WAN Technologies

Question 1

MPLS

Answer 1

• Learning from ATM and Frame Relay
  
  • Packets through the WAN have a label
  • Routing decisions are easy
• Any transport medium, any protocol inside
  
  • IP packets, ATM cells, Ethernet frames
  • OSI layer 2.5 (!)
• Increasingly common WAN technology
  
  • Ready-to-network

Question 2

MPLS pushing and popping

Answer 2

• Labels are “pushed” onto packets as they enter the MPLS cloud
• Labels are “popped” off on the way out

Question 3

ATM

Answer 3

• Asynchronous Transfer Mode
  
  • A common protocol transported over SONET
• 53-byte “cells” spaced evenly apart
  
  • 48-byte for data, 5-byte routing header
• High throughput, real-time, low latency
  
  • Data, voice, and video
• Max speeds of OC-192
  
  • Limits based on segmentation and reassembly (SAR)

Question 4

Frame relay

Answer 4

• One of the first cost-effective WAN types
  
  • Departure from circuit-switched T1s

• LAN traffic is encapsulated into frame relay frames

• Frames are passed into the “cloud”
  
  • Magically appear out the other side

• Usually 64 Kbits/s through DS3 speeds

• Effectively replaced by MPLS
  
  • And other WAN technologies

Question 5

PPP (Point-to-point protocol)

Answer 5

• Create a network connection between two devices
  
  • OSI layer 2 / data link protocol
  • Communicate using many different protocols

• Works almost anywhere
• Dial-up connections, serial links, mobile phone, DSL
(PPPoE)

• Provides additional data link functionality
  
  • Authentication
  • Compression
  • Error detection
  • Multilink

Question 6

PPPoE

Answer 6

• Encapsulate point-to-point protocol over Ethernet
  
  • The past with the present
• Common on DSL networks
  
  • Telephone providers know PPP
• Easy to implement
  
  • Support in most operating systems
  • No routing required
  • Similar to existing dialup architecture

• Allows competition
• Once connected, data is switched to the appropriate
ISP

Question 7

DMVPN

Answer 7

• Dynamic Multipoint VPN
  
  • Common on Cisco routers
• Your VPN builds itself
  
  • Remote sites communicate to each other
• Tunnels are built dynamically, on-demand
  
  • A dynamic mesh

Question 8

SIP trunking

Answer 8

• Session Initiation Protocol
  
  • Control protocol for VoIP
• Traditional PBX connectivity uses T1/ISDN
  
  • 23 voice channels, 1 signaling channel
  • When the lines are full, you get a busy signal
• SIP trunking
  
  • Use SIP/VoIP to communicate to an IP-PBX provider
• More efficient use of bandwidth
  
  • Less expensive than ISDN lines
  • More phone system options