the end user experience.
The objective of this document is to avoid such roundtrips as well
as allow applications to successfully receive some level of
bandwidth allotment that it can use for its sessions.
While the ADSPEC provides an indication of the bandwidth available
along the path and can be used by the receiver in creating the
FLOWSPEC, it does not prevent failures or multiple round-trips as
described above. The intermediary routers provide a best attempt
estimate of available bandwidth in the ADSPEC object. However, it
does not take into account external policy considerations
(RFC 2215). In addition, the available bandwidth at the time of
creating the ADSPEC may not be available at the time of an actual
request in an RESV message. These reasons may cause the RESV message
to be rejected. Therefore, the ADSPEC object cannot, by itself,
satisfy the requirements of the current generations of real-time
applications.
It needs to be noted that the ADSPEC is unchanged by this new
mechanism. If ADSPEC is included in the PATH message, it is
suggested that the receiver use this object in determining
the flow specification.
This document creates a means for conveying more than one
"bandwidth" within the same RSVP reservation set-up (both PATH and
RESV) messages to optimize the determination of an agreed upon
bandwidth for this reservation. Allowing multiple traffic
specifications within the same PATH message allows the sender to
communicate to the receiver multiple "bandwidths" that match the
different sending rates that the sender is capable of transmitting
at. This allows the receiver to convey this multiple "bandwidths"
in the RESV so those can be considered when RSVP makes the actual
reservation admission into the network. This allows the applications
to dynamically adapt their data stream to available network
resources.
The concept of RSVP signaling is shown in a single direction below,
in Figure 1. Although the TSPEC is opaque to RSVP, it is shown
along with the RSVP messages for completeness. The RSVP messages
themselves need not be the focus of the reader. Instead, the
number of round trips it takes to establish a reservation is the
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focus here.
Sender Rtr-1 Rtr-2 ... Rtr-N Receiver
| | | | |
| PATH (with a TSPEC & ADSPEC) |
|------------->|--------->|----//--->|-------------->|
| | | | |
| RESV (with a FLOWSPEC) |
|<-------------|<---------|<---//----|<--------------|
| | | | |
Figure 1. Concept of RSVP in a Single Direction
Figure 1 shows a successful one-way reservation using RSVP and
IntServ.
Figure 2 shows a scenario where the RESV message, containing a
FLOWSPEC, which is generated by the Receiver, after considering
both the Sender TSPEC and the ADSPEC, is rejected by an intermediary
router.
Sender Rtr-1 Rtr-2 ... Rtr-N Receiver
| | | | |
| PATH (with 1 TSPEC wanting 12Mbps) |
|------------->|--------->|----//--->|-------------->|
| | | | |
| RESV (with 1 FLOWSPEC wanting 12Mbps) |
| | X <--//----|<--------------|
| | | | |
| ResvErr (with Admission control Error=2) |
| | |----//--->|-------------->|
| | | | |
Figure 2. Concept of RSVP Rejection due to Limited Bandwidth
The scenario above is where multiple TSPEC and multiple FLOWSPEC
optimization helps. The Sender may support multiple bandwidths
for a given application (i.e., more than one codec for voice or
video) and therefore might want to establish a reservation with the
highest (or best) bandwidth that the network can provide for a
particular codec.
For example, bandwidths of:
12Mbps,
4Mbps, and
1.5Mbps
for the three video codecs the Sender supports.
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This document will discuss the overview of the proposal to include
multiple TSPECs and FLOWSPECs RSVP in section 2. In section 3, the
overview of the entire solution is provided. This section also
contains the new parameters which are defined in this document. The
multiple TSPECs in a PATH message and the multiple FLOWSPEC in a
RESV message, both for controlled load and guaranteed service are
described in this section. Section 4 will cover the rules of usage
of this IntServ extension. This section contains how this document
needs to extend the scenario of when a router in the middle of a
reservation cannot accept a preferred bandwidth (i.e., FLOWSPEC),
meaning previous routers that accepted that greater bandwidth now
have too much bandwidth reserved. This requires an extension to RFC
4495 (RSVP Bandwidth Reduction) to cover reservations being
established, as well as existing reservations. Section 4 also
includes the merging rules.
2. Overview of Proposal for Including Multiple TSPECs and FLOWSPECS
Presently, this is the format of a PATH message [RFC2205]:
<PATH Message> ::= <Common Header> [ <INTEGRITY> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <POLICY_DATA> ... ]
[ <sender descriptor> ]
<sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC>
^^^^^^^^^^^^
[ <ADSPEC> ]
where the SENDER_TSPEC object contains a single traffic
specification.
