Internet DRAFT - draft-wang-ccamp-flexe-control-analysis
draft-wang-ccamp-flexe-control-analysis
Internet Engineering Task Force Q. Wang, Ed.
Internet-Draft X. Niu, Ed.
Intended status: Informational ZTE Corporation
Expires: May 7, 2020 Y. Xu
CAICT
November 4, 2019
Analysis for FlexE control
draft-wang-ccamp-flexe-control-analysis-03
Abstract
This document gives some analysis about the control of FlexE.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. General Introduction of FlexE . . . . . . . . . . . . . . 3
3.1.1. FlexE Group . . . . . . . . . . . . . . . . . . . . . 3
3.1.2. FlexE Client . . . . . . . . . . . . . . . . . . . . 4
3.1.3. Encapsulation of FlexE Client into FlexE Group . . . 4
3.1.4. MAC Frame . . . . . . . . . . . . . . . . . . . . . . 5
3.1.5. Encapsulation of MAC frames into FlexE Client . . . . 5
3.2. General requirements . . . . . . . . . . . . . . . . . . 5
3.2.1. Configuration Mode for FlexE client . . . . . . . . . 6
3.2.2. Configuration of FlexE group . . . . . . . . . . . . 6
3.2.3. Allocate Resources for FlexE Client . . . . . . . . . 7
3.3. Control Requirements Derived . . . . . . . . . . . . . . 8
4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
OIF published the first version of FlexE Implementation Agreement in
March 2016, aiming to provide a generic mechanism for supporting a
variety of Ethernet MAC rates that may or may not correspond to any
existing Ethernet PHY rate. ITU-T SG15 has endorsed the OIF FlexE
data plane as parts of [ITU-T G.872], [ITU-T G.709], [ITU-T G.798]
and [ITU-T G.8023]. The Recommendations depend on or are based on
the FlexE data plane.
This draft is intended to trigger discussion of the FlexE control
requirements. What kind of models should we use when configuring
FlexE capable equipment, how to configure the FlexE group and FlexE
client, and what kind of parameters do we need to take into
consideration when configuring FlexE group and FlexE client. The
analysis is based on the description in section 7 and 8 of [ITU-T
G.8023] and FlexE IA 2.0.
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2. Terminology
2.1. Requirements Language
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 [RFC2119].
3. Analysis
3.1. General Introduction of FlexE
The FlexE shim is built into the Ethernet PCS (physical coding
sublayer). If a FlexE group is configured, a corresponding n*100G
(or n*50G, n*200G, n*400G) PCS module which may support multiple
FlexE clients is created as well.
The difference between the FlexE and the traditional Ethernet is that
the traditional Ethernet PCS has a 1:1 relationship with the client
MAC flow, while with FlexE one bonded huge PCS module can be used to
transport more than one FlexE client i.e., the relationship is 1:n.
3.1.1. FlexE Group
A FlexE Group is consisted of from 1 to n 100G FlexE instances, which
are carried over from 1 to m 100G, 200G or 400G Ethernet PHYs. A
FlexE group can also consisted of from 1 to n 50G FlexE instances,
which are carried over from 1 to m 50G Ethernet PHYs. All PHYs in
the group must operate at the same rate.
A FlexE Instance is a unit of information consisting of 50G or 100G
of capacity, which is able to carry FlexE Client data, together with
its associated overhead. Section monitoring overhead is added/
extracted as one 66B block at the FlexE group source and destination
(i.e., trail termination) to determine the status of the FlexE group.
Currently, only RPF (Remote PHY Fault) indication is used to report
the status of one FlexE group.
The set of FlexE Instances in the FlexE Group (not necessarily
consecutive FlexE Instance numbers) are indicated in the "FlexE Map"
field of the FlexE overhead. The full FlexE map is sent on all FlexE
Instances of the FlexE Group so that it is possible for the FlexE
demux to verify that the same FlexE Instance numbers are configured
at the FlexE mux as at the FlexE demux, and can tell whether all
expected FlexE Instances are being received.
