Table Of Contents
Cloud Data Center
Hierarchical Network Architecture
The Virtualized Multi-tenant Data Center (VMDC) reference architecture defines an end-end system suitable for service deployment in a public or private "Cloud" model. Though this document focuses mainly on design considerations specific to aspects of the data center, the "big picture" is that the end-to-end system includes the wide area network (WAN), multiple "provider" data centers, and the tenant's resources on their premise. In the public cloud case, the tenant would typically be located remotely, and have their own data center resources on site in addition to resources within the cloud; in the private case, the tenant could reside locally in another organizational unit logically separated from the IT data center or be located at another facility.
Figure 1-1 System Overview
•Cloud Data Center
Cloud Data Center
At a macro level, the Cloud data center consists of network, storage, and compute resources, but it is important to keep in mind that it is part of a larger end-to-end system which includes the following components:
1. Data Center (typically interconnected in a system of multiple data centers).
2. Wide Area Backbone or IP/Next Generation Network (NGN) (public provider backbone) network.
3. Public Internet Access
4. The Tenant Premise—In the private case, the "tenant" can be an organization unit with their own compute resources separated logically from the IT data center, or could be accessing their private cloud remotely in a mobile fashion via Secure Sockets Layer (SSL) or IPSec VPN connection, or in a branch or alternative data center/campus In the public case, the "Enterprise-grade" tenant will typically be accessing their resources within the cloud remotely from within their Enterprise environment (i.e., within the Enterprise data center or campus).
5. Management—This is a superset of normal data center administration functions over storage, compute, and network resources, including elements which allow for more dynamic resource allocation and automated processes (i.e., an administrative or tenant user portal, service catalog, and workflow automation).
This section discusses the following aspects of the Cloud data center:
•Hierarchical Network Architecture
Hierarchical Network Architecture
The data center within the VMDC 2.2 reference architecture is based upon the classic multi-layer hierarchical network model. In general, such a model implements three layers of hierarchy:
•Core Layer, characterized by a high degree of redundancy and bandwidth capacity and thus optimized for availability and performance.
•Aggregation Layer, characterized by a high degree of high-bandwidth port density capacity and thus optimized for traffic distribution and link fan-out capabilities to access layer switches. Functionally, the nodes in the aggregation layer typically serve as the L2/L3 boundary.
•Access Layer, serving to connect hosts to the infrastructure and thus providing network access, typically at Layer 2 (L2) (i.e., LANs or VLANs).
Figure 1-2 shows these three layers of the hierarchical model.
Figure 1-2 Three-Layer Hierarchical Model
Benefits of such a hierarchical model include scalability, resilience, performance, maintainability, and manageability. The hierarchical design represents a structured approach to building the infrastructure, allowing for relatively easy expansion in modular increments. Redundant nodes and links at each level insure no single point of failure, while link aggregation can be engineered for optimal bandwidth and performance through the aggregation and core layers. Devices within each layer perform the same functions; this consistency simplifies troubleshooting and configuration. The effect is ease of maintenance at lower operational expense.
Figure 1-3 shows the following functional layers that comprise the VMDC data center:
Figure 1-3 Functional Layers Within the VMDC Data Center
The Network layer includes the WAN/PE router, which forms the data center perimeter to the Enterprise wide area or provider IP/NGN backbone and to the public Internet. These perimeter nodes may be dedicated to Layer 3 (L3) routing functions or may be multi-service in nature, providing L2 interconnects between data centers as well as L3 services. WAN/PE routers validated within the VMDC reference system architecture include: the Cisco CRS-1, Cisco ASR 9000, Cisco Catalyst 7600, Catalyst 6500, and ASR 1000. The Network layer also includes the aforementioned, classic three-layer hierarchy of switching nodes. Within the VMDC reference architecture, this portion of the infrastructure is comprised of Nexus 7000 systems, serving as the core (i.e., Nexus 7010) and aggregation (i.e., Nexus 7018) nodes, and the Nexus 5000 system as the access nodes. As shown in Figure 1-10, validated VMDC topologies feature two variants of the three-layer hierarchical model: a collapsed core/aggregation version, and a collapsed aggregation/access version. These allow for fine-tuning of port capacity and bandwidth to the level of aggregation or access density required to accommodate current and anticipated scale requirements.
