Recommendation ITU-T G.8251 specifies the maximum network limits of jitter and wander that shall not be exceeded and the minimum equipment tolerance to jitter and wander that shall be provided at any relevant interfaces which are based on the optical transport network (OTN). The requirements for the jitter and wander characteristics that are specified in this Recommendation must be adhered to in order to ensure interoperability of equipment produced by different manufacturers and a satisfactory network performance. Amendment 1 to Recommendation ITU-T G.8251 includes the following change: – Add fgOTN timing specification. – Replace the OCh term with OTSi and OTSiG. – Remove non-inclusive terms.