Assuming a backbone network is implemented as a set of routers connected together by point-to-point circuits, integrated services must be implemented by putting in place the appropriate queuing strategies in the routers. Typically, theory tells us that Weighted Fair Queuing of IP packets (or hierarchical round robin service) will provide at least a baseline for implementation. In fact, for controlled load, simple priority queuing schemes may suffice. There are a number of other service disciplines being researched.
Where routers are interconnected by other types of links, particularly shared media (LANs, Satellite channels etc.), or switches, then the interconnect technology must be controlled as well. In the standards work, specifications are emerging for mapping the Guaranteed Service and Controlled Load to run over Token Ring, SMDS, Frame Relay, and a variety of Transfer Capabilities and QoS Classes on switched ATM networks.
For non-deterministic (but popular) subnetworks such as Ethernet, the technology must be enhanced somehow. This is a matter for current development.
When an IP network is operated across ATM switches (i.e. hosts and routers are interconnected by ATM clouds), then there are interworking units that map RSVP requests into Q.2931 requests. On other types of links (e.g. shared LANS), other techniques are used to provide the service guarantees. These classes of traffic are roughly in line with those developed in the Broadband Integrated Services Digital Networks standards communities (the ITU and ATM Forum), for ATM networks (ATM stands for Asynchronous Transfer Mode). They define the equivalent services in terms of the bandwidth rather than delay model, but the intent is similar. UBR, ABR, VBR and CBR stand for Unspeci fied, Available, Variable and Constant bitrate services respectively. ATM is seen in some quarter s to be the multiple service network of the future. It is clear that it is able to convey roughly the same services as are being devised for IP, which should lead to the possibility of layering one service on the other fairly easily.