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(C) Herbert Haas
2005/03/11
Today
No collisions no distance limitations !
Gigabit Ethernet becomes WAN
technology !
Over 100 km link span already
Combine several links to "Etherchannels"
Acts as single link from the spanning-tree view
• Cisco: Port Aggregation Protocol (PAgP)
• IEEE 802.1ad: Link Aggregation Control Protocol
(LACP)
1 Gbit/s or even 10 Gbit/s long reach connection !!!
Today, Gigabit and even 10 Gigabit Ethernet is available. Only twisted pair and
more and more fiber cables are used between switches, allowing full duplex
collision-free connections. Since collisions cannot occur anymore, there is no
need for a collision window anymore! From this it follows, that there is virtually
no distance limit between each two Ethernet devices.
Recent experiments demonstrated the interconnection of two Ethernet Switches
over a span of more than 100 km! Thus Ethernet became a WAN technology!
Today, many carriers use Ethernet instead of ATM/SONET/SDH or other rather
expensive technologies. GE and 10GE is relatively cheap and much simpler to
deploy. Furthermore it easily integrates into existing low-rate Ethernet
environments, allowing a homogeneous interconnection between multiple
Ethernet LAN sites. Basically, the deployment is plug and play.
If the link speed is still too slow, so-called "Etherchannels" can be configured
between each two switches by combining several ports to one logical connection.
Note that it is not possible to deploy parallel connections between two switches
without an Etherchannel configuration because the Spanning Tree Protocol (STP)
would cut off all redundant links.
Depending on the vendor, up to eight ports can be combined to constitute one
"Etherchannel".