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Swvlan

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Swvlan

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  2. 2. E0 192.168.1.150 E0 192.168.3.150 LAN - 192.168.1.0/24 LAN - 192.168.3.0/24 HYDERABAD OFFICE BANGLORE OFFICE E0 192.168.2.150 LAN - 192.168.2.0/24 CHENNAI OFFICE 2
  3. 3. Frame Relay • Frame Relay is a data link layer packet-switching protocol that uses digital circuits. • It is used for medium to longer distances and for longer connectivity. • Leased lines also provide longer connectivity but a physical circuit is used to make connection between 2 sites and the same circuit path is used always. • Frame Relay connections use logical circuits to make connections between 2 sites. These logical circuits are referred to as Virtual Circuits(VCs). • Multiple VCs can exist on the same physical connection. • VCs are Full duplex. 3
  4. 4. Advantages of Frame Relay • VCs overcome the scalability problems of leased lines by providing multiple logical circuits over the same physical connection. • Only one serial interface of a router is needed to handle the VC connections to multiple sites Whereas using leased lines multiple serial interfaces are needed to connect to multiple sites. • VCs provide full connectivity at a much lower price compared to leased lines. 4
  5. 5. Frame Relay Terminology • Sub-interfaces • Uses Shared bandwidth • Local Management interface(LMI): – used between the Frame relay DTE(eg.Router) and the Frame Relay DCE(eg. Frame Relay switch) – Defines how the DTE interacts with the DCE – Locally significant – Provides VCs status information(a keep-alive mechanism) – LMI standards : Cisco, ANSI, Q933a The DTE and DCE must have the same LMI signaling type 5
  6. 6. Frame Relay Terminology • Data Link Connection Identifier(DLCI) : – used to identify each VC on a physical interface (i.e.) Each VC has a unique local address called a DLCI number. – switch will map to the destination depending on the DLCI number – Inverse ARP is used to map DLCIs to next hop addresses. – Mapping can also be done manually. – Its Locally significant. – These numbers are given by the Frame relay service providers, Service providers assign DLCIs in the range of 16 to 1007. 6
  7. 7. Frame Relay Terminology • Virtual circuits are of two types: – Permanent Virtual Circuits – PVCs – Switched Virtual Circuits –SVCs • Permanent Virtual Circuit : – similar to a dedicated leased line , permanent connection. – used when constant data is being generated. • Switched Virtual Circuit : – also called as Semi-permanent virtual circuit – similar to a circuit switched connection where the VC is dynamically built and then torn down once the data has been sent. – used when data has to be sent in small amounts 7 and at periodic intervals.
  8. 8. Frame Relay Terminology • Committed Information Rate(CIR) : – Average data rate measured over a fixed period of time that the carrier guarantees for a VC. – committed bandwidth • Burst Rate(BR) : – Average data rate provider guarantees for a VC. – Excess bandwidth 8
  9. 9. Frame Relay Terminology • FECN and BECN : – Forward Explicit Congestion Notification – Backward Explicit Congestion Notification • When congestion occurs switch marks the FECN and BECN bits in the frame header. • FECN is sent to the destination • BECN is sent to the source • Thereby notifying both source and destination about the congestion. • FECN = 0 and BECN =0 implies no congestion. 9
  10. 10. Frame Relay Terminology • FECN and BECN : – Forward Explicit Congestion Notification – Backward Explicit Congestion Notification • When congestion occurs switch marks the FECN and BECN bits in the frame header. • FECN is sent to the destination • BECN is sent to the source • Thereby notifying both source and destination about the congestion. • FECN = 0 and BECN =0 implies no congestion. 9

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