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FRAME RELAY

FRAME RELAY. E0 192.168.1.150. E0 192.168.3.150. LAN - 192.168.1.0/24. LAN - 192.168.3.0/24. E0 192.168.2.150. HYDERABAD OFFICE. BANGLORE OFFICE. LAN - 192.168.2.0/24. CHENNAI OFFICE. Frame Relay.

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FRAME RELAY

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  1. FRAME RELAY

  2. E0 192.168.1.150 E0 192.168.3.150 LAN - 192.168.1.0/24 LAN - 192.168.3.0/24 E0 192.168.2.150 HYDERABAD OFFICE BANGLORE OFFICE LAN - 192.168.2.0/24 CHENNAI OFFICE

  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.

  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.

  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

  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.

  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 and at periodic intervals.

  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

  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.

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