 
Summary: Distributed Synchronization Protocols for SDH
Networks
Yehuda Afek \Lambda Tal Lev y
Computer Science Department
TelAviv University
Israel 69978
Abstract
In this paper we design distributed protocols for synchronization in SDH networks.
We start by suggesting a new abstraction to model the communication of control infor
mation in SDH/SONET frame headers. The new model is then used in the construction
of realistic and faulttolerant distributed protocols for the timing distribution problem.
In this problem the nodes of an SDH/SONET network should be synchronized to trans
mit at the same rate; otherwise the data carried by the network may be impaired. The
presented protocols ensure that (1) all the nodes derive their transmission clock from
one source, (2) that this source is the highest quality clock available in the network
and (3) that the path along which the clock at a node is derived is the shortest path
from the source to the node. The design of the presented protocol employs modern
techniques from the field of distributed computing adapted to the model and tools
available in a real SDH/SONET network.
Keywords: Synchronization, SDH, SONET, Transmission rates, clock distribution.