For the PATH message, the focus of this document is to modify the
<sender_descriptor> in such a way to include more than one traffic
specification. This solution does this by retaining the existing
SENDER_TSPEC object above, highlighted by the '^^^^' characters, and
complementing it with a new optional MULTI_TSPEC object to convey
additional traffic specifications in this PATH message. No other
object within the PATH message is affected by this IntServ
extension.
This extension modifies the sender descriptor by specifically
augmenting it to allow an optional <MULTI_TSPEC> object after the
optional <ADSPEC>, as shown below.
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<sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC>
[ <ADSPEC> ] [ <MULTI_TSPEC> ]
^^^^^^^^^^^
As can be seen above, the MULTI_TSPEC is in addition to the
SENDER_TSPEC - and is only to be used, per this extension, when
more than one TSPEC is to be included in the PATH message.
Here is another way of looking at the proposal choices:
+---------------------+
| Existing TSPEC |
| |
| +----------+ |
| | TSPEC1 | |
| +----------+ |
| |
+---------------------+
+---------------------+
| Additional TSPECs |
| |
| +---------------+ |
| | MULTI_TSPEC | |
| | Object | |
| | +--------+ | |
| | | TSPEC2 | | |
| | +--------+ | |
| | +--------+ | |
| | | TSPEC3 | | |
| | +--------+ | |
| | +--------+ | |
| | | TSPEC4 | | |
| | +--------+ | |
| +---------------+ |
| |
+---------------------+
Figure 3. Encoding of Multiple Traffic Specifications in
the TSPEC and MULTI_TSPEC objects
This solution is backwards compatible with existing implementations
of [RFC2205] and [RFC2210], as the multiple TSPECs and FLOWSPECs are
inserted as optional objects and such objects do not need to be
processed, especially if they are not understood.
This solution defines a similar approach for encoding multiple flow
specifications in the RESV message. Flow specifications beyond the
first one can be encoded in a new "MULTI_FLOWSPEC" object contained
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in the RESV message.
In this proposal, the original SENDER_TSPEC and the FLOWSPEC are
left untouched, allowing routers not supporting this extension to
process the PATH and the RESV message without issue. Two new
additional objects are defined in this document. They are the
MULTI_TSPEC and the MULTI_FLOWSPEC for the PATH and the RESV
message, respectively. The additional TSPECs (in the new MULTI_TSPEC
Object) are included in the PATH and the additional FLOWSPECS (in
the new MULTI_FLOWSPEC Object) are included in the RESV message as
new (optional) objects. These additional objects will have a class
number of 11bbbbbb, allowing older routers to ignore the object(s)
and forward each unexamined and unchanged, as defined in section
3.10 of [RFC 2205].
NOTE: it is important to emphasize here that including more than
one FLOWSPEC in the RESV message does not cause more than one
FLOWSPEC to be granted. This document requires that the
receiver arrange these multiple FLOWSPECs in the order of
preference according to the order remaining from the
MULTI_TSPECs in the PATH message. The benefit of this
arrangement is that RSVP does not have to process the rest of
the FLOWSPEC if it can admit the first one.
3. Multi_TSPEC and MULTI_FLOWSPEC Solution
For the Sender Descriptor within the PATH message, the original
TSPEC remains where it is, and is untouched by this IntServ
extension. What is new is the use of a new <MULTI_TSPEC> object
inside the sender descriptor as shown here:
<sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC>
[ <ADSPEC> ] [ <MULTI_TSPEC> ]
^^^^^^^^^^^
The preferred order of TSPECs sent by the sender is this:
- preferred TSPEC is in the original SENDER_TSPEC
- the next in line preferred TSPEC is the first TSPEC in the
MULTI_TSPEC object
- the next in line preferred TSPEC is the second TSPEC in the
MULTI_TSPEC object
- and so on...
