Bring Your Own Device (BYOD) is now common in enterprises, especially in vertical industries like education and healthcare. So service discovery―the ability to automatically detect devices and services on networks and to set policies to safeguard networks―has become vital.
There are many service-discovery protocols and techniques available that have been used for various use cases. Bonjour uses Multicast Domain Name System (mDNS) as its underlying mechanism to discover the services nearby. Apple developed Bonjour in 2002 to replace AppleTalk. Due to its open standards design and wide adoption, Bonjour/mDNS was integrated with Microsoft Windows 10, Google Android devices, and with Cisco Webex, making it a de facto standard.
Bonjour was designed for use in a single network (with a single subnet or a single VLAN), such as a home network, where consumer devices like Apple TVs and printers could be discovered by Macbook, iPhones, and iPads.
With many devices making their way into enterprises, Cisco has extended Bonjour functionality beyond single Layer 2 broadcast domains, to scale and avoid bottlenecks across services-rich enterprise networks and to optimize network bandwidth in the core and access layers. Additionally, Cisco Digital Network Architecture (DNA) Service for Bonjour on Cisco DNA Center also introduces a new dashboard application that shows service discovery gateways connected to the controller and the service instances. It allows network administrators to control which services can be shared across specific network segments.
Local Area Bonjour
Casting an image or a video stream from an iPhone to a TV requires an iPhone to discover the TV using mDNS so that it can send that file or data to be casted on the screen. This deployment is called Local Area Bonjour. As shown in Figure 1, a switch could have multiple virtual LANs (VLANs) and by design each of these VLANs map to a different subnet. In such a scenario, if a service querier (e.g., an iPhone) is present in VLAN A, and a service provider (e.g., Apple TV) is present in VLAN B―which is a typical enterprise scenario―it will be unable to discover the service as the multicast from the querier won’t reach the service provider.
Cisco introduced the Service Discovery Gateway feature, which enables mDNS to operate across Layer 2 boundaries or different subnets. An mDNS gateway can provide transport for service discovery across Layer 2 boundaries by filtering, caching, and extending services from one Layer 2 domain (subnet) to another. Prior to implementation of this feature, mDNS was limited in scope to within a subnet due to the use of link-local scoped multicast addresses.
Wide Area Bonjour
Wide Area Bonjour extended the concept of service provider and service querier in different closets or service discovery gateways that need to discover each other (Figure 2). The mDNS gateways are connected to and synchronize services with Cisco DNA Center. The service is shared when another gateway requests it.
Cisco’s mDNS gateway solution helps cache services and respond to service queriers on request, enabling the network administrator to configure service policies to control the sharing of services across subnets.
Using Wide Area Bonjour, network administrators don’t need to bridge these VLANs across network segments anymore, so no service flooding is necessary, thereby reducing the multicast traffic in the core network. This saves a lot of network bandwidth, both in the core and access layers, making the network bandwidth available for other types of traffic while still enabling it to handle service discovery.
The Cisco Wide Area Bonjour solution eliminates the single Layer 2 domain constraint and expands the scope to enterprise-grade, traditional wired and wireless networks, including overlay networks such as Cisco Software-Defined Access (SD-Access) and industry-standard Border Gateway Protocol (BGP) Ethernet VPN (EVPN) with Virtual Extensible LAN (VXLAN). The Cisco Catalyst 9000 series LAN switches and wireless LAN controllers follow the industry standard, RFC 6762-based mDNS specification to support interoperability with various compatible wired and wireless consumer products in enterprise networks.
The Cisco DNA Service for Bonjour
Cisco has now integrated Bonjour service discovery features into Cisco DNA Center. The new Cisco DNA Service for Bonjour features a software-defined, controller-based solution that includes a dashboard that shows the service discovery gateways connected to the controller and the number of service instances in a Wide Area Bonjour topology (Figure 3). It allows network administrators to control which services can be shared across which network segment.
The new Cisco DNA Service for Bonjour enables end-to-end service-oriented enterprise networks that augment all the key benefits to zero-configuration mDNS technology. With services and feature-rich user devices proliferating on enterprise networks, Cisco DNA Service for Bonjour can help improve the ability of IT and end-users to access, manage, share, print, and synchronize data regardless of their network boundaries. The seamless integration and security provided by the solution is compelling, providing IT organizations with complete control of access security, role and location-based discovery, and management of devices across the enterprise network.
For more information, read Cisco DNA Service for Bonjour
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