The Extreme Networks Solution for Apple Bonjour Traffic Management A SOLUTION WHITE PAPER

Transcription

1 The Extreme s Solution for Apple Bonjour Traffic Management A SOLUTION WHITE PAPER

2 WHITE PAPER The Extreme s Solution for Apple Bonjour Traffic Management Introduction to Apple Bonjour TABLE OF CONTENTS Introduction to Apple Bonjour 2 Challenges with Apple Bonjour 3 in the enterprise The Extreme s solution 4 The BYOD (Bring Your Own Device) movement has introduced an explosive proliferation of smart devices into the enterprise environment. With the recent release and popularity of the iphone 5 and mini ipads, it is expected that the growth of Apple products will accelerate in the enterprise. Many companies and institutions that five years ago had no Apple products at all, or at best a few Macs for specialized uses, have now accepted iphones and ipads as standard mobile devices, with hundreds, thousands, or even tens of thousands of these devices active on their networks. These consumer devices have enabled employees to become more mobile and productive. Unlike other BYOD devices, Apple products connect and access networks by a mechanism called Bonjour. Apple s Bonjour is a zero configuration network (Zeroconf) multicast Domain Naming System (mdns) protocol used by Apple devices to enable the automatic and easy discovery of computers, devices, and services on IP networks. Bonjour (like other multicast services like Avahi and Microsoft s UPnP) uses industry standard IP protocols to allow devices to automatically discover each other without the need to enter IP addresses or configure DNS servers. The elegance of this approach is that it brings simplicity and ease-of-use to the users of network devices and services. Eliminating the need to set up services such as Dynamic Host Configuration Protocol, DNS, and DNS Service Directory, Bonjour enables each device to continuously publish and discover services. By broadcasting Bonjour service messages, printers, servers, and other shared devices can advertise the services they offer. Client devices then monitor Bonjour advertisements and connect to the appropriate servers, as wit h any other service. The protocol also allows for a device to request services (Service Discovery) on the network as well as respond to incoming requests, which in some cases means a single device can be both a client and a server at the same time. The automatic discovery makes it easy for clients like ipads and Macbooks to easily use a printer using AirPrint or mirror a display to a projector using AirPlay The Extreme s Solution for Apple Bonjour Traffic Management White Paper 2

3 ipad ipad Self-assigned address, name resolution and service publication Self-assigned address, name resolution and service publication 1. Address selection Is Available? Self-assign No response 2. Names selection Self-assign appletv.local Is appletv.local Available? No response 3. Service startup Start up service on port Service Annoucement Register SRV record AppleTV_movies._top_local. appletv_local.local:1010 [not yet notified] Now available [sees service] AppleTV.movies._top.local Query by service type Response CHALLENGES WITH APPLE BONJOUR IN THE ENTERPRISE Service Discovery Any services of type _movies_tcp in the domain local? AppleTV_movies._tcp.local. EXISTING GATEWAY SOLUTIONS FOR BONJOUR DO NOT SOLVE THE PROBLEM As a result of these challenges, a few vendors have announced Bonjour Gateways (GWs) to address these issues. This approach is typically a software-based solution where the gateway participates in multiple VLANs. As a member of all the VLANs, it can then forward traffic from one VLAN to another. This means all Bonjour traffic (request or advertisement), are replicated to all VLANs. The problem is that if you have a large number of devices, the amount of multicast traffic becomes excessive (more noise ) and consumes critical bandwidth that will impact application performance. This will potentially cripple the network and impact user experience. In fact, Apple recently acknowledged that Bonjour proxy/gateway vendors that include Xirrus, Aruba, Cisco, Aerohive and Ruckus - are making the multicast flooding problem worse. On the downside, Bonjour generates a lot of chatty traffic or noise on the network. During the Service Discovery process, when a device is browsing for services, it sends queries such as Any services of type X in the domain? It issues an initial query and then sends subsequent queries exponentially less often, after 1 second, 2 seconds, 4 seconds, 8 seconds, and so on, at up to a maximum interval of one hour. Likewise, when a service starts up on the network, it announces its presence with the same exponential back-off algorithm. With iphones, ipads and other Apple devices often going to sleep and then being woken up, this process is often repeated several times a day. While this is not an issue in a small home network because of a relatively few number of devices, in an enterprise network the amount of such traffic can be substantial. With hundreds or thousands of Apple clients on a network, multicast traffic quickly swells to startling percentages (some universities report instances where this discovery traffic amounts to 90% of the network s load). The Extreme s Solution for Apple Bonjour Traffic Management White Paper 3

