WAN Optimization Concepts

Client/server architecture

Traffic across a WAN typically consists of clients on a client network communicating across a WAN with a remote server network. The clients do this by starting communication sessions from the client network to the server network. These communication sessions can be open text over the WAN or they can be encrypted by SSL VPN or IPsec VPN.

To optimize these sessions, you can add WAN optimization security policies to the client-side FortiGate unit to accept sessions from the client network that are destined for the server network. The client-side FortiGate unit is located between the client network and the WAN. WAN optimization security policies include WAN optimization profiles that control how the traffic is optimized.

The client-side FortiGate unit must also include the IP address of the server-side FortiGate unit in its WAN optimization peer configuration. The server-side FortiGate unit is located between the server network and the WAN, The peer configuration allows the client-side FortiGate unit to find the server-side FortiGate unit and attempt to establish a WAN optimization tunnel with it.

For the server-side FortiGate unit you must add a security policy with wanopt as the Incoming Interface. This security policy allows the FortiGate unit to accept WAN optimization sessions from the client-side FortiGate unit. For the server-side FortiGate unit to accept a WAN optimization connection it must have the client-side FortiGate unit in its WAN optimization peer configuration.

WAN optimization profiles are only added to the client-side WAN optimization security policy. The server-side FortiGate unit employs the WAN optimization settings set in the WAN optimization profile on the client-side FortiGate unit.

Client/server architecture

When both peers are identified the FortiGate units attempt to establish a WAN optimization tunnel between them. WAN optimization tunnels use port 7810. All optimized data flowing across the WAN between the clientside and server-side FortiGate units use this tunnel. WAN optimization tunnels can be encrypted use SSL encryption to keep the data in the tunnel secure.

WAN optimization peers

Any traffic can be sent through a WAN optimization tunnel. This includes SSL and IPsec VPN traffic. However, instead of configuring SSL or IPsec VPN for this communication you can add SSL encryption using the WAN optimization tunnel.

In addition to basic identification by peer host ID and IP address you can configure WAN optimization authentication using certificates and pre-shared keys to improve security. You can also configure FortiGate units involved in WAN optimization to accept connections from any identified peer or restrict connections to specific peers.

The FortiClient application can act in the same manner as a client-side FortiGate unit to optimize traffic between a computer running FortiClient and a FortiGate unit.

WAN optimization peers

The client-side and server-side FortiGate units are called WAN optimization peers because all of the FortiGate units in a WAN optimization network have the same peer relationship with each other. The client and server roles just relate to how a session is started. Any FortiGate unit configured for WAN optimization can be a client-side and a server-side FortiGate unit at the same time, depending on the direction of the traffic. Client-side FortiGate units initiate WAN optimization sessions and server-side FortiGate units respond to the session requests. Any FortiGate unit can simultaneously be a client-side FortiGate unit for some sessions and a server-side FortiGate unit for others.

WAN optimization peer and tunnel architecture

To identify all of the WAN optimization peers that a FortiGate unit can perform WAN optimization with, you add host IDs and IP addresses of all of the peers to the FortiGate unit configuration. The peer IP address is actually the IP address of the peer unit interface that communicates with the FortiGate unit.

Protocol optimization

Protocol optimization techniques optimize bandwidth use across the WAN. These techniques can improve the efficiency of communication across the WAN optimization tunnel by reducing the amount of traffic required by Protocol optimization and MAPI

communication protocols. You can apply protocol optimization to Common Internet File System (CIFS), FTP, HTTP, MAPI, and general TCP sessions. You can apply general TCP optimization to MAPI sessions.

For example, CIFS provides file access, record locking, read/write privileges, change notification, server name resolution, request batching, and server authentication. CIFS is a fairly “chatty” protocol, requiring many background transactions to successfully transfer a single file. This is usually not a problem across a LAN. However, across a WAN, latency and bandwidth reduction can slow down CIFS performance.

When you select the CIFS protocol in a WAN optimization profile, the FortiGate units at both ends of the WAN optimization tunnel use a number of techniques to reduce the number of background transactions that occur over the WAN for CIFS traffic.

If a policy accepts a range of different types of traffic, you can set Protocol to TCP to apply general optimization techniques to TCP traffic. However, applying this TCP optimization is not as effective as applying more protocolspecific optimization to specific types of traffic. TCP protocol optimization uses techniques such as TCP SACK support, TCP window scaling and window size adjustment, and TCP connection pooling to remove TCP bottlenecks.

