Requirements for Control Plane and User Plane Separated BNG Protocol
draft-cuspdt-rtgwg-cusp-requirements-00
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| Authors | Sujun Hu , Lu Huang , Rong Gu , Victor Lopez , Jun Song , Zitao Wang | ||
| Last updated | 2017-10-26 | ||
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draft-cuspdt-rtgwg-cusp-requirements-00
rtgwg S. Hu
Internet-Draft L. Huang
Intended status: Informational R. Gu
Expires: April 29, 2018 China Mobile
Victor. Lopez
Telefonica
Jun. Song
Michael. Wang
Huawei
October 26, 2017
Requirements for Control Plane and User Plane Separated BNG Protocol
draft-cuspdt-rtgwg-cusp-requirements-00
Abstract
This document introduces the Control Plane and User Plane separated
BNG architecture and defines a set of associated terminology. This
document also defines a set of protocol requirements to Control Plane
and User Plane Separated BNG (CUSP).
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Concept and Terminology . . . . . . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
3. CU Separated BNG Model . . . . . . . . . . . . . . . . . . . 3
3.1. Internal interfaces between the CP and UP . . . . . . . . 5
4. The usage of CU separation BNG protocol . . . . . . . . . . . 6
5. Control Plane and User Plane Separation Protocol Requirements 7
5.1. Transmit information tables . . . . . . . . . . . . . . . 7
5.2. Scalability . . . . . . . . . . . . . . . . . . . . . . . 7
5.3. Message Priority . . . . . . . . . . . . . . . . . . . . 8
5.4. Reliability . . . . . . . . . . . . . . . . . . . . . . . 8
5.5. Support for Secure Communication . . . . . . . . . . . . 8
5.6. Version negotiation . . . . . . . . . . . . . . . . . . . 8
5.7. Capability Exchange . . . . . . . . . . . . . . . . . . . 9
5.8. CP primary/backup capability . . . . . . . . . . . . . . 9
5.9. Event Notification . . . . . . . . . . . . . . . . . . . 9
5.10. Query Statistics . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Normative References . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
BNG is an Ethernet-centric IP edge router, and the aggregation point
for the user traffic. To provide centralized session management,
flexible address allocation, high scalability for subscriber
management capacity, and cost-efficient redundancy, the CU separated
BNG is introduced [BBF-CloudCO]. The CU separated Service Control
Plane could be virtualized and centralized, which is responsible for
user access authentication and setting forwarding entries of user
plane. The routing control and forwarding plane, i.e. BNG user plane
(local), could be distributed across the infrastructure.
This document introduces the Control Plane and User Plane separated
BNG architecture and modeling. This document also defines the
protocol requirements to Control Plane and User Plane Separated BNG
(CUSP).
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2. Concept and 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].
2.1. Terminology
BNG: Broadband Network Gateway. A broadband remote access server
(BRAS, B-RAS or BBRAS) routes traffic to and from broadband remote
access devices such as digital subscriber line access multiplexers
(DSLAM) on an Internet service provider's (ISP) network. BRAS can
also be referred to as a Broadband Network Gateway (BNG).
CP: Control Plane. The CP is a user control management component
which support to manage UP's resources such as the user entry and
user's QoS policy
UP: User Plane. UP is a network edge and user policy implementation
component. The traditional router's Control Plane and forwarding
plane are both preserved on BNG devices in the form of a user plane.
3. CU Separated BNG Model
The following figure describes the architecture of CU separation BNG
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+------------------------------------------------------------------+
| Neighboring policy and resource management systems |
| |
| +-------------+ +-----------+ +---------+ +----------+ |
| |Radius Server| |DHCP Server| | EMS | | MANO | |
| +-------------+ +-----------+ +---------+ +----------+ |
+------------------------------------------------------------------+
+------------------------------------------------------------------+
| CU-separated BNG system |
| +--------------------------------------------------------------+ |
| |+----------+ +----------+ +------++------++-----------+ | |
| || Address | |Subscriber| |Radius||PPPoE/|| UP | | |
| ||management| |management| | ||IPoE ||management | | |
| |+----------+ +----------+ +------++------++-----------+ | |
| |+----------+ +----------+ +------++------++-----------+ | |
| | CP | |
| +--------------------------------------------------------------+ |
| +---------------------------+ +--------------------------+ |
| | +------------------+ | | +------------------+ | |
| | | Routing control | | | | Routing control | | |
| | +------------------+ | ... | +------------------+ | |
| | +------------------+ | | +------------------+ | |
| | |Forwarding engine | | | |Forwarding engine | | |
| | +------------------+ UP | | +------------------+ UP| |
| +---------------------------+ +--------------------------+ |
+------------------------------------------------------------------+
Architecture of CU Separation BNG
Briefly, a CU separated BNG is made up of a Control Plane (CP) and a
set of User Planes (UPs) [BBF-CloudCO], [I-D.draft-gu-nfvrg-cloud-
bng-architecture]. The Control Plane is a user control management
component which support to manage UP's resources such as the user
entry and user's QoS policy, for example, the access bandwidth and
priority management. This Control Plane could be virtualized and
centralized. The functional components inside the BNG Service
Control Plane can be implemented as VNFs and hosted in a NFVI. The
User Plane Management module in the BNG control plane centrally
manages the distributed BNG user planes (e.g. load balancing), as
well as the setup, deletion, maintenance of channels between control
planes and user planes [BBF-CloudCO], [I-D.draft-gu-nfvrg-cloud-bng-
architecture]. And the User Plane (UP) is a network edge and user
policy implementation component. It can support the forwarding plane
functions on traditional BNG devices, such as traffic forwarding,
QoS, and traffic statistics collection, and it can also support the
control plane functions on traditional BNG devices, such as routing,
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multicast, etc.[BBF-CloudCO],[I-D.draft-gu-nfvrg-cloud-bng-
architecture]
3.1. Internal interfaces between the CP and UP
To support the communication between the Control Plane and User
Plane, several interfaces are involved. The Figure 2 illustrates the
internal interfaces of CU Separated BNG.
