E3Switch DS3 Operating Information Manual
Also see for DS3: Operating information
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Chapter 6: InteroperabilityPause FramesUnless disabled in the settings or through autonegotiation, the converter sends pause command frames toattached LAN equipment when the converter's incoming LAN buffers become nearly full. The converterignores pause command frames sent to it.VoIP / Video or High-CoS Priority FramesIn certain firmware, receive queue space is reserved in the converter to allow frames with high 802.1p class-of-service (CoS) priority settings to bypass existing frames waiting to be transmitted to the DS3/E3. Thisallows voice, video and other high-priority traffic to experience low-latency transmission. Firmware allowsthe “high” CoS level to be configured.Telecom/WANThe converter can transmit over a variety of E3 or T3/DS3 links (with appropriate media converters) suchas fiber optic, microwave radio, laser, copper, satellite, or a combination; however, the attachment interfaceis always via 75-ohm copper coaxial rather than optical. The point-to-point telecom link must beunchannelized, i.e., not subdivided into T1 or E1 channels. The telecom link may be either framed orunframed and supports both M13, M23, clear-channel, C-Bit, and G.751 framing. C-Bit framing issuggested for DS3 links.Certain firmware allows subrate/fractional WAN connectivity.Fiber/Copper Media ConvertersTransition Networks DS3/E3 Coax to Fiber Media Converter, SCSCF3014-100 has been reported to lackthe ability to properly maintain separate DS3/E3 transmit clock speeds in each direction and are notrecommended. This problem typically manifests itself as frame slips or loss of telecom signal lock in onedirection at a rapid, consistent periodic rate, which is proportional to the difference in clock speeds of eachtelecom direction. If such media converters are already in use, setting the DS3/E3 transmit clock source ofone of the WAN units to “loop” may alleviate problems.Routers and SwitchesThe configuration of routing tables of the PPPoE equipment attached to the E3Switch converter is beyondthe scope of this document.Chapter 7: Telecom ConnectionsFraming and Physical LinkThe converter can transmit the LAN data over a variety of E3, T3/DS3 links (with the appropriate mediaconverter) such as fiber optic, microwave radio, laser, copper, satellite, or a combination. The convertermay be used with a standard (i.e., M13, M23, clear-channel, C-Bit or G.751) framed or unframed, E3 orT3/DS3 link with AMI and HDB3 or B3ZS encoding. The link must be unchannelized, i.e., not subdividedinto T1/E1 channels. C-Bit framing is recommended for DS3 links. Newer firmware supports PMDLCircuit ID on C-Bit links.Certain firmware supports sub-rate/fractional WAN.Each converter generates the timing clock of its transmitted bit-stream, within E3 and T3/DS3 standards,either locally, or locked to either port's received bit-rate. The incoming clock rates are displayed at theunit's HTTP management page.Telecom CablingFor the E3 or T3/DS3 connection, two 75-ohm coaxial cables (one transmit and one receive) with BNCconnectors are required at each end. It is important that 75-ohm cable be used and not 50-ohm cable. Forlong connections or in electrically noisy environments it may be important to use a high-quality 75-ohm16 |
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