Wan Services (Sonet, Metro, VPLS, MPLS)

SONET / SDH

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)

•  Hybrid 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
• DISADVANTAGES:
  • 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?