The composition of the flow descriptor list in a Resv message
depends upon the reservation style. Therefore, the following shows
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the inclusion of the MULTI_FLOWSPEC object with each of the styles:
WF Style:
<flow descriptor list> ::= <WF flow descriptor>
<WF flow descriptor> ::= <FLOWSPEC> [MULTI_FLOWSPEC]
FF style:
<flow descriptor list> ::=
<FLOWSPEC> <FILTER_SPEC> [MULTI_FLOWSPEC] |
<flow descriptor list> <FF flow descriptor>
<FF flow descriptor> ::=
[ <FLOWSPEC> ] <FILTER_SPEC> [MULTI_FLOWSPEC]
SE style:
<flow descriptor list> ::= <SE flow descriptor>
<SE flow descriptor> ::=
<FLOWSPEC> <filter spec list> [MULTI_FLOWSPEC]
<filter spec list> ::= <FILTER_SPEC>
| <filter spec list> <FILTER_SPEC>
3.1 New MULTI_TSPEC and MULTI-RSPEC Parameters
This extension to Integrated Services defines two new parameters
They are:
1. <parameter name> Multiple_Token_Bucket_Tspec, with a parameter
number of 125.
2. <parameter name> Multiple_Guaranteed_Service_RSpec with a
parameter number of 124
These are IANA registered in this document.
The original SENDER_TSPEC and FLOWSPEC for Controlled Service
maintain the <parameter name> of Token_Bucket_Tspec with a parameter
number of 127. The original FLOWSPEC for Guaranteed Service
maintains the <parameter name> of Guaranteed_Service_RSpec with a
parameter number of 130.
3.2 Multiple TSPEC in a PATH Message
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Here is the object from [RFC2210]. It is used as a SENDER_TSPEC in a
PATH message:
31 24 23 16 15 8 7 0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1 | 0 (a) | reserved | 7 (b) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2 | X (c) |0| reserved | 6 (d) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3 | 127 (e) | 0 (f) | 5 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4 | Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5 | Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6 | Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7 | Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4. SENDER_TSPEC in PATH
(a) - Message format version number (0)
(b) - Overall length (7 words not including header)
(c) - Service header, service number
- '1' (Generic information) if in a PATH message;
(d) - Length of service data, 6 words not including
per-service header
(e) - Parameter ID, parameter 127 (Token Bucket TSpec)
(f) - Parameter 127 flags (none set)
(g) - Parameter 127 length, 5 words not including per-service
header
For completeness, Figure 4 is included in its original form for
backwards compatibility reasons, as if there were only 1 TSPEC in
the PATH. What is new when there are more than one TSPEC in
this reservation message is the new MULTI_TSPEC object in Figure 5
containing, for example, 3 (Multiple_Token_Bucket_Tspec) TSPECs in a
PATH message.
31 24 23 16 15 8 7 0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1 | 0 (a) | reserved | 19 (b) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2 | 5 (c) |0| reserved | 18 (d) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3 | 125 (e) | 0 (f) | 5 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4 | Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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5 | Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6 | Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7 | Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
9 | 125 (e) | 0 (f) | 5 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
10 | Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
11 | Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 | Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
13 | Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
14 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
15 | 125 (e) | 0 (f) | 5 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 | Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
17 | Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
18 | Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
19 | Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5. MULTI_TSPEC Object
(a) - Message format version number (0)
(b) - Overall length (19 words not including header)
(c) - Service header, service number 5 (Controlled-Load)
(d) - Length of service data, 18 words not including
per-service header
(e) - Parameter ID, parameter 125 (Multiple Token Bucket TSpec)
(f) - Parameter 125 flags (none set)
(g) - Parameter 125 length, 5 words not including per-service
header
Figure 5 shows the 2nd through Nth TSPEC in the PATH in the
preferred order. The message format (a) remains the same for a
second TSPEC and for other additional TSPECs.
The Overall Length (b) includes all the TSPECs within this object,
plus the 2nd Word (containing fields (c) and (d)), which MUST NOT be
repeated. The service header fields (e),(f) and(g) are repeated for
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each TSPEC.
The Service header, here service number 5 (Controlled-Load) MUST
remain the same.
Each TSPEC is six 32-bit Words long (the per-service header plus the
5 values that are 1 Word each in length), therefore the length is in
6 Word increments for each additional TSPEC. Case in point, from
the above Figure 5, Words 3-8 are the first TSPEC (2nd preferred),
Words 9-14 are the next TSPEC (3rd preferred), and Words 15-20 are
the final TSPEC (and 4th preferred) in this example of 3 TSPECs in
this MULTI_TSPEC object. There is no limit placed on the number of
TSPECs a MULTI_TSPEC object can have. However, it is RECOMMENDED to
administratively limit the number of TSPECs in the MULTI_TSPEC
object to 9 (making for a total of 10 in the PATH message).
