which often also provides handling and performance monitoring of online advertising campaigns. Ad networks generate revenues (paid by advertisers for access to publishers' ad space inventory) that are shared between the network manager (as intermediation fees) and publishers. In the EEA, Google's AdSense, Yahoo!Publisher Network, DrivePM (belonging to the Microsoft group), TradeDoubler, Zanox, AdLink, Interactive Media, AOL, Tomorrow Focus and 24/7 (belonging to the WPP group) and a significant number of other smaller players are active as ad networks.
An ad exchange provides a marketplace where advertisers and publishers buy and sell ad space on a real-time basis. The main difference between ad exchanges and ad networks is that ad networks aggregate ad inventory from publishers, which is then re-sold by the platform manager to advertisers, whereas an ad exchange is a (virtual) marketplace where publishers and advertisers can virtually meet to find and execute transactions. Networks tend to be “closed” systems with a finite number of buyers and sellers, whereas exchanges tend to be “open” systems whereby any buyer or seller can access the platform and trade. Open ad exchanges allow both advertisers and ad networks to buy ad space. In the EEA, inter alia Rightmedia (belonging to the Yahoo! group), AdECN (belonging to the Microsoft group), Tomorrow Focus and Quigo are active as ad exchanges.
"Media agencies" buy aggregated media space from publishers and resell it to their clients, which are advertisers, usually within the provision of a wider service generally defined as media campaign planning. Most of the agencies already offering this service for offline ads are now also present in online advertising, but some agencies have also developed which are only specialised in online ads. Media agencies can buy online advertising space directly from publishers, but also through ad networks or ad exchanges.
Media agencies provide a range of advertising campaign and planning services and act as intermediaries between media owners and advertisers, purchasing media space on behalf of their advertising clients. In this respect their business is at least partially overlapping with the activity of ad networks. In the EEA, WPP, Aegis and Publicis are some of the largest media agencies.
Intermediation can take place both for search and for non-search advertising. Ad networks that provide search intermediation either own or outsource a third party search "tool". The intermediation, therefore, specifically takes place in respect of the sale of ad space generated on the search result pages of publishers who use the search tool on their website. In the EEA, Google provides this service through its AFS product, and also syndicates its product to other intermediaries (ad pepper, Interactive Media). Yahoo! and Mediaplex-ValueClick provide search intermediation with their in-house tools.
25. The major providers of non-search ad intermediation include Google, through its AdSense network (notably, with its AFC product), Yahoo! (through its Blue Lithium network, its Yahoo! Publishers Network and its Right Media Exchange), Microsoft (through its DRIVEpm network and its AdECN exchange), AOL/Time Warner (active in the EEA through its networks Advertising.com and Lightningcast), ValueClick, as well as TradeDoubler, Zanox, AdLink, Interactive Media (belonging to Deutsche Telekom) and Tomorrow Focus.