Protocol optimization and MAPI

By default the MAPI service uses port number 135 for RPC port mapping and may use random ports for MAPI messages. The random ports are negotiated through sessions using port 135. The FortiOS DCE-RPC session helper learns these ports and opens pinholes for the messages. WAN optimization is also aware of these ports and attempts to apply protocol optimization to MAPI messages that use them. However, to configure protocol optimization for MAPI you should set the WAN optimization profile to a single port number (usually port 135). Specifying a range of ports may reduce performance.

Byte caching

Byte caching breaks large units of application data (for example, a file being downloaded from a web page) into small chunks of data, labeling each chunk of data with a hash of the chunk and storing those chunks and their hashes in a database. The database is stored on a WAN optimization storage device. Then, instead of sending the actual data over the WAN tunnel, the FortiGate unit sends the hashes. The FortiGate unit at the other end of the tunnel receives the hashes and compares them with the hashes in its local byte caching database. If any hashes match, that data does not have to be transmitted over the WAN optimization tunnel. The data for any hashes that does not match is transferred over the tunnel and added to that byte caching database. Then the unit of application data (the file being downloaded) is reassembled and sent to its destination.

The stored byte caches are not application specific. Byte caches from a file in an email can be used to optimize downloading that same file or a similar file from a web page.

The result is less data transmitted over the WAN. Initially, byte caching may reduce performance until a large enough byte caching database is built up.

To enable byte caching, you select Byte Caching in a WAN optimization profile.

Byte caching cannot determine whether or not a file is compressed (for example a zip file), and caches compressed and non-compressed versions of the same file separately.

WAN optimization transparent mode

Dynamic data chunking for byte caching

Dynamic data chunking can improve byte caching by improving detection of data chunks that are already cached in changed files or in data embedded in traffic using an unknown protocol. Dynamic data chunking is available for HTTP, CIFS and FTP.

Use the following command to enable dynamic data chunking for HTTP in the default WAN optimization profile.

config wanopt profile edit default config http set prefer-chunking dynamic

end

By default dynamic data chunking is disabled and prefer-chunking is set to fix.

WAN optimization transparent mode

WAN optimization is transparent to users. This means that with WAN optimization in place, clients connect to servers in the same way as they would without WAN optimization. However, servers receiving packets after WAN optimization “see” different source addresses depending on whether or not transparent mode is selected for WAN optimization. If transparent mode is selected, WAN optimization keeps the original source address of the packets, so servers appear to receive traffic directly from clients. Routing on the server network should be configured to route traffic with client source IP addresses from the server-side FortiGate unit to the server and back to the server-side FortiGate unit.

Some protocols, for example CIFS, may not function as expected if transparent mode is not selected. In most cases, for CIFS WAN optimization you should select transparent mode and make sure the server network can route traffic as described to support transparent mode.

If transparent mode is not selected, the source address of the packets received by servers is changed to the address of the server-side FortiGate unit interface that sends the packets to the servers. So servers appear to receive packets from the server-side FortiGate unit. Routing on the server network is simpler in this case because client addresses are not involved. All traffic appears to come from the server-side FortiGate unit and not from individual clients.

Do not confuse WAN optimization transparent mode with FortiGate transparent mode. WAN optimization transparent mode is similar to source NAT. FortiGate Transparent mode is a system setting that controls how the FortiGate unit (or a VDOM) processes traffic.

Configuring Transparent mode

You can configure transparent mode by selecting Transparent in a WAN Optimization profile. The profile is added to an active WAN Optimization policy.

FortiClient WAN optimization

When you configure a passive WAN Optimization policy you can accept the active policy transparent setting or you can override the active policy transparent setting. From the GUI you can do this by setting the Passive Option as follows:

• default use the transparent setting in the WAN Optimization profile added to the active policy (client-side configuration).
• transparent impose transparent mode (override the active policy transparent mode setting). Packets exiting the FortiGate keep their original source addresses.
• non-transparent impose non-transparent mode (override the active policy transparent mode setting). Packets exiting the FortiGate have their source address changed to the address of the server-side FortiGate unit interface that sends the packets to the servers.

From the CLI you can use the following command:

config firewall policy set wanopt-passive-opt {default | transparent | non-transparent}

end

FortiClient WAN optimization

PCs running the FortiClient application are client-side peers that initiate WAN optimization tunnels with serverside peer FortiGate units. However, you can have an ever-changing number of FortiClient peers with IP addresses that also change regularly. To avoid maintaining a list of such peers, you can instead configure WAN optimization to accept any peer and use authentication to identify FortiClient peers.