The TSPECS are included in the order of preference by the message
generator (PATH) and MUST be maintained in that order all the way to
the Receiver. The order of TSPECs that are still grantable, in
conjunction with the ADSPEC at the Receiver, MUST retain that
order in the FLOWSPEC and MULTI_FLOWSPEC objects.
3.3 Multiple FLOWSPEC for Controlled-Load service
The format of an RSVP FLOWSPEC object requesting Controlled-Load
service is the same as the one used for the SENDER_TSPEC given in
Figure 4.
The format of the new MULTI_FLOWSPEC object is given below:
31 24 23 16 15 8 7 0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1 | 0 (a) | reserved | 19 (b) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2 | 5 (c) |0| reserved | 18 (d) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3 | 125 (e) | 0 (f) | 5 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4 | Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5 | Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6 | Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7 | Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
9 | 125 (e) | 0 (f) | 5 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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10 | Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
11 | Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 | Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
13 | Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
14 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
15 | 125 (e) | 0 (f) | 5 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 | Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
17 | Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
18 | Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
19 | Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5. Multiple FLOWSPEC for Controlled-Load service
(a) - Message format version number (0)
(b) - Overall length (19 words not including header)
(c) - Service header, service number 5 (Controlled-Load)
(d) - Length of controlled-load data, 18 words not including
per-service header
(e) - Parameter ID, parameter 125 (Multiple Token Bucket TSpec)
(f) - Parameter 125 flags (none set)
(g) - Parameter 125 length, 5 words not including per-service
header
This is for the 2nd through Nth TSPEC in the RESV, in the
preferred order.
The message format (a) remains the same for a second TSPEC and
for additional TSPECs.
The Overall Length (b) includes the TSPECs, plus the 2nd Word
(fields (c) and (d)), which MUST NOT be repeated. The service header
fields (e),(f) and(g), which are repeated for each TSPEC.
The Service header, here service number 5 (Controlled-Load) MUST
remain the same for the RESV message. The services, Controlled-Load
and Guaranteed MUST NOT be mixed within the same RESV message. In
other words, if one TSPEC is a Controlled Load service TSPEC, the
remaining TSPECs MUST be Controlled Load service. This same rule
also is true for Guaranteed Service - if one TSPEC is for Guaranteed
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Service, the rest of the TSPECs in this PATH or RESV MUST be for
Guaranteed Service.
The Length of controlled-load data (d) also increases to account for
the additional TSPECs.
Each FLOWSPEC is six 32-bit Words long (the per-service header plus
the 5 values that are 1 Word each in length), therefore the length
is in 6 Word increments for each additional TSPEC. Case in point,
from the above Figure 5, Words 3-8 are the first TSPEC (2nd
preferred), Words 9-14 are the next TSPEC (3rd preferred), and Words
15-20 are the final TSPEC (and 4th preferred) in this example of 3
TSPECs in this FLOWSPEC. There is no limit placed on the number of
TSPECs a particular FLOWSPEC can have.
Within the MULTI_FLOWSPEC, any SENDER_TSPEC that cannot be reserved
- based on the information gathered in the ADSPEC, is not placed in
the RESV or based on other information available to the receiver.
Otherwise, the order in which the TSPECs were in the PATH message
MUST be in the same order they are in the FLOWSPEC in the RESV.
This is the order of preference of the sender, and MUST be
maintained throughout the reservation establishment, unless the
ADSPEC indicates one or more TSPECs cannot be granted, or the
receiver cannot include any TSPEC due to technical or administrative
constraints or one or more routers along the RESV path cannot grant
a particular TSPEC. At any router that a reservation cannot honor a
TSPEC, this TSPEC MUST be removed from the RESV, or else another
router along the RESV path might reserve that TSPEC. This rule
ensures this cannot happen.
Once one TSPEC has been removed from the RESV, the next in line
TSPEC becomes the preferred TSPEC for that reservation. That router
MUST generate a ResvErr message, containing an ERROR_SPEC object
with a Policy Control Failure with Error code = 2 (Policy Control
Failure), and an Error Value sub-code 102 (ERR_PARTIAL_PREEMPT) to
the previous routers, clearing the now over allocation of bandwidth
for this reservation. The difference between the previously
accepted TSPEC bandwidth and the currently accepted TSPEC bandwidth
is the amount this error identifies as the amount of bandwidth that
is no longer required to be reserved. The ResvErr and the RESV
messages are independent, and not normally sent by the same router.