The Services layer comprises network and security services such as firewalling, server load balancing, SSL offload, intrusion prevention, network analysis, and gateway functions. A distinct difference arises between the conventional data center services layer and "cloud" data center services layer in that the solution set for the latter must support application of L4 - L7 services at a per-tenant level, through logical abstraction of the physical resources. Centralized services are most useful in applying policies that are broadly applicable across a range of tenants (or workgroups in the private case). Within the VMDC reference architecture, the Data Center Services Node (DSN) provides firewalling and server load balancing services, in a service module form factor (i.e., the ACE30 and FWSM or ASA-SM modules); alternatively, these are available in appliance form-factors. This layer also serves as the termination point for remote access IPSec or SSL VPNs; within the VMDC architecture, the Cisco ASA 5580 appliance connected to the DSN fulfills this function, securing remote tenant access to cloud resources.
The Compute layer includes several sub-systems. The first is a virtual access switching layer, which allows for extension of the L2 network across multiple physical compute systems. This virtual access switching layer is of key importance in that it also logically extends the L2 network to individual virtual machines within physical servers. The feature-rich Cisco Nexus 1000V generally fulfills this role within the architecture. Depending on the level of software functionality (i.e., QoS or security policy) or scale required, the VM-FEX may be a hardware-based alternative to the Nexus 1000V. A second sub-system is that of virtual (i.e., vApp-based) services. These may include security, load balancing, and optimization services. Services implemented at this layer of the infrastructure will complement more centralized service application, with unique applicability directly to a specific tenant or workgroup and their applications. Specific vApp based services validated within the VMDC architecture as of this writing include the Cisco Virtual Security Gateway (VSG), providing a security policy enforcement point within the tenant virtual data center or Virtual Private Data Center (VPDC). The third sub-system within the Compute layer is the computing resource. This includes physical servers, hypervisor software providing compute virtualization abilities, and the virtual machines thus enabled. The Cisco Unified Computing System (UCS), featuring redundant 6100 Fabric Interconnects, UCS 5108 Blade Chassis, and B-Series Blade or C-Series RackMount servers, comprise the compute resources utilized within the VMDC reference architecture.
The Storage layer provides storage resources. Data stores will reside in SAN (block-based) or NAS (file-based) storage systems. SAN switching nodes implement an additional level of resiliency, interconnecting multiple SAN storage arrays to the compute resources, via redundant FC (or perhaps Fibre Channel over Ethernet (FCoE)) links.
The Management layer consists of the "back-end" hardware and software resources required to manage the multi-tenant infrastructure. These include domain element management systems, as well as higher level service orchestration systems. The domain management systems currently validated within VMDC include Cisco UCS Manager, VMware vCenter, and vCloud Director for compute resource allocation; EMC's UIM and Cisco Fabric Manager for storage administration; and Cisco VSM and Virtual Network Management Center (VNMC) for virtual access and virtual services management. Automated service provisioning, including cross-resource service orchestration functions, are provided by BMC's Cloud Lifecycle Management (CLM) system. Service orchestration functions were not in scope for this VMDC system release.
Previous iterations of the VMDC reference architecture defined resource containers called "pods" that serve as the basis for modularity within the Cloud data center. As a homogenous modular unit of network, compute, and storage resources, the pod concept allows one to address environmental, physical, logical, and application-level requirements in a consistent way. The pod serves as a blueprint for incremental build-out of the Cloud data center in a structured fashion; when resource utilization within a pod reaches a pre-determined threshold (i.e., 70-80%), the idea is that one simply deploys a new pod. From a service fulfillment and orchestration perspective, a pod represents a discrete resource management domain.
