Rec. ITU-T G.8261/Y.1361 (04/2008) iii
CONTENTS
Page
1 Scope ............................................................................................................................ 1
2 References..................................................................................................................... 1
3 Definitions .................................................................................................................... 3
3.1 Terms defined elsewhere................................................................................ 3
3.2 Terms defined in this Recommendation......................................................... 3
4 Abbreviations................................................................................................................ 5
5 Conventions .................................................................................................................. 6
6 General.......................................................................................................................... 6
6.1 Packet network synchronization requirements............................................... 7
6.2 TDM timing requirements.............................................................................. 8
6.3 Synchronization network engineering in packet networks............................. 8
6.4 Timing requirements at edge versus timing requirements in core networks.. 9
6.5 PNT domain and CES domain ....................................................................... 9
7 Reference timing signal distribution over packet networks (PNT domain) ................. 9
7.1 Plesiochronous and network synchronous methods ....................................... 9
7.2 Packet-based methods .................................................................................... 11
8 Timing recovery for constant bit rate services transported over packet networks
(CES domain) ............................................................................................................... 12
8.1 Network synchronous operation..................................................................... 12
8.2 Differential methods....................................................................................... 13
8.3 Adaptive methods........................................................................................... 14
8.4 Reference clock available at the TDM end systems....................................... 14
9 Network limits .............................................................................................................. 15
9.1 CES network limits......................................................................................... 15
9.2 PNT network limits ........................................................................................ 20
10 Impact of impairments in the packet network on timing distribution and service
clock recovery............................................................................................................... 25
10.1 Packet transfer delay and delay variation....................................................... 26
10.2 Impacts from packet impairments .................................................................. 31
11 Impact of the reference clock impairment on the service clock recovery .................... 32
11.1 Impairments for the network synchronous operation methods ...................... 32
11.2 Impairments for the differential method......................................................... 33
12 Results and consequences of the different synchronization methods over packet
network reference models............................................................................................. 34
12.1 CES domain recommendations ...................................................................... 34
12.2 PNT domain recommendations ...................................................................... 36
Annex A – Proposed network architecture for synchronous Ethernet..................................... 38
A.1 PRC Location ................................................................................................. 38
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