An important trend in networking is the migration of packet-based
technologies from Local Area Networks to Metropolitan Area
Networks. The rapidly increasing volume of data traffic in metro
networks is challenging the capacity limits of existing transport
infrastructures based on circuit-oriented technologies like SONET and
ATM. Inefficiencies associated with carrying increasing quantities of
data traffic over voice-optimized circuit-switched networks makes it
difficult to provision new services, and increases the cost of
building additional capacity beyond the limits of most carriers'
capital expense budgets. Packet-based transport technology, a natural
fit with the now ubiquitous IP protocol, is considered by many to be
the only alternative for scaling metro networks to meet the demand.
Ethernet has quickly become the leading technology for packet
transport in the metro. As an alternative to circuit-oriented
transport technologies like SONET and ATM, Optical Gigabit Ethernet
technology, capable of supporting fiber spans of more than 50 miles,
is a good match for carrying Internet Protocol data traffic. Since
nearly all IP packets begin and end their trip across the Internet as
Ethernet frames, carrying data in a consistent packet format from
start to finish throughout the entire transport path eliminates the
need for additional layers of protocol and synchronization that result
in extra costs and complexities. In addition to efficient handling of
IP packets, Ethernet has the advantages of familiarity, simplicity,
and low cost.
Figure 1 - The Next Step in Packet Based Transport
Gigabit Ethernet is only the first step in the evolution of
packet-based transport in the MAN. Though well suited for
point-to-point and mesh network topologies, it is difficult to deploy
Ethernet in ring configurations due to fairness problems and the
spanning tree protocol. Yet, most of the existing fiber plant in metro
areas is in ring form, because the incumbent transport technology,
SONET, is typically deployed over fiber rings. Ring topology enables
SONET to implement a fast (sub 50ms) protection mechanism that can
restore connectivity using an alternate path around the ring in case
of fiber cuts or equipment failure. Unlike SONET, Ethernet does not
have a built-in fast protection mechanism. There are, therefore, great
benefits in a new technology that can fully exploit fiber rings (in
particular, ring resiliency) while retaining all the inherent
advantages of a packet-based transport mechanism like Ethernet.
The emerging solution for metro data transport applications is Packet Ring
technology. It offers two key features that have heretofore been
exclusive to SONET: efficient support for ring topology and fast
recovery from fiber cuts and link failures. At the same time, Packet
Ring technology can provide data efficiency, simplicity, and cost
advantages that are typical to Ethernet. Even though there is
currently no standard for Packet Rings operating at Gigabit speeds and
higher, many vendors are developing and introducing Packet Ring
technologies to address this emerging market.
DSL is NOT dying... in fact every RBOC and ILEC has long list of orders waiting to be filled... they are only limited by available man power and capital not by the demand for the service. Until we get fiber to the majority of business sites and homes... some form of DSL (HDSL, ADSL, SDSL, VDSL, etc) will have a very long life in the access network.
Is this a trick question? Lots of vendors make SONET ADMS that will mux anything from T1 to OC12 into an OC-48. The Alcatel 1603SMX does this with a combination T1/STS-1 cross connect matrix.
If the guy is looking for a box that still doesn't work (and has been way over-hyped), then he's got the right one baby! it's going to take Ciena another 12 to 18 months to clean up the K2 mess.
What are you really asking? Are you asking about an all-optical device? The answer to that would be, of course, no. Are you asking about an o-e-o device? The answer to that would be, of course!
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