Figure 1-4 Pod Concept
In general practice, the pod concept may serve simply as a framework, with designers defining their own variants tuned to specific environmental or performance characteristics. Figure 1-4 shows that a pod can be defined at different levels of modularity, supporting growth in differing increments. However, within the VMDC reference architecture, a general purpose utility compute pod extends from the compute and storage layers to the L2 ports on the aggregation nodes serving as the L2/L3 boundary and up to and including components within the network services layer. The port and MAC address capacity of the aggregation nodes are thus key factors in determining how many pods a single pair of aggregation nodes will support within the Cloud data center.
Special Purpose Pods
A major premise behind building general purpose homogeneous compute pods and applying logical segmentation overlays to meet business or security policy requirements is that this maximizes utilization of resources. However, in some cases there may be a unique requirement - for ease of operation, special performance tuning, or to meet special security objectives - to physically separate some of the compute nodes out from a general purpose pod and place them in a dedicated, perhaps application-specific pod. The VMDC architecture provides the flexibility to build special purpose pods. Such is the case with the management pod concept.
Back-end management compute nodes may be placed within a general purpose compute pod, and logically isolated and firewalled from production hosts. For smaller, less complex or more streamlined environments, this is an excellent option. However, in larger environments, a separate pod dedicated to back-end management servers (i.e., bare metal and virtualized) is recommended. In the various VMDC 2.X releases, the as-tested systems have in fact included a separate access pod in which servers are dedicated to back-end infrastructure management functions. The benefits of this option include creation of a more discrete troubleshooting domain in the event of instability or failures. The architecture flexibility allows for logical isolation and firewalling or for dedicated firewalls (physical or in vApp form) to be placed on the perimeter of the management container. In practice, role-based access controls (RBAC) tied to directory services would be applied to categorize and limit user access and change control authority as per their functional roles within the organization.
The Integrated Compute Stack
An Integrated Compute Stack (ICS) represents another potential unit of modularity within the VMDC Cloud data center, representing a sub-component within the pod. An ICS is a pre-integrated collection of storage, compute, and network resources, up to and including L2 ports on a pair of access switching nodes. Figure 1-5 shows the location of the ICS within a pod. Multiples of ICSs will be deployed like building blocks to fill the capacity of a pod.
Figure 1-5 ICS Concept
Working with eco-system partners, Cisco currently supports two ICS options:a Vblock and a flexpod. A Vblock comprises Cisco UCS and EMC storage systems, offered in several combinations to meet price, performance, and scale requirements. Similarly, a Flexpod also combines UCS compute and storage resources, however in this case, NetApp storage systems apply. Flexpods are offered in a range of sizes designed to achieve specific workload requirements. The VMDC reference architecture will accommodate more generic units of compute and storage, including storage from other third-party vendors, however the business advantage of an ICS is that pre-integration takes the guesswork out of balancing compute processing power with storage input/output operations per second (IOPS) to meet application performance requirements.
The VMDC SAN architecture remains unchanged from previous (2.0) programs. It follows current best practice guidelines for scalability, high availability, and traffic isolation. Key design aspects of the architecture include:
•Leverage of Cisco Data Center Unified Fabric to optimize and reduce LAN and SAN cabling costs
•High availability through multi-level redundancy (link, port, fabric, Director, RAID)
•Risk mitigation through fabric isolation (multiple fabrics, VSANs)
•Data store isolation through NPV/NPIV virtualization techniques, combined with zoning and LUN masking.