+----------------------------------+
| |
| BRAS-CP |
| |
+--+--------------+--------------+-+
| | |
Service | Control | Management |
Interface | Interface | Interface |
| | |
+--+--------------+--------------+-+
| |
| BRAS-UP |
| |
+-----------------+----------------+
|
|
+--------+--------+
| |
| Access Network |
| |
+--------+--------+
|
+----+----+
| |
| User |
| |
+---------+
Internal interfaces between the CP and UP
Service interface: The CP and UP use this interface to establish
VXLAN tunnels with each other and transmit PPPoE and IPoE packets
over the VXLAN tunnels.
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Control interface: The CP uses this interface to deliver service
entries, and the UP uses this interface to report service events to
the CP.
Management interface: The CP uses this interface to deliver
configurations to the UP. This interface runs NETCONF.
4. The usage of CU separation BNG protocol
-----------------
//// \\\\
//// \\\\
// Cloud \\
| |
| |
| |
| |
| +-----------------+ |
| | Control Plane | |
\\ | | //
\\\\ +------+----------+ ////
\\\\ | ////
-----------------
|
+--------+----------+-------------+-----+
| | | |
User's information IP ddress QoS: .......
May Including: | CIR; :
User ID; | PIR; |
User MAC; | CBS; |
Access method(PPPoE, | PBS; |
IPoE, etc) | ......
..... | | |
+-------------------V--------------+
|
+-----------+
| -------
| /// \\\
+------+ +-------v---------+ +--------+ | |
| OLT | | User Plane | | Core | | Internet
| +-------+ +-------+ Routing-----+ |
+------+ +-----------------+ +--------+ \\\ ///
-------
CU Separation BNG
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As shown in above figure, when users access to the BNG network, the
control plane solicits these users' information (such as user's ID,
user's MAC, user's access methods, for example via PPPoE/IPoE),
associates them with available bandwidth which are reported by User
planes, and based on the service's requirement to generate a set of
tables, which may include user's information, UP's IP segment, and
QoS, etc. Then the control plane can transmit these tables to the
User planes. User planes receive these tables, parses it, matches
these rules, and then performs corresponding actions.
5. Control Plane and User Plane Separation Protocol Requirements
This section specifies some of the requirements that the CU
separation protocol SHOULD support.
5.1. Transmit information tables
The Control Plane and User Plane Separation Protocol MUST allow the
CP to send tables to each User Plane device.
a) The current BNG service requires that the UP should support at
least 2000 users being accessed every second. And every user
requires at least 2000 bytes. To achieve high performance, the CU
Separation protocol SHOULD be lightweight.
b) CU separation protocol should support XML/binary data which
serves as the encoding format. It allows user information data be
read, saved, and manipulated with tools specific to XML/binary.
c) Furthermore, in order to provide centralized session
management, high scalability for subscriber management capacity,
and cost-efficient redundancy, batching ability should be
involved. The CU Separation protocol should be able to group an
ordered set of commands to a UP device. Each such group of
commands SHOULD be sent to the UP in as few messages as possible.
Furthermore, the protocol MUST support the ability to specify if a
command group MUST have all-or-nothing semantics.
5.2. Scalability
The CU Separation protocol SHOULD be able to supporting at least
hundreds of UP devices and tens of thousands of ports. For example,
the protocol field sizes corresponding to UP or port numbers SHALL be
large enough to support the minimum required numbers. This
requirement does not relate to the performance of the system as the
number of UPs or ports in the system grows.
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5.3. Message Priority
The CU Separation protocol MUST provide a means to express the
protocol message priorities.
5.4. Reliability
In Network, a heartbeat is a periodic signal generated by hardware or
software to indicate normal operation or to synchronize other parts
of network system.