Together, the WAN optimization peers apply the WAN optimization features to optimize the traffic flow over the WAN between the clients and servers. WAN optimization reduces bandwidth requirements, increases throughput, reduces latency, offloads SSL encryption/decryption and improves privacy for traffic on the WAN.

For more details, see FortiClient WAN optimization on page 1.

Operating modes and VDOMs

To use WAN optimization, the FortiGate units can operate in either NAT/Route or Transparent mode. The clientside and server-side FortiGate units do not have to be operating in the same mode.

As well, the FortiGate units can be configured for multiple virtual domain (VDOM) operation. You configure WAN optimization for each VDOM and configure one or both of the units to operate with multiple VDOMs enabled.

If a FortiGate unit or VDOM is operating in Transparent mode with WAN optimization enabled, WAN optimization uses the management IP address as the peer IP address of the FortiGate unit instead of the address of an interface.

WAN optimization tunnels

All optimized traffic passes between the FortiGate units or between a FortiClient peer and a FortiGate unit over a WAN optimization tunnel. Traffic in the tunnel can be sent in plain text or encrypted using AES-128bit-CBC SSL.

WAN optimization tunnels

WAN optimization tunnels

Both plain text and the encrypted tunnels use TCP destination port 7810.

Before a tunnel can be started, the peers must be configured to authenticate with each other. Then, the clientside peer attempts to start a WAN optimization tunnel with the server-side peer. Once the peers authenticate with each other, they bring up the tunnel and WAN optimization communication over the tunnel starts. After a tunnel has been established, multiple WAN optimization sessions can start and stop between peers without restarting the tunnel.

Tunnel sharing

You can use the tunnel-sharing WAN optimization profile CLI keyword to configure tunnel sharing for WAN optimization rules. Tunnel sharing means multiple WAN optimization sessions share the same tunnel. Tunnel sharing can improve performance by reducing the number of WAN optimization tunnels between FortiGate units. Having fewer tunnels means less data to manage. Also, tunnel setup requires more than one exchange of information between the ends of the tunnel. Once the tunnel is set up, each new session that shares the tunnel avoids tunnel setup delays.

Tunnel sharing also uses bandwidth more efficiently by reducing the chances that small packets will be sent down the tunnel. Processing small packets reduces network throughput, so reducing the number of small packets improves performance. A shared tunnel can combine all the data from the sessions being processed by the tunnel and send the data together. For example, suppose a FortiGate unit is processing five WAN optimization sessions and each session has 100 bytes to send. If these sessions use a shared tunnel, WAN optimization combines the packets from all five sessions into one 500-byte packet. If each session uses its own private tunnel, five 100-byte packets will be sent instead. Each packet also requires a TCP ACK reply. The combined packet in the shared tunnel requires one TCP ACK packet. The separate packets in the private tunnels require five.

Use the following command to configure tunnel sharing for HTTP traffic in a WAN optimization profile.

config wanopt profile edit default config http set tunnel-sharing {express-shared | private | shared}

end

Tunnel sharing is not always recommended and may not always be the best practice. Aggressive and nonaggressive protocols should not share the same tunnel. An aggressive protocol can be defined as a protocol that is able to get more bandwidth than a non-aggressive protocol. (The aggressive protocols can “starve” the non-

aggressive protocols.) HTTP and FTP are considered aggressive protocols. If aggressive and non-aggressive protocols share the same tunnel, the aggressive protocols may take all of the available bandwidth. As a result, the performance of less aggressive protocols could be reduced. To avoid this problem, rules for HTTP and FTP traffic should have their own tunnel. To do this, set tunnel-sharing to private for WAN optimization rules that accept HTTP or FTP traffic.

It is also useful to set tunnel-sharing to express-shared for applications, such as Telnet, that are very interactive but not aggressive. Express sharing optimizes tunnel sharing for Telnet and other interactive applications where latency or delays would seriously affect the user’s experience with the protocol.

Set tunnel-sharing to shared for applications that are not aggressive and are not sensitive to latency or delays. WAN optimization rules set to sharing and express-shared can share the same tunnel.

WAN optimization and user and device identity policies, load balancing and traffic shaping

Please note the following about WAN optimization and firewall policies:

• WAN optimization is not compatible with firewall load balancing.
• WAN optimization is compatible with source and destination NAT options in firewall policies (including firewall virtual IPs). If a virtual IP is added to a policy the traffic that exits the WAN optimization tunnel has its destination address changed to the virtual IPs mapped to IP address and port.
• WAN optimization is compatible with user identity-based and device identity security policies. If a session is allowed after authentication or device identification the session can be optimized.

