LOAD BALANCING WHITE PAPER OPTIONS FOR HANDLING MULTIPLE ISP LINES AT HOTELS

Transcription

1 LOAD BALANCING WHITE PAPER OPTIONS FOR HANDLING MULTIPLE ISP LINES AT HOTELS Agoura Road, Suite 102 Agoura Hills, CA Main Sales

2 CONTENTS 1 RELATED DOCUMENTS 3 2 GLOSSARY OF TERMS 3 3 PURPOSE 3 4 BACKGROUND Definitions and Concepts Load Balancing Link Aggregation Channel Bonding Link Failover Combined Load Balancing and Link Failover ISP Link Selection Criteria User-Based ISP Selection versus Random ISP Selection Traffic Type-Based ISP Selection Additional Concepts Regarding ISP Link Selection Link Availability Detection Method and Time Traffic Balancing and Weighting Load Rebalancing upon Link Recovery 6 5 HOTEL REQUIREMENTS AND TYPICAL USE CASES Examples of Typical Common Deployment Scenarios Load Balancing Across Multiple Low-Speed Links Failover to Standby ISP Link Separate Guest HSIA and Admin ISP Links with Failover Between Each ISP Link Guest HSIA Failover Only, to Admin Network Sharing of Guest HSIA Network and Hotel Admin Network Among Multiple ISP Links Load Balancing with Users Connected to a Preferred ISP Link 11 6 SUMMARY AND CONCLUSIONS Nomadix, Inc. All rights reserved. 2

3 1. RELATED DOCUMENTS Load Balancing Data Sheet 2. GLOSSARY OF TERMS The following table describes commonly used terms throughout the document. TERM DSL ISP HSIA WAN NSE DESCRIPTION Digital Subscriber Line Internet Service Provider High-Speed Internet Access Wide Area Network Nomadix Service Engine 3. PURPOSE The availability of fast and high-quality HSIA is now a must for all hotels using multiple ISP/WAN sources, which, in many cases, now make the use of ISP load-balancing and/or failover features a necessary requirement. The purpose of this document is to outline various options and solutions for properties handling multiple ISP connections for the provision of HSIA and/or back-office IT requirements. Options may include the installation of third-party load balancing appliances from vendors such as Elfiq or Peplink, or the use of the load-balancing features available in Nomadix NSE release 8.2 which is scheduled for general availability in June Nomadix, Inc. All rights reserved. 3

4 4. BACKGROUND 4.1 DEFINITIONS AND CONCEPTS Load Balancing Load balancing refers to the general process of balancing user traffic across multiple ISP connections. The Nomadix NSE supports load balancing Link Aggregation Link aggregation refers to the process of linking multiple ISP connections to an appliance and having the sum of the ISP bandwidth shared among all users. However, one individual connection is limited to the speed of the ISP connection that is currently being used. For example, a hotel may aggregate 5 x 1.5Mbps DSL connections together. This means that a total of 7.5Mbps of bandwidth is available to be shared by all users, but a single user can receive a maximum of 1.5Mbps. The Nomadix NSE supports link aggregation. In most cases link aggregation and load balancing are effectively the same thing Channel Bonding Channel bonding is a process whereby a single high-speed link is provided by bonding multiple low-speed circuits together at the property. This process has been used extensively in the past where legacy telephony type circuits such as T1 (1.5Mbps) or E1 (2mbps) are the only local loop options available for an ISP to bring a high-speed connection into a property. The ISP uses special functions in the router installed at the property to bond the multiple slow-speed lines together into a single high-speed service. Some appliances support channel bonding. Nomadix does not. Usually where channel bonding is used, it must be integrated with the ISP-owned switch Link Failover Link failover (sometimes referred to ISP redundancy) is the process of providing a second (or occasionally more) ISP link as a backup to the primary ISP link. In the event that the primary link fails, all traffic is rerouted to the backup link, until the primary link again becomes available. All load-balancing appliances, as well as the Nomadix NSE and NITO, support link failover. The most effective use of link failover is to ensure that ISP/WAN links fail independently Combined Load Balancing and Link Failover This is the process where both load balancing and link failover are combined together. It represents the best of both worlds. Where multiple ISP links are used in load balancing mode, when one or more links fail, all traffic is automatically rerouted to the remaining surviving links. When the failed links recover, new connections are routed toward these until the normal balanced configuration is reached. Most third-party load balancers, as well as the Nomadix NSE and Nomadix NSE, support combined mode ISP Link Selection Criteria In a load-balancing scenario, some criteria must be used to decide which ISP is selected for outgoing traffic. A number of factors influence this decision, including: 2013 Nomadix, Inc. All rights reserved. 4