In CU separation BNG, the heartbeat is sent between CP and UPs at a
regular interval in the order of seconds. If the CP/UP does not
receive a heartbeat for a time--usually a few heartbeat intervals--
the CP/UP that should have sent the heartbeat is assumed to have
failed.
The CU separation protocol should support some kind of heartbeat
monitor mechanism. And this mechanism should have ability to
distinguish whether the interruption is an actual failure. For
example, in some scenarios (i.e. CP/UP update, etc), the connection
between the UP and CP need to be interrupted. In this case, the
interruption should not be reported.
5.5. Support for Secure Communication
As mentioned above, CP may send some information tables to the UP
which may critical to the functioning of a network (e.g, User
Information, IPv4/IPv6 information) and may reflect the business
relationships (e.g, QoS, service level agreements, etc). Therefore,
it MUST be supported to ensure the integrity of all CU Separation
protocol messages and protect against man-in-the-middle attacks.
And the CP Separation protocol should support multiple security
mechanisms to satisfy various scenarios. For example, when the
special lines are implemented between the CP and UPs, the key chain
SHOULD be supported. And if some VPNs are deployed between the CP
and UPS, the TLS SHOULD be supported. In case of the CP and UPs
cross several domains (i.e. cross third-party network), the IPsec
SHOULD be supported.
5.6. Version negotiation
The CU separation BNG may consist of different vendor's devices.
Since different vendors' device may implement different version of
protocol, therefore, the CU separation protocol should provide some
mechanisms to perform the version negotiation.
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The version negotiation is the process that the CU separation BNG's
Control-Plane uses to evaluate the protocol versions that are
supported by the control-plane and the user-plane devices, and select
the protocol version it will use when communicating with the exchange
user-plane devices. The process is a "negotiation" because it
requires identifying the most recent protocol version that is
supported by both the control-plane and the user-plane devices.
5.7. Capability Exchange
The UP Capability Report displays the devices profile, service
capability, and other assigned capabilities within the CU separation
BNG. The CU separation protocol should provide some mechanism to
exchange the UP device's capability
5.8. CP primary/backup capability
A backup CP for disaster recovery is required for the CU separation
BNG network. And the CUSP should provide some mechanism to implement
the backup CP:
a) In some scenarios, there are maybe two CP devices which declare
that they are the primary CP. In this situation, the CUSP should
support or associate with some mechanisms to determine which CP is
the primary device.
b) In the some scenarios the primary CP downs, the CUSP should
support to switching between primary and backup CP.
5.9. Event Notification
The CUSP protocol SHOULD be able to asynchronously notify the CP of
events on the UP such as failures or change in available resources or
capabilities. There are some scenarios may initiate the event
notification:
a) Sending response message: As mentioned above, the control plane
solicits these users' information, associates them with available
bandwidth, and based on the service's requirement to generate a
set of tables. Then the control plane transmit these tables to
the User planes. The UPs should respond with an event
notification to inform the CP that the tables are received.
b) User trace: The user trace mechanism can support the Control
Plane to trace and monitor the network state for users (for
example the real-time bandwidth, etc) , debug the user's
application. Therefore, the UPs SHOULD be able to notify the CP
with the User trace message.
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c) Sending statistics parameters: In CU separation BNG, the User-
plane will report the traffic statistics parameters to the
Control-plane, such as the ingress packets, ingress bytes, egress
packets, egress bytes, etc. These parameters can help to
measurement the BNG network status. The Control-Plane can base on
the statistics parameters to allocate available network resources.
Therefore, the UPs SHOULD be able to notify the CP with statistics
parameters.
d) Report the result of User Detect: "User Detect" message will be
send periodically to detect user dial-up and disconnect. The UPs
SHOULD be able to notify the CP with the result of User Detect.
5.10. Query Statistics
The CUSP protocol MUST provide a means for the CP to be able to query
statistics (monitor performance) from the UP.
6. Security Considerations
None.
7. IANA Considerations
None.
8. 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,
<https://www.rfc-editor.org/info/rfc2119>.
Authors' Addresses
Sujun Hu
China Mobile
32 Xuanwumen West Ave, Xicheng District
Beijing, Beijing 100053
China
Email: shujun_hu@outlook.com
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Lu Huang
China Mobile
32 Xuanwumen West Ave, Xicheng District
Beijing, Beijing 100053
China
Email: hlisname@yahoo.com
Rong Gu
China Mobile
32 Xuanwumen West Ave, Xicheng District
Beijing, Beijing 100053
China
Email: gurong_cmcc@outlook.com
Victor Lopez
Telefonica
Sur 3 building, 3rd floor, Ronda de la Comunicacion s/n
Madrid 28050
Spain
Email: victor.lopezalvarez@telefonica.com
Jun Song
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: song.jun@huawei.com
Michael Wang
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: wangzitao@huawei.com
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