Traffic shaping

Traffic shaping works for WAN optimization traffic that is not in a WAN optimization tunnel. So traffic accepted by a WAN optimization security policy on a client-side FortiGate unit can be shaped on ingress. However, when the traffic enters the WAN optimization tunnel, traffic shaping is not applied.

In manual mode:

• Traffic shaping works as expected on the client-side FortiGate unit. l Traffic shaping cannot be applied to traffic on the server-side FortiGate unit.

In active-passive mode:

• Traffic shaping works as expected on the client-side FortiGate unit.
• If transparent mode is enabled in the WAN optimization profile, traffic shaping also works as expected on the server-side FortiGate unit. l If transparent mode is not enabled, traffic shaping works partially on the server-side FortiGate unit.

WAN optimization and HA

You can configure WAN optimization on a FortiGate HA cluster. The recommended best practice HA configuration for WAN optimization is active-passive mode. When the cluster is operating, all WAN optimization WAN optimization, web caching and memory usage

sessions are processed by the primary unit only. Even if the cluster is operating in active-active mode, HA does not load-balance WAN optimization sessions.

You can also form a WAN optimization tunnel between a cluster and a standalone FortiGate unit or between two clusters.

In a cluster, only the primary unit stores the byte cache database. This database is not synchronized to the subordinate units. So, after a failover, the new primary unit must rebuild its byte cache. Rebuilding the byte cache can happen relatively quickly because the new primary unit gets byte cache data from the other FortiGate unit that it is participating with in WAN optimization tunnels.

WAN optimization, web caching and memory usage

To accelerate and optimize disk access and to provide better throughput and less latency FortiOS WAN optimization uses provisioned memory to reduce disk I/O and increase disk I/O efficiency. In addition, WAN optimization requires a small amount of additional memory per session for comprehensive flow control logic and efficient traffic forwarding.

When WAN optimization is enabled you will see a reduction in available memory. The reduction increases when more WAN optimization sessions are being processed. If you are thinking of enabling WAN optimization on an operating FortiGate unit, make sure its memory usage is not maxed out during high traffic periods.

In addition to using the system dashboard to see the current memory usage you can use the get test wad 2 command to see how much memory is currently being used by WAN optimization. See “get test {wad | wccpd} <test_level>” for more information.

Manual (peer-to-peer) and active-passive WAN optimization

Inside FortiOS: WAN Optimization

Enterprises deploying FortiOS can leverage WAN optimization to provide fast and secure application responses between locations on a Wide Area Network (WAN). The web caching component of FortiOS WAN optimization extends this protection and performance boost to cloud services.

Centralize without compromising your WAN performance

Many multi-location enterprise environments reduce costs and consolidate resources by centralizing applications or providing applications in the cloud. Efficient and high-speed communication between applications and their users is critical. Remote sites don’t always have access to high bandwidth, but users at all sites expect consistent network performance. Minimizing user impact and improving performance is especially vital when applications designed for local area networks (LANs) are on the cloud.

Even applications that work fine on a local LAN, such as Windows File Sharing (CIFS), email exchange (MAPI), and many others, suffer from bandwidth limitations and latency issues when accessed over a WAN. This results in a loss of productivity and a perceived need for expensive network upgrades. FortiOS’s WAN Optimization provides an inexpensive and easy way to deploy a solution to this problem.

FortiOS is commonly deployed in central offices, satellite offices, and in the cloud to provide secure communications across a WAN using IPsec or SSL VPN. This installed infrastructure can be leveraged to add more value by using WAN Optimization to accelerate WAN traffic and web caching to accelerate could services.

FortiOS WAN Optimization

FortiOS includes license-free WAN Optimization on most current FortiGate devices. WAN Optimization is a comprehensive solution that maximizes your WAN performance and provides intelligent bandwith management and unmatched consolidated security performance. WAN Optimization reduces your network overhead and removes unneccessary traffic for a better overall performance experience. Efficient use of bandwidth and better application performance will remove the need for costly WAN link upgrades between data centers and other expensive solutions for your network traffic growth.

Protocol optimization

Protocol optimization is effective for applications designed for the LAN that do not function well on low bandwidth high latency networks. FortiOS protocol optimization improves the efficiency of CIFS, FTP, HTTP, MAPI, and general TCP sessions.

