Advertisers can either build their own in-house technology for this purpose (e.g. eBay) or purchase "advertising ad serving tools" from third parties.
30. Ad serving tools provided on a stand-alone basis by different suppliers and to different customers (publishers and advertisers) present a high degree of interoperability. In other words, there are no major problems of intercommunication between an advertiser using a provider of "advertising ad serving tools" and a publisher using a different provider of "publisher ad serving tools" or its own in-house technology.
Sales channels in the online advertising sector
There are currently different ways through which publishers can sell advertising space, using various combinations of intermediation services and ad serving technology. These methods are non-exclusive and publishers tend to use different sales channels at the same time for different parts of their inventory. In particular, intermediation and ad serving tools can be sold independently or as a "bundle" (that is to say an ad network offering both intermediation services in addition to the ad serving tools). The same applies for advertisers (since they can use a variety of distribution channels).
These different channels are schematized in the Table 1 below.