The hierarchical, pod-based infrastructure model described in this document lends itself to two possible attachment points for storage: within the pod and/or at the aggregation nodes - i.e., distributed or centralized. In practice, which option is most suitable for a particular deployment will depend on application characteristics and anticipated traffic patterns for interactions involving data store access. Companies often employ both options in order to satisfy specific application requirements and usage patterns. In terms of the VMDC validation work, the focus to date has been on consideration of storage as a distributed, pod-based resource. This is based on the premise that in a hierarchical, cloud-type data center model, it is more efficient in terms of performance and traffic flow optimization to locate data store resources as close to the tenant hosts and vApps as possible. In this context, given the two hierarchical topology variants defined (i.e., collapsed core/aggregation and collapsed aggregation/ access), we have two methods of attaching Fiber Channel storage components into the infrastructure: the first follows the ICS model of attachment via the Nexus 5000; the second provides for attachment at the UCS Fabric Interconnect, Figure 1-6.
Figure 1-6 FC SAN Attachment Options
In both scenarios, Cisco's unified fabric capabilities are leveraged with converged network adapters (CNAs) providing "SAN-ready" servers, and N-Port Virtualizer on the UCS Fabric Interconnect or Nexus 5000 top-of-rack (ToR) switches enabling each aggregated host to be uniquely identified and managed through the fabric and over uplinks to the SAN systems. Multiple FC links are used from each (redundant) Nexus 5000 or UCS Fabric Interconnect to the MDS SAN switches, in order to match the current maximum processing capability of the SAN system and thus eliminate lack of bandwidth between the SAN components and their point of attachment to the network infrastructure as a potential bottleneck.
Though the diagrams above show simple SAN switching topologies, it is important to note that if greater SAN port switching capacity is required, the architecture supports (is validated with) more complex, two-tier core-edge SAN topologies, documented in the VMDC 2.0 "Compact Pod Implementation Guide," and the Cisco SAN switching best practice guides, available at http://www.cisco.com/en/US/prod/collateral/ps4159/ps6409/ps5990/ white_paper_C11-515630.html.
The VMDC compute architecture is based upon the premise of a high degree of server virtualization, driven by data center consolidation, the dynamic resource allocation requirements fundamental to a "cloud" model, and the need to maximize operational efficiencies while reducing capital expense (CAPEX). The architecture is thus based upon three key elements:
1. Hypervisor-based virtualization: in this as in previous system releases, VMware's vSphere plays a key role, enabling the creation of virtual machines on physical servers by logically abstracting the server environment in terms of CPU, memory, and network touch points into multiple virtual software containers.
2. Unified Computing System (UCS): unifying network, server and I/O resources into a single, converged system, the Cisco UCS provides a highly resilient, low-latency unified fabric for the integration of lossless 10-Gigabit Ethernet and FCoE functions with x-86 server architectures. The UCS provides a stateless compute environment that abstracts I/O resources and server personality, configuration and connectivity, facilitating dynamic programmability. Hardware state abstraction makes it easier to move applications and operating systems across server hardware.
3. The Cisco Nexus 1000V provides a feature-rich alternative to VMware's Distributed Virtual Switch, incorporating software-based VN-link technology to extend network visibility, QoS, and security policy to the virtual machine level of granularity.
This system release utilizes VMware's vSphere 4.1 as the compute virtualization operating system. A complete list of new enhancements available with vSphere 4.1 is available online. Key "baseline" vSphere functionality leveraged by the system includes ESXi boot from SAN, VMware High Availability (VMware HA), and Distributed Resource Scheduler (DRS).
Fundamental to the virtualized compute architecture is the notion of clusters; a cluster consists of two or more hosts with their associated resource pools, virtual machines, and data stores. Working in conjunction with vCenter as a compute domain manager, vSphere's more advanced functionality, such as HA and DRS, is built around the management of cluster resources. vSphere supports cluster sizes of up to 32 servers when HA and/or DRS features are utilized. In general practice however, the larger the scale of the compute environment and the higher the virtualization (VM, network interface, and port) requirement, the more advisable it is to use smaller cluster sizes in order to optimize performance and virtual interface port scale. Therefore, in VMDC large pod simulations, cluster sizes are limited to eight servers; in smaller pod simulations, cluster sizes of 16 or 32 are utilized. As in the VMDC 2.0 release, three compute profiles (Gold, Silver, and Bronze) are created to represent large, medium, and small workload types. Gold has 1 vCPU/core and 16G RAM; Silver has .5 vCPU/core and 8G RAM, and Bronze has .25 vCPU/core and 4G of RAM.