Inside FortiOS: WAN Optimization                                                                                                      Web caching

For example, CIFS, which is a fairly “chatty” protocol, requires many background transactions to successfully transfer a single file. When transferring the file, CIFS sends small chunks of data and waits sequentially for each chunk’s arrival and acknowledgment before sending the next. This large amount of request/acknowledgement traffic can delay transfers. FortiOS CIFS WAN Optimization removes this chatiness and gets on with the job of transferring the file.

TCP protocol optimization uses techniques such as SACK support, window scaling and window size adjustment, and connection pooling to remove common WAN TCP bottlenecks.

Web caching

In an enterprise environment, multiple users will often want to get the same content (for example, a sales spreadsheet, a corporate presentation or a PDF from a cloud service, or a software update). With FortiOS Web caching, content from the cloud, from the web or from other sites on the WAN is download once and cached on the local FortiGate device. When other uses access the same content they download it from the cache. The result is less bandwidth use and reduced latency for the file requester.

FortiOS web caching also recognizes requests for Windows or MS-Office updates and downloads the new update file in the background. Once downloaded to the cache, the new update file is available to all users and all subsequent requests for this update are rapidly downloaded from the cache.

Byte caching

Byte caching improves caching by accelerating the transfer of similar, but not identical content. Byte caching accelerates multiple downloads of different email messages with the same corporate disclaimer by downloading the disclaimer over the WAN once and then downloading all subsequent disclaimers from a local FortiGate unit. Byte caching reduces the amount of data crossing the WAN when multiple different emails with the same or similar attachments or different versions of an attachment are downloaded from a corporate email server to different locations over the WAN.

Server Monitoring and Management                                                                      Inside FortiOS: WAN Optimization

Dynamic data chunking

Dynamic data chunking detects and optimizes persistent data chunks in changed files or in data embedded in traffic that uses an unknown protocol. For example, dynamic chunking can cache data in Lotus notes traffic and make the data chunks available for email and other protocols.

Data Deduplication

Byte caching breaks large units of application data, like an email attachment or a file download, into manageable small chunks of data. Each chunk of data is labeled with a hash, and chunks with their respective hashes are stored in a database on the local FortiGate unit. When a remote user request a file, the WAN Optimization sends the hashes, rather than the actual data. The FortiGate unit at the other end of the WAN tunnel reassembles the data from its own hash database, only downloading chunks that it is missing. Deduplication, or the process of eliminating duplicate data, will reduce space consumption. In addition to reducing the amount of data downloaded across the WAN, byte caching is not application specific and assists by accelerating all of the protocols supported by WAN Optimization.

Server Monitoring and Management

The health and performance of real servers can be monitored from the FortiGate GUI. Virtual servers and their assigned real servers can be monitored for health status, if there have been any monitor events, number of active sessions, round trip time and number of bytes processed. Should a server become problematic and require

administration, it can be gracefully removed from the Real Server pool to enable disruption free maintenance. When a removed real server is able to operate it can gracefully be added back to the virtual server.

SSL acceleration

SSL is used by many organizations to keep WAN communications private. WAN Optimization boosts SSL acceleration properties of FortiGate FortiASIC hardware by accelerating SSL traffic across the WAN. The FortiGate unit handles SSL encryption/decryption for corporate servers providing SSL encrypted connections over the WAN.

VPN replacement

FortiOS WAN optimization supports secure SSL-encrypted tunnels between FortiGate units on the WAN. Employing secure WAN Optimization tunnels can replace IPsec VPNs between sites. The result is a single, relatively simple configuration that supports optimization and privacy of communication across the WAN and uses FortiGate SSL acceleration to provide high performance.

Inside FortiOS: WAN Optimization                                                                          Road warriors and home workers

Road warriors and home workers

The drive to give employees greater flexibility and reduce operational costs has led to more remote workers, both at home and on the road. Whether accessing the office from a hotel, public wireless hotspot, or home, the problem is the same: low bandwidth and high latency harming application performance. WAN Optimization is integrated into FortiClient, which can be installed on PCs and wireless devices to optimize communication between remote workers and their offices.

Reduce your…

• Capital outlay: Organizations only need to purchase a single device per location. l Licensing costs: WAN Optimization is included with FortiOS. Additional licenses are not needed.
• Network complexity: Small offices that may not have the space or power connections for multiple devices do not need to worry: no additional devices are required.

