I have been asked to put forth the pro & cons of a link when delivered as traditional SDH (OC3) and as ethernet services. Here ethernet would mean only the last handoff and the SP backend would still be SDH
I cannot think of any advantage except for the cost savings in buying a OC3 module if i go with ethernet option
are there any other risk and qos factors that i might need to consider
we have used Enet over SDH a lot for various links (at 10, 100 and Gig speeds), and it is pretty good in general - the pipes are usually wire speed or close, and the kit benefits from SDH reliability.
couple of points:
if you get Enet over SDH for the pipe, then you probably get VC based bandwidth - you need to know what you have so you can limit your traffic to stay inside the rate unless the pipe is "qos aware" - a lot of the SDH GFP kit doesnt seem to be, or the SP doesnt turn that on.
you probably want to know if the SDH is on 1 or more paths, and what happens under fault conditions - you might lose maybe 50% of the capacity.
1 advantage is that it is Ethernet - you can use a switch rather than a software based router at the end of the link.
We had some problems with 100 Mbps as using SDH it is often set up as 2 VC-3s, giving only 97 Mbps. If you overdrive the Ethernet link, then since the SDH doesnt understand QoS that gives some problems. Rate limit the end points and it works very well.