Your SlideShare is downloading. ×
Towards an Open Data Center with an Interoperable Network (ODIN) Volume 3: Software Defined Networking and OpenFlow
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Towards an Open Data Center with an Interoperable Network (ODIN) Volume 3: Software Defined Networking and OpenFlow

708
views

Published on

This volume of the Open Datacenter Interoperable Network (ODIN) describes software defined networking (SDN) and OpenFlow. SDN is used to simplify network control and management, automate network …

This volume of the Open Datacenter Interoperable Network (ODIN) describes software defined networking (SDN) and OpenFlow. SDN is used to simplify network control and management, automate network virtualization services, and provide a platform from which to build agile ....

Published in: Technology

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
708
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
67
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. Towards an Open Data Center with an Interoperable Network (ODIN)Volume 3: Software Defined Networking and OpenFlowMay 2012 ® Towards an Open Data Center with an Interoperable Network (ODIN) Volume 3: Software Defined Networking and OpenFlow Casimer DeCusatis, Ph.D. Distinguished Engineer IBM System Networking, CTO Strategic Alliances IBM Systems and Technology Group May 2012
  • 2. Towards an Open Data Center with an Interoperable Network (ODIN)Volume 3: Software Defined Networking and OpenFlowPage 2Executive Overview This volume of the Open Datacenter Interoperable Network (ODIN) describes software defined networking (SDN) and OpenFlow. SDN is used to simplify network control and management, automate network virtualization services, and provide a platform from which to build agile network services. SDN leverages both IETF network virtualization overlays and the ONF OpenFlow standards. OpenFlow is an emerging industry standard protocol which moves the network control plane into software running on an attached server. The flow of network traffic can then be controlled dynamically, without the need to rewire the data center network. Some of the benefits of this approach include better scalability, larger layer 2 domains and virtual devices, faster convergence, and better scalability. These technologies form the basis for networking as a service (NaaS) in modern data centers.3.1 Software-Defined Networking While networks have supported significant innovations in compute and storage, networking technologies have not tracked the expanding levels of virtualization and programmability of these technologies. Networks thus are increasing in complexity due to the increased demand for multi- tenancy, higher bandwidths, and the emergence of on-demand resource and application models in the Cloud. As a result, network protocols, not initially designed with these requirements in mind, are becoming cumbersome to configure and maintain, limiting scalability and agility. Software-Defined Networking (SDN) was created to address these challenges by altering the traditional paradigm for network control. By decoupling the control and data planes, introducing programmability, centralizing intelligence, and abstracting applications from the underlying network infrastructure; highly scalable and flexible networks can be designed that readily adapt to changing business needs. Consider the design of conventional data center networks. The network control plane implements many complex networking protocols, each of which requires millions of lines of code. Each protocol may be thought of as a programming language, with its own usage rules. As with any language, the proper context and meaning can only be understood by someone familiar with both the vocabulary (syntax) and the grammar (semantics). The typical operation of a networking device is analogous to the complexity of learning to speak multiple languages. Further, the availability of new features and functions on these devices is limited by the development priorities of the companies who develop this equipment. For these reasons, there are advantages to introducing an open networking language and an open switch programming model, known as software-defined networking, similar to the use of Linux as an alternative to vendor proprietary server operating systems. Open networking simplifies the network control and management, and responds to the need for more agile deployment of network services. Such an approach is also complimentary to other trends in the networking industry, including increasing data rates, higher levels of virtualization, and intelligent management with more extensive automation. SDN offers substantial benefits that may be realized within the data center. These include multi- vendor environments, more granular network control (at the session, user, or device level), and improved automation and management. SDN also promotes innovation from network equipment providers by supporting the introduction of new capabilities or upgrades without the need to access individual networking devices, and reducing inter-dependencies between network services and infrastructure. SDN paves the way to a dynamic and flexible network architecture that protects existing investments, yet future-proofs the network to support rapidly changing business needs. Ultimately, the network evolves from infrastructure to a business-critical service delivery platform.