5 Identity of the users: Is a random ISP section used or is it desirable to have certain users steered towards a particular ISP? For random ISP: Should subscriber, destination address or session-based link selection be used? User-Based ISP Selection versus Random ISP Selection User-based ISP selection is the process whereby the ISP link that is selected in a load-balanced environment is based on the identity of the user. For example, all users from guest rooms may be steered towards one ISP link, and all meeting-room users steered towards another ISP link only used for meetings and conferences. The alternative is to use random ISP selection, whereby the load balancer or NSE selects the ISP to be used according to the current load conditions. The Nomadix NSE uses random ISP selection by default. Using Radius VSA, the NSE supports the assigning of specific users to specific ISPs Traffic Type-Based ISP Selection Traffic-type based ISP selection refers to the process whereby the selection of ISP is based on the type of traffic being sent (usually defined by TCP or UDP port numbers) rather than the identity of the source user itself. For example, a load balancer may be set up so that all HTTP (TCP port 80) traffic is sent out through one link, and everything else is sent through the other link. Some third-party load balancers support this functionality; Nomadix does not Additional Concepts Regarding ISP Link Selection Load balancing generally requires the use of Network Address and Port Translation (NAPT), whereby multiple subscribers using unique, private IP addresses are translated to one (or sometimes a few) public IP addresses provided by the ISP. Where multiple ISP links are available, the load balancer or ISP must choose which ISP link (and associated public IP) to perform the NAPT translation to in accordance with the desired load and current traffic conditions. Every traffic session from a user (i.e. source to destination IP address pair) requires an individual NAPT session creation. The selection of ISP links for each NAPT session can be based on three broad criteria: 1. NAPT sessions from the same source IP (i.e. user) always use the same ISP link. 2. NAPT sessions from the same source IP (and to the same destination IP) use the same ISP link. 3. NAPT sessions from the same source IP can use any ISP link. If there is a large number of different source IP addresses, then statistically each method will load balance equally as well. When there are only a few (or just one) source IP addresses, which can be the case when a gateway is connected to a third-party load balancer, then only options two or three will provide effective load balancing. However using options two and three can in some instances interrupts the normal operation of some applications, including legacy VPNs and some specialized applications such as video conferencing, which use multiple TCP and/or UDP sessions that must appear to the far end as originating from the same source address. Most third-party load balancers allow the use of options one, two and three. The Nomadix NSE, which has complete visibility of the many subscriber source IP addresses, only uses option one Nomadix, Inc. All rights reserved. 5

6 Link-Availability Detection Method and Time Load balancing and failover requires some form of monitoring of each ISP link to determine the availability for executing load-balancing and failover decisions. Generally, link monitoring is accomplished by two different methods: 1. Periodic probing of predefined hosts using HTTP or ICMP ping requests. 2. Periodic DNS queries to the DNS servers provided by each ISP. Some third-party load balancers provide only option one. The Nomadix NSE can be configured to use either method. In general, option two is simpler to configure and provides a more complete link test (an ISP with broken DNS is useless). The period between successive link tests is usually configured, and is typically set to between 30 seconds and 60 seconds. This represents the maximum time for which a user will remain connected to a failed ISP connection before being rerouted to a working ISP link in an ISP-failure scenario Traffic Balancing and Weighting Load balancers have some form of weighting of traffic between links to achieve a desired balance scenario. With the Nomadix NSE, traffic is balanced by individual subscriber numbers and weighted according to the speed of the ISP connected to each port. For example, if an NSE has two 10M links connected and currently has 100 active subscribers, then 50 users would be connected to each link. If the ISP links were 10 Mbps and 40Mbps, then 20 users would be connected to the 10M link, and 80 users to the 40M link. Some third-party load balancers provide more advanced (and complex to configure) balancing and weighting tools Load Rebalancing upon Link Recovery Load balancing and failover with well-configured link-availability detection provide fast and effective recovery from ISP link-failure occurrences. Additional consideration must be taken as to what actions to implement when a failed ISP link recovers. In general, these actions can include: 1. Do nothing and wait for normal coming and going of subscribers to achieve the desired balance. 2. Execute a hard rebalancing of ISP links. 3. Execute graceful rebalancing of ISP links. With option one, when a broken ISP link is restored, no explicit action to be taken to restore the desired balance of subscribers to ISP links. However, as subscribers time out and new subscribers appear, the desired balance will be restored. With a relatively short idle timeout, this should normally occur within a few hours. With option two, when a link is restored, the load balancer will immediately reallocate users to different ISP links to achieve the desired balance condition, including active TCP and UDP sessions. This may have the effect of breaking existing sessions, as their current NAPT sessions will be torn down and new external source IP address used. This may cause a one- to two-second traffic interruption, which will not be noticed in most cases. However, some SSL or VPN connections may be interrupted. With option three, an immediate rebalance is attempted, but any active TCP or UDP sessions are left intact until they time out naturally. Until such timeouts occur, some subscribers may wind up with different sessions being NATed to different ISP links and, therefore, different IP addresses. Currently the Nomadix NSE supports only option one and two, and option three is planned for future releases Nomadix, Inc. All rights reserved. 6