The UCS-based compute architecture has the following characteristics:
•It comprises multiple UCS 5100 series chassis (5104s), each populated with eight (half-width) server blades.
•Each server has dual 10GigE attachment - i.e., to redundant A and B sides of the internal UCS fabric.
•The UCS is a fully redundant system, with two 2100 Series Fabric Extenders per chassis and two 6100 Series Fabric Interconnects per pod.
•Internally, four uplinks per Fabric Extender feeding into dual Fabric Interconnects pre-stage the system for the maximum bandwidth possible per server; this means that for server to server traffic within the UCS fabric, each server will have 10GigE bandwidth.
•Each UCS 6100 Fabric Interconnect aggregates via redundant 10GigE EtherChannel connections into the access switch (i.e., Nexus 7000). The number of uplinks provisioned will depend upon traffic engineering requirements. For example, in order to provide an eight-chassis system with an 8:1 oversubscription ratio for internal fabric bandwidth to aggregation bandwidth, a total of 80G (8x10G) of uplink bandwidth capacity must be provided per UCS system (Figure 2-20).
•Similarly to the Nexus 5000 FC connectivity in the compact pod design, an eight-port FC GEM in each 6140 Expansion Slot provides 4Gig FC to the Cisco MDS 9513 SAN switches (i.e., 6140 chassis A, 4 x 4G FC to MDS A and 6140 chassis B, 4 x 4G FC to MDS B). In order to maximize IOPS, the aggregate link bandwidth from the UCS to the MDS should match the processing capability of the storage controllers.
The Nexus 1000V functions as the virtual access switching layer, providing per-VM policy and policy mobility.
Virtualization of compute and storage resources enables sharing across an organizational entity. In contrast, virtualized multi-tenancy, a concept at the heart of the VMDC reference architecture, refers to the logical isolation of shared virtual compute, storage, and network resources. In essence, this is "bounded" or compartmentalized sharing. A tenant is a user community with some level of shared affinity. For example, within an Enterprise, a tenant may be a business unit, department, or workgroup. Depending upon business requirements or regulatory policies, a tenant "compartment" may stretch across physical boundaries, organizational boundaries, and even between corporations. A tenant container may reside wholly within their private cloud or may extend from the tenant's Enterprise to the provider's facilities within a public cloud. The VMDC architecture addresses all of these tenancy use cases through a combination of secured datapath isolation and a tiered security model which leverages classical security best practices and updates them for the virtualized multi-tenant environment.
Tenancy Use Cases
Earlier VMDC releases (2.0 and 2.1) presented four tenancy models. High-level, logical depictions of these models are shown in Figure 1-7. The first three provided a baseline, simple set of tenant containers, which were combined with different levels of network services in a tiered fashion - hence the Bronze, Silver, and Gold nomenclature. The two most interesting containers from this set are Bronze and Gold. Bronze seemingly is the most basic, but simplicity broadens its applicability. One tends to think of these containers as single-tenant in nature, but in practice, a Bronze container may be used to support multiple tenants, with homogenous requirements; i.e., similar workload profiles, QoS, or security policies, or perhaps this is a community of interest using the same application set. A Gold container, with both firewalling and server load balancing applied, assumes a higher degree of security and availability is required as a baseline in order to support the tenant applications. As in the Silver container, multiple VLANs support logical segmentation for N-tiered applications. The idea is that one could combine these tenant containers together in various combinations to support more complex scenarios if desired. The fourth container type demonstrates a further incremental evolution of tenancy models from simple multi-segment containers toward logical approximations of a virtual data center overlay on the physical shared infrastructure. With the notion of a separate front-end and back-end set of zones, each of which may have a different set of network services applied, the Palladium container begins to more closely align with traditional zoning models in use in physical IT deployments.
