Information AboutEthernet-over-sonet |
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Ethernet over SONET (EOS) refers to a set of protocols which allow Ethernet traffic to be carried over Synchronous Optical Network networks in a effcient and flexible way. Ethernet over SONET takes Ethernet frames which are to be sent on the SONET link and processes them through an "encapsulation" block (typically Generic Framing Procedures or GFP) to create a synchronous steam of data from the asynchronous Ethernet packets. The sychronous stream of data from the encapsulation block is then passed through a mapping block which typically uses Virtual Concatenation to route the stream of bits over one or more SONET paths. The SONET paths may be high order (STS-3c, STS-1) or low order (VT-1.5) paths. Up to 64 VT1.5 paths can be concatenated together to form a single larger virtually concatenated group. Up to 256 STS-1 or STS-3c paths can be concatenated together to form a single larger virtually concatenated group. The paths within a group are referred to as "members". An virtually concatenated group is typically referred to by the notation A 10-Mbps Ethernet link is often transported over an VT-1.5-7v which allows the full bandwidth to be carried for all packet sizes. A 100-Mbps Ethernet link is often transported over an STS-1-2v which allows the full bandwidth to be carried when smaller packets are used (< 250 bytes) and Ethernet flow control restricts the rate of traffic for larger packets. A 1000-Mbps (or 1 GigE) Ethernet link is often transported over an STS-1-21v or an STS-3c-7v which allows the full bandwidth to be carried for all packets. The bandwidths possible are shown in the table below: An additional protocol Link Capacity Adjustment Scheme allows the two endpoints of the SONET paths to negociate which paths are working and can carry traffic and which paths should not be used to carry traffic. |
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