  • 3. Towards an Open Data Center with an Interoperable Network (ODIN)Volume 3: Software Defined Networking and OpenFlowPage 3 By abstracting the control and management aspects of a network into a logical software program, SDN allows real-time programmability and manageability of networks comparable to what is achieved on computers. It can leverage a centralized logical network view easily manipulated via software to implement complex networking rules. This allows networks to achieve unprecedented levels of scalability and flexibility, as well as dynamic behaviors matching cloud service-oriented dynamics.Figure 3.1 – Software-Defined Network Architecture Figure 3.1 depicts a logical view of the SDN architecture. The infrastructure layer sends control information via an interface to SDN control Software in the control layer, where an abstracted view of the network is created and the configuration or status of the underlying infrastructure is maintained. Network Services are generated leveraging the information contained in the SDN controller software. Business applications then have access to network configuration and infrastructure information via an API interface to these network services. Unlike traditional networks where this information often can only be accessed manually and one network device at a time, here information is exchanged in real time and can be processed automatically using algorithms and programs. SDN provides a new approach for managing end-to-end connectivity by maintaining a centralized, global view of the network. By centralizing network state in the control layer, management, configuration, security, and network resources are optimized through flexible, dynamic and automated SDN programs. Global, controlled access to the data plane offers the potential for unprecedented programmability, as network behavior easily can be adapted to the needs of business applications. Such flexibility enables the scalability and flexibility needed to keep up with dramatic shifts in user behavior, the ever-growing appetite for increased bandwidths, and a range of new services. Another important benefit of the SDN architecture is enhanced automation, allowing networks to accommodate highly elastic and rapidly changing demands of users or cloud-based applications. Cloud-based applications can now be managed through intelligent orchestration and provisioning systems, beyond the compute and storage space and including the network. SDN open the door
  • 4. Towards an Open Data Center with an Interoperable Network (ODIN)Volume 3: Software Defined Networking and OpenFlowPage 4 for on-demand resource allocation, self-service provisioning, and truly virtualized networking. SDN is used for many purposes, including simplifying network control and management, automating network virtualization services, and providing a platform from which to build agile network services. To accomplish these goals, SDN leverages both IETF network virtualization overlays and the ONF OpenFlow standards. We will discuss each of these approaches in the following sections.3.2 Virtual Network Overlays Server virtualization brings with it new data center networking requirements. In addition to the regular requirements of interconnecting physical servers, network designs for virtualized data centers have to support the following:  Huge number of endpoints. Today physical hosts can effectively run tens of virtual machines, each with its own networking requirements. In a few years, a single physical machine will be able to host 100 or more virtual machines.  Large number of tenants fully isolated from each other. Scalable multi-tenancy support requires a large number of networks that have address space isolation, management isolation, and configuration independence. Combined with a large number of endpoints, these factors will make multi-tenancy at the physical server level an important requirement in the future.  Dynamic network and network endpoints. Server virtualization technology allows for dynamic and automatic creation, deletion and migration of virtual machines. Networks must support this function in a transparent fashion, without imposing restrictions due to, e.g., IP subnet requirements  A decoupling of the current tight binding between the networking requirements of virtual machines and the underlying physical network Rather than treat virtual networks simply as an extension of physical networks, these requirements can be met by creating virtual overlay networks in a way similar to creating virtual servers over a physical server: independent of physical infrastructure characteristics, ideally isolated from each other, dynamic, configurable and manageable. Hypervisor based overlay networks (which take advantage of virtual Ethernet switches) can provide networking services to virtual servers in a data center. Virtual Ethernet switches form part of the platform for creating agile network services; they can also aid in simplifying network control and management and automating network virtualization services. Overlay networks are a method for building one network on top of another. The major advantage of overlay networks is their separation from the underlying infrastructure in terms of address spaces, protocols and management. Overlay networks allow a tenant to create networks designed to support specific distributed workloads, without regards to how that network will be instantiated on the data centers physical network. In standard, TCP/IP networks, overlays are usually implemented by tunneling. The overlay network payload is encapsulated within an overlay header and delivered to the destination by tunneling over the underlying infrastructure. As multiple networking product providers have recognized overlay networks as a way to meet the growing needs of virtualized data centers, multiple solutions have been proposed. Recently the industry has begun work to find common areas of standardization. The first step towards this goal has been to publish a common problem statement through the IETF and forming a working group to standardize on solutions. For the remainder of this discussion, we will focus on Distributed Overlay Virtual Ethernet (DOVE).