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3.1.2. FlexE Client
A FlexE Client is an Ethernet flow based on a MAC data rate that may
or may not correspond to any Ethernet PHY rate. The FlexE Client MAC
rates supported by a FlexE Groups could be 10Gb/s, 40Gb/s, or m*25Gb/
s. The FlexE Client MAC rates supported by FlexE Groups may support
all, or only a subset of these FlexE Client rates. Each FlexE Client
is presented to the FlexE Shim as a 64B/66B encoded bit stream
according to clause 82 of [IEEE 802.3]. The FlexE client has the
semantics of an Ethernet PHY and there is no new layer network
defined for FlexE client, as both FlexE group and FlexE client are
processed in Ethernet PHY layer. From the network management point
of view, the FlexE client can be created accordingly and the
corresponding calendar slots of one FlexE group are allocated to one
FlexE client. The FlexE client could be generated internally within
a system, or created from a traditional Ethernet PHY. What kind of
FlexE clients will be created depends on the operator's needs.
According to the description in clause 8.1 of [ITU-T G.8023], there
is no overhead defined for monitoring a FlexE client, so the concept
of network connection for FlexE client in the equipment does not
exist. It is not correct to treat FlexE client as a network layer.
One FlexE client can be generated internally within one system, it
can also be formed by converting from the standard Ethernet signal,
e.g, a 10GBASE-R signal could be converted to a 10G FlexE Client
format by performing idle insertion/deletion. FlexE Clients do not
need to be produced or received in the same manner at both ends of
the connection.
3.1.3. Encapsulation of FlexE Client into FlexE Group
In order to distribute the FlexE client over PHYs of one FlexE group,
a number of management information command should be sent to the
processing function which performs the encapsulation of FlexE client
over FlexE group.
[ITU-T G.8023] specifies the equipment function blocks for Flex
Ethernet interface, which are between equipment management function
and atomic function within one network element. According to the
description in clause 7.2 of [ITU-T G.8023], the management
information commands sent to the source adaptation function from
equipment management function are listed below:
TxCC, TxCCA, TxCCB, TxCR, TxCA
TxGID, TxPHYMAP
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The TxCC, TxCCA and TxCCB are used to configure the calendar for use,
which could be type A or type B calendar configuration, slots
allocated for a specific FlexE client and FlexE client number.
TxCR and TxCA are used to coordinate the switch of calendar
configuration between the FlexE source and destination node.
The TxGID is used to configure the FlexE group identifier. The
TxPHYMAP is used to configure the set of PHYs in the FlexE group. If
200G and 400G are used, the 100G FlexE instance should be used in the
case of PHYMAP.
The built-in function multiplexer performs the action of assigning
the individual FlexE Client to specific calendar slots of the FlexE
group according to the input management information.
At the destination side, the Demultiplexer function could use
activate the FlexE Client and assigns the calendar slots of the FlexE
group payload area to the individual FlexE client accordng to
external configuration or the client calendar information carried in
the overhead. Expected group ID, PHYMAP and calendar allocation
information are needed sometimes to help verify the correctness of
FlexE configuration.
However, not all of the management information listed in [ITU-T
G.8023] need to be exposed to the external management system, as some
of them may be inferred, e.g., Calendar configuration(CC), which
could be inferred by comparing the original and new configuration.
3.1.4. MAC Frame
Defined in IEEE.
3.1.5. Encapsulation of MAC frames into FlexE Client
The external management information commands used as input to the
encapsulation/adaptation function are defined by [IEEE 802.3],
according to the description in [ITU-T G.8023]. The [IEEE 802.3]
process mainly includes the 64B/66B encoding, as well as MAC frame
check sequence generation and frame counting. The FlexE client
stream is generated at the determined FlexE Client MAC rate and
64B/66B encoded.
