Chapter 5: Operating Modes and Configuration
Chapter 6: Interoperability
LAN
The LAN ports of the gateway support, at a minimum, all 100BaseTX Full-Duplex Ethernet connections up
to maximum line lengths and are set to auto-MDI/MDIX to automatically detect/correct crossover vs
straight LAN cable and autonegotiate for full-duplex and pause frame modes with the attached LAN
equipment. Passwords may be purchased to upgrade to enhanced LAN port modes as described elsewhere
in this manual.
The gateway will pass all unerrored packets which do not exceed 1650 bytes in packet length (9600 with
jumbo frames enabled). This length allows QinQ, stacked VLAN, and extended packet-length router
protocols to be passed without concern. The management agent accepts and responds with packets having
MTU of 1350 bytes in order to automatically allow room for security protocol overheads.
Autonegotiation problems
There are rare cases with older LAN equipment in which it may be necessary to disable autonegotiation. If
CRC-errors or short packet errors are seen in the management statistics of the LAN port, the attached LAN
equipment has probably configured itself to half-duplex mode and colliding packets are being lost. In such
a case, autonegotiation should be disabled on both the gateway and the attached LAN equipment with both
forced to 100BaseTX full-duplex. Autonegotiation interoperability and standards were not well understood
by the industry at the inception of 100BaseTX, resulting in some older LAN equipment not understanding
the gateway's autonegotiation advertisement of strictly full-duplex capability.
It is highly desirable to leave autonegotiation enabled so that changing attached LAN equipment does not
result in the new equipment defaulting to half-duplex if set to autonegotiate.
SFP LAN Port 1
This port is designed to be compatible with inexpensive, high-quality, copper or fiber-optic, SFP
transceivers from Finisar, which allows LAN connections of 10km or more. Most other industry-standard
SFP transceivers will work as well; however, fiber-optic features such as temperature and optical
transmit/receive power and alarms will only be available if using Finisar transceivers. Non-Finisar copper,
RJ45 SFP transceivers may only operate in 1000Base-T mode, while recommended transceivers from
Finisar, and possibly Avago or 3Com will operate in 100Base-TX mode as well.
Pause Frames
The gateway generates no pause frames and ignores pause command frames sent to it.
Telecom
The gateway can transmit over a variety of E3 or T3/DS3 links (with appropriate media gateways) such as
fiber optic, microwave radio, laser, copper, satellite, or a combination; however, the attachment interface is
always via 75-ohm copper coaxial rather than optical. The TDM circuit may be either framed or unframed
and supports both M13, M23, clear-channel, C-Bit, and G.751 framing. C-Bit framing is suggested for DS3
links.
Fiber/Copper Media Gateways
Transition Networks DS3/E3 Coax to Fiber Media Gateway, SCSCF3014-100 has been reported to lack the
ability to properly maintain separate DS3/E3 transmit clock speeds in each direction and are not
recommended. This problem typically manifests itself as frame slips or loss of TDM signal lock in one
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