Cabletron Systems NBR-420 사용자 설명서

Appendix C: Network Planning and Configuration

-

Network propagation delay is the amount of time it takes a packet 
to travel from the sending device to the receiving device. Total 
propagation delay allowed for the entire network must not exceed 
25.6 

µ

s in one direction (51.2 

µ

s round trip). If the total 

propagation delay between any two nodes on the network exceeds 
25.6 

µ

s, you must use bridges.

•

Length - The maximum possible multimode fiber optic cable length is 
2 

k

m (2187.2 yards). However, IEEE 802.3 FOIRL specifications 

specify a maximum of 1 km (1093.6 yards).

When connecting a single mode fiber optic link segment to an EPIM-F3, 
ensure the network meets the following requirements:

•

Cable Type - Fiber optic link segments should consist of
8/125 to 12/125 

µ

m single mode fiber optic cabling. You can also use

62.5/125 

µ

m multimode cable with the EPIM-F3; however, multimode 

cable allows for greater optical loss, and limits the possible distance to 
2 km.

•

Attenuation - You must test the fiber optic cable with a fiber optic 
attenuation test set adjusted for a 1300 nm wavelength. This test 
verifies that the signal loss in a cable falls within the acceptable level 
of 10.0 dB or less for any given single mode fiber optic link.

•

Budget and Propagation Delay - When you determine the maximum 
fiber optic cable length to incorporate fiber runs into your network, you 
must calculate and consider the fiber optic budget (a total loss of 
10.0 dB or less is permissible between stations) and total network 
propagation delay.

-

To determine the fiber optic budget, combine the optical loss due 
to the fiber optic cable, in-line splices, and fiber optic connectors. 
Typical loss for a splice and connector (together) equals 1 dB or 
less.