This aspect of this document is the extension to RFC 2205 (RSVP).
If a RESV cannot grant the final TSPEC, normal RSVP rules apply with
regard to the transmission of a particular ResvErr.
3.4 Multiple FLOWSPEC for Guaranteed service
The FLOWSPEC object, which is used to request guaranteed service
contains a TSPEC and RSpec. Here is the FLOWSPEC object from
[RFC2215] when requesting Guaranteed service:
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31 24 23 16 15 8 7 0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1 | 0 (a) | Unused | 10 (b) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2 | 2 (c) |0| reserved | 9 (d) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3 | 127 (e) | 0 (f) | 5 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4 | Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5 | Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6 | Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7 | Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
9 | 130 (h) | 0 (i) | 2 (j) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
10 | Rate [R] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
11 | Slack Term [S] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6. FLOWSPEC for Guaranteed service
(a) - Message format version number (0)
(b) - Overall length (9 words not including header)
(c) - Service header, service number 2 (Guaranteed)
(d) - Length of per-service data, 9 words not including
per-service header
(e) - Parameter ID, parameter 127 (Token Bucket TSpec)
(f) - Parameter 127 flags (none set)
(g) - Parameter 127 length, 5 words not including parameter header
(h) - Parameter ID, parameter 130 (Guaranteed Service RSpec)
(i) - Parameter xxx flags (none set)
(j) - Parameter xxx length, 2 words not including parameter header
The difference in structure between the Controlled-Load FLOWSPEC and
Guaranteed FLOWSPEC is the RSPEC, defined in [RFC2212].
For completeness, Figure 6 is included in its original form for
backwards compatibility reasons, as if there were only 1 FLOWSPEC in
the RESV. What is new when there is more than one TSPEC in the
FLOWSPEC in a RESV message is the new MULTI_FLOWSPEC object in
Figure 7 containing, for example, 3 FLOWSPECs requesting Guaranteed
Service.
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31 24 23 16 15 8 7 0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1 | 0 (a) | Unused | 28 (b) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2 | 2 (c) |0| reserved | 27 (d) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3 | 125 (e) | 0 (f) | 5 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4 | Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5 | Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6 | Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7 | Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
9 | 124 (h) | 0 (i) | 2 (j) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
10 | Rate [R] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
11 | Slack Term [S] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 | 125 (e) | 0 (f) | 5 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
13 | Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
14 | Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
15 | Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 | Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
17 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
18 | 124 (h) | 0 (i) | 2 (j) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
19 | Rate [R] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | Slack Term [S] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
21 | 125 (e) | 0 (f) | 5 (g) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
22 | Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
23 | Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 | Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
25 | Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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26 | Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
27 | 124 (h) | 0 (i) | 2 (j) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 | Rate [R] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
29 | Slack Term [S] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7. Multiple FLOWSPECs for Guaranteed service
(a) - Message format version number (0)
(b) - Overall length (9 words not including header)
(c) - Service header, service number 2 (Guaranteed)
(d) - Length of per-service data, 9 words not including
per-service header
(e) - Parameter ID, parameter 125 (Token Bucket TSpec)
(f) - Parameter 125 flags (none set)
(g) - Parameter 125 length, 5 words not including parameter header
(h) - Parameter ID, parameter 124 (Guaranteed Service RSpec)
(i) - Parameter 124 flags (none set)
(j) - Parameter 124 length, 2 words not including parameter header
There MUST be 1 RSPEC per TSPEC for Guaranteed Service. Therefore,
there are 5 words for Receiver TSPEC and 3 words for the RSPEC.
Therefore, for Guaranteed Service, the TSPEC/RSPEC combination
occurs in increments of 8 words.
4. Rules of Usage
The following rules apply to nodes adhering to this specification:
4.1 Backward Compatibility
If the recipient does not understand this extension, it ignores this
MULTI_TSPEC object, and operates normally for a node receiving this
RSVP message.
4.2 Applies to Only a Single Session
When there is more than one TSPEC object or more than one FLOWSPEC
object, this MUST NOT be considered for more than one flow created.
These are OR choices for the same flow of data. In order to attain
three reservations between two endpoints, three different
reservation requests are required, not one reservation request with
3 TSPECs.
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4.3 No Special Error Handling for PATH Message
If a problem occurs with the PATH message - regardless of this
extension, normal RSVP procedures apply (i.e., there is no new
PathErr code created within this extension document) - resulting in
a PathErr message being sent upstream towards the sender, as usual.
