rtgwg S. Hu
Internet-Draft China Mobile
Intended status: Informational V. Lopez
Expires: April 25, 2019 Telefonica
F. Qin
Z. Li
China Mobile
T. Chua
Singapore Telecommunications Limited
Donald. Eastlake
M. Wang
J. Song
Huawei
October 22, 2018
Requirements for Control Plane and User Plane Separated BNG Protocol
draft-cuspdt-rtgwg-cusp-requirements-03
Abstract
This document introduces the Control Plane and User Plane separated
BNG (Broadband Network Gateway) architecture and defines a set of
associated terminology. It also specifies a set of protocol
requirements for communication between the BNG-CP and the BNG-UPs in
the Control Plane and User Plane Separated BNG.
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 https://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."
This Internet-Draft will expire on April 25, 2019.
Hu, et al. Expires April 25, 2019 [Page 1]
Internet-Draft Requirements for CUSP October 2018
Copyright Notice
Copyright (c) 2018 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
(https://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 Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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. Message Priority . . . . . . . . . . . . . . . . . . . . 7
5.3. Reliability . . . . . . . . . . . . . . . . . . . . . . . 7
5.4. Support for Secure Communication . . . . . . . . . . . . 8
5.5. Version negotiation . . . . . . . . . . . . . . . . . . . 8
5.6. Capability Exchange . . . . . . . . . . . . . . . . . . . 9
5.7. CP primary/backup capability . . . . . . . . . . . . . . 9
5.8. Event Notification . . . . . . . . . . . . . . . . . . . 9
5.9. Query Statistics . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
A Broadband Network Gateway (BNG) is an Ethernet-centric IP edge
router and the aggregation point for 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 [TR-384]. The CU
separated Service Control Plane could be virtualized and centralized;
Hu, et al. Expires April 25, 2019 [Page 2]
Internet-Draft Requirements for CUSP October 2018
it is responsible for user access authentication and sending
forwarding entries to user planes. 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 for Control Plane and User Plane Separated BNG
(CUSP).
2. Concept and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2.1. Terminology
BNG: Broadband Network Gateway. A broadband remote access server
(BRAS, B-RAS or BBRAS) that 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 manages UP's resources such as the user entry and user's QoS
policy.
CUSP: Control Plane and User Plane Separated BNG Protocol.
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
Figure 1 shows the architecture of CU separated BNG
Hu, et al. Expires April 25, 2019 [Page 3]
Internet-Draft Requirements for CUSP October 2018
+------------------------------------------------------------------+
| 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| |
| +---------------------------+ +--------------------------+ |
+------------------------------------------------------------------+
Figure 1. Architecture of CU Separated BNG
Briefly, a CU separated BNG is made up of a Control Plane (CP) and a
set of User Planes (UPs) [TR-384], [I-D.cuspdt-rtgwg-cu-separation-
bng-deployment]. The Control Plane is a user control management
component which manages UP's resources such as the user entry and
user's Quality of Service (QoS) policy, for example, the access
bandwidth and priority management. This Control Plane could be
virtualized and centralized. The functional modules inside the BNG
Service Control Plane can be implemented as Virutl Network Functions
(VNFs) and hosted in a Network Function Virtualization Infrastructure
(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, update, and maintenance
of channels between control planes and user planes [TR-384], [I-
D.cuspdt-rtgwg-cu-separation-bng-deployment]. The User Plane (UP) is
a network edge and user policy implementation component. It can
support the forwarding plane functions on traditional BNG devices,
Hu, et al. Expires April 25, 2019 [Page 4]
Internet-Draft Requirements for CUSP October 2018
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, multicast, etc [TR-384], [I-D.cuspdt-
rtgwg-cu-separation-bng-deployment].
3.1. Internal interfaces between the CP and UP
To support communication between the Control Plane and User Plane,
several interfaces are involved. Figure 2 illustrates the three
internal interfaces of CU Separated BNG.
+----------------------------------+
| |
| BNG-CP |
| |
+--+--------------+--------------+-+
| | |
1.Service | 2.Control | 3.Management|
Interface | Interface | Interface |
| | |
+--+--------------+--------------+-+
| |
| BNG-UP |
| |
+----------------------------------+
Figure 2. Interfaces between the BNG-CP and the BNG-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.