  • 5. Towards an Open Data Center with an Interoperable Network (ODIN)Volume 3: Software Defined Networking and OpenFlowPage 5 Distributed Overlay Virtual Ethernet (DOVE) DOVE is a layer 2/3 overlay network which employs packet encapsulation to form instances of overlay networks that separate the virtual networks from the underlying infrastructure and from each other. The separation means separate address spaces, ensuring that virtual network traffic is seen only by network endpoints connected to their own virtual network, and allowing different virtual networks to be managed by different administrators. A DOVE network instance can be created and deleted and virtual machines can be attached to and detached from the DOVE network instance as needed. Upon creation, every DOVE instance is assigned a unique identifier and all the traffic sent over this overlay network carries the DOVE instance identifier in the encapsulation header in order to be delivered to the correct destination virtual machine. In principle, DOVE can also be extended across multiple data centers over long distances. • Switches learn MAC addresses of physical hosts and not of VMs • Routers route IP addresses of physical hosts and not of VMs • Switches and routers are not aware of VMs and DOVE Networks Data Center Network DOVE Network 1 DOVE Network 2 DOVE Network 3 Host 3 Host 6 Host 2 VM VM VM VM Host 5 VM VM VM VM Host 1 VM VM VM VM Host 4 VM VM VM VM VAN VM VM Module VM VM VM Module VM VAN VM VAN Module VAN Module DOVE Switch 1 DOVE Switch 2Figure 3-2 -– DOVE Switches Figure 3.2 shows DOVE switches residing in data center hosts and providing network service for hosted virtual machines so that virtual machines are connected to independent isolated overlay networks. As virtual machine traffic never leaves physical hosts in a non-encapsulated form, physical network devices are not aware of virtual machines, their addresses, and their connectivity patterns. Virtual machines connect to a DOVE network through network nodes located in physical hosts known as DOVE switches. DOVE switches are similar in function to the traditional hypervisor switches but also function as overlay network nodes. Virtual machine interfaces are marked as being connected to a specific DOVE instance by the DOVE switch that resides in each DOVE enabled physical host in a data center. DOVE switches are in the network I/O path of the virtual machines and capture the virtual machine’s traffic, identify it as belonging to a particular DOVE network, add the appropriate DOVE header, and then use the physical infrastructure to deliver the encapsulated packet to the DOVE switch on the destination physical server. Upon receiving the encapsulated packet from the physical network, the DOVE switch parses and removes the encapsulation header and delivers the packet to the correct destination virtual machine as
  • 6. Towards an Open Data Center with an Interoperable Network (ODIN)Volume 3: Software Defined Networking and OpenFlowPage 6 identified both by the target virtual machine address in the packet and by the virtual network identifier in the encapsulation header. When the source and destination virtual machines reside on the same physical server, the DOVE switch on that server delivers the packet directly without using the physical network infrastructure. In addition to providing data delivery, DOVE switches participate in control plane protocols to exchange and distribute information about virtual machine location, virtual machine addresses, virtual machine migration events, etc. DOVE networks connect to other non-DOVE networks through special purpose edge appliances known as DOVE gateways. The DOVE gateways receive encapsulated packets from DOVE switches in physical servers, strip the DOVE headers and forward the packets to the non-DOVE network using the appropriate network interfaces. A DOVE gateway provides connectivity between a virtual machine attached to a DOVE network and the external public network. A DOVE gateway is also used to connect systems to the DOVE network without requiring them to be run on DOVE capable hypervisors. Using DOVE, virtual switches learn the MAC address of their physical host, not the VMs, and route traffic using IP addressing. In this way, DOVE enables a single MAC address for each physical server (or dual redundant addresses for high availability), significantly reducing the size of TCAM and ACL tables. This overlay is transparent to physical switches external to the server, and is thus compatible with other networking protocols (including Layer 3 ECMP or TRILL). DOVE separates virtual networks from both the underlying infrastructure and from each other, ensuring that virtual network traffic is seen only by network endpoints connected to their own virtual network, and allowing different virtual networks to be managed by different administrators. A DOVE network instance can be created and deleted and virtual machines can be attached to and detached from the DOVE network instance as needed. Upon creation, every DOVE instance is assigned a unique identifier and all the traffic sent over this overlay network carries the DOVE instance identifier in the encapsulation header in order to be delivered to the correct destination virtual machine. DOVE meets the growing requirements of virtualized data centers by supporting the creation of a very large number of virtual networks that are independent from the underlying physical infrastructure, isolated from each other, can be separately managed and configured, have independent address spaces and are dynamic. DOVE may be thought of as a multipoint tunnel for communication between systems, including discovery mechanisms and provisions for attachment to non-DOVE networks. Overlay networks allow the virtual network to be defined through software and decouple the virtual network from the limitations of the physical network. Therefore the physical network is wired and configured once and the subsequent provisioning of the virtual networks does not require physical network to be re-wired or re-configured. Overlay networks hide the MAC addresses of the VMs from the physical infrastructure which significantly reduces the size of TCAM and ACL tables. This overlay is transparent to physical switches external to the server, and is thus compatible with other networking protocols (including Layer 3 ECMP or Layer 2 TRILL). This allows L3 routing along with ECMP to be more effectively utilized and reducing the problems of larger broadcast domains within the data center. As the virtual network is independent of the physical network topology, these approaches enable the ability to reduce the broadcast domains within a data center while still retaining the ability to support VM migration. In other words where VM migration typically required flat layer 2 domains, overlay networking technologies allow segmenting a data center while still supporting VM migration across the data center and potentially between different data centers.
