Afar NX-2E1, Operator'S Manual

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NetCrossing Gateway NX-2E1/T1 Operator’s Manual
2-4
The packet format and overhead for bridge and route modes are shown in the tables 2.1 and 2.2
below. Tables 2.3 and 2.4 show some examples of packet sizes and WAN data rates in E1 and T1
mode respectively. Note that these numbers are per line. If you have two TDM lines active the data
rate doubles.
Table 2.1 – WAN packet (Bridge mode) Table 2.2 – WAN packet (Route mode)
Field Bytes Field Bytes
Ethernet Destination Address 6 Ethernet Destination Address 6
Ethernet Source Address 6 Ethernet Source Address 6
Ethernet Packet Length/Type 2 Ethernet Packet Length/Type 2
SNAP header 8 IP/UDP header 28
Gateway link control 6 Gateway link control 6
Payload
E1: 32 x Number of Time Slots
T1: 24 x Number of Time Slots Payload
E1: 32 x Number of Time Slots
T1: 24 x Number of Time Slots
CRC 4 CRC 4
Total Packet Overhead: 32 Total Packet Overhead: 52
Table 2.3 – WAN data rates (E1 mode)
Bridge Route
Payload Time slots Pkt rate Pkt size
(bytes)
Data rate
(Kbps)
Pkt size
(bytes)
Data rate
(Kbps)
Unframed N/A 250 1056 2112 1076 2152
31 250 1024 2048 1044 2088
24 250 800 1600 820 1640
16 250 544 1088 564 1128
Framed 8 250 288 576 308 616
4 250 160 320 180 360
2 250 96 192 116 232
1 250 64 128 84 168