ted by the network. For the performance limits for packet-based frequency, the following is a quote from G.8261 that provides a guide to the overall requirements for a typical deployment: As an example, the typical wander that is tolerated by end applications can be expressed in terms of [ITU-T G.823] and [ITU-T G.824] traffic masks. G.8261.1] defines the conditions under which a packet network is suitable to support packet-based methods, and [ITU-T G.8263] specifies the related clock characteristics. This basically means that the frequency accuracy that comes out the end of a packet-based syn- chronization chain is aligned to the TDM traffic masks, such as those for E1/T1. It is ITU-T G.8261.1 that defines an output wander limit for frequency at the final clock in the network chain. That output wander limit is aligned with the G.823 limits (TDM version of a chain of frequency clocks) and aimed at meeting the frequency requirement of 16 ppb for the mobile cellular radio use case (see Figure 9-15). 16 ppb 18 us Observation 0.05 0.2 interval T (s) Figure 9-15 Packet-Based Frequency Wander Limit MTIE Mask-Based on Figure 4 of G.8261.1 Recommendation G.8261.1 has a second function that applies to packet-based frequency timing: it defines a model for PDV network limits. Of course, these network limits must be compatible with the minimum limit of PDV that the final clock in the chain is required to tolerate. The tolerance for clock PDV is specified in the recommendation on frequency clock performance, G.8263. Just be aware that for PTP, there is an amount of PDV that will prevent a slave clock aligning at all. Basically, the PDV must allow at least 1% of packets to arrive in a cluster close to the minimal pos- sible transit time, or what is called the floor delay. This 1% is taken over a 200-second sliding win- dow, and the cluster is defined in G.8261.1 as up to 150 us from the floor delay. The method of se- lection is up to the implementation, and there is a lot of information on several approaches in G.8260. Figure 