Figure 1-7 Initial Four VMDC Tenancy Models
New Tenancy Models Introduced in VMDC 2.2
Two new tenancy models are introduced in VMDC 2.2. The first incrementally evolves the virtual data center concept, providing more expansion of protected front-end and back-end zones while furthering the notion of separate public (i.e., Internet) or shared (i.e., campus/inter-organizational) access from private access. It also includes secured remote IPSec or SSL VPN access. In this case, the term "private" can mean that the virtual data center is routed over the private Enterprise WAN or through the public Cloud provider's IP/NGN via a private MPLS VPN. In the public cloud scenario, this type of virtual data center linked to the tenant Enterprise via an L2 or L3 MPLS VPNs is commonly termed a virtual private data center (VPDC). MPLS VPNs are often used by public Cloud providers as transport for hybrid managed cloud services. As indicated in the left model in Figure 1-8, such services may include IP addressing, security (i.e., firewalling, managed DMZ, zoning, secured remote VPN access), and server resiliency solutions.
In contrast, the second container model represents a "raw" container, so-called because in this case, the tenant provides and manages their own network services and IP addressing within their container, with the public provider offering a seamless extension of the tenant's data center within the public cloud. This is effectively two "Bronze" containers connected via an L2 VPN - i.e., an extended Ethernet. The key benefit of this hybrid tenancy model is that the Enterprise maintains control of their resources within the public cloud; virtual machine migration is controlled by the Enterprise and may be accomplished with minimal modifications to server or virtual machine configurations, as IP readdressing is not required.
Figure 1-8 Two New Tenancy Models
Another concept at the heart of the VMDC reference architecture is the notion of differentiated service tiering; simply put, tenants may have unique requirements in terms of network throughput, compute processing, storage performance, or data store privacy characteristics, and a successful multi-tenant deployment must be able to address these needs.
By definition, in a cloud-based model, compute, storage, and network infrastructure are abstracted and delivered "as a service." To tailor workload characteristics or application performance to specific needs, the cloud administrator has various methods at hand for providing differentiated service tiers and insuring that tenant privacy and service level agreement (SLA) objectives are met:
•Tiered Workload Definitions—The secret to building a cloud-ready infrastructure is in categorizing the set of applications that must be supported and distilling these into their basic workload characteristics. Once these are reasonably well-understood, they can in most cases be addressed by a set of standard service profiles. For example, characteristics which apply to the ICS include virtual machine attributes (CPU ratio, memory and associated storage capacity); storage attributes (RAID levels, disk types and speeds, and protection mechanisms); and support for various degrees of application tiering.
•Availability Mechanisms—Availability mechanisms may be applied at various layers of the infrastructure to insure that communication requirements are met. For example, within a vSphere cluster, DRS and vMotion or Fault Tolerance may be used to provide optimal resource allocation, even in the event of server failure. Similarly, within the SAN, data protection mechanisms such as snapshots, cloning, and backup archiving help to insure that data store integrity is preserved through various types of failure scenarios. Network services, such as server load balancing, encryption, advanced routing and redundancy, can further help to achieve availability targets. The larger the shared domain (ICS, pod, or entire data center level), the broader the impact of the availability mechanisms utilized at that particular layer of the hierarchy. As these typically do not come without added cost, the goal would be to insure that broadly scoped availability methods meet minimum targeted requirements for the entire tenant community.