7 5. HOTEL REQUIREMENTS AND TYPICAL USE CASES Before choosing and implementing a load-balancing and/or failover solution, it is important to understand and define the requirements of the property. These may differ depending on local ISP conditions, ISP costs, and individual chain and property requirements. Factors to be considered include but are not limited to: 1. Is load balancing or just ISP failover required? 2. Is aggregation of multiple low-speed links required? 3. How reliable are different local ISP services? 4. What are the relative costs of different ISP services? 5. Do ISP links need to be shared between guests and back-office users? 6. Is there a requirement to have certain users connected to a particular ISP? 1. Is Load Balancing or Just ISP Failover Required? In issue one, it may be a requirement to provide just a backup service to the primary ISP service in the case that the main HSIA ISP fails. The backup service may be on a pay-to-use basis through a 3G or 4G wireless modem, or be a low-cost lower-tier service (such as a cable modem service) that is only used when the main ISP link is down, on the basis that providing a reduced HSIA service is better than no service at all. Alternatively, the hotel may have multiple ISP links and may want to be able to fully utilize all of them under normal conditions. The Nomadix NSE supports both failover only and combined load balancing with failover. 2. Is Aggregation of Multiple Low-Speed Links Required? With issue two, in some instances, suitable high-speed internet services required to meet the aggregate needs of the hotel may not be available or are simply too expensive. In this case it may be desirable to aggregate multiple lower-cost lower-speed lines together. The Nomadix AG2400 and AG5600 can aggregate services from up to three ISP links, and the AG5800 can handle up to five links. 3. How Reliable are Different Local ISP Services? With issue three, it is important to consider the relative quality of each ISP link. If a second link is much lower quality than the main ISP link, then it should only be used as a backup link in failover mode (and not in a load-balanced environment). If the link quality is the same, then load balancing with failover should be used. 4. What are the Relative Costs of Different ISP Services? With issue four, it is important to consider the relative cost of links. If all links have a fixed monthly charge, then ideally they should be used in a load-balanced mode so that costly links are not sitting unused. If an ISP link has a relatively low monthly charge with high per-megabyte data usage charges, then it should only be used in failover mode as a backup to a main ISP link Nomadix, Inc. All rights reserved. 7

8 5. Do ISP Links Need to be Shared Between Guests and Back-Office Users? With issue five, it may be requirement to share ISP bandwidth between guest HSIA and hotel admin networks, or to have each network available as a fallback network for the other. Both scenarios can be handled with the Nomadix NSE. See examples and below. 6. Is it Required to Have Certain Users Connected to a Particular ISP? With issue six, it may be desirable to have certain users connected to particular ISP links. (See example below) With the use of a preferred WAN radius attribute, above gateway management systems accomplish the task. For example, paying users may be connected to an expensive high-quality link and free users connected to a lower-quality link, with link failover still available if the preferred link fails. 5.1 SOME EXAMPLES OF TYPICAL COMMON DEPLOYMENT SCENARIOS ARE OUTLINED BELOW Load Balancing Across Multiple Low-Speed Links In the example below, a hotel has access to only low-speed DSL-based ISP circuits, and wishes to aggregate five such links together. The Nomadix NSE is configured with load balancing between all links. 5 x ISP circuit to be shared equally amongst all subscribers ISP 1 ISP 2 ISP 3 ISP 4 ISP 5 Guest HSIA Network 2013 Nomadix, Inc. All rights reserved. 8