Client/server architecture

Example topologies relevant to WAN Optimization

FortiGate WAN optimization consists of a number of techniques that you can apply to improve the efficiency of communication across your WAN. These techniques include protocol optimization, byte caching, web caching, SSL offloading, and secure tunneling. Protocol optimization can improve the efficiency of traffic that uses the

CIFS, FTP, HTTP, or MAPI protocol, as well as general TCP traffic. Byte caching caches files and other data on

FortiGate units to reduce the amount of data transmitted across the WAN. Web caching stores web pages on FortiGate units to reduce latency and delays between the WAN and web servers. SSL offloading offloads SSL decryption and encryption from web servers onto FortiGate SSL acceleration hardware. Secure tunneling secures traffic as it crosses the WAN.

You can apply different combinations of these WAN optimization techniques to a single traffic stream depending on the traffic type. For example, you can apply byte caching and secure tunneling to any TCP traffic. For HTTP and HTTPS traffic, you can also apply protocol optimization and web caching.

You can configure a FortiGate unit to be an explicit web proxy server for both IPv4 and IPv6 traffic and an explicit FTP proxy server. Users on your internal network can browse the Internet through the explicit web proxy server or connect to FTP servers through the explicit FTP proxy server. You can also configure these proxies to protect access to web or FTP servers behind the FortiGate unit using a reverse proxy configuration.

Web caching can be applied to any HTTP or HTTPS traffic, this includes normal traffic accepted by a security policy, explicit web proxy traffic, and WAN optimization traffic.

You can also configure a FortiGate unit to operate as a Web Cache Communication Protocol (WCCP) client or server. WCCP provides the ability to offload web caching to one or more redundant web caching servers.

FortiGate units can also apply security profiles to traffic as part of a WAN optimization, explicit web proxy, explicit FTP proxy, web cache and WCCP configuration. Security policies that include any of these options can also include settings to apply all forms of security profiles supported by your FortiGate unit.

Basic WAN optimization topology

The basic FortiGate WAN optimization topology consists of two FortiGate units operating as WAN optimization peers intercepting and optimizing traffic crossing the WAN between the private networks.

Security device and WAN optimization topology

Out-of-path WAN Optimization topology

FortiGate units can be deployed as security devices that protect private networks connected to the WAN and also perform WAN optimization. In this configuration, the FortiGate units are configured as typical security devices for the private networks and are also configured for WAN optimization. The WAN optimization configuration intercepts traffic to be optimized as it passes through the FortiGate unit and uses a WAN optimization tunnel with another FortiGate unit to optimize the traffic that crosses the WAN.

You can also deploy WAN optimization on single-purpose FortiGate units that only perform WAN optimization. In the out of path WAN optimization topology shown below, FortiGate units are located on the WAN outside of the private networks. You can also install the WAN optimization FortiGate units behind the security devices on the private networks.

The WAN optimization configuration is the same for FortiGate units deployed as security devices and for singlepurpose WAN optimization FortiGate units. The only differences would result from the different network topologies.

Out-of-path WAN Optimization topology

In an out-of-path topology, one or both of the FortiGate units configured for WAN optimization are not directly in the main data path. Instead, the out-of-path FortiGate unit is connected to a device on the data path, and the device is configured to redirect sessions to be optimized to the out-of-path FortiGate unit.

Single-purpose WAN optimization topology

The following out-of-path FortiGate units are configured for WAN optimization and connected directly to FortiGate units in the data path. The FortiGate units in the data path use a method such as policy routing to redirect traffic to be optimized to the out-of-path FortiGate units. The out-of-path FortiGate units establish a WAN optimization tunnel between each other and optimize the redirected traffic.

Out-of-path WAN optimization

Topology for multiple networks

One of the benefits of out-of-path WAN optimization is that out-of-path FortiGate units only perform WAN optimization and do not have to process other traffic. An in-path FortiGate unit configured for WAN optimization also has to process other non-optimized traffic on the data path.

The out-of-path FortiGate units can operate in NAT/Route or Transparent mode.

Other out-of-path topologies are also possible. For example, you can install the out-of-path FortiGate units on the private networks instead of on the WAN. Also, the out-of-path FortiGate units can have one connection to the network instead of two. In a one-arm configuration such as this, security policies and routing have to be configured to send the WAN optimization tunnel out the same interface as the one that received the traffic.

Topology for multiple networks

As shown in below, you can create multiple WAN optimization configurations between many private networks. Whenever WAN optimization occurs, it is always between two FortiGate units, but you can configure any FortiGate unit to perform WAN optimization with any of the other FortiGate units that are part of your WAN.