  • 7. Towards an Open Data Center with an Interoperable Network (ODIN)Volume 3: Software Defined Networking and OpenFlowPage 73.3 OpenFlow Since part of its mission is to create the most relevant software-defined networking (SDN) standards, the Open Networking Foundation (ONF) is driving the standardization of OpenFlow. The OpenFlow specification is controlled and published by a recently-formed, nonprofit industry trade organization called the Open Network Foundation (ONF), which will license the trademark “OpenFlow Switching” to companies who adopt this standard. The ONF is led by a board of directors from six companies that own and operate some of the largest networks in the world (including Deutsche Telekom, Facebook, Google, Microsoft, Verizon, Yahoo, Goldman Sachs, and NTT). These companies are expected to lead the next generation of OpenFlow adoption. OpenFlow is a component which enables implementation of SDN, and it is the only standardized SDN-oriented communication protocol between the network infrastructure and control layers. There are many benefits of a standard which opens the control plane of the switch network, and a flow paradigm that offers granular traffic control. OpenFlow also offers a global view of the network, including traffic statistics, and is fully compatible with existing Layer 2 and 3 protocols. In contrast to a traditional switch, which provides a separate management/control plane for each switch element in the network, OpenFlow extracts the control plane from the network. In this environment, networking services (security, multi-pathing, and more) run like apps on a software- defined network stack. The use of OpenFlow to enable an ecosystem of network apps development, as opposed to the closed, vendor proprietary approach used today, represents an important change in the way networks services will be deployed in the future. OpenFlow allows direct access and manipulation of the forwarding or data plane of network infrastructure devices such as switches and routers, both physical and virtual (hypervisor-based). In this way, OpenFlow can be compared to the instruction set of a CPU. The protocol specifies basic primitives that can be used by an external software program on the network to program the forwarding plane of network infrastructure devices, just like the instruction set of a CPU would program a computer system. OpenFlow is an emerging technology with the potential to increase the value of data center services dramatically. Implementing OpenFlow can provide network administrators with greater control over their resources, integrated network and server management, and an open management interface for routers and switches. An OpenFlow switch consists of three parts, as illustrated in figure 3.3:Figure 3.3 – Basic OpenFlow architecture
  • 8. Towards an Open Data Center with an Interoperable Network (ODIN)Volume 3: Software Defined Networking and OpenFlowPage 8 ● Flow Table—Tells the switch how to process each data flow by associating an action with each flow table entry ● Secure Channel—Connects the switch to a remote control processor (called the Controller) so commands and packets can be sent between the controller and the switch ● OpenFlow Protocol—Provides an open, standardized interface for the controller to communicate with the switch and to remove, add, or change flow control entries The OpenFlow Protocol allows entries in the Flow Table to be defined by a server external to the switch. For example, a flow could be a TCP connection, all the packets from a particular MAC or IP address, or all packets with the same VLAN tag. Each flow table entry has a specific action associated with a particular flow, such as forwarding the flow to a given switch port (at line rate), encapsulating and forwarding the flow to a controller for processing, or dropping a flow’s packets (for example, to help prevent denial of service attacks). There are many applications for OpenFlow in modern networks. For example, a network administrator could create on-demand ‘express lanes’ for voice and data traffic that are time-sensitive. Software could also be used to combine several fiber optic links into a larger virtual pipe to handle a particularly heavy flow of traffic temporarily. When the data rush is over, the links would automatically separate under the supervision of the controller. In cloud computing environments, OpenFlow improves scalability and enables resources to be shared efficiently among different services in response to the number of users. There are different types of messages used by an OpenFlow controller. The switch-controller connection is discovered using a symmetric protocol (like a Hello packet) and maintained