4.4 Preference Order to be Maintained
When more than one TSPEC is in a PATH message, the order of TSPECs
is decided by the Sender and MUST be maintained within the
SENDER_TSPEC. The same order MUST be carried to the FLOWSPECs by
the receiver. No additional TSPECS can be introduced by the receiver
or any router processing these new objects. The deletion of TSPECs
from a PATH message is not permitted. The deletion of the TSPECs
when forming the FLOWSPEC is allowed by the receiver in the
following cases:
- If one or more preferred TSPECs cannot be granted by a router as
discovered during processing of the ADSPEC by the receiver, then
they can be omitted when creating the FLOWSPEC(s) from the TSPECs.
- If one or more TSPECs arriving from the sender is not preferred by
the receiver, then the receiver MAY omit any while creating the
FLOWSPEC. A good reason to omit a TSPEC is if, for example, it
does not match a codec supported by the receiver's application(s).
The deletion of the TSPECs in the router during the processing of
this MULTI_FLOWSPEC object is allowed in the following cases:
- If the original FLOWSPEC cannot be granted by a router then the
router may discard that FLOWSPEC and replace it with the topmost
FLOWSPEC from the MULTI_FLOWSPEC project. This will cause the
topmost FLOWSPEC in the MULTI_FLOWSPEC object to be removed. The
next FLOWSPECs becomes the topmost FLOWSPEC.
- If the router merges multiple RESV into a single RESV message,
then the FLOWSPEC and the multiple FLOWSPEC may be affected
The preferred order of the remaining TSPECs or FLOWSPECs MUST be
kept intact both at the receiver as well as the router processing
these objects.
4.5 Bandwidth Reduction in Downstream Routers
If there are multiple FLOWSPECs in a single RESV message, it is
quite possible that a higher bandwidth is reserved at a previous
downstream device. Thus, any device that grants a reservation that
is not the highest will have to inform the previous downstream
routers to reduce the bandwidth reserved for this particular
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session.
The bandwidth reduction RFC [RFC4495] has the ability to partially
preempt existing reservations. However, it does not address the need
that this draft addresses. RFC 4495 defines an ability to preempt
part of an existing reservation so as to admit a new incoming
reservation with a higher priority, in lieu of tearing down the
whole reservation with lower priority. It does not specify the
capability to reduce the bandwidth a RESV set up along the data path
before the reservation is realized (from source to destination),
when a subsequent router cannot support a more preferred FLOWSPEC
contained in that RESV. This document will extend the RFC 4495
defined error to work for previous hops while a reservation is being
established.
4.6 Merging Rules
RFC 2205 defines the rules for merging as combining more than one
FLOWSPEC into a single FLOWSPEC. In the case of MULTI_FLOWSPECs,
merging of the two (or more) MULTI_FLOWSPEC MUST be done to arrive
at a single MULTI_FLOWSPEC. The merged MULTI_FLOWSPEC will contain
all the flow specification components of the individual
MULTI_FLOWSPECs in descending orders of bandwidth. In other words,
the merged FLOWSPEC MUST maintain the relative order of each of the
individual FLOWSPECs. For example, if the individual FLOWSPEC order
is 1,2,3 and another FLOWSPEC is a,b,c, then this relative ordering
cannot be altered in the merged FLOWSPEC.
A byproduct of this is the ordering between the two individual
FLOWSPECs cannot be signaled with this extension. If two (or more)
FLOWSPECs have the same bandwidth, they are to be merged into one
FLOWSPEC using the rules defined in RFC 2205. It is RECOMMENDED
that the following rules are used for determining ordering (in TSPEC
and FLOWSPEC):
For Controlled Load - in descending order of BW based on the
Token Bucket Rate 'r' parameter value
For Guaranteed Service - in descending order of BW based on the
RSPEC Rate 'R' parameter value
The resultant FLOWSPEC is added to the MULTI_FLOWSPEC based on its
bandwidth in descending orders of bandwidth.
As a result of such merging, the number of FLOWSPECs in a
MULTI_FLOWSPEC object should be the sum of the number of FLOWSPECs
from individual MULTI_FLOWSPEC that have been merged *minus* the
number of duplicates.
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4.7 Other Considerations
- RFC 4495 articulates why a ResvErr is more appropriate to use for
reducing the bandwidth of an existing reservation vs. a ResvTear.