3.2. General requirements
It can be derived from section 2.1.2 and section 2.1.5 that process
involved when producing the FlexE Client from MAC frames is 64b/66b
encoding, and this encoding has already been defined by [IEEE 802.3].
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as no extra overhead is added during this process. Therefore,
configuration for mapping MAC frames into FlexE client from external
management system is not needed. In addition to the above analysis,
this draft also consider other aspects of requirements for FlexE
control/management.
Configuration mode for FlexE
Configuration of FlexE group
Creation of FlexE client and allocation of one or more FlexE group
calendar slot resources to a FlexE client.
3.2.1. Configuration Mode for FlexE client
There are two different configuration modes for bring one FlexE
client into service. The first one is static model, which is to use
external management system to configure the FlexE client and
resources allocated for the FlexE client at source and destination
FlexE shims. In this case, the CR/CA mechanism does not work.
Verification of configuration consistency at FlexE source and
destination site by comparing the in-band FlexE overhead with the
configuration at FlexE destination are needed; The other one is
MASTER/SLAVE mode, which is to use the FlexE overhead to coordinate
the resource configuration between FlexE source and destination, the
external resource configuration information is only sent the source
node.
3.2.2. Configuration of FlexE group
It can be concluded from the above analysis that external
configuration tools should be involved to bring one FlexE group into
service. The initial configuration commands could be from external
management system, SDN controller etc.
A FlexE group must be configured first before any client signals are
carried over it. When a new FlexE Group is brought into service, the
initial configuration must be provisioned for both ends, and the
initial configuration must be the same for both direction. The group
is configured to be consist of from 1 to n 100G FlexE Instances
carried over from 1 to m PHYs of the same rate (100GBASE-R, 200GBASE-
R, or 400GBASE-R). The group could also be configured to be consist
of from 1 to n 50G FlexE Instances carried over from 1 to m PHYs of
the same rate (50GBASE-R). A PHY number may correspond to the
physical port ordering on equipment, but the FlexE Shim at each end
of the group must identify each PHY in the group using the same PHY
number, and each FlexE Instance with the same FlexE Instance number.
In certain cases, it may be desirable not to populate all 100G FlexE
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instances on a 200G or 400G PHY, and these so-called unequipped FlexE
instance should also be configured. Unequipped instances must always
be the highest numbered instance(s) on a PHY of the FlexE Group, and
there must always be at least one equipped 100G FlexE Instance on
every PHY.
If aware case is needed to be considered, unavailable slot
information should be configured at FlexE aware node to discard
unavailable slot first, so as to put the rest of available slots onto
the lower rate physical port. Unavailable slots are placed at the
end of each relevant sub-calendar (the highest numbered slots).
3.2.3. Allocate Resources for FlexE Client
The FlexE client MAC flows are encapsulated in one or more FlexE
calendar slots.
According to the analysis in section 3.2.1, there are two different
configuration modes. For the first one, static mode, after the FlexE
group is configured, the FlexE client resource allocation information
are sent both to FlexE souce and destination to help create the FlexE
client. A number of expected configuration parameters are sent to
FlexE destination to help verify the correctness of configuration at
both sides. Information sent can be found in [draft-xiaobn-ccamp-
flexe-yang-mod]. For the Master/slave mode, the FlexE client
resource allocation information are only sent to the FlexE source
site. The FlexE source site first create the FlexE clients, and then
the built-in multiplexer at the FlexE source site allocates the
calendar slots to a specific FlexE client according to the input from
external management system, and insert these configuration
information into the FlexE overhead. When these overheads arrives at
the destination site, the demultiplexer function at the destination
site extracts FlexE overhead first and get the information of
calendar slot allocation information. Based on these information,
the FlexE destination site finish the configuration of FlexE clients.
In order to verify the correctness of the resource configuration, the
expected FlexE group ID, PHY number and instance number information,
FlexE client number and slot allocation information for a specific
FlexE client should also be configured to FlexE destination site.