using periodic echo request/reply messages. There are also specific unidirectional messages sent from the controller to the switch, or from the switch to the controller. For example, the controller may configure the switch, query the switch capabilities, manage flow tables, or direct packets across the network. Asynchronous messages may also pass from the switch to the controller which announce changes in the switch state, network status, packet errors, or which send ingress packets to the controller (such as ARPs from a VM). OpenFlow provides a basic set of global management abstractions, which can be used to control features such as topology changes and packet filtering. OpenFlow takes advantage of the fact that most modern Ethernet switches and routers contain flow tables, which run at line rate and are used to implement functions such as quality of service (QoS), security firewalls, and statistical analysis of data streams. OpenFlow standardizes a common set of functions that operate on these flows and will be extended in the future as the standard evolves. The rules within OpenFlow allow filtering on the N-tuples of an Ethernet frame, as shown in figure 3.4. A match-action table provides logical mapping to a list of instructions which describe how to handle a packet. The packet and byte counters are used to collect statistics on the interface. Different style masks can be implemented to filter and redirect traffic as desired (for example, certain packets might be routed to a firewall, others to a load balancer, or some combination of network appliances).
  • 9. Towards an Open Data Center with an Interoperable Network (ODIN)Volume 3: Software Defined Networking and OpenFlowPage 9Figure 3.4 - OpenFlow Rules, Match-Action Tables, and Statistics As previously discussed, there are many potential applications for OpenFlow in modern data center networks. Cloud computing environments which use multi-tenancy and resource pooling can benefit from OpenFlow traffic steering capabilities. OpenFlow provides the isolation required to host multiple tenants on the same server. Resource pooling helps reduce the need for multiple appliances (load balancers, firewalls, and more) in each vertically oriented network stack. This in turn reduces the number of physical appliances in the data center, reducing capital expense and energy consumption; by load balancing across previously under-utilized appliances, overall performance remains essentially unaffected.Summary SDN and OpenFlow represent emerging industry standards which hold the potential to reduce capex and opex in the data center network. These approaches support highly virtualized data centers and automate functions such as traffic filtering. By separating the data plane and control plane within a switch, this approach enables use cases such as multi-tenancy and resource pooling in cloud computing data centers. OpenFlow enables deterministic traffic flows for more predictable network performance, as well as both lower and more consistent traffic latency. OpenFlow is also used for policy driven content distribution, automated network configuration, and dynamic reprovisioning of bandwidth on demand. Further, the interoperability of multiple SDN controllers and networking resources helps promote interoperability and insure faster time to value in heterogeneous multi-vendor networks.
  • 10. Towards an Open Data Center with an Interoperable Network (ODIN)Volume 3: Software Defined Networking and OpenFlowPage 10Technical References Metzler, Dr. Jim Metzler Ashton Metzler & Associates Co-Founder, Webtorials Analyst Division Networking Track Chair, Interop. “The 2011 Cloud Networking Report,” produced and distributed by: WebTutorials, in association with:Interop. Retrieved from: http://www.webtorials.com/content/2011/11/2011-cloud-networking-report.html OpenFlow For more information on OpenFlow, please visit www.opennetworkingfoundation.org Or see the following articles: Open Networking Foundation Pursues New Standards: http://www.nytimes.com/2011/03/22/technology/internet/22internet.html?_r=1&ref=technology How Software Will Redefine Networking: http://gigaom.com/2011/03/21/open-networking-foundatio/ Tech Titans Back OpenFlow Networking Standard: http://www.datacenterknowledge.com/archives/2011/03/22/tech-titans-back-openflow-networking- standard/ A Case for Overlays in DCN Virtualization: http://www.itc23.com/fileadmin/ITC23_files/papers/DC-CaVES-m1569472213.pdf IETF Problem Statement: Overlays for Network Virtualization: http://tools.ietf.org/html/draft-narten-nvo3-overlay-problem-statement-01 Virtual Network Services for Federated Cloud Computing: http://domino.watson.ibm.com/library/Cyberdig.nsf/papers/3ADF4AD46CBB0E6B852576770056 B848/$File/H-0269.pdf