- Refreshes only include the TSPECs that were accepted. One SHOULD
be sent immediately upon the Sender receiving the RESV, to
ensure all routers in this flow are synchronized with which TSPEC
is in place.
- Periodically, it might be appropriate to attempt to increase the
bandwidth of an accepted reservation with one of the TSPECs that
were not accepted by the network when the reservation was first
installed. This SHOULD NOT occur too regularly. This document
currently offers no guidance on the frequency of this bump request
for a rejected TSPEC from the PATH.
4.8 Known Open Issues
Here are the know open issues within this document:
o Both the idea of MULTI_RSPEC and MULTI_FLOWSPEC need to be
fleshed out, and IANA registered.
o Need to ensure the cap on the number of TSPECs and FLOWSPECs is
viable, yet controlled.
5. Security considerations
The security considerations for this document do not exceed what is
already in RFC 2205 (RESV) or RFC 2210 (IntServ), as nothing in
either of those documents prevent a node from requesting a lot of
bandwidth in a single TSPEC. This document merely reduces the
signaling traffic load on the network by allowing many requests that
fall under the same policy controls to be included in a single
round-trip message exchange.
Further, this document does not increase the security risk(s) to
that defined in RFC 4495, where this document creates additional
meaning to the RFC 4495 created error code 102.
A misbehaving Sender can include too many TSPECs in the
MULTI_TSPEC object, which can lead to an amplification attack. That
said, a bad implementation can create a reservation for each TSPEC
received from within the Resv message. The number of TSPECs in the
new MULTI_TSPEC object is limited, and the spec clearly states that
only a single reservation is to be set up per Resv message.
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6. IANA considerations
This document IANA registers the following new parameter name in the
Integ-serv assignments at [IANA]:
Registry Name: Parameter Names
Registry:
Value Description Reference
-------- -------------------------------------------- ---------
125 Multiple_Token_Bucket_Tspec [RFCXXXX]
124 Multiple_Guaranteed_Service_RSpec [RFCXXXX]
Where RFCXXXX is replaced with the RFC number assigned to this
Document.
7. Acknowledgments
The authors wish to thank Fred Baker, Joe Touch, Bruce Davie, Dave
Oran, Ashok Narayanan, Lou Berger, Lars Eggert, Arun Kudur and Janet
Gunn for their helpful comments and guidance in this effort.
And to Francois Le Faucheur, who provided text in this version.
8. References
8.1. Normative References
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997
[RFC2205] R. Braden, Ed., L. Zhang, S. Berson, S. Herzog, S. Jamin,
"Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997
[RFC2210] J. Wroclawski, "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997
[RFC2212] S. Shenker, C. Partridge, R. Guerin, "Specification of
Guaranteed Quality of Service", RFC 2212, September 1997
[RFC2215] S. Shenker, J. Wroclawski, "General Characterization
Parameters for Integrated Service Network Elements",
RFC 2212, September 1997
[RFC4495] J. Polk, S. Dhesikan, "A Resource Reservation Protocol
(RSVP) Extension for the Reduction of Bandwidth of a
Reservation Flow", RFC 4495, May 2006
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8.2. Informative References
[IANA] http://www.iana.org/assignments/integ-serv
Authors' Addresses
James Polk
3913 Treemont Circle
Colleyville, Texas, USA
+1.817.271.3552
mailto: jmpolk@cisco.com
Subha Dhesikan
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134 USA
mailto: sdhesika@cisco.com
Appendix A: Alternatives for Sending Multiple TSPECs
This appendix describes the discussion within the TSVWG of which
approach best fits the requirements of sending multiple TSPECs
within a single PATH or RESV message. There were 3 different
options proposed, of which - 2 were insufficient or caused more harm
than other options.
Looking at the format of a PATH message [RFC2205] again:
<PATH Message> ::= <Common Header> [ <INTEGRITY> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <POLICY_DATA> ... ]
[ <sender descriptor> ]
<sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC>
^^^^^^^^^^^^
[ <ADSPEC> ]
For the PATH message, the focus of this document is with what to do
with respect to the <SENDER_TSPEC> above, highlighted by the '^^^^'
characters. No other object within the PATH message will be affected
by this IntServ extension.
