Internet DRAFT - draft-pan-sdn-bod-problem-statement-and-use-case
draft-pan-sdn-bod-problem-statement-and-use-case
IETF Ping Pan
Internet Draft (Infinera)
Lyndon Ong
(Ciena)
Shane Amante
(Level 3)
Expires: April 31, 2012 October 31, 2011
Software-Defined Network (SDN) Use Case for
Bandwidth on Demand Applications
draft-pan-sdn-bod-problem-statement-and-use-case-01.txt
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Abstract
Bandwidth on Demand services are offered by network operators in
industry and research sectors to support the needs of selected
customers needing high bandwidth point-to-point connections.
Without a standard interface for controlling the use of network
resources, user applications and services are subject to limits of
layering, security and interoperability across multiple vendors of
network equipment.
In this document, we argue the necessity in providing network
information to the applications, thereby enabling the applications
to directly provision network elements associated with the relevant
applications.
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Table of Contents
1. Introduction...................................................3
2. Related Work...................................................4
3. Problem Definition.............................................4
4. The Role of an SDN Layer.......................................6
5. Use Cases......................................................7
5.1. Scheduled/ Dynamic Bandwidth On-Demand Service............7
5.2. Multi-Layer BoD Support...................................8
5.3. Virtualized Network Service...............................9
5.4. BoD Actions Supported by the SDN Orchestrator.............9
6. Security Consideration........................................10
7. IANA Considerations...........................................10
8. Normative References..........................................10
9. Acknowledgments...............................................11
1. Introduction
Bandwidth on Demand services are offered by network operators in
industry and research sectors to support the needs of selected
customers needing high bandwidth point-to-point connections. Such
services take advantage of dynamic control of the underlying network
to set up forwarding and resource allocation as requested by the
customer. Some control is given directly to the customer via a
portal so that there is no need to go through an intermediate
stage of service order provisioning on the part of the network
operator.
Currently such services are often based on management interfaces to
vendor equipment that are vendor-specific, and as a result the
operator must redesign its supporting control application for each
vendor domain, or limit their offering to a single vendor domain.
In this document, we propose that providing a common interface to
networks of different vendors and technologies would enable the
network provider to offer Bandwidth on Demand and other services
that are faster to deploy across a wide range of network equipment
by using additional network information.
Here are some of the conventions used in this document. 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].
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2. Related Work
There has been much work in this area in recent years. OpenFlow has
defined an architecture for offering virtualized network control
through a centralized controller and proxies called FlowVisors.
These allow users to configure forwarding of packets within slices
of the network partitioned off for their use. The controller is
designed to control each network element directly through a
dedicated control interface. It is not designed to work with
existing control plane protocols.
More generally, TMF has developed models and interfaces for
operations and administration of networks through the north-bound
interface provided by the element management system. These
interfaces are not intended for real-time control of the network
element and need to take into account variations in the design and
features of different types of equipment.
PCE is a client-server protocol that operates in MPLS networks that
enables the network operators to compute and potentially provision
optimal point-to-point and point-to-multipoint connections. However,
PCE does not interface with applications to optimize traffic from
user applications.
3. Problem Definition
Figure 1 illustrates the relationship between application and
network today, where customer control of bandwidth on demand is
provided through applications created by the network operator
supporting the user interface, features and backend accounting for
the service. Such applications are used in single domain
deployments and have limited visibility of underlying IP/MPLS and
Transport networks and, most importantly, resource availability on
those networks.
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+-------------+ +-------------+
| Application | | Application |
| #1 | | #2 |
+-------------+ +-------------+
| |
| |
+------------------+ +------------------+
| Network | | Network |
| Domain #1 | | Domain #2 |
+------------------+ +------------------+
Figure 1: Application to network relationship today
This presents a number of challenges and problems. Without a
standard interface to the network elements that comprise one or more
network domains and their associated control software, each
bandwidth on demand supporting application must be built for a
specific set of vendor equipment and is not easily generalizable to
different vendors or even different equipment offered by a single
vendor. While signaling interfaces such as the UNI could offer
standardized access to network control, such interfaces have not
been adopted because they provide minimal security and functionality
and are designed for more of a peer relationship between network
elements, traditionally at only a single (peer) layer of the
network.
Similarly, bandwidth on demand applications must be designed for a
single technology, which restricts the range of use and potential
users. If Domain #1 uses SDH, for example, and Domain #2 uses OTN
it may be necessary to design supporting Application #2 from scratch
even though Application #1 has been successfully offering service.
Ideally the interface should allow some level of technology
independence, as well as potentially integration to permit control
of multiple layers simultaneously (esp. packet and circuit).
Third, the application is generally limited to simple services
connecting a source to destination, because interfaces hide network
topology and do not allow visualization of the topology for
different customer views. For some services users may wish to
exercise control over path routing aspects such as shared risk,
required latency characteristics or inclusion or exclusion of areas
for policy reasons.
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4. The Role of an SDN Layer
To solve the above problem, the proposal is to introduce a software-
driven network (SDN) layer (as shown in Figure 2), that is
responsible for network virtualization, programmability and
monitoring, between supporting applications and the network.