  • 11. Towards an Open Data Center with an Interoperable Network (ODIN)Volume 3: Software Defined Networking and OpenFlowPage 11For More InformationIBM System Networking http://ibm.com/networking/IBM PureSystems http://ibm.com/puresystems/IBM System x Servers http://ibm.com/systems/xIBM Power Systems http://ibm.com/systems/powerIBM BladeCenter Server and options http://ibm.com/systems/bladecenterIBM System x and BladeCenter Power Configurator http://ibm.com/systems/bladecenter/resources/powerconfig.htmlIBM Standalone Solutions Configuration Tool http://ibm.com/systems/x/hardware/configtools.htmlIBM Configuration and Options Guide http://ibm.com/systems/x/hardware/configtools.htmlTechnical Support http://ibm.com/server/supportOther Technical Support Resources http://ibm.com/systems/supportLegal Information This publication may contain links to third party sites that are not under the control of or maintained by IBM. Access to anyIBM Systems and Technology Group such third party site is at the users own risk and IBM is notRoute 100 responsible for the accuracy or reliability of any information, data, opinions, advice or statements made on these sites. IBMSomers, NY 10589. provides these links merely as a convenience and theProduced in the USA inclusion of such links does not imply an endorsement.May 2012 Information in this presentation concerning non-IBM productsAll rights reserved. was obtained from the suppliers of these products, publishedIBM, the IBM logo, ibm.com, BladeCenter, and VMready are announcement material or other publicly available sources.trademarks of International Business Machines Corp., IBM has not tested these products and cannot confirm theregistered in many jurisdictions worldwide. Other product and accuracy of performance, compatibility or any other claimsservice names might be trademarks of IBM or other related to non-IBM products. Questions on the capabilities ofcompanies. A current list of IBM trademarks is available on non-IBM products should be addressed to the suppliers ofthe web at ibm.com/legal/copytrade.shtml those products.InfiniBand is a trademark of InfiniBand Trade Association. MB, GB and TB = 1,000,000, 1,000,000,000 and 1,000,000,000,000 bytes, respectively, when referring toIntel, the Intel logo, Celeron, Itanium, Pentium, and Xeon are storage capacity. Accessible capacity is less; up to 3GB istrademarks or registered trademarks of Intel Corporation or its used in service partition. Actual storage capacity will varysubsidiaries in the United States and other countries. based upon many factors and may be less than stated.Linux is a registered trademark of Linus Torvalds. Performance is in Internal Throughput Rate (ITR) ratio basedLotus, Domino, Notes, and Symphony are trademarks or on measurements and projections using standard IBMregistered trademarks of Lotus Development Corporation benchmarks in a controlled environment. The actualand/or IBM Corporation. throughput that any user will experience will depend on considerations such as the amount of multiprogramming in theMicrosoft, Windows, Windows Server, the Windows logo, user’s job stream, the I/O configuration, the storageHyper-V, and SQL Server are trademarks or registered configuration and the workload processed. Therefore, notrademarks of Microsoft Corporation. assurance can be given that an individual user will achieveTPC Benchmark is a trademark of the Transaction Processing throughput improvements equivalent to the performance ratiosPerformance Council. stated here.UNIX is a registered trademark in the U.S. and/or other Maximum internal hard disk and memory capacities maycountries licensed exclusively through The Open Group. require the replacement of any standard hard drives and/or memory and the population of all hard disk bays and memoryOther company, product and service names may be slots with the largest currently supported drives available.trademarks or service marks of others. When referring to variable speed CD-ROMs, CD-Rs, CD-RWsIBM reserves the right to change specifications or other and DVDs, actual playback speed will vary and is often lessproduct information without notice. References in this than the maximum possible.publication to IBM products or services do not imply that IBMintends to make them available in all countries in which IBMoperates. IBM PROVIDES THIS PUBLICATION “AS IS”WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSOR IMPLIED, INCLUDING THE IMPLIED WARRANTIES OFMERCHANTABILITY AND FITNESS FOR A PARTICULARPURPOSE. Some jurisdictions do not allow disclaimer ofexpress or implied warranties in certain transactions;therefore, this statement may not apply to you. QCW03021USEN-00

×