hat the new operator builds an access network of its own. It is very costly to build a full copper network with pairs to all possible subscribers in an area. This might be profitable only if the result is a market share of 50 % or more in the area. Normally, the incumbent has already connected all the high and medium income people Understanding Changing Telecommunications - Building a Successful Telecom Business living in the area, and profitability for the new operator would also require churn - an overflow of established subscribers to the new operator. A cheaper strategy is to invest, initially, in an 'access core', sometimes called a feeder network, which uses multiplexed systems over fibre or radio. If copper for some reason is available it could be equipped with HDSL or SHDSL systems, and later VDSL systems. 'The last mile' or drop to the subscriber is expensive, and a 'pay as you grow' invest- ment strategy should be chosen. Fixed and mobile radio systems fulfil this requirement. 4.6.4 PEERING (REVENUE AND COST) The traffic conditions in the Internet differ from conditions in telephony networks. The part that initiates a session sends a limited amount of traffic towards the server. The server answers interactively, often with considerable amounts of traffic. This gives an asymmet- rical pattern with most traffic generated by the B-side. However for small offices/home offices the situation may be different. For interconnect purposes the ISPs have 'peering' agreements (peer to peer = 'on equal footing'). Between two top tier peers there is no accounting when using transport resources of the cooperating peering ISP. The ISPs are ranked in a hierarchical order: primary, secondary etc. Secondary ISPs buy 'transit' from primary ISPs. 'Transit' means that the ISP is allowed to utilize all the peering agreements of the primary ISP. Peering agreements are usually 'free' between operators of approximately the same size. Peering is mutually beneficial to both operators, since they both will increase their performance