The ADSPEC is optional in IntServ; therefore it might or might not
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be in the RSVP PATH message. Presently, the SENDER_TSPEC is limited
to one bandwidth associated with the session. This is changed in
this extension to IntServ to multiple bandwidths for the same
session. There are multiple options on how the additional bandwidths
may be added:
Option #1 - creating the ability to add one or more additional
(and complete) SENDER_TSPECs,
or
Option #2 - create the ability for the one already allowed
SENDER_TSPEC to carry more than one bandwidth amount
for the same reservation.
or
Option #3 - create the ability for the existing SENDER_TSPEC to
remain unchanged, but add an optional <MULTI_TSPEC>
object to the <sender descriptor> such as this:
<sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC>
[ <ADSPEC> ] [ <MULTI_TSPEC> ]
^^^^^^^^^^^
Here is another way of looking at the option choices:
+--------------------+----------------------+---------------------+
| Option#1 | Option#2 | Option#3 |
| | | |
| +----------+ | +---------------+ | +----------+ |
| | TSPEC1 | | | MULTI_TSPEC | | | TSPEC1 | |
| +----------+ | | Object | | +----------+ |
| | | +--------+ | | |
| +----------+ | | | TSPEC1 | | | +---------------+ |
| | TSPEC2 | | | +--------+ | | | MULTI_TSPEC | |
| +----------+ | | +--------+ | | | Object | |
| | | | TSPEC2 | | | | +--------+ | |
| +----------+ | | +--------+ | | | | TSPEC2 | | |
| | TSPEC3 | | | +--------+ | | | +--------+ | |
| +----------+ | | | TSPEC3 | | | | +--------+ | |
| | | +--------+ | | | | TSPEC3 | | |
| +----------+ | | | TSPEC4 | | | | +--------+ | |
| | TSPEC4 | | | +--------+ | | | +--------+ | |
| +----------+ | +---------------+ | | | TSPEC4 | | |
| | | | +--------+ | |
| | | +---------------+ |
| | | |
+--------------------+----------------------+---------------------+
Figure 3. Concept of Option Choice
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Option #1 and #2 do not allow for backward compatibility. If the
currently used SENDER_TSPEC and FLOWSPEC objects are changed, then
unless all the routers requiring RSVP processing are upgraded, this
functionality cannot be realized. As it is unlikely that all routers
along the path will have the necessary enhancements as per this
extension at one given time, therefore, it is necessary this
enhancement be made in a way that is backward compatible. Therefore,
option #1 and option #2 has been discarded in favor of option #3,
which had WG consensus in a recent IETF meeting.
Option #3: This option has the advantage of being backwards
compatible with existing implementations of [RFC2205] and [RFC2210],
as the multiple TSPECs and FLOWSPECs are inserted as optional
objects and such objects do not need to be processed, especially if
they are not understood.
Option#3 applies to the FLOWSPEC contained in the RESV message as
well. In this option, the original SENDER_TSPEC and the FLOWSPEC are
left untouched, allowing routers not supporting this extension to be
able to process the PATH and the RESV message without issue. Two new
additional objects are defined in this document. They are the
MULTI_TSPEC and the MULTI_FLOWSPEC for the PATH and the RESV
message, respectively. The additional TSPECs (in the new MULTI_TSPEC
Object) are included in the PATH and the additional FLOWSPECS (in
the new MULTI_FLOWSPEC Object) are included in the RESV message as
new (optional) objects. These additional objects will have a class
number of 11bbbbbb, allowing older routers to ignore the object(s)
and forward each unexamined and unchanged, as defined in section
3.10 of [RFC 2205].
We state in the document body that the top most FLOWSPEC of the new
MULTI_FLOWSPEC Object in the RESV message replaces the existing
FLOWSPEC when it is determined by the receiver (perhaps along
with the ADSPEC) that the original FLOWSPEC cannot be granted.
Therefore, the ordering of preference issue is solved with Option#3
as well.
NOTE: it is important to emphasize here that including more than
one FLOWSPEC in the RESV message does not cause more than one
FLOWSPEC to be granted. This document requires that the
receiver arrange these multiple FLOWSPECs in the order of
preference according to the order remaining from the
MULTI_TSPECs in the PATH message. The benefit of this
arrangement is that RSVP does not have to process the rest of
the FLOWSPEC if it can admit the first one.
Additional details of these options can be found in the
draft-polk-tsvwg-...-01 version of this appendix (which includes the
RSVP bit mapping of fields in the TSPECs, if the reader wishes to
search for that doc.
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