9 5.1.2 Failover to Standby ISP Link In this example, the hotel has a high-quality 100M Ethernet service. But to guarantee continuous HSIA service, the hotel has a backup ISP service from a low-cost wireless provider, which charges on a data-volume basis. The hotel only wants to use this link when the main ISP circuit is not available. The Nomadix NSE is configured for failover only from the WAN to port Eth2 on the NSE. Main ISP Circuit ISP 1 100Mbps Ethernet Back Up ISP Circuit ISP 2 20Mbps Wireless Separate Guest HSIA and Admin ISP Links, with Failover Between Each ISP Link Guest HSIA Network In this scenario, the hotel has separate HSIA and hotel admin ISP circuits. Under normal circumstances, guests will be connected to the guest HSIA ISP, and hotel admin users will connect to the admin ISP. If either link fails, then failover to the other link will occur. If the guest HSIA link fails, the guests will be connected to the admin ISP link until the guest HSIA link is restored. If the admin ISP link fails, the admin users will be connected to the guest HSIA link until the admin ISP is restored. The Nomadix NSE is configured with load balancing and failover. All guests use ISP 1 as the preferred WAN, and the admin network router uses ISP2 as the preferred WAN. Main ISP Circuit for HSIA (Back up for Hotel Admin) Main ISP circuit for Hotel Admin Network (Back up for Guest HSIA) ISP 1 100Mbps Ethernet ISP 2 20Mbps Ethernet Freedom Internet HSIA Subscriber Network Hotel Admin Network 2013 Nomadix, Inc. All rights reserved. 9

10 5.1.4 Guest HSIA Failover Only, to Admin Network In this scenario, the hotel has separate ISP circuits for the guest HSIA network and hotel admin network. The hotel wants the admin network to be available as a backup link in case the guest HSIA ISP link fails. There is no backup for the admin ISP network. ISP Circuit for Guest HSIA ISP 1 100Mbps Ethernet ISP circuit for Hotel Admin Network (Back up for Guest HSIA) ISP 2 20Mbps Ethernet The Nomadix NSE is configured with link failover between the WAN port and port ETH2, which is connected to the hotel admin network router. HSIA Subscriber Network Hotel Admin Network Sharing of Guest HSIA Network and Hotel Admin Network Among Multiple ISP Links In this scenario, multiple ISP links are connected to the Nomadix NSE in a similar method to option 5.1, but both the guest HSIA network and the hotel admin network are connected to the NSE and share the aggregate bandwidth of the combined ISP links. ISP 1 5 x ISP circuit to be shared equally amongst all subscribers ISP 2 ISP 3 ISP 4 ISP 5 The Nomadix NSE is configured for load balancing, and the back office router s MAC address is registered as a device in the NSE with an appropriate bandwidth limit. Guest HSIA Network Hotel Admin Network 2013 Nomadix, Inc. All rights reserved. 10

11 5.1.6 Load Balancing with Users Connected to a Preferred ISP Link In this scenario, the hotel has purchased 2 x ISP links for guest HSIA. One is a high-quality, high-cost business grade ISP circuit, and the other is a low-cost, lower-grade domestic service provided by the local cable TV operator. The hotel has a number of bill plan options including free-to-use and pay-to-use premium plans. Under normal circumstances, the hotel wants guests who have selected a free plan to use the low-cost link, and guests who have selected a premium service to use the higher-cost business-grade ISP connection. If either link fails, guests should failover to the other link until the preferred link is restored. The Nomadix NSE is configured with load balancing. High Quality Business Grade ISP for Premium Users Lower Quality ISP for Free to Use users ISP 1 100Mbps Ethernet ISP 2 20Mbps Wireless Guest HSIA Network Premium Users FTU Users 2013 Nomadix, Inc. All rights reserved. 11

12 6. SUMMARY AND CONCLUSIONS With the need for very high-availability guest HSIA, the installation and monitoring of multiple ISP links at a hotel has become an important requirement for many hotels. The use of third-party load balancers has proven to be an effective solution in the past. However, with the release of Nomadix NSE 8.2 software, the integrated load balancing and failover features available natively to the NSE now eliminate the need for the installation of a third-party appliance in most cases. The advantages of the Nomadix solution include: Lower cost: The cost of the load-balancing license in the Nomadix NSE is much lower than the cost of a third-party load balancer appliance, so the hotel will save money. Increased reliability: With the elimination of one more network appliance in the data path of the guest HSIA network, overall systems reliability is improved. Easy configuration: Third-party load balancers can be complex to configure, and the configuration of the load balancer needs to match the gateway. The Nomadix load balancing and failover features have been designed to be easy to understand, configure and monitor. Configuring and testing an additional ISP link takes just a few minutes. Continuity of Nomadix plug and play features such as INAT: When using a third-party load balancer, some Nomadix gateway features ensure trouble-free guest connectivity (such as INAT for VPN use) will not operate correctly. When using the Nomadix load-balancing feature, these other features keep working normally Nomadix, Inc. All rights reserved. 12