WAN optimization among multiple networks

You can also configure WAN optimization between FortiGate units with different roles on the WAN. FortiGate units configured as security devices and for WAN optimization can perform WAN optimization as if they are single-purpose FortiGate units just configured for WAN optimization.

WAN optimization with web caching

WAN optimization with web caching

You can add web caching to a WAN optimization topology when users on a private network communicate with web servers located across the WAN on another private network.

WAN optimization with web caching topology

The topology above is the same as that shown in WAN optimization with web caching on page 214 with the addition of web caching to the FortiGate unit in front of the private network that includes the web servers. You can also add web caching to the FortiGate unit that is protecting the private network. In a similar way, you can add web caching to any WAN Optimization topology.

WAN optimization and web caching with FortiClient peers

FortiClient WAN optimization works with FortiGate WAN optimization to accelerate remote user access to the private networks behind FortiGate units. The FortiClient application requires a simple WAN optimization configuration to automatically detect if WAN optimization is enabled on the FortiGate unit. Once WAN optimization is enabled, the FortiClient application transparently makes use of the WAN optimization and web caching features available.

FortiClient WAN optimization topology

Explicit Web proxy topologies

You can configure a FortiGate unit to be an explicit web proxy server for Internet web browsing of IPv4 and IPv6 web traffic. To use the explicit web proxy, users must add the IP address of the FortiGate interface configured for the explicit web proxy to their web browser proxy configuration.

214

Explicit FTP proxy topologies

Explicit web proxy topology

If the FortiGate unit supports web caching, you can also add web caching to the security policy that accepts explicit web proxy sessions The FortiGate unit then caches Internet web pages on a hard disk to improve web browsing performance.

Explicit web proxy with web caching topology

Explicit FTP proxy topologies

You can configure a FortiGate unit to be an explicit FTP proxy server for FTP users. To use the explicit web proxy, FTP users must connect to and authenticate with the explicit FTP proxy before connecting to an FTP server.

Explicit FTP proxy topology

You can also configure reverse explicit FTP proxy. In this configuration, users on the Internet connect to the explicit web proxy before connecting to an FTP server installed behind a FortiGate unit.

Reverse explicit FTP proxy topology

Web caching topologies

Web caching topologies

FortiGate web caching can be added to any security policy and any HTTP or HTTPS traffic accepted by that security policy can be cached on the FortiGate unit hard disk. This includes WAN optimization and explicit web proxy traffic. The network topologies for these scenarios are very similar. They involved a FortiGate unit installed between users and web servers with web caching enabled.

A typical web-caching topology includes one FortiGate unit that acts as a web cache server. Web caching is enabled in a security policy and the FortiGate unit intercepts web page requests accepted by the security policy, requests web pages from the web servers, caches the web page contents, and returns the web page contents to the users. When the FortiGate unit intercepts subsequent requests for cached web pages, the FortiGate unit contacts the destination web server just to check for changes.

Web caching topology

You can also configure reverse proxy web-caching. In this configuration, users on the Internet browse to a web server installed behind a FortiGate unit. The FortiGate unit intercepts the web traffic (HTTP and HTTPS) and caches pages from the web server. Reverse proxy web caching on the FortiGate unit reduces the number of requests that the web server must handle, leaving it free to process new requests that it has not serviced before.

Reverse proxy web caching topology

WCCP topologies

You can operate a FortiGate unit as a Web Cache Communication Protocol (WCCP) router or cache engine. As a router, the FortiGate unit intercepts web browsing requests from client web browsers and forwards them to a WCCP cache engine. The cache engine returns the required cached content to the client web browser. If the cache server does not have the required content it accesses the content, caches it and returns the content to the client web browser.

WCCP topologies

WCCP topology

FortiGate units can also operate as WCCP cache servers, communicating with WCCP routers, caching web content and providing it to client web browsers as required.

WCCP is transparent to client web browsers. The web browsers do not have to be configured to use a web proxy.

Centralize without compromising your WAN performance                                        Inside FortiOS: WAN Optimization

Secure Web Gateway, WAN Optimization, Web Caching and WCCP

You can use FortiGate WAN optimization and web caching to improve performance and security of traffic passing between locations on your wide area network (WAN) or from the Internet to your web servers. You can also use the FortiGate unit as an explicit FTP and web proxy server. If your FortiGate unit supports web caching, you can also add web caching to any HTTP sessions including WAN optimization, explicit web proxy and other HTTP sessions.

the next sections of this document describes how FortiGate WAN optimization, web caching, explicit web proxy, explicit FTP proxy and WCCP work and also describes how to configure these features.

