-defined limits, including limits on static asymmetry. Control of static asymmetries can be achieved in case of assisted partial timing support. Use of this profile in unassisted mode would require careful considerations on how to control static asymmetries. G.8275.2 is the recommended profile where full timing support from the network is not an option for operators. However, as mentioned in the preceding scope, and throughout this book, the engin- eer must be careful how it is deployed, as switching PTP over unaware, non-PTP-aware network elements can lead to significant degradation in time accuracy. This recommendation includes the following main topics, annexes, and appendixes: Details on the use of PTP for phase/time distribution, including selection of some PTP options available in IEEE 1588-2008. This includes the PTP mapping (IP unicast), message types, BMCA, unicast negotiation, and which types of clocks are supported. Annex A, "ITU-T PTP profile for time distribution with partial timing support from the network (unicast mode)" (contains the main details such as allowed values for datasets, TLVs, flag val- ues, and SO on). Annex B, "Options to establish the PTP topology using the Alternate BMCA" (moved to G.8275 along with Annex C, Annex E, and Appendix IV). Annex C, "Inclusion of an external phase/time input interface on a PTP clock" (moved to G.8275). Annex F, "Mapping from PTP clockClass values to quality levels." This annex covers the qual- ity levels that a PTP clock will output on its frequency interfaces. Appendix IV, "Description of PTP clock modes and associated contents of Announce mes- sages" (moved to G.8275). Appendix VI, "Considerations of PTP over IP transport in ring topologies" (discusses the seri- ous issues that can arise when deploying PTPoIP in a ring topology). Appendix VIII, "Operations over link aggregation" (discusses the issues that arise with the transfer of PTPoIP in a topology that includes Link Aggregation Group [LAG] or "Ethernet/port bundles"). As with G.8275.1, there are n