Network Working Group S. Shah
Internet-Draft K. Patel
Intended status: Standards Track Cisco Systems
Expires: May 4, 2016 S. Bajaj
Juniper Networks
L. Tomotaki
Verizon
M. Boucadair
France Telecom
November 01, 2015
Inter-domain SLA Exchange
draft-ietf-idr-sla-exchange-06
Abstract
Network administrators typically enforce Quality of Service (QoS)
policies according to Service Level Agreement (SLA) with their
providers. The enforcement of such policies often relies upon
vendor-specific configuration language. Both learning of SLA, either
thru SLA documents or via some other out-of-band method, and
translating them to vendor specific configuration language is a
complex, many times manual, process and prone to errors. This
document proposes an in-band method of SLA signaling, which can help
to simplify some of the complexities, where BGP is available as the
routing protocol.
This document defines an optional transitive attribute to signal SLA
parameters in-band, across administrative boundaries (considered as
Autonomous Systems (AS)), thus simplifying and facilitating some of
the complex provisioning tasks.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
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This Internet-Draft will expire on May 4, 2016.
Copyright Notice
Copyright (c) 2015 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. QoS Attribute Definition . . . . . . . . . . . . . . . . . . 4
3.1. SLA, QoS attribute sub-type, Definition . . . . . . . . . 5
4. Originating SLA Notification . . . . . . . . . . . . . . . . 15
4.1. SLA Contexts . . . . . . . . . . . . . . . . . . . . . . 15
4.1.1. SLA Advertisement for Point-to-Point Connection . . . 16
4.1.2. SLA Advertisement for Destination AS Multiple Hops
Away . . . . . . . . . . . . . . . . . . . . . . . . 16
5. SLA Attribute Handling at Forwarding Nodes . . . . . . . . . 16
5.1. BGP Node Capable of Processing QoS Attribute . . . . . . 16
5.2. SLA Attribute Handling at Receiver . . . . . . . . . . . 17
6. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 18
7. Traffic Class Mapping . . . . . . . . . . . . . . . . . . . . 18
8. Deployment Considerations . . . . . . . . . . . . . . . . . . 18
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
11. Security Considerations . . . . . . . . . . . . . . . . . . . 21
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
12.1. Normative References . . . . . . . . . . . . . . . . . . 21
12.2. Informative References . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction
Typically there is a contractual Service Level Agreement (SLA) for
QoS established between a customer and a provider or between
providers. This QoS SLA defines the nature of the various traffic
classes and services needed within each traffic class. The contract
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may include full line-rate or sub line-rate without additional
traffic classes, or it may contain additional traffic classes and
service definitions for those traffic classes. Finer granular
traffic classes may be based on some standard code points (like DSCP)
or specific set of prefixes.
Once the SLA is established, QoS SLA parameters are enforced in some
or all participating devices by deriving those parameters into
configuration information on respective devices. SLA parameters may
have to be exchanged through organizational boundaries, thru SLA
documents or via some other off-band method to an administrator
provisioning actual devices. In a subsequent step, administrator
requires to translate SLA to QoS policies using router (vendor)
specific provisioning language. In a multi-vendor network,
translating SLAs into technology-specific and vendor-specific
configuration requires to consider specificities of each vendor.
There does not exist any standard protocol to translate SLA
agreements into technical clauses and configurations and thus both
the steps of out of band learning of negotiated SLA and provisioning
them in a vendor specific language can be complex and error-prone.
As an example for voice service, the Provider may negotiate QoS
parameters (like min/max rates) for such traffic based upon the EF
code-point in Diffserv-enabled [RFC2475] networks. The Administrator
at the CE side not only will have to know that Provider's service for
voice traffic is EF-based but will also have to know how to implement
DSCP EF classification rule along with Low Latency Service, and
possibly min/max rate enforcement for the optimal use of bandwidth,
as per vendor specific provisioning language.
An in-band signaling method of propagating SLA parameters from the
provider, PE in an example above, to contractual devices, CE in an
example above, can help eliminate manual administrative process
described above. The provider may have SLA negotiated with the
Customer via some defined off-band method (based on the specifics
defined by the Provider or using protocols like [CPNP]). The Inter-
domain SLA exchange proposal described in this document does not pre-
requisite any specific method of establishing SLAs). The Provider
provisions established SLA on the Provider device. This SLA instance
then can be signaled to the Customer via in-band signaling protocol.
In reaction to this signal, receiver router may translate that to
relevant QoS policy definition on the device.
For an in-band signaling, we propose to use BGP as a transport. The
details of SLA parameters are specific to the granularity of traffic
classes and their respective treatment, which is independent of the
BGP protocol itself. Though we find BGP as a suitable transport for
inter-domain SLA exchange for the following reasons:
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- The need to exchange SLA parameters between domains(Autonomous
Systems (AS)), where in use-cases described in this document,
BGP is a suitable protocol for inter-domain exchange [RFC4271]
[RFC4364].
- There is no specifically defined protocol available today for
SLA exchange.
- BGP updates already advertise specific set of prefixes (flow
or flow-group). Other QoS-related attributes, apart from the
the use of SLA advertisement, can be added to these updates
in the future.
The proposal is to define a new BGP attribute to advertise/learn SLA
details in-band. The proposed attribute is intended to advertise SLA
from one AS to a list of destined ASes. The advertised QoS
information could be for the incoming traffic to the advertiser, that
is advertising SLA or could be for the outgoing traffic from the
advertiser or could be for both directions. Reception of and
reaction to advertised SLAs are optional for the receiver.
We propose QoS as an optional transitive attribute, keeping SLA
advertisement as one of the sub-types of QoS attribute. This is to
keep the QoS attribute open for extensions. For example, SLA
Negotiation and Assurance is out of scope of this document but can be
envisioned as another sub-type.
2. Terminology
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 [RFC2119].
3. QoS Attribute Definition
The QoS Attribute proposed here is an optional transitive attribute
(attribute type code to be assigned by IANA). SLA is defined as one
of the sub-types in the QoS attribute. The QoS attribute is only
applicable to the NLRI advertised in the BGP update message.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr flag | Attr type QoS | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ ~
| QoS Attr length/Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+..........................
Attribute flags
highest order bit (bit 0) -
MUST be set to 1, since this is an optional attribute
2nd higher order bit (bit 1) -
MUST be set to 1, since this is a transitive attribute
3.1. SLA, QoS attribute sub-type, Definition
The value field of the QoS Attribute contains TLVs, followed to QoS
Attribute flags described in the previous section. One of the TLVs
that we define is a tuple of (SLA sub-type, Length, Value).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QoS Attr flags| subType | subtype Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+..........................
QoS Attr flags
8-bit = 0000-0000, All the bits are currently un-used. The space
is made available for the purpose of future use. For now
they all MUST be set to 0 when QoS attribute is added in
the BGP update message and MUST be ignored when received
subType
8-bit
0x00 = reserved
0x01 = SLA
0x02 - 0x0f = for future use
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subType Length
16-bit
Length of the content to follow pertaining to specified
subType.
Value for the SLA sub-type is as described below. These details
contain information about 1) sender and receiver(s) and 2) SLA
parameters. SLA Parameters include SLA event type (such as
Advertise) and contents associated to that event type.
The format of SLA message is,
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 32-bit Source AS (Advertiser) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 32-bit Destination AS count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| variable list of destination AS |
~ .... ~
| .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Event | SLA id | SLA length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Content as per SLA Event |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Source AS
32-bit source AS number. This is the AS that is advertising SLA
0 = ignore Source and Destination AS list from this Value field
Note that AS = 0, used in message outside of QoS attribute,
is illegal in normal BGP operations. AS = 0 inside the QoS
attribute may be used simply as a flag to tell receiver to
ignore Source and Destination AS list from inside the QoS
attribute.
Destination AS count
32-bit destination AS count to take variable length AS list.
This count has no functional value when Source AS is 0.
0 = QoS attribute is relevant to every receiver of the message
Destination AS list
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32-bit destination AS number
....
.... [as many as AS count]
SLA Event
4-bits
0x0 = reserved
0x1 = ADVERTISE
0x2 to 0xf, for future use
SLA Id
16-bit identifier unique within the scope of source AS
The significance of an SLA identifier is in the context of the
source that is advertising SLA parameters. The SLA identifier
is not globally unique but it MUST be unique within the source
AS (advertiser).
If advertised SLA id is different from earlier advertised one,
for the same prefix, previous SLA content MUST be replaced
with the new advertised one.
SLA is aggregate for all the traffic to prefixes for a given
AFI/SAFI that share same source AS and SLA id.
SLA Length
12-bits - Total length of the SLA content to follow
Content as per SLA event
The SLA content is optional for an advertised SLA id. The
value of the SLA length field in such case would be 0. If SLA
content does not exist in BGP update messages with advertised
QoS attribute, that contains the SLA sub-type, then receiver
MUST inherit prior advertised SLA content for the same SLA id
from the same Source AS. If there does not exist any prior SLA
to relate to the advertised SLA id, then receiver can ignore
the SLA advertisement and continue with the rest of the BGP
message processing and forwarding rules. Note that such
condition MUST not discard the attribute. All defined
forwarding rules for this attribute still MUST apply.
The only event prescribed in this document is ADVERTISE.
The format of SLA ADVERTISE event message is,
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|dir| Traffic Class count | Class Desc Len| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~
| |
~ Traffic Class Description ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Elements Count| |
+-+-+-+-+-+-+-+-+ ~
| |
~ Traffic Class Elements TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Count| |
+-+-+-+-+-+-+-+-+ ~
| Traffic Class Service TLVs |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Repeat from Traffic Class Description for next Traffic Class ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Repeat from direction for SLA in the other direction ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
dir (Direction)
02-bit for incoming traffic to source AS or outgoing traffic
from source AS,
0x0 = reserved
0x1 = incoming, to source AS from destination AS
0x2 = outgoing, from source AS towards destination AS
0x3 = for future use
Traffic Class count (Classifier Groups count)
16-bit, count of number of classifier groups
00 = Advertisement to invalidate previous advertised SLA if any
Traffic Class Descr Length
08-bit, length of the description
0 = No description
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Traffic Class Description
Description of the Traffic Class in UTF-8 encoding
Traffic Class Elements Count in a Traffic Class,
08-bit count of classifier elements in a specific Traffic Class
00 = this has relative definition. It means classify rest all
traffic that is not classified via earlier described
Traffic Classes.
It is RECOMMENDED that Traffic Class that has 0 elements
is present last in the advertised list of Traffic Classes.
If Advertised message has it positioned somewhere else,
then receiver MUST re-order it, for the forwarding purpose,
to the last position in the advertised list of Traffic
Classes from a given source AS. QoS attribute advertised
from a specific source MUST NOT have more than one such
Traffic Classes (Traffic Class with 0 elements count). If
there are more than one such Traffic Classes present then
it is an error condition which should follow handling of
such BGP message as described in Error handling section.
Classifier Element values (optional),
08-bit = IPFIX Element Identifier
08-bit = size, in octets, of the value field
variable-length field = contains actual value
Given IPFIX [RFC5102] has well defined identifier set for a
large number of packet attributes, IPFIX IANA registry is
("https://www.ietf.org/assignments/ipfix") chosen to specify
packet classification attributes. However, since not all
identifiers from IPFIX would be applicable to this proposal,
only a limited set identified here can be supported by BGP
SLA exchange. Any new element identifier, in the future added
to the IPFIX IANA registry, is not automatically supported
for this proposal. Only the IPFIX elements indicated in this
document below remain supported.
+----+----------------------------+
| ID | Name |
+----+----------------------------+
|195 | ipDiffServCodePoint |
|203 | mplsTopLabelExp |
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|244 | dot1qPriority |
| 8 | sourceIPv4Address |
| 27 | sourceIPv6Address |
| 9 | sourceIPv4PrefixLength |
| 29 | sourceIPv6PrefixLength |
| 44 | sourceIPv4Prefix |
|170 | sourceIPv6Prefix |
| 12 | destinationIPv4Address |
| 28 | destinationIPv6Address |
| 13 | destinationIPv4PrefixLength|
| 30 | destinationIPv6PrefixLength|
| 45 | destinationIPv4Prefix |
|169 | destinationIPv6Prefix |
| 4 | protocolIdentifier |
| 7 | sourceTransportPort |
| 11 | destinationTransportPort |
+----+----------------------------+
Any traffic classifier element advertised in the QoS attribute
is only applicable to the NLRI advertised for a given AFI/SAFI
within the BGP update message. If a receiver receives a BGP
update message with QoS/SLA attribute for an NLRI that is not
supported by a receiver then receiver MUST not install an
advertised SLA and continue to forward this attribute further
if it is not the last receiver of an attribute.
Traffic Class Service count (for a Traffic Class under definition)
08-bit count of service attributes fields to follow with
type/value pair
List of service types and relevant values are discussed below
00 = no bounded service (also means Best Effort)
Traffic Class Service (optional),
16-bit = Traffic Class Service Type
08-bit = size, in octets, of the value field
variable-length field = contains actual value
- 0x00 = reserved
- 0x01 = TRAFFIC_CLASS_TSPEC
160-bits TSpec Parameter
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The TRAFFIC_CLASS_TSPEC parameter consists of the (r), (b), (p),
(m) and (M) parameters as described in Invocation Information
section of [RFC2212]. Note that inheriting the definition of
TSpec here does not enable RFC2212 functionality. Only the
values of the Traffic Specification are used in this
specification.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Rate (r) (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Burst Size (b) (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Rate (p) (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Policed Unit (m) (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Packet Size (M) (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Parameter (r) indicates min-rate of the traffic class. This rate
indicates the minimum rate, measured in octets of Layer 2 (L2)
datagrams per second, that the service advertiser is providing
for a given class of traffic on advertiser's hop. Note that it
does not necessarily translate to a minimum rate service to the
receiver of an SLA unless the traffic class definition clearly
represents a sole receiver of an SLA. If there is no SLA for
min-rate, the value of (r) MUST be set to 0.
Parameter (b) indicates maximum burst size, measured in octets of
L2 datagram size. Since queuing delay can be considered a
function of burst size (b) and min-rate (r), in presence of non-
zero parameter (r), parameter (b) represents bounded delay for
the Traffic Class. This delay is a single hop queuing delay when
SLA is to be implemented at the resource constrained bottleneck.
In other words this burst size can be considered as a buffer
size. Value of 0 for parameter (b) means the advertiser does not
mandate specific bounded delay.
Parameter (p) indicates max-rate of the traffic class. Just like
min-rate, max-rate, measured in octets of L2 packets per second,
field here also indicates service provided by advertiser. If
advertiser does not have any specific value to set for a given
class of traffic, it MAY be set to physical interface line rate
or any other indirect limit that may affect this class' maximum
rate. In absence of any such known value, it MUST be set to
positive infinity. Value 0 is considered an error.
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Parameters (r), (b) and (p) are each set as 32-bit IEEE floating
point numbers. Positive infinity is represented as an IEEE single
precision floating-point number with an exponent of all ones and
a sign mantissa of all zeros. The format of IEEE floating-point
numbers is further summarized in [RFC4506].
The minimum policed unit (m) and maximum packet size (M)
parameters have no relevance for the purpose of SLA exchange.
Thus they MUST be ignored.
- 0x02, L2_OVERHEAD
08-bit, value
By default specification of rate and other packet size related
parameters, advertised in an SLA, includes L2 overhead. For the
receiver next hop,this overhead is the L2 overhead of the local
link where advertised SLA is received. However, in cases where
advertised SLA is for a receiver multiple hops away, L2 overhead
consideration from the source perspective may be different from
the local L2 overhead at the receiver. Explicit notification of
size of L2 overhead from a sender, in such cases, is useful for
a receiver to distinguish local L2 overhead from the sender
advertised one. When receiver choose to react to an advertised
SLA and if this service type is present in advertised SLA,
receiver MUST use advertised L2 overhead over local L2 overhead.
If SLA is required to consider only IP packet size, sender may
advertise this service with a value of 0.
- 0x03 = MINRATE_IN_PROFILE_MARKING
08-bit = IPFIX Element Identifier
08-bit = size, in octets, of the value field
variable-length field = contains actual value
00 Identifier = drop, variable-length for this id is 0.
+----+----------------------------+
| ID | Name |
+----+----------------------------+
|195 | ipDiffServCodePoint |
|203 | mplsTopLabelExp |
|244 | dot1qPriority |
+----+----------------------------+
- 0x04 = MINRATE_OUT_PROFILE_MARKING
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08-bit = IPFIX Element Identifier
08-bit = size, in octets, of the value field
variable-length field = contains actual value
00 Identifier = drop, variable-length for this id is 0.
+----+----------------------------+
| ID | Name |
+----+----------------------------+
|195 | ipDiffServCodePoint |
|203 | mplsTopLabelExp |
|244 | dot1qPriority |
+----+----------------------------+
- 0x05 = MAXRATE_IN_PROFILE_MARKING
08-bit = IPFIX Element Identifier
08-bit = size, in octets, of the value field
variable-length field = contains actual value
00 Identifier = drop, variable-length for this id is 0.
+----+----------------------------+
| ID | Name |
+----+----------------------------+
|195 | ipDiffServCodePoint |
|203 | mplsTopLabelExp |
|244 | dot1qPriority |
+----+----------------------------+
- 0x06 = MAXRATE_OUT_PROFILE_MARKING
08-bit = IPFIX Element Identifier
08-bit = size, in octets, of the value field
variable-length field = contains actual value
00 Identifier = drop, variable-length for this id is 0.
+----+----------------------------+
| ID | Name |
+----+----------------------------+
|195 | ipDiffServCodePoint |
|203 | mplsTopLabelExp |
|244 | dot1qPriority |
+----+----------------------------+
In the case when MINRATE_IN_PROFILE_MARKING,
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MINRATE_OUT_PROFILE_MARKING, MAXRATE_IN_PROFILE_MARKING and
MAXRATE_OUT_PROFILE_MARKING are all advertised,
- MINRATE_IN_PROFILE_MARKING takes highest precedence
(that is over MAXRATE_IN_PROFILE_MARKING)
- MAXRATE_IN_PROFILE_MARKING takes precedence over
MINRATE_OUT_PROFILE_MARKING
- and MAXRATE_OUT_PROFILE_MARKING takes precedence over
MINRATE_OUT_PROFILE_MARKING
- 0x07 = DROP_THRESHOLD
03-bit count of drop-priority fields to follow with
(type, type-value, burst size) tuple
04-bit, drop priority type
08-bit = IPFIX Element Identifier
08-bit = size, in octets, of the value field
variable-length field = contains actual value
32-bit = Burst Size
(32-bit IEEE floating point number)
+----+----------------------------+
| ID | Name |
+----+----------------------------+
|195 | ipDiffServCodePoint |
|203 | mplsTopLabelExp |
|244 | dot1qPriority |
+----+----------------------------+
This finer granular drop threshold does not require separate
buffer space from the aggregate buffer space. It is just an
indicator beyond which code-point specific traffic to be
discarded when occupancy of aggregate buffers reached to that
threshold.
- 0x08 = RELATIVE_PRIORITY
04-bit, priority value
lower the value, higher the priority
Relative priority indicates scheduling priority. For example
voice traffic, which requires lowest latency compared to any
other traffic, may have lowest value advertised in relative
priority. For two different traffic classification groups
where one application group may be considered more important
than the other but from a scheduling perspective does not
require to be distinguished with a different priority, relative
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priority for those classification groups may be advertised with
the same value.
- 0x09 = SUB_TRAFFIC_CLASSES
variable-length, repeats all content described above from Traffic
Class count onwards.
For SLAs where a specific Traffic Class may further have
different sub-services for a sub-group of Classifier Elements,
this service type SHOULD be used to further divide Traffic Class
in multiple sub-classes. Each sub-class is then defined with
their own classifier elements and service types.
4. Originating SLA Notification
The QoS attribute MUST only be added by the originator and MUST NOT
be added during BGP propagation.
SLA messages SHOULD NOT be sent periodically just for the purpose of
keep alive. Some sort of SLA policy change may be considered as a
trigger for the advertisement.
For any modified SLA parameters, the originator MUST re-advertise the
entire set of SLA parameters. There is no provision to advertise
partial set of parameters. To invalidate previously advertised SLA
parameters, a message MUST be sent with the same SLA id for the same
source with the Traffic Class count set to 0.
4.1. SLA Contexts
In certain cases, the advertisement may relate to an SLA for
aggregate traffic over a point-to-point connection between a specific
destination and a specific source. A point-to-point connection may
be the physical link, that connects two BGP peers, or may be a
virtual link (e.g. a tunnel). A BGP update message, in such cases,
with source AS number and NLRI prefix of source end-point can
uniquely identify physical/virtual link and so establishes advertised
SLA's context for that point to point link.
In the simplest case where Provider (e.g. PE) and Customer (e.g.
CE) devices are directly connected via a physical link and have only
a single link between them, CE can uniquely identify the forwarding
link to PE with AS number of the PE and NLRI prefix being an IP
address of PE, to CE (that is the next hop address from CE to PE).
SLA advertised thru BGP update message from PE to CE, with PE's AS
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number and IP address, establishes SLA context for the aggregate
traffic through link CE to PE. SLA advertised thru BGP update
message from PE to CE, with PE's AS number and any other prefix
establishes SLA for that specific prefix, subset of traffic under CE
to PE link.
Even though this example is in the context of IP prefixes, SLA
exchange does not have to be limited to the IP address family (IPv4
and IPv6). SLA advertisement is generic to all forms of NLRI types
that are supported by the BGP protocol specification (like IPv4,
IPv6, VPN-IPv4, VPN-IPv6).
4.1.1. SLA Advertisement for Point-to-Point Connection
When SLA messages are intended to be advertised for the point-to-
point connection (physical or logical), the message is destined for
the next hop and advertised message is in the context of the prefix
of the source end-point of the point to point connection.
The destination AS number set to, within QoS SLA attribute, typically
is of the neighbor BGP speaker's. Alternatively, source AS and
destination AS count MAY be set to 0.
4.1.2. SLA Advertisement for Destination AS Multiple Hops Away
When SLA messages are to be advertised beyond next hop, value of
source AS, in the QoS attribute, MUST be set by the originator of the
update message. If such an update is meant to be for a specific list
of AS(es) as receivers, then the list of destination AS MUST be
explicitly described in the QoS attribute message to avoid flooding
of the QoS attribute data in the network beyond those destinations.
When a new prefix is added in the AS, AS for which SLA parameters
have already been advertised before for other existing prefixes, and
if traffic to this new prefix is subject to the same SLA advertised
earlier then BGP update for this new prefix may include QoS attribute
containing just an SLA id, an id that was advertised earlier. The
corresponding Update message does not require to have the whole SLA
content. SLA id is sufficient to relate SLA parameters to new
advertised prefix.
5. SLA Attribute Handling at Forwarding Nodes
5.1. BGP Node Capable of Processing QoS Attribute
If a BGP node is capable of processing QoS attribute, it optionally
MAY process the QoS attribute. If advertised SLA has a list of
destination ASes, it MAY trim the list and so count of destination AS
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to exclude ones that are not required in further announcement of BGP
updates.
BGP node MUST drop SLA related sub-type from the QoS attribute, if
there is no more AS from the destination list in the forwarding path.
The rest of the QoS attribute contents MAY be forwarded if there
exist other sub-types of QoS attribute and forwarding rules meets
other sub-types requirements. If there is no other sub-types in the
QoS attribute content then the node MUST drop the entire QoS
attribute all together. The other attributes and NLRI information
may be announced further if they meet rules defined by other
attributes and BGP protocol.
Except extracting the entire SLA sub-type of the QoS attribute and
trimming the list of destination AS list, all other content MUST NOT
be modified by any intermediate receivers of the message.
5.2. SLA Attribute Handling at Receiver
Reception of and processing of advertised QoS SLA content are
optional for the receiver.
While reacting to SLA advertisement
- receiver SHOULD invalidate previous advertised SLA parameters if
one exists for the same SLA id and source AS. If the new
advertised SLA has a non-zero traffic count, then the new
advertised SLA SHOULD be installed. If new advertised SLA update
is with Traffic Class count 0, then no action is required.
- When BGP update messages are triggered only as a result of SLA
policy change, BGP update message forwarding beyond intended
receivers are not necessary. If receiver device implementation
supports policy based filtering then receiver MAY implement a
policy to filter such messages based on prefix and attribute.
If SLA advertised to the next hop neighbor, the receiver may
implement advertised SLA for the whole link, where the link could be
physical or virtual link, connected to the neighbor. If SLA
advertised to is not the next hop neighbor then receiver may
establish advertised SLA for that specific prefix list under the
relevant link. It is completely up to the receiver to decide for
which prefixes it should accept advertised SLA and for which ones it
won't.
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6. Error Handling
Error conditions, while processing of the QoS attribute, SHALL be
handled with the approach of attribute-discard as described in [IDR-
ERR]. In such condition, receiver SHOULD also cleanup any previously
installed SLA state for the same prefix.
7. Traffic Class Mapping
It is possible that switching/routing methods used in 2 different
ASes could be different. For example, Provider may tunnel Customer's
IP traffic thru MPLS cloud. In such cases traffic class definition
for QoS services may differ in both ASes. For the meaningful use of
advertised SLA in such cases, receiver is required to map traffic
class from one type to the other.
In the example given, traffic classification in Customer AS could be
IP Diffserv-based whereas traffic classification in Provider AS could
be MPLS TC-based. Thus for advertised MPLS TC-based SLA would
require to map traffic class from IP Diffserv-based to MPLS TC type
[RFC3270].
There are well-defined recommendations that exist for traffic class
mapping between two technologies, eg. RFC3270 for mapping between
DSCP and MPLS TC. Receiver MAY use those defined recommendations for
traffic class mapping or MAY define its own as per its network
Traffic Class service definition to map to advertised Traffic
Classes. It is completely up to the receiver how to define such
traffic class mapping.
8. Deployment Considerations
One of the use cases is for a Provider to advertise contracted SLA
parameters to Customer Edge (CE) in cases where eBGP is deployed
between PE and CE. The SLA parameters may already be provisioned by
the provider on the PE device (facing CE). This provisioned SLA
parameters are then advertised thru proposed BGP QoS attribute to the
CE device. CE device may read the attribute and SLA sub-type content
to implement the QoS policy on the device.
Contracted SLA from PE to CE may be full line-rate or sub line-rate
or finer granular controlled services. SLA advertise can be useful
when contracted service is sub-rate of a link and/or when for finer
granular traffic classes that are controlled (e.g. voice, video
services may be capped to certain rate)
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_______________
__________ / \
/ \ / \
/ \ / \
|CustomerSite|-----| Provider |
\ C/E P\E /
\__________/ \ /
\_______________/
AS 3 AS 2
SLA_ADVERTISE: AS2 to AS3
NLRI = PE ip address
Another use case can be to advertise SLAs among different network
sites within one Enterprise network. In Hub and Spoke deployments,
Administrator may define SLAs at spoke and advertise QoS SLA
parameters to the Hub thru BGP updates. In the figure below, each
spoke (AS1 and AS2) are connected to Hub (AS3) via a VPN tunnel. As
shown, AS2 can advertise SLA to AS3 in the context of that tunnel ip
address.
AS 2
_______________ ________
/ \ / \
__________ / \-----| Spoke2 |
/ \ / \ \________/
| Hub |-----| Provider | ________
\__________/ \ / / \
\ /-----| Spoke1 |
AS 3 \_______________/ \________/
AS 1
SLA_ADVERTISE: AS2 to AS3
NLRI = AS2 tunnel address
SLA_ADVERTISE: AS1 to AS3
NLRI = AS1 tunnel address
Deployment options are not limited to involving CEs, PE-to-CE or CE-
to-CE, only. For any contract between two providers, SLA parameters
may be advertised from one to the other.
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9. Acknowledgements
Thanks to Fred Baker, David Black, Sue Hares and Benoit Claise for
their suggestions and to Christian Jacquenet, Ken Briley, Rahul
Patel, Fred Yip, Lou Berger, Brian Carpenter, Bertrand Duvivier,
Bruno Decraene for the review.
10. IANA Considerations
This document defines a new BGP optional transitive path attribute,
called QoS Attribute. IANA action is required to allocate a new
code-point in the BGP path Attributes registry.
IANA is requested to create a registry for QoS Attribute subTypes.
This is a registry of 1 octet value, to be assigned on a standards
action/early allocation basis. The initial assignments are:
QoS Attribute subTypes
- - - - - - - - - - - -
Reserved 0x00
SLA 0x01
IANA is requested to create a registry for SLA Event Types. This is
a registry of 4-bits value, to be assigned on a standards action/
early allocation basis. The initial assignments are:
QoS Attribute SLA Event Types
- - - - - - - - - - - - - - -
Reserved 0x00
ADVERTISE 0x01
IANA is requested to create a registry to define QoS SLA Direction.
This is the direction in forwarding path, advertised QoS SLA is
applicable to.
QoS SLA Direction
- - - - - - - - -
Reserved 0x00
to Source AS from destination AS 0x01
from source AS to destination AS 0x02
QoS SLA Traffic Class Element Types will be referring to existing
IPFIX IANA types as described in section 3.1.
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IANA is requested to create a registry for QoS SLA Traffic Class
Service Types. This is a registry of 2 octet values, to be assigned
on a standards action/early allocation basis. The initial
assignments are:
Traffic Class Service Type
- - - - - - - - - - - - - -
Reserved 0x00
TRAFFIC_CLASS_TSPEC 0x01
L2_OVERHEAD 0x02
MINRATE_IN_PROFILE_MARKING 0x03
MINRATE_OUT_PROFILE_MARKING 0x04
MAXRATE_IN_PROFILE_MARKING 0x05
MAXRATE_OUT_PROFILE_MARKING 0x06
DROP_THRESHOLD 0x07
RELATIVE_PRIORITY 0x08
SUB_TRAFFIC_CLASSES 0x09
11. Security Considerations
The QOS attribute defined in this document SHOULD be used by the
managed networks for enforcing Quality of Service Policies and so
there should not be any risks for identity thefts. To strengthen the
security for the QOS attribute, RPKI based origin validation
[RFC7115] MAY be used. In addition to the RPKI based origin
validation, BGP Path Validation [I-D.ietf-sidr-bgpsec-protocol]
procedures could be used over BGP QOS attribute and its associated
prefix in producing the digital signature that can be carried within
the signature SLA for the messages. This would help prevent any man-
in-the-middle attracks.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2212] Shenker, S., Partridge, C., and R. Guerin, "Specification
of Guaranteed Quality of Service", RFC 2212,
DOI 10.17487/RFC2212, September 1997,
<http://www.rfc-editor.org/info/rfc2212>.
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[RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
Protocol Label Switching (MPLS) Support of Differentiated
Services", RFC 3270, DOI 10.17487/RFC3270, May 2002,
<http://www.rfc-editor.org/info/rfc3270>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<http://www.rfc-editor.org/info/rfc4271>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <http://www.rfc-editor.org/info/rfc4364>.
[RFC4506] Eisler, M., Ed., "XDR: External Data Representation
Standard", STD 67, RFC 4506, DOI 10.17487/RFC4506, May
2006, <http://www.rfc-editor.org/info/rfc4506>.
[RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
Meyer, "Information Model for IP Flow Information Export",
RFC 5102, DOI 10.17487/RFC5102, January 2008,
<http://www.rfc-editor.org/info/rfc5102>.
[RFC7115] Bush, R., "Origin Validation Operation Based on the
Resource Public Key Infrastructure (RPKI)", BCP 185,
RFC 7115, DOI 10.17487/RFC7115, January 2014,
<http://www.rfc-editor.org/info/rfc7115>.
[IDR-ERR] Scudder, J., Chen, E., Mohapatra, P., and K. Patel,
"Revised Error Handling for BGP UPDATE Message, I-D.draft-
ietf-idr-error-handling", June 2012.
12.2. Informative References
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<http://www.rfc-editor.org/info/rfc2475>.
[RFC7297] Boucadair, M., Jacquenet, C., and N. Wang, "IP
Connectivity Provisioning Profile (CPP)", RFC 7297,
DOI 10.17487/RFC7297, July 2014,
<http://www.rfc-editor.org/info/rfc7297>.
[BGP-SEC] Lepinski, M., "BGPsec Protocol Specification, I-D.draft-
ietf-sidr-bgpsec-protocol", June 2015.
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[CPNP] Boucadair, M. and C. Jacquenet, "Connectivity Provisioning
Negotiation Protocol (CPNP), I-D.boucadair-connectivity-
provisioning-protocol", Sep 2014.
[BGPSLA-IMPL]
Shah, S. and K. Patel, "Inter-domain SLA Exchange
Implementation Report, I-D.draft-svshah-idr-sla-exchange-
impl", Feb 2015.
Authors' Addresses
Shitanshu Shah
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
US
Email: svshah@cisco.com
Keyur Patel
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
US
Email: keyupate@cisco.com
Sandeep Bajaj
Juniper Networks
1194 N. Mathilda Avenue
Sunnyvale, CA 94089
US
Email: sbajaj@juniper.net
Luis Tomotaki
Verizon
400 International
Richardson, TX 75081
US
Email: luis.tomotaki@verizon.com
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Mohamed Boucadair
France Telecom
Rennes 35000
France
Email: mohamed.boucadair@orange.com
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