Internet subscribers and services have grown even during the recent recession. As a result, Internet traffic volume and content are changing constantly. These changes increase pressure on Internet Service Providers (ISPs) by making bandwidth provisioning and management difficult, especially to maintain required Quality of Service (QoS) levels. Peer to Peer (P2P) traffic associated with File Sharing Applications (FSA) is the most influential factor in changing Internet traffic content and volume. Traffic data for 900 subscribers to an ISP was collected over two months in a period before the rapid growth of P2P. In this paper we study the potential effect of P2P video streaming, under both restricted (Bandwidth Throttling) and unrestricted conditions, on the QoS experienced by subscribers without high P2P usage. Under unrestricted conditions, our results show that QoS for these subscribers will be substantially degraded by this kind of P2P traffic; however, when ISPs exercise bandwidth throttling to shape traffic, the QoS can be considerably improved.