Wide Area Networking Protocols

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Wide Area Networking Protocols

• Frame Relay

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Topics

• Choosing WAN services to meet customer
  requirements
• Implementing Frame Relay
• Frame Relay Troubleshooting

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WAN Components

• Customer Premises Equipment (CPE)
• Demarcation point (demarc) service providers
  interface to customer premises
• Central Office (CO) connection point to
  providers switching network (POP)
• Local loop demarc to CO
• Toll network trunk line in WAN providers
  network

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WAN Connection Types
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Leased Lines

• Point-to-point dedicated, always-on connection
  leased from provider
• No setup procedures required before transmitting
  data
• Best choice when cost is not a concern
• Uses synchronous serial lines up to 45 Mbps and
  HDLC or PPP encapsulation

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Circuit Switching

• Used primarily for voice transmission
• Cost effective use only what you need
• End-to-end connection required before data
  transmission can occur
• Support low bandwidth transmissions using dial-up
  modems or ISDN

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Packet Switching

• Allows users to share bandwidth to save money
• Designed to look like a leased line, with charges
  more like circuit-switching
• Good for bursty transmissions, not for constant
  transfers
• Frame relay and X.25
• Speeds from 56K to T3 (45Mbps)

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Terminal and Communications Equipment in WAN
Circuits
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WAN Service Options

• Frame Relay successor of X.25
• ISDN both data and voice over existing phone
  lines
• LAPB X.25 connection-oriented data-link layer
  protocol
• LAPD ISDN data-link layer protocol
• HDLC Low overhead data-link layer protocol
  derived from IBMs SDLC
• PPP Industry standard data-link layer protocol
• ATM uses 53 byte cells and external clocking to
  provide speed also provides QoS

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Frame Relay

• High-performance, cost effective non-broadcast
  multi-access network (NBMA)
• Descendent of X.25 technology used on modern
  reliable digital links
• Leaves out X.25 error checking
• Supported Protocols
• IP, AppleTalk, Novell, Banyan Vines, and many
  others

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Before Frame Relay
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After Frame Relay
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Frame Relay

• Purpose
• Provide communications network between customer
  DTEs
• More complex than leased line technology
• Uses PVC or SVC and DLCI numbers to identify PVC
• requires fewer physical ports and links than
  leased lines

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Committed Information Rate (CIR)

• Customers purchase less bandwidth than what they
  might need
• Cost savings
• Good for bursty traffic
• Not good for constant amounts of data transmission

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Frame Relay CIR

• Frame Relay allows sharing of bandwidth by
  multiple customers
• The CIR is the bandwidth leased to the customer
• Access Rate
• Maximum transmission capacity available on frame
  relay links
• Committed Information Rate
• Rate guaranteed by provider
• Bursts (data transmitted) over CIR will be
  dropped if capacity is unavailable

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Frame Relay Terminology
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Encapsulation Types

• Frame Relay - Cisco default
• IETF - for non-Cisco devices

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Data Link Connection Identifiers (DLCIs)

• Frame Relay PVCs are identified by DLCIs
• IP end devices are mapped to DLCIs
• DLCIs are advertised to all remote sites as the
  same PVC

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Sub-interfaces

• Permit the assignment of different network-layer
  protocols (IP, IPX) on a single interface

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Monitoring Frame Relay

• sho frame ?
• ip show frame relay IP statistics
• lmi show frame relay lmi statistics
• map Frame-Relay map table
• pvc show frame relay pvc statistics
• route show frame relay route
• traffic Frame-Relay protocol statistics

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Troubleshooting Frame Relay
Why cant RouterA talk to RouterB? Hint Consider
the DLCI number shown
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Troubleshooting Frame Relay
Why is RIP not sent across the PVC? Hint Recall
that Frame Relay is a NBMA network