4 Extreme s believes a GW-based solution is not a practical way to solve the noisy traffic or VLAN crossover problem for Bonjour messages, for the following reasons: A gateway creates a bottleneck (since all the traffic is going through one GW server) and also poses a single point of failure risk Gateways multiply the amount of traffic as they replicate it to other VLAN subnets, so they make the noisy traffic problem worse. Gateway solutions are not location aware, which can cause problems such as the inability to perform digital rights management (DRM) of content announced through multicast discovery services. Gateway solutions are protocol dependent today they support mdns/bonjour what if an enterprise has devices that generate mdns/bonjour and Microsoft s UPnP? What if new protocols arise? Even gateways that claim support for smart filtering by replicating only selective traffic (based on higher protocol information) will not scale. This is because a softwarebased solution means network traffic must go through the server and move all the way up the stack to reach the application layer for filtering. This is inefficient and leads to higher latency. THE EXTREME NETWORKS SOLUTION The Extreme s solution is not gateway based but rather policy-based, with intelligent rules implemented at the wireless access points and switches. This solution addresses and manages more than just the Bonjour service - it s a solution that efficiently handles all multicast discovery services, including Bonjour, by using our Mobile IAM and the distributed intelligence in our switches, allowing for the provisioning and enforcement of dynamic policies. Specifically, we address the following issues: 1. To manage inter-vlan communication, we do the following: We build a bonjour VLAN to contain all bonjour traffic within just one VLAN (not replicated on all VLANs) so that all devices that require the service will see it. For example, instead of copying one packet to three different VLANs where clients may need the bonjour service, we copy one packet to a VLAN and make that VLAN available to all devices that need it. This is possible by distributing the intelligence (filtering and traffic classification capabilities) to all ports in the traffic path of these messages through Extreme s Coreflow Switching technology. Policy-enabled networks and Mobile IAM provides a very flexible and intelligent way of managing Bonjour services several attributes including device, user, software and location can be used in the policy. For example you may not want someone in the US streaming a movie to a location in China. The Extreme s Solution for Apple Bonjour Traffic Management White Paper 4

5 2. To manage the heavy bonjour traffic, we can do one or both of the following: Filter bonjour multicast traffic at the Wireless Controller, essentially turning off broadcast traffic Control device access by selectively blocking/allowing or rate-limiting traffic based on various rules using localized policy, regardless of which VLANs the devices are in. In summary, we believe the best approach to solving the Bonjour issues described in this paper is not by using a gateway, because of the performance issues described above. Instead, we believe it should be done by using local policy to contain the bonjour traffic in one or multiple domains based on users roles, devices as well as their locations, regardless of the number of VLANs. This solution minimizes any performance or bandwidth issues while providing the flexibility of allowing users access to only the services they require! Compare this policy-based approach, as shown in the figure below, to the gateway-based solution as shown in Competitive Bonjour Gateways at Scale in the figure on the previous page. Phone Extreme s, Inc. All rights reserved. Extreme s and the Extreme s logo are trademarks or registered trademarks of Extreme s, Inc. in the United States and/or other countries. All other names and trademarks are the property and trademarks of their respective owners. For additional information on Extreme s Trademarks please see Specifications and product availability are subject to change without notice The Extreme s Solution for Apple Bonjour Traffic Management White Paper 5