rks (fixed and mobile) to provide better and optimized traffic management by maximization of the network utilization while having no or minimal effect on most end-users. Bandwidth (bitrates) allocation. The bandwidth (or data rate) offered to a given end-user or dedicated to a concrete type of traffic (e.g. audio, video, Web) may be actively controlled. End-users can be offered a minimum guaranteed rate or they can be limited (according to the bitrate cap) to a maximum bitrate. One should note that bandwidth allocation for data services does not cause packet loss by itself, unless it is below the required bitrate for a particular OTT service flow. Meanwhile, all OTT flows that use the TCP/IP protocol stack normally experience certain packet losses due to TCP congestion windows behavior, which in most TCP versions increases over time, either exponentially (in the Slow Start phase) or linearly (in the congestion avoidance phase), increasing the bitrate for the given OTT application flow until loss occurs (loss occurs when the aggregated bitrate from all OTT flows of that user's broadband access reaches the bandwidth allocation for that user's Internet access). Table 6.8 provides the specifics of different types of traffic management interventions regarding the OTT services. However, the same also refers to real-time QoS-enabled Table 6.8 Type of traffic management interventions. Type of Possible Intervention Protocol Negative impact of intervention actions applied in layers the intervention approach TCP/IP Packet pri- Prioritization Core IP Layer 3 Retransmission Data loss TCP/IP oritization or deprior- network of packets interactive traffic ization Layer 4 is effectively managed by de-prioritizing this traffic type Bandwidth Bitrate Broadband/ Layer 2 Reduced Reduced quality Video traffic is allocation guarantee or ultra- throughput (e.g. video codec best managed by bitrate cap broadband Layer 3 (service main- may drop to a prioritizing in the access tained, but at lower access network network lower speed) resolut