Pertemuan 24 Frame Relay Concepts

Discussion Topics Introducing Frame Relay Frame Relay terminology Frame Relay stack layered support Frame Relay bandwidth and flow control Frame Relay address mapping/topology Frame Relay LMI Stages of Inverse ARP and LMI operation

Frame Relay Operation

Frame Relay Switches

Frame Relay Concepts

Virtual Circuits

Local Significance of DLCIs The data-link connection identifier (DLCI) is stored in the Address field of every frame transmitted.

Terminology The connection through the Frame Relay network between two DTEs is called a virtual circuit (VC). Virtual circuits may be established dynamically by sending signaling messages to the network. In this case they are called switched virtual circuits (SVCs). Virtual circuits can be configured manually through the network. In this case they are called permanent virtual circuits (PVCs).

Frame Relay Stack Layered Support

Frame Relay Functions

Bandwidth and Flow Control Bit counter Example 1

Frame Relay Concepts Queue

Frame Relay Concepts

Frame Relay Concepts

Selecting a Frame Relay Topology Full Mesh Purpose: This figure is a transition discussion to illustrate the need for subinterfaces. Now that students are familiar with the concept and configuring of Frame Relay, they are ready to consider the issues and solutions related to broadcast updates in an NBMA Frame Relay network. Emphasize: Compare the different topologies described. Explain that by default interfaces that support Frame Relay are multipoint connection types. This type of connection is not a problem when only one PVC is supported by a single interface; but it is when multiple PVCs are supported by a single interface. In this situation, broadcast routing updates received by the central router cannot be broadcast to the other remote sites. Broadcast routing updates are issued by distance vector protocols. Link-state and hybrid protocols use multicast and unicast addresses. Partial Mesh Star (Hub and Spoke)

LAPF Frame – Address Field 6-bits 4-bits

Data Link Control Identifier The 10-bit DLCI associates the frame with its virtual circuit It is of local significance only - a frame will not generally be delivered with the same DLCI with which it started Some DLCI’s are reserved

Local Management Interface (LMI) Three types of LMIs are supported by Cisco routers: Cisco — The original LMI extensