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authorMark D. Gray <mark.d.gray@intel.com>2016-05-26 14:47:27 +0100
committerMark D. Gray <mark.d.gray@intel.com>2016-06-07 09:40:56 +0100
commitf5fd9fa807f85a09466b740a475007b13654dce2 (patch)
tree3f61343b78ff41761177642b254fea2097889fdb /specs/High-Priority-Traffic-Path.rst
parent7f666d1ac67abdafd91ae1b3dc31010f6c28c62f (diff)
specs: Enable gerrit build of specs documentation
This patch allows gerrit to parse the spec documentation and publishes to artifacts on merge. Change-Id: Ib9d5b1229975d2b9819320af22973008885c4f58 Signed-off-by: Mark D. Gray <mark.d.gray@intel.com>
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-..
- This work is licensed under a Creative Commons Attribution 3.0 Unported
- License.
-
- http://creativecommons.org/licenses/by/3.0/legalcode
-
-==========================================
-High Priority Traffic Path
-==========================================
-
-https://wiki.opnfv.org/display/ovsnfv/OVSFV+Requirement+-+High+Priority+Traffic+Path
-
-Problem description
-===================
-
-A network design may need to adequately accommodate multiple classes of traffic, each
-class requiring different levels of service in critical network elements.
-
-As a concrete example, a network element managed by a service provider may be
-handling voice and elastic data traffic. Voice traffic requires that the end-to-end
-latency and jitter is bounded to some numerical limit (in msec) accuracy in order to ensure
-sufficient quality-of-service (QoS) for the participants in the voice call.
-Elastic data traffic does not impose the same demanding requirements on the network
-(there will be essentially no requirement on jitter. For example, when downloading a
-large file across the Internet, although the bandwidth requirements may be high there
-is usually no requirement that the file arrives within a bounded time interval.
-
-Depending on the scheduling algorithms running on the network element,
-frames belonging to the data traffic may get transmitted before frames
-belonging to the voice traffic introducing unwanted latency or jitter.
-Therefore, in order to ensure deterministic latency and jitter characteristics
-end-to-end, each network element through which the voice traffic traverses
-must ensure that voice traffic is handled deterministically.
-
-Hardware switches have typically been designed to ensure certain classes
-of traffic can be scheduled ahead of other classes and are also
-over-provisioned which further ensures deterministic behavior when
-handling high priority traffic. However, software switches (which includes
-virtual switches such as Open vSwitch) may require modification in order
-to achieve this deterministic behavior.
-
-Use Cases
----------
-
-1. Program classes of service
-
-The End User specifies a number of classes of service. Each class of service
-will be represented by the value of a particular field in a frame. The class
-of service determines the priority treatment which flows in the class will
-receive, while maintaining a relative level of priority for other classes and
-a default level of treatment for the lowest priority class of service. As
-such, each class of service will be associated with a priority. The End User
-will associate classes of service and priorities to ingress ports with the
-expectation that frames that arrive on these ingress ports will get
-scheduled following the specified priorities.
-
-Note: Priority treatment of the classes of service cannot cause any one of
-the classes (even the default class) from being transferred at all. In other
-words, a strict priority treatment would likely not be successful for serving
-all classes eventually, and this is a key consideration.
-
-2. Forward high priority network traffic
-
-A remote network element sends traffic to Open vSwitch. The remote network
-element, indicates the class of service to which this flow of traffic belongs
-to by modifying a pre-determined but arbitrary field in the frame as specified
-in Use Case 1. Some examples include the Differentiated Services Code Point
-(DSCP) in an IP packet or the Priority Code Point (PCP) in an Ethernet frame.
-The relative priority treatment that frames get processed by Open vSwitch can be guaranteed by the
-values populated in these fields when the fields are different. If the fields
-are the same, ordering is not deterministic.
-
-For example: Packet A is sent with a DSCP value of 0 and packet B is sent
-with a value of 46; 0 has a lower priority than 46. Packet A arrives
-before packet B. If Open vSwitch has been configured as such, Packet
-B will be transmitted before Packet A.
-
-Proposed change
-===============
-
-TBD
-
-Alternatives
-------------
-
-TBD
-
-OVSDB schema impact
--------------------
-
-TBD
-
-User interface impact
----------------------
-
-TBD
-
-Security impact
----------------
-
-TBD
-
-Other end user impact
----------------------
-
-TBD
-
-Performance Impact
-------------------
-
-TBD
-
-Other deployer impact
----------------------
-
-TBD
-
-Developer impact
-----------------
-
-TBD
-
-Implementation
-==============
-
-Assignee(s)
------------
-
-Who is leading the writing of the code? Or is this a blueprint where you're
-throwing it out there to see who picks it up?
-
-If more than one person is working on the implementation, please designate the
-primary author and contact.
-
-Primary assignee:
- <email address>
-
-Other contributors:
- <email address>
-
-Work Items
-----------
-
-TBD
-
-Dependencies
-============
-
-TBD
-
-Testing
-=======
-
-In order to test how effectively the virtual switch handles high priority traffic
-types, the following scheme is suggested.::
-
- +---------------------------+ Ingress Traffic Parameters
- | | +-------------------------------------------+
- | |
- | | Packet Size: The size of the Ethernet frames
- | |
- | | Tmax: RFC2544 Max. Throughput for traffic of
- | PHY0 <-------+ "Packet Size"
- | |
- | | Total Offered Rate: The offered rate of both
- | | traffic classes combined expressed as a % of
- | | Tmax
- | |
- | | Ingress Rates are expressed as a percentage
- | | of Total Offered Rate.
- | |
- | | Class A:
- | OVS | Ethernet PCP = 0 (Background)
- | (BR0) | Ingress Rate : rate_ingress_a(n) Mfps
- | |
- | | Class B:
- | | Ethernet PCP = 7 (Highest)
- | | Ingress Rate : rate_ingress_b(n) Mfps
- | |
- | | Egress Traffic Measurements
- | | +-------------------------------------------+
- | | Class A:
- | | Egress Throughput : rate_egress_a(n) Mfps
- | | Egress Latency : max_lat_egrees_a(n) ms
- | | Egress Jitter : max_jit_egress_a(n) ms
- | PHY1 +------->
- | | Class B:
- | | Egress Throughput : rate_egress_b(n) Mfps
- | | Egress Latency : max_lat_egrees_b(n) ms
- +---------------------------+ Egress Jitter : max_jit_egress_b(n) ms
-
-
-Open vSwitch is configured to forward traffic between two ports agnostic to the
-traffic type. For example, using the following command:
-
-ovs-ofctl add-flow br0 in_port=0,actions=output:1
-
-The test will be carried out with the functionality to enable high-priority
-traffic enabled and disabled in order to guage the change in performance for
-both cases.
-
-Two classes of traffic will be generated by a traffic generator. In the example
-above, the classes are differentiated using the Ethernet PCP field. However,
-another means for differentiating traffic could be used, depending the
-prioritization scheme that is developed.
-
-Tests should be performed for each combination of:
-
-* Packet Sizes in (64, 512)
-* Total Offered Rate in (80, 120, 150)
-* rate_ingress_b(n) / rate_ingress_a(n) in (0.1, 0.2, 0.5)
-
-For each set, the following metrics should be collected for each traffic
-class over a specified time period:
-
-Egress Throughput (Mfps)
-Maximum Egress Latency (ms)
-Maximum Egress Jitter (ms)
-
-Documentation Impact
-====================
-
-TBD
-
-References
-==========
-
-Please add any useful references here. You are not required to have any
-reference. Moreover, this specification should still make sense when your
-references are unavailable. Examples of what you could include are:
-
-* Links to mailing list or IRC discussions
-
-- http://lists.opnfv.org/pipermail/opnfv-tech-discuss/2015-December/007193.html
-- http://ircbot.wl.linuxfoundation.org/meetings/opnfv-ovsnfv/2016/opnfv-ovsnfv.2016-03-07-13.01.html
-
-* Links to relevant research, if appropriate
-
-- https://wiki.opnfv.org/download/attachments/5046510/qos_mechanisms.pdf?version=1&modificationDate=1459187636000&api=v2
-
-* Related specifications as appropriate
-
-* Anything else you feel it is worthwhile to refer to
-
-
-History
-=======
-
-Optional section intended to be used each time the spec
-is updated to describe new design, API or any database schema
-updated. Useful to let reader understand what's happened along the
-time.
-
-.. list-table:: Revisions
- :header-rows: 1
-
- * - Release Name
- - Description
- * - Colorado
- - Introduced