The FlexE client port is an internal port which only perform the
function of encapsulating upper layer packets into MAC frames,
64b/66b encoding. The bandwidth capability of these internal ports
should be known by external management/control tools in order to be
used by the upper layer (e.g., MPLS-TP) flow correctly.
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3.3. Control Requirements Derived
a. Using external control/management system to configure FlexE
group, which may include the configuration of group number, PHY
number and instance number, as well as correlation between
logical PHY number and physical port number. A number of
expected configuration parameters are also needed to help verify
the consistency between FlexE source and destination.
b. Using external control/management system to create the FlexE
client, which include the FlexE client number, FlexE client type
and slots allocation information. Different configuration mode
for FlexE client are needed.
c. External control command could be provide to trigger the switch
of calendar slots.
d. Interworking between 5G slot granularity capable node and 25G
slot granularity node.
e. Configuration of unequipped instance, unavailable slots, which
include the number of unequipped instance and number of
unavailable slots on each instances
f. An interface needs to be defined for a FlexE client in the case
that an Ethernet PHY signal (e.g., 40GBASE-R) is directed towards
a FlexE client interface or delivered from one FlexE shim to
another in the case of equipment which terminates the FlexE
group. This interface is used to indicate the conversion of
Ethernet PHY signal to FlexE client signal, as only idle
insertion/deletion is performed during this process in the former
case, while in the latter case, this interface is used to
indicate the "switch" of FlexE client.
g. Different kinds of alarms should be taken into consideration when
modelling FlexE technology, which may include PHY failed, skew
exceed threshold, inconsistent configuration between two ends.
4. Summary
According to the analysis in section 2, the main control/management
requirement for FlexE technology is to configure the FlexE group and
FlexE client. Once a FlexE group is configured and the FlexE client
ports is created, slots allocation is configured, use of the FlexE
technology is the same as that in traditional Ethernet.
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5. Acknowledgements
6. IANA Considerations
This memo includes no request to IANA.
7. Security Considerations
None.
8. References
8.1. Normative References
[ITU-T_G709]
ITU-T, "ITU-T G.709: Optical Transport Network Interfaces;
07/2016", http://www.itu.int/rec/T-REC-
G..709-201606-P/en, July 2016.
[ITU-T_G798]
ITU-T, "ITU-T G.798: Characteristics of optical transport
network hierarchy equipment functional blocks", August
2018.
[ITU-T_G8023]
ITU-T, "ITU-T G.8023: Characteristics of equipment
functional blocks supporting Ethernet physical layer and
Flex Ethernet interfaces", , 2016.
[ITU-T_G872]
ITU-T, "ITU-T G.872: The Architecture of Optical Transport
Networks; 2017", http://www.itu.int/rec/T-REC-G.872/en,
January 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
8.2. Informative References
[I-D.izh-ccamp-flexe-fwk]
Hussain, I., Valiveti, R., Pithewan, K., Wang, Q.,
Andersson, L., Zhang, F., Chen, M., Dong, J., Du, Z.,
zhenghaomian@huawei.com, z., Zhang, X., Huang, J., and Q.
Zhong, "GMPLS Routing and Signaling Framework for Flexible
Ethernet (FlexE)", draft-izh-ccamp-flexe-fwk-00 (work in
progress), October 2016.
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[I-D.xiaobn-ccamp-flexe-yang-mod]
NIU, X., Wang, Q., Xu, Y., and S. Munagapati, "A YANG Data
Model for Flex Ethernet(FlexE)", draft-xiaobn-ccamp-flexe-
yang-mod-01 (work in progress), May 2019.
Authors' Addresses
Qilei Wang (editor)
ZTE Corporation
Nanjing
CN
Email: wang.qilei@zte.com.cn
Xiaobing Niu (editor)
ZTE Corporation
Beijing
CN
Email: niu.xiaobing@zte.com.cn
Yunbin Xu
CAICT
Beijing
CN
Email: xuyunbin@caict.ac.cn
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