Cisco ME-3400G-12CS-A-RF - Ethernet Access Switch Manual de usuario Pagina 34

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© 2009 Cisco Systems, Inc. All rights reserved.
35
Cisco PublicBRKBBA-2006
Main Issues with PONs
Data sent to all users on the tree: inefficient Video multicast & VoD
IGMP Proxy and snooping with limited support. IGMP process distributed between OLT(Proxy) and
ONT(Snooper) instable. Zapping degrades with large number of channels selected. No state of IGMP on
ONT kept. Troubleshooting by “mirroring” PONT tree, no focus on one sub (trace per user) possible
Asymmetrical
Strong encryption required to prevent eavesdropping
No resilience
–OLT optics is single point of failure for entire tree
–corrupt CPE can impact entire PON tree
Jamming is very easy
–just transmit continuous light and the whole tree is OOS
In case of technology change all terminations on a tree need to be replaced
(simultaneously?)
Every endpoint (OLT, ONT, ...) has to operate at the aggregate bitrate
–e.g., a GPON ONT delivering 100 Mbit/s to an end customer has to operate at 2.5 Gbit/s
All FTTH deployments that we are aware of universally assume a take rate of 25...35%.
–Theoretical maximum number of customers per tree is rarely reached due to take-up rates
–Only 25-35% of interfaces need to be accommodated on switches in a Eth. P2P scenario rather than
100% in PON
OLT
ONT
ONT
ONT
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