## 3 Service Level Agreements in IP/Optical Networks  
Connectivity between two geographically dispersed locations is usually provided by an independent third party called a service provider. The SLA is then a contract agreed upon between the service provider and the service consumer, and is the basis for guaranteeing QoS because it specifies in measurable terms the services furnished by the provider and the penalties assessed if the provider cannot meet the goals established. In other words, the SLA details the attributes of the service provided to the customer. These parameters span bandwidth, fault tolerance, recovery time, reliability, availability, response time, packet/burst loss and bit error rate, to name a few. In circuit-switched networks, QoS also includes maximum connection establishment delays and blocking probability. In the Internet, the reality is that end-to-end SLAs are scarce, and SLAs among Internet service providers are limited, which gives an idea of the complexity of managing QoS in deployed optical networks. Besides, the choice of 'optical QoS' parameters to be included in SLAs and the ways in which these parameters shall be measured or interpreted is still an ongoing debate. It goes without saying that guaranteeing QoS is a must for IP/optical networks. The applications being deployed across the public Internet today are increasingly mission-critical, whereby business success can be jeopardized by poor network performance. In other words, IP/optical networks will not be much promising unless they can guarantee a predictable performance as specified by the QoS parameters established in the SLAs. Transmission performance is a key factor regarding QoS in optical networks because optical signals carry huge amounts of data, which means that poor transmission quality has a dramatic impact on QoS. For this reason, there are many works in the literature on impairment-aware lightpath provisioning (IA-RWA), e.g., [5], and fault management schemes adapted to IP/optical networks, especially for all-optical transport networks, e.g., [18]. The QoS requirements of future applications encompass the individualization of services and stricter quality parameters such as latency, jitter or capacity. In other words, IP/optical networks will not only transport more IP data, but they will also have to offer differentiated QoS requirements and traffic patterns. Finally, some emerging applications, e.g., grid computing, need greater flexibility in the usage of network resources, which involves establishing and releasing connections as if they were virtualized resources that can be controlled by other elements or layers. In this context, traffic-driven lightpath provisioning (described in Section 2.2) arises as a very interesting candidate solution to solve the major challenges described above. On the other hand, the European AGAVE project introduced the concept of parallel Internets to enable end-to-end service differentiation across multiple administrative domains. These are coexisting parallel networks composed of interconnected, per-domain network planes and allow for differentiation in terms of QoS, availability and resilience [19]. \begin{table}
\begin{tabular}{c c} \hline
**Flow identifier parameters** & **Flow behavior parameters** \\ \hline TCP/UDP port numbers & Duration \\ IP addresses & Number of packets in the flow \\ Network segments (subnets and autonomous system) & Throughput (Bps, bits per second) \\ Protocols & Throughput (Pps, packets per second) \\ Type of service (ToS) & \\ \hline \end{tabular}
\end{table} 
Table 1: Network parameters to detect elephant flows. The rationale behind AGAVE is that SLAs are established between customers and service providers (SP), while connectivity-provisioning agreements are established between service providers and IP network providers (INP). Internally, SP have service-interconnection agreements.