This chapter provides an overview of common terms, new features, upgrade instructions, technical and environmental specifications, and a description of the status lights for the system.

This section provides information about product dependencies and compatibility.

This table summarizes the software requirements for the SteelHead.

To manage SteelHeads, you need to use an SCC of the same version. You cannot manage SteelHeads running a later version than the version the SCC is running. For details about SCC compatibility across versions, see the SteelCentral Controller for SteelHead Installation Guide.

We recommend that you deploy the SteelHead behind your firewall. These firewall settings are required for the SteelHead:

Secure transport requires communication on the management plane, control plane, and data plane. Consider the following port usage:

The causes for slow throughput in WANs are well known: high delay (round-trip time or latency), limited bandwidth, and chatty application protocols. Large enterprises spend a significant portion of their information technology budgets on storage and networks, much of it spent to compensate for slow throughput, by deploying redundant servers and storage, and the required backup equipment. SteelHeads enable you to consolidate and centralize key IT resources to save money, reduce capital expenditures, simplify key business processes, and improve productivity.

With the SteelHead, you can solve a range of problems affecting WANs and application performance, including:

The Riverbed Optimization System (RiOS) intercepts client-server connections without interfering with normal client-server interactions, file semantics, or protocols. All client requests are passed through to the server normally, while relevant traffic is optimized to improve performance.

RiOS uses these optimization techniques:

SteelHeads and Client Accelerator can reduce WAN bandwidth utilization by 65% to 98% for TCP-based applications using data streamlining. In addition to traditional techniques like data compression, RiOS also uses a Riverbed proprietary algorithm called scalable data referencing (SDR). SDR breaks up TCP data streams into unique data chunks that are stored in the hard disk (RiOS data store) of the device running RiOS (a SteelHead or Client Accelerator host system). Each data chunk is assigned a unique integer label (reference) before it’s sent to a peer RiOS device across the WAN. When the same byte sequence is seen again in future transmissions from clients or servers, the reference is sent across the WAN instead of the raw data chunk. The peer RiOS device uses this reference to find the original data chunk on its RiOS data store, and reconstruct the original TCP data stream.

SteelHeads use a generic latency optimization technique called transport streamlining. Transport streamlining uses a set of standards and proprietary techniques to optimize TCP traffic between SteelHeads. These techniques:

Application streamlining

In addition to data and transport streamlining optimizations, RiOS supports a rich set of application protocols that includes but is not limited to Microsoft Exchange, CIFS, SMB, SharePoint, HTTP/HTTPS, Lotus Notes, FCIP, SRDF, and SnapMirror.

These solutions maximize multiple WAN services based on business needs, service quality, and costs. Path selection redirects specific traffic or applications through one of three alternate paths determined by destination availability in cascading order. The path selection technology deterministically redirects select traffic and application flows through alternate networks based on service metrics, such as path availability, application priority, and policies you create.

Traffic classification

The SteelHead application flow engine, which covers more than 1,300 individual applications and processes, uses information to understand where data is coming from, which application sent it, and what function that application is trying to accomplish. The application flow engine utilizes a variety of techniques, often in combination, such as port-based classification, application signature matching, protocol dissection, behavioral classification, and others. Path selection classifies traffic using the full assortment of packet rules including IP addresses, 5-tuple, differentiated services code point (DSCP), TCP, user datagram protocol (UDP) port numbers, and so on. In this way, operators can instruct SteelHead solutions to precisely associate applications to networks based on their nature, performance requirements, and business criticality.

After the SteelHead has selected the right path, the next step is for it to steer traffic to the newly selected path. This operation is transparent to the client, server, and any networking devices such as routers or switches. RiOS forwards packets either directly using distinct SteelHead physical interfaces, or indirectly using (MAC) address rewriting. When these forwarding methods aren’t possible. For example, with virtual in-path deployments or where the SteelHead solution is not in the same Layer-2 domain, RiOS uses DSCP marking with upstream policy-based routing.

The SteelHead monitors end-to-end path availability and quality. You define the endpoint IP address for every path, and the SteelHead sends an Internet Control Message Protocol (ICMP) ping every two seconds. To validate availability, each path can have a different remote host.

If three consecutive pings are missed, the system considers the path to be unavailable, and selects the backup path. Every application has a default and a prioritized set of backup paths. Should the default path be unavailable, the higher-priority backup is instantly used (and then the lower one if needed). Operators can block certain types of applications when the primary path becomes unavailable, with a goal of reserving the remaining available bandwidth for more critical applications. As soon as the default path becomes available, traffic is routed back to it.

Management streamlining refers to the methods that Riverbed has developed to simplify the deployment and management of RiOS devices. These methods include:

For detailed information about how the SteelHead works and deployment design principles, see the SteelHead Deployment Guide.

You configure optimization of traffic using the Management Console or the Riverbed CLI. You configure the type of traffic a SteelHead optimizes and specify the type of action it performs using:

In-Path rules

In-path rules determine the action a SteelHead takes when a connection is initiated, usually by a client. In-path rules are used only when a connection is initiated. Because connections are usually initiated by clients, in-path rules are configured for the initiating, or client-side SteelHead. You configure one of these types of in-path rule actions:

Peering rules

Peering rules determine how a SteelHead reacts when it sees a probe query. Peering rules are an ordered list of fields a SteelHead uses to match with incoming SYN packet fields: for example, source or destination subnet, IP address, VLAN, or TCP port, as well as the IP address of the probing SteelHead. This is especially useful in complex networks. These types of peering rules are available:

For detailed information about in-path and peering rules and how to configure them, see the SteelHead User Guide.

All SteelHead models and in-path network interface cards support a fail-to-wire mode. In the event of a failure or loss of power, the SteelHead goes into bypass mode and the traffic passes through uninterrupted.

Many in-path network interface cards (NICs) also support a fail-to-block mode in which case if there’s a failure or loss of power, the SteelHead LAN and WAN interfaces power down and stop bridging traffic. The default failure mode is fail-to-wire mode.

If there’s a serious problem with the SteelHead or it’s not powered on, it goes into bypass mode to prevent a single point of failure. If the SteelHead is in bypass mode, you are notified in these ways:

When the fault is corrected, new connections receive optimization; however, connections made during the fault aren’t optimized. To force all connections to be optimized, enable the kickoff feature. Generally, connections are short-lived and kickoff is not necessary. For detailed information about enabling the kickoff feature, see the SteelHead User Guide and the SteelHead Deployment Guide.

When the SteelHead is in bypass mode the traffic passes through uninterrupted. Traffic that was optimized might be interrupted, depending on the behavior of the application-layer protocols. When connections are restored, they succeed, although without optimization.

In an out-of-path deployment, if the server-side SteelHead fails, the first connection from the client fails. After detecting that the SteelHead is not functioning, a ping channel is setup from the client-side SteelHead to the server-side SteelHead. Subsequent connections are passed through unoptimized. When the ping succeeds, processing is restored and subsequent connections are intercepted and optimized.

For detailed information about the ping command, see the Riverbed Command-Line Interface Reference Manual.

In fail-to-block mode, if the SteelHead has an internal software failure or power loss, the SteelHead LAN and WAN interfaces power down and stop bridging traffic.

When fail-to-block mode is enabled, a failed SteelHead blocks traffic along its path, forcing traffic to be rerouted onto other paths (where the remaining SteelHeads are deployed). This is only useful if the network has a routing or switching infrastructure that can automatically divert traffic off of the link once the failed SteelHead blocks it.

You set fail-to-block mode in the SteelHead CLI. For detailed information, see the SteelHead Deployment Guide.

This section provides information specific to upgrading and downgrading the SteelHead. For more general information and procedures, see Riverbed Software Licenses, Upgrades, and Image Signing.

RiOS is backward compatible with previous RiOS versions. However, to obtain the full benefits of the new features in the software, you must upgrade the client-side and server-side SteelHeads on any given WAN link. After you have upgraded all linked appliances, all the benefits of the features and enhancements are available.

The SteelHead uses image signing verification to ensure that software upgrades and downgrades are authentic Riverbed images.

Upgrading from RiOS 8.6 to 9.0 and later requires additional user permissions for path selection and QoS. For example, a user with QoS read/write permission in a previous version will no longer have permission to configure a QoS rule. In RiOS 9.0 and later, a user needs read/write permission for network settings in addition to read/write permission for QoS.

This table summarizes the changes to the user permission requirements for RiOS 9.0 and later.

Consider the following before upgrading RiOS:

To find allowed upgrades between RiOS versions and recommended upgrade paths, use the Software Upgrade tool on the Riverbed Support site at https://support.riverbed.com. The tool includes all of the recommended intermediate RiOS versions.