Wan Services (Sonet, Metro, VPLS, MPLS)


Sonet ( Synchronous Optical Networking)

  • American National Standards Institute (ANSI)
  • Used in US / Canada
  • Synchronous transport signals (STS) used for speed

Synchronous Digital Hierarchy

  • International Telecommunications union (ITU)
  • Used everywhere expect US / Canada
  • Synchronoous transport Modules (STM) used for speed)

Metro Ethernet

Ethernet Multipoint Services ( EMS )

  • Same as EWS, Full mesh
  • Traffic QinQ

Ethernet Relay Multipoint Services (ERMS)

  • ┬áHybrid of EMS / ERS
  • Allows a mesh of EMS Sites with specific VLAN ers Destination

VPLS ( Vlan private lan service )

  • EMS Enviroment where customer connections emulate an ethernet switch
  • Each EMS enviroment is seen as a VLAN from the SP perspective
    • Layer 2 STP based troubles
    • Entire enviornment subsceptable to outages
    • Multicast/broadcast to all sites
    • Routers peer in full mesh (scaling / peformance / flaps )
    • All customers could be impacted by a layer 2 loop

MPLS (Multprotocol label switching)

  • Layer 3:
    • IP only
    • Service provider works with customer router
    • simpler QoS design
  • Layer 2:
    • Support for any protocol
    • Blends multiple l2 addressing mathods (dlc, mac, vpi/vci)
    • Customer controler all Layer3
  • Redistribution of BGP into IGP may skew Administrative Distance (backdoor routes)
  • Carrier managed routers cause pain:
    • Solve by adding a second router behind the carrier router
    • GRE tunneling networks through
    • Handling FHRP redundancy (with multiple connections)

Choosing and Monitoring the Service Provider

  • Research the underlying technology
  • If budget allows, roll out two service providers to test
  • See the service provicer as a valued partner relationship
  • Ask out of the box questions
    • How skilled are your techs
    • How neat is your install
    • Do you label your devices and ports
    • How old is your equipment?



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