Tag Archives: TDM

CCDA Notes – WAN

Additions/subtractions needed? Let me know.

WAN Categories

  1. Circuit Switched – created only when needed. i.e. ISDN and dial-up.
  2. Leased Lines – dedicated connection. TDM based.
  3. Packet switched – shared bandwidth using virtual circuits. i.e. Frame Relay.
  4. Cell Switched – ATM
  5. Broadband – xDSL, Cable, Wireless

Time Division Multiplexing (TDM)

  1.  Multiple channels such as voice, video, and data can be combined
  2. DS1 or T1 provides 24 time slots of 64kbps each and one 8 kbps control time slot

Frame Relay

  1. NBMA
  2. DLCI = L2 addressing
  3. LMI reports VC status.
  4. LMI has 3 types. Cisco, ANSI, Q.933A. Auto tries all three.
  5. Multipoint interfaces require L2-to-L3 address resolution. Done via inverse-ARP or static “frame-relay map”.
  6. Physical interface is multipoint by default. i.e Serial0/1
  7. Static L2-to-L3 mappings override dynamic mappings.
  8. “frame-relay interface-dlci <dlci #>” on point-to-point subifs. LMI does not communicate DLCI number on subifs.

Inverse-ARP

  1.  Enabled automatically when a supported protocol is cfgd. i.e. “ip address 8.8.8.8 255.255.255.0”
  2. Requests are sent out all circuits assigned to the interface for all supported protocols.
  3. Requests can be disabled via “no frame-relay inverse-arp”. Replies can not be disabled.
  4. Automatically supports multicast/broadcast via a replicated unicast.

SONET/SDH

  1. Circuit-based ring topology.
  2. Optical
  3. ATM or Packet Over SONET(POS)
  4. Optical carrier rates. i.e. OC-1 =51.85 Mbps  OC-255=13.21 Gbps