•Secure Isolation—In a multi-tenant environment, the ability to securely contain and isolate tenant traffic is a fundamental requirement, protecting tenant resources and providing risk mitigation in the event that a specific tenant's privacy is breached. Like availability, isolation mechanisms are applied in a multi-layered fashion in order to implement the requisite infrastructure protection and security zoning policies on a per-tenant basis. In practice, techniques fall into two categories of physical and logical isolation mechanisms. However, VMDC analysis focuses mainly on logical mechanisms. These include various L2 and L3 mechanisms, such as multiple vNICs (i.e., for specific control or data traffic), 802.1q VLANs, MPLS VRFs, VSANs, combined with access control mechanisms (i.e., RBAC and directory services, IPSec or SSL VPNs), and packet filtering and firewall policies.
•Service Assurance Mechanisms—Service assurance is a function of availability and QoS policies. The implementation of QoS policies allows for differentiated classification and treatment of traffic flows per tenant per service tier during periods of congestion.
•Management—The ability to abstractly represent per-tenant resources and services in the form of a service catalog is a prerequisite for automated service fulfillment and service assurance functions; i.e., the "day 1" and "day 2" management tasks which are so essential to operating under an Infrastructure as a Service (IaaS) model. The service catalog is effectively the highest level of abstraction for the underlying cloud resources. Accurate representations of these resources as policy-based tenancy models to the service catalog rely on interactions directly with domain element managers or middleware management layers via standardized interfaces (i.e., APIs, MIBS, etc.). The more intelligent the middleware layer, the less work has to be done at higher levels in the management framework to understand the tenancy models and commission or decommission resources on a per-tenant basis.
Previous VMDC releases were modeled based on three baseline categories of tenant network services tiers—Bronze, Silver, and Gold— represented in terms of firewalling, server load balancing, SSL offload, and QoS policy (i.e., hree data classes of service), combined with three workload models, each with specific compute attributes, associated storage characteristics, and business continuance services. Figure 1-9 shows a high-level conceptual illustration of these models, demonstrating a variety of ways in which these resources and services can be applied in combination to meet business or application requirements in a tiered fashion.
Figure 1-9 VMDC Service Tiers
This system release leverages the end-to-end architecture defined in VMDC 2.0. This document revisits foundational principals of high availability and modular growth, and describes enhancements to the system in the areas of tenant isolation and security in general, and introduces a new QoS framework for accommodation of multimedia and collaboration applications.
As a brief recap, in VMDC 2.0, we defined two system topologies mainly focused on 10 Gb compute farms, each featuring a variant for 1 Gb compute farms (Figure 1-10). In the first, UCS systems with B-series blade servers provided the compute resource. In the second, C-series rackmount servers were the focus, though it is possible to add other third-party servers. These can be used in combination to meet various storage and server use cases. Note for example, the use of the 2248 Fabric Extender to expand the Nexus 1G port capacity (lower left quadrant Figure 1-10). In this release, we focus on enhancements to the "10G Large Pod" variant displayed in the upper right quadrant in Figure 1-10.
Figure 1-10 VMDC 2.X Topology Options
The end-to-end physical topology characterized in this release is depicted in Figure 1-11.
Figure 1-11 Physical Topology View
Figure 1-12 provides a high-level view of the corresponding logical topology.
Note This architecture provides flexibility for mixing and matching services to specific groups of tenants (this diagram does not depict all service flows), and not all tenants will require server load balancing and hybrid firewalling.
Figure 1-12 Logical Topology Overview
L2 Multi-site VPN Topology
Also included in this release is an analysis of hybrid cloud interconnect use cases and associated L2 transport scenarios. The ASR 9000 DC Edge devices were in this instance serving as multiservice nodes for L2VPN and L3VPN transport between data centers. The diagram is included here for completeness, however, design and implementation guidance are provided in the following two documents:
•VMDC 2.2 VPLS Implementation Guide
•VMDC 2.2 EoMPLS DCI for Hybrid Cloud with vCloud Director Design and Implementation Guide Supplement
Figure 1-13 L2VPN Topology
Figure 1-14 VMDC 2.2 Component Matrix