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 uses NETCONF.
The CUSP (Control plane and User plane Separated BNG protocol)
defines the control interface, and specifies the communication
between the centralized control plane and user planes. This protocol
should be designed to support establishing and maintaining a
conversation between CP and UPs, and transporting the tables that are
specified in [draft-cuspdt-rtgwg-cu-separation-infor-model].
Hu, et al. Expires April 25, 2019 [Page 5]
Internet-Draft Requirements for CUSP October 2018
4. The usage of CU separation BNG protocol
-----------------
//// \\\\
//// \\\\
// Cloud \\
| |
| |
| |
| |
| +-----------------+ |
| | Control Plane | |
\\ | | //
\\\\ +------+----------+ ////
\\\\ | ////
----+------------
| Control Interface (CUSP)
+--------+----------+-------------+-----+
| | | |
User's information IP address QoS: .......
May Include: | CIR; :
User ID; | PIR; |
User MAC; | CBS; |
Access method(PPPoE, | PBS; |
IPoE, etc) | ......
..... | | |
+-------------------V--------------+
|
+-----------+
| -------
| /// \\\
+------+ +-------v---------+ +--------+ | |
| OLT | | User Plane | | Core | | Internet |
| +-------+ +-------+ Routing+-----+ |
+------+ +-----------------+ +--------+ \\\ ///
-------
Figure 3. CU Separation BNG protocol usage
As shown in Figure 3, when users access the BNG network, the control
plane solicits user information (such as user's ID, user's MAC,
user's access methods, for example via PPPoE/IPoE), associates users
with available bandwidth which is reported by User planes, and, based
on the service's requirement, generates 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
Hu, et al. Expires April 25, 2019 [Page 6]
Internet-Draft Requirements for CUSP October 2018
planes receive these tables, parse them, and then perform
corresponding actions.
5. Control Plane and User Plane Separation Protocol Requirements
This section specifies the requirements for the CU separation
protocol.
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 data encoded as either
XML or binary. It allows user information data to be read, saved,
and manipulated with tools specific to XML or binary.
c) In order to provide centralized session management, high
scalability for subscriber management capacity, and cost-efficient
redundancy, batching ability should be provided. 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 practical. Furthermore, the
protocol MUST support the ability to specify if a command group
MUST have all-or-nothing semantics.
d) The CU Separation protocol SHOULD be able to support 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.
5.2. Message Priority
The CU Separation protocol MUST provide a means to express the
protocol message priorities.
5.3. Reliability
Heartbeat is a periodic signal generated by hardware or software to
test for some aspects of normal operation or to synchronize other
parts of network system.
Hu, et al. Expires April 25, 2019 [Page 7]
Internet-Draft Requirements for CUSP October 2018
In the CU separation BNG, a heartbeat is sent between CP and UPs at a
regular interval on 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
monitoring 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.
5.4. Support for Secure Communication
As mentioned above, CP may send some information tables to the UP
which may be critical to the network function (e.g, User Information,
IPv4/IPv6 information) and may reflect the business information (e.g,
QoS, service level agreements, etc). Therefore, supporting the
integrity of all CU Separation protocol messages and protecting
against man-in-the-middle attacks MUST be supported.
The CP Separation protocol should support security in a variety of
scenarios. For example, the connections between the CP and UPs could
be dedicated lines, VPNs within one domain, or could cross several
domains, that is, cross third party networks. Thus it is likely that
more than one security mechanism SHOULD be supported. TLS and IPsec
are good candidates for such mechanisms.
5.5. Version negotiation
The CU separated BNG may consist of different vendors' devices
implementing different versions of protocol. Threfore, the CU
separation protocol MUST provide some mechanisms to perform the
version negotiation.
Version negotiation is the process that the CU separated BNG's
Control-Plane uses to evaluate the protocol versions supported by
both the control-plane and the user-plane devices. Then a suitable
protocol version is selected for communication in CUSP. 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 or determining that they have no version in
common.
Hu, et al. Expires April 25, 2019 [Page 8]
Internet-Draft Requirements for CUSP October 2018
5.6. Capability Exchange
The UP Capability Report displays the device's profile, service
capability, and other assigned capabilities within the CU separated
BNG. The CU separation protocol should MUST provide some mechanism
to exchange the UP device's capabilities.
5.7. CP primary/backup capability
A backup CP for failure recovery is required for the CU separated BNG
network. And the CUSP should provide some mechanism to implement the
backup CP:
a) In some scenarios, there may be two CP devices both declaring
the primary CP. Thus the CUSP should support or associate with
some mechanisms to determine which CP is the primary device.
b) In the scenario of the primary CP down, the CUSP should support
switching between primary and backup CP.
5.8. Event Notification
The CUSP protocol SHOULD be able to asynchronously notify the CP of
events on the UP such as failures and changes in available resources
and capabilities. Some scenarios that may initiate event
notifications are listed below.
a) Sending response message: As mentioned above, the control plane
solicits users' information, associates them with available
bandwidth, and generates a set of tables based on the service's
requirement. Then the control plane transmits these tables to the
conresponding User plane. The UP 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 tracing and monitoring the network status for users (for
example the real-time bandwidth, etc), to help debug the user's
application. Therefore, the UPs SHOULD be able to notify the CP
with the User trace message.
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 measure the
BNG network performance. Available network resources can be
allocated basing on the statistics parameters by the BNG-CP.
Therefore, the UPs SHOULD be able to notify the CP with statistics
parameters.
Hu, et al. Expires April 25, 2019 [Page 9]
Internet-Draft Requirements for CUSP October 2018
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.
5.9. Query Statistics
The CUSP protocol MUST provide a means for the CP to be able to query
statistics (performance monitoring) from the UP.
6. Security Considerations
As this is an Informational requirements document, detailed technical
Security Considerations are not included. However, Section 5.4
covers general security requirements and Section 5.7 covers backup
requirements relevant to some denial of service scenarios.
7. IANA Considerations
This document requires no IANA actions.
8. References
8.1. Normative References
[I-D.cuspdt-rtgwg-cu-separation-bng-deployment]
Gu, R., Hu, S., and Z. Wang, "Deployment Model of Control
Plane and User Plane Separation BNG", draft-cuspdt-rtgwg-
cu-separation-bng-deployment-00 (work in progress),
October 2017.
[I-D.cuspdt-rtgwg-cu-separation-infor-model]
Wang, Z., Gu, R., Lopezalvarez, V., and S. Hu,
"Information Model of Control-Plane and User-Plane
separation BNG", draft-cuspdt-rtgwg-cu-separation-infor-
model-00 (work in progress), February 2018.
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Hu, et al. Expires April 25, 2019 [Page 10]
Internet-Draft Requirements for CUSP October 2018
8.2. Informative References
[TR-384] Broadband Forum, ""Cloud Central Office Reference
Architectural Framework",", BBF TR-384, January. 2018.
Authors' Addresses
Shujun Hu
China Mobile
32 Xuanwumen West Ave, Xicheng District
Beijing, Beijing 100053
China
Email: shujun_hu@outlook.com
Victor Lopez
Telefonica
Sur 3 building, 3rd floor, Ronda de la Comunicacion s/n
Madrid 28050
Spain
Email: victor.lopezalvarez@telefonica.com
Fengwei Qin
China Mobile
32 Xuanwumen West Ave, Xicheng District
Beijing, Beijing 100053
China
Email: qinfengwei@chinamobile.com
Zhenqiang Li
China Mobile
32 Xuanwumen West Ave, Xicheng District
Beijing, Beijing 100053
China
Email: lizhenqiang@chinamobile.com
Hu, et al. Expires April 25, 2019 [Page 11]
Internet-Draft Requirements for CUSP October 2018
Tee Mong Chua
Singapore Telecommunications Limited
31 Exeter Road, #05-04 Comcentre Podium Block
Singapore City 239732
Singapore
Email: teemong@singtel.com
Donald Eastlake, 3rd
Huawei
1424 Pro Shop Court
Davenport, FL 33896
USA
Email: d3e3e3@gmail.com
Michael Wang
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: wangzitao@huawei.com
Jun Song
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: song.jun@huawei.com
Hu, et al. Expires April 25, 2019 [Page 12]