Wired Intelligent Edge

As you may already know, Aruba has released a new series of switches for the Core and Aggregation layers of your campus.

These new switches are:

• 8400 Switch: A modular switch built for the highest performance and availability
• 8320 10GbE SFP+ Switch: A fixed format switch with 48 10GbE (SFP/SFP+) and 6 40GbE ports (QSFP+)
• 8320 10GBASE-T Switch: A fixed format switch with 48 10GBASE-T (RJ45) and 6 40 GbE ports (QSFP+)
• 8320 40GbE Switch: A fixed format switch with 32 40GbE ports (QSFP+)

These switches run the NEW ArubaOS-CX. This next generation OS has been designed and developed from the ground up to satisfy the needs of the campus backbone in the foreseable future.

ArubaOS-CX offers unprecedented automation capabilities and visibility  into your backbone switches with a complete REST interface and the innovative Network Analytic Engine.

In a series of short technical articles we will introduce different hardware and software features, highlighting those that make these products unique and special.

Aruba 8400 Switch

Line Cards (Switching Modules)

There are 3 line card models for the 8400 Switch:

• Aruba 8400X 32-port 10GbE SFP/SFP+ Advanced Module (JL363A)
• Aruba 8400X 8-port 40GbE QSFP+ Advanced Module (JL365A)
• Aruba 8400X 6-port 40GbE/100GbE QSFP28 Advanced Module (JL366A)

These 3 models share the same ASIC and architecture, with extremely large packet buffers (1.5GB the first 2 and 3GB the 3rd.) and large tables.

Switch Fabric Modules

These modules are used interconnect line cards and transport traffic between them.

There is a single switch fabric model:

Aruba 8400X 7.2 Tbps Fabric Module (JL367A)

Three of them can be installed in the chassis. The recommended number of fabrics will depend on the number and type of line cards and number of used ports.

Forwarding Plane Architecture (from a macro point of view)

The 8400 chassis implements a mid-plane, direct plug, orthogonal architecture. In this design, line cards are placed vertically in the front slots of the chassis while the fabrics are placed horizontally in the back.

Line cards connect to fabrics via “orthogonal connectors”. These connections have the advantage of:

• Connecting directly without the need of an intermediate connector or trace on the mid plane
• Provide extremely high speed, up to 400 Gbps (in each direction), of which 300 Gbps are used today
• Reduce the amount of power required for data transmission between line cards and fabrics

In future 8400 Switch articles, we will describe:

• Management modules
• Other accessories (fan trays, power supplies, etc.)
• Forwarding architecture from a micro point of view, including Virtual Output Queues, multicast handling and more

Aruba 8400 Switch

Management modules

The Aruba 8400 switch has two slots for management modules to provide redundancy. The following module model performs the management and control tasks for the whole chassis: Aruba 8400 Management Module (JL368A).

The management module has been specifically designed to satisfy the demands of the new operating system’s architecture and features. For that purpose, it includes:

• An Intel Broadwell CPU
• 32 GB of DRAM
• 120 GB of storage in a Solid-State Drive

With this amount of processing power, the management module becomes an optimal platform not just for the traditional networking features but also to host the Network Analytics Engine (NAE) and allow NAE agents to monitor the state of different components (hardware and software) of the switch and store information on the internal storage. Also, multiple snapshots of the switch’s configuration state called checkpoints can be stored.

The management module has different paths to communicate with each component in the system:

• A low speed bus (LSB) to exchange control information with low complexity components like fans and temperature sensors
• A PCIe bus to exchange information with line cards, for example, to set the operational mode of the ASICs and maintain the forwarding, filtering and QOS tables
• Three orthogonal connectors to send and receive traffic across the fabrics and line cards, and communicate with other network devices like management stations and routing peers

Finally, both management modules are interconnected using the IEEE 10GbE standard for backplane 10GBASE-KR. This high performance connection allows for a real time state synchronization so the standby management module is always ready for a switch-over and even in the remote case of a fail-over.

Aruba 8400 Switch

Power system

The 8400 switch uses the Aruba X382 54VDC 2700W AC Power Supply (JL372A). Four of them can be installed in an 8400 chassis.

This PSU can connect to an AC power source either at 110V or 220V and provides up to 2700 Watts.

When connected to a 200-240V source, two power supplies are enough to provide energy to a fully loaded chassis, and a 3^rd and 4^th PSU would provide redundancy

When connected to a 110-120V source four PSUs are required to provide energy to a fully loaded chassis

ArubaOS-CX Architecture

The new operating system for the Aruba 8400 and 8320 switches has some special characteristics. The most important is its architecture.

In any legacy OS architecture each software module (or daemon) has and operates its own data and when it needs to interact with another module it makes a call to the other module requesting a piece of information or passing that information. That makes the daemons highly dependent on each other, for example, the development of the modules must be done in synch. Also, if, once the OS is running, a failure or exception in one module can force a reboot of the whole system. Finally, management interfaces are difficult to keep up to date.

In ArubaOS-CX all data, from all modules/daemons, is shared in a central “in-memory” database. That means that every module uses this data repository to ready and write the data used in its own processes. This data repository is called the Current State Database or CSDB. Compared to the legacy architecture, a DB centric OS can be developed faster, its modules are independent from each other, so the system is more resilient, and any management interface only needs to read from and write to the CSDB.

In this OS the configuration is just a “state” in the CSDB, and it can be managed in a simpler way (compared to the legacy “configuration file”).

Because ArubaOS-CX uses this CSDB, the REST API is a natural part of it instead of and add-on like in legacy systems.

In subsequent articles we will explore the CSDB and we will describe how the REST interface and the Network Analytic Engine use this architecture to enable the network administrator to automate operations, gain deeper and faster visibility, monitor in real time and trigger event-based information collection and much more.