When client and server applications attempt to communicate with each other, the network intercepts and redirects this traffic to the WAEs so that they can act on behalf of the client application and the destination server.
The WAEs examine the traffic and use built-in application policies to determine whether to optimize the traffic or allow it to pass through your network unoptimized. Intelligent protocol adapters reduce the number of roundtrip responses common with chatty application protocols.
Data caching provided with the file services feature and data compression reduce the amount of data sent over the WAN, which increases data transfer rates. These solutions improve application response time on congested links by reducing the amount of data sent across the WAN. TCP optimization features improve network throughput by reducing the number of TCP errors sent over the WAN and maximizing the TCP window size that determines the amount of data that a client can receive at one time. The following steps describe how your WAAS network optimizes a connection between a branch office client and a destination server:.
A branch office client attempts to connect to the destination server over the native application port. The branch WAE performs the following actions:. The branch WAE passes along the client request through the network to its original destination server. The data center WAE performs the following actions:. If the data center WAE has optimization disabled, then an optimized connection will not be established and the traffic passes over the network unoptimized. Note If unoptimized traffic reaches a WAE, the WAE forwards the traffic in pass-through mode without affecting the performance of the application using the passed-through connection.
Cisco WAAS contains the following services that help optimize traffic over your wide area network:. TFO protects communicating clients and servers from negative WAN conditions, such as bandwidth constraints, packet loss, congestion, and retransmission. The receive window size determines the amount of space that the receiver has available for unacknowledged data. Windows scaling allows TCP endpoints to take advantage of available bandwidth in your network and not be limited to the default window size specified in the TCP header.
Increasing TCP's initial window size provides the following advantages:. With an initial window of at least two segments, the receiver generates an ACK response after the second data segment arrives, eliminating the wait on the timeout. This increased buffer helps the two WAEs participating in the connection keep the link between them full, increasing link utilization.
Selective Acknowledgement SACK is an efficient packet loss recovery and retransmission feature that allows clients to recover from packet losses more quickly than the default recovery mechanism used by TCP.
Deploying Cisco Wide Area Application Services (2nd Edition)
By default, TCP uses a cumulative acknowledgement scheme that forces the sender to either wait for a roundtrip to learn if any packets were not received by the recipient or to unnecessarily retransmit segments that may have been correctly received. SACK allows the receiver to inform the sender about all segments that have arrived successfully, so the sender only needs to retransmit the segments that have actually been lost.
When your network experiences a packet loss event, BIC TCP reduces the receiver's window size and sets that reduced size as the new value for the minimum window. BIC TCP then sets the maximum window size value to the size of the window just before the packet loss event occurred.
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Because packet loss occurred at the maximum window size, the network can transfer traffic without dropping packets whose size falls within the minimum and maximum window size values. If BIC TCP does not register a packet loss event at the updated maximum window size, that window size becomes the new minimum. If a packet loss event does occur, that window size becomes the new maximum. These compression technologies reduce the size of transmitted data by removing redundant information before sending the shortened data stream over the WAN.
By reducing the amount of transferred data, WAAS compression can reduce network utilization and application response times. When a WAE uses compression to optimize TCP traffic, it replaces repeated data in the stream with a much shorter reference, then sends the shortened data stream out across the WAN. The receiving WAE uses its local redundancy library to reconstruct the data stream before passing it along to the destination client or server. The WAAS compression scheme is based on a shared cache architecture where each WAE involved in compression and decompression shares the same redundancy library.
LZ compression operates on smaller data streams and keeps limited compression history. DRE operates on significantly larger streams typically tens to hundreds of bytes or more and maintains a much larger compression history. Large chunks of redundant data is common in file system operations when files are incrementally changed from one version to another or when certain elements are common to many files, such as file headers and logos.
Even though TFO optimizes traffic over a WAN, protocol messages between branch office clients and remote servers can still cause slow application response time. To resolve this issue, each WAAS device contains application proxies that can respond to messages locally so that the client does not have to wait for a response from the remote server.
The application proxies use a variety of techniques including caching, command batching, prediction, and resource prefetch to decrease the response time of remote applications. Cisco WAAS uses application-intelligent software modules to apply these acceleration features.
In a typical Common Internet File System CIFS application use case, the client sends a large number of synchronous requests that require the client to wait for a response before sending the next request. Compressing the data over the WAN is not sufficient for acceptable response time. If all these requests are sent over a ms round-trip WAN, the response time is at least 70 seconds x 0.
Each WAAS device uses application policies to match specific types of traffic to an application and to determine whether that application traffic should be optimized and accelerated. For more information, see the "File Services for Desktop Applications" section.
Secure NFS traffic is not accelerated. The SSL accelerator also provides secure management of the encryption certificates and keys. Microsoft Outlook clients are supported. The video accelerator automatically splits one source video stream from the WAN into multiple streams to serve multiple clients on the LAN. The Windows print accelerator supports Windows and Windows Server print servers. You must enable the accelerator on both of the peer WAEs at either end of a WAN link for all application accelerators to operate. By fulfilling the client's request locally, the WAE minimizes the traffic sent over the WAN and reduces the time it takes branch office users to access files and many desktop applications, allowing enterprises to consolidate their important information into data centers.
Note WAAS version 4. The new transparent mode requires no core, edge, or connectivity configuration. You configure the legacy mode the same as in WAAS version 4.
These two modes are mutually exclusive. We recommend using the new transparent mode if you have no need to interoperate with WAAS 4. This provides users with faster first-time file access, and makes more efficient use of available bandwidth. This service accelerates print traffic between clients and a Windows print server located in the data center.
This option requires no configuration but does require that the CIFS accelerator and Windows print acceleration be enabled. You can install a Windows print server in a virtual blade on the branch WAE, which allows you to manage printing by using standard Windows print server functionality.
All three of these services eliminate the need for a separate hardware print server in the branch office. The WAAS software allows you to configure a virtual blade, which allows you to add services running in their own operating environments to your WAAS system. You can install an operating system and applications to work with your WAAS system and provide additional services for the users on your network.
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The default administrator username is admin and the password is default. Ensure that your web browser is set to use Unicode UTF-8 character encoding. The number of concurrent sessions is unlimited by default. To change the number of permitted concurrent sessions, set the System. Note A user must log off the Central Manager to end a session.
If a user closes the browser or connection without logging off, the session is not closed until after it times out after minutes.
If the number of concurrent sessions permitted also is exceeded for that user, there is no way for that user to regain access to the Central Manager GUI until after the timeout expires. You can click the Devices link to return to the Manage Devices page. If you are managing a device group, this link is named Device Groups and it returns you to the Manage Device Groups page.
To switch to a different device, select the radio button next to the device and click the Switch button. If you are managing a device group, the name of this link is Switch DeviceGroup, and it allows you to switch to a different device group, just like for devices. Drawers may contain different functions when a particular device or device group is selected than when you are in the global context.
Allows you to go to the Dashboard and Alerts displays for your entire WAAS network and allows you to choose a specific device or device group for which to configure WAAS services and general settings. Management Requirements Checklist Security Requirements Checklist Link Aggregation Using EtherChannel Using the Standby Interface Feature Web Cache Communication Protocol Application Control Engine Egress Methods for Intercepted Connections Nonredundant Branch Office Redundant Branch Office Serial Clustering Large Nonredundant Branch Office Off-Path Redundant Topology Policy-Based Routing Interception Content Switching WCCP Scalability Application Control Engine Scalability Initial Setup Script and Device Setup Command-Line Interface Central Manager Overview Centralized Management System Service Device Activation Role-Based Access Control Integration with Centralized Authentication Device Configuration, Monitoring, and Management Status and Health Monitoring Software Upgrade and Downgrade Transport Flow Optimization Data Redundancy Elimination Persistent LZ Compression Automatic Discovery Enabling and Disabling Features TFO Blacklist Operation Tuning TFO Buffers Application Groups Traffic Classifiers Negotiating Policies Skip to navigation Press Enter.
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