+-------------+ +-------------+ +-------------+
| Application | | Application | | Application |
| #1 | | #2 | | #3 |
+-------------+ +-------------+ +-------------+
| | |
| | |
+---------------------------------------------------+
| SDN Layer |
| (Network virtualization, programmability |
| and Monitoring) |
+---------------------------------------------------+
| |
| |
+------------------+ +------------------+
| Physical Network | | Physical Network |
| Domain #1 | | Domain #2 |
+------------------+ +------------------+
Figure 2: Application to network relationship for SDN
The purpose of the SDN Layer is to enable the applications
supporting bandwidth on demand services to access information about
and control (aggregate) traffic flows at various layers of the
network through a standard, secure and customizable interface.
Applications can visualize the traffic flows at the network layer,
and manage the mapping or binding between its traffic flows from
edge-to-edge through the associated networks.
The implementation of an SDN Layer involves interfacing among
different types of applications and different types of network
domains, based on technology or vendor, administrative or policy
control. Standardized interfaces must be defined to support this.
The architecture should be agnostic as to the type of network
control plan used in a supporting domain. The focus of work should
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be on providing richer access to control of network resources rather
than on the scheme for network control used in the domain.
5. Use Cases
5.1. Scheduled/ Dynamic Bandwidth On-Demand Service
Figure 3 illustrates the flow of a scheduled or dynamic bandwidth
service. In the simplest case, connectivity may already be provided
between user-specified endpoints, however the bandwidth allocated
between endpoints can be varied within some overall limit based on a
predefined schedule or on spontaneous customer request. Note that
allowing bandwidth to be partitioned so that a scheduling
application has control over some pre-allocated set of resources is
necessary to support the scheduled BoD service. Also, the SDN layer
ideally hides the specific technology used to support the
connection, offering control of the service with associated rate,
latency and recovery features.
In more sophisticated services, the customer may be allowed to
create new connections within a specified set of endpoints and
delete such connections when the connectivity is no longer required.
User
Req's +------------+
-------->| Controller |
+------------+
|
| <----- North-bound protocol to adjust connections
|
\|/
+---------+ +--------+
| PE1 | | PE2 |
| |===== Provisioned Connection ===>| |
+---------+ +--------+
Figure 3: Scheduled/Dynamic BoD Service
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5.2. Multi-Layer BoD Support
User
Req's +------------+
-------->| Controller |
+------------+
|
| <----- North-bound protocol to map packets to circuits
|
\|/
+--------------------+ +--------------------+
Pkt | PE1 | Transport | PE2 | Pkt
====>| Classifer<->Tunnel |<=== Circuit ===>| Classifer<->Tunnel |====>
+--------------------+ +--------------------+
Figure 4: Multi-Layer BoD service
Figure 4 illustrates a BoD service that supports multi-layer network
control. This extends allows the network operator's supporting
applications to combine control of packet forwarding through
guaranteed bandwidth tunnels that connect sites in a (virtual)
private network as requested dynamically by the BoD customer.
Different transport network technologies may be used to provide the
server layer transport functions so that the application can evolve
easily with new transport technologies.
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5.3. Virtualized Network Service
User
Req's +------------+
-------->| Controller |
+------------+
/|\ |
Topology --->| |<----- North-bound protocol to adjust connections
Gathering | |
| \|/
+---------+ +--------+
| PE1 | | PE2 |
| |===== Provisioned Connection ===>| |
+---------+ +--------+
Figure 5: Virtualized network service
Figure 5 illustrates the flow of a virtualized network service that
offers some degree of topology visibility and control in addition to
the features of scheduled or dynamic BoD. For some customers it may
be desirable to provide visibility into the topology of the
resources they control, in order for the customer so they may
control the physical and/or virtual topology of the resources used
within their dedicated domain.
If this topology information is provided together with associated
cost, latency, SRLG, etc. for the links and nodes in the topology,
the customer is provided with additional flexibility to manipulate
routing of their data flows so as to balance the cost, latency,
energy efficiency or survivability using knowledge of client
applications and their particular needs and priorities.
At this time such visibility is not possible to provide, as
protocols provide either no visibility into topology or full
visibility into topology. For security reasons it is likely that a
supporting network operator will want to limit visibility and
control to some virtualized topology using functionality provided by
the SDN orchestrator.
5.4. BoD Actions Supported by the SDN Orchestrator
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The following summarizes actions that would be supported by
the SDN orchestrator as part of a BoD service:
- increase or decrease bandwidth on an existing path between
two, or more, network clients;
- dynamically learn if resources are available, (e.g.: bandwidth,
latency, SRLG, etc.) to create a path between two, or more,
network clients;
- create a path and assign associated characteristics, (e.g.:
bandwidth, latency, SRLG, etc.) that connect two, or more, network
clients;
- configure mapping of packets, Ethernet frames, OTN frames, etc.
from a client interface into a specified network path (or paths)
connecting the appropriate ingress and egress client interfaces;
- configure some partition of network resources (e.g., links and
link capacity connecting some set of nodes and client endpoints)
to be controlled by a specific application;
- provide real or virtual topology information (links, nodes and
associated information such as costs, latency, etc.) for this
partition to the associated application.
6. Security Consideration
TBD
7. IANA Considerations
This document has no actions for IANA.
8. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[2] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail
Consortium and Demon Internet Ltd., November 1997.
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9. Acknowledgments
This work is based on the conversation with many people, including
Thomas Nadeau and Benson Schliesser.
Authors' Addresses
Ping Pan
Email: ppan@infinera.com
Lyndon Ong
Email: lyong@ciena.com
Shane Amante
Email: shane@level3.net
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