Before you begin

Before you begin to configure WAN optimization, Web caching, explicit proxies or WCCP, take a moment to note the following:

• To use WAN optimization and web caching, your FortiGate unit must support these features and not all do. In general your FortiGate unit must include a hard disk to support these features. See “FortiGate models that support WAN optimization” on page 209. Most FortiGate units support Explicit Web and FTP proxies.
• To be able to configure WAN optimization and web caching from the web manager you should begin by going to System > Feature Visibility and turning on WAN Opt. & Cache.
• To be able to configure the Web and FTP proxies from the web manager you should begin by going to System > Feature Visibility and turning on Explicit Proxy.
• If you enable virtual domains (VDOMs) on the FortiGate unit, WAN optimization, web caching, and the explicit web and FTP proxies are available separately for each VDOM.
• This guide is based on the assumption that you are a FortiGate administrator. It is not intended for others who may also use the FortiGate unit, such as FortiClient administrators or end users.
• FortiGate WAN optimization is proprietary to Fortinet. FortiGate WAN optimization is compatible only with

FortiClient WAN optimization, and will not work with other vendors’ WAN optimization or acceleration features.

• FortiGate web caching, explicit web and FTP proxies, and WCCP support known standards for these features. See the appropriate chapters of this document for details.

At this stage, the following installation and configuration conditions are assumed:

• For WAN optimization you have already successfully installed two or more FortiGate units at various locations across your WAN.
• For web caching, the explicit proxies and WCCP you have already successfully installed one or more FortiGate units on your network.
• You have administrative access to the web-based manager and/or CLI. l The FortiGate units are integrated into your WAN or other networks l The operation mode has been configured. l The system time, DNS settings, administrator password, and network interfaces have been configured. l Firmware, FortiGuard Antivirus and FortiGuard Antispam updates are completed.

Secure Web Gateway, WAN Optimization, Web Caching and

WCCP                                                                                             FortiGate models that support WAN optimization

• You Fortinet products have been registered. Register your Fortinet products at the Fortinet Technical Support web site, https://support.fortinet.com.

FortiGate models that support WAN optimization

WAN optimization is available on FortiGate models with internal storage that also support SSL acceleration.

Internal storage includes high-capacity internal hard disks, AMC hard disk modules, FortiGate Storage Modules (FSMs) or over 4 Gbytes of internal flash storage. All of these storage locations can provide similar web caching and byte caching performance. If you add more than one storage location (for example, by creating multiple partitions on a storage device, by using more than one FSM, or by using an FSM and AMC hard disk in the same FortiGate unit) you can configure different storage locations for web caching and byte caching.

Distributing WAN optimization, explicit proxy, and web caching to multiple CPU Cores

By default WAN optimization, explicit proxy and web caching is handled by half of the CPU cores in a FortiGate unit. For example, if your FortiGate unit has 4 CPU cores, by default two will be used for WAN optimization, explicit proxy and web caching. You can use the following command to change the number of CPU cores that are used.

config system global set wad-worker-count <number>

end

The value for <number> can be between 1 and the total number of CPU cores in your FortiGate unit. Adding more cores may enhance WAN optimization, explicit proxy and web caching performance and reduce the performance of other FortiGate systems.

Toggling Disk Usage for logging or wan-opt

Both logging and WAN Optimization use hard disk space to save data. In FortiOS, you cannot use the same hard disk for WAN Optimization and logging.

• If the FortiGate has one hard disk, then it can be used for either disk logging or WAN optimization, but not both. By default, the hard disk is used for disk logging.
• If the FortiGate has two hard disks, then one disk is always used for disk logging and the other disk is always used for WAN optimization.

On the FortiGate, go to System > Advanced > Disk Settings to switch between Local Log and WAN Optimization.

You can also change disk usage from the CLI using the following command:

configure system global set disk-usage {log | wanopt} end

You can configure WAN Optimization from the CLI or the GUI. To configure WAN Optimization from the GUI you must go to System > Feature Visibility and turn on WAN Optimization.

Enabling WAN Optimization affects more than just disk logging

In addition to affecting WAN Optimization, the following table shows other features affected by the FortiGate disk configuration.

Features affected by Disk Usage as per the number of internal hard disks on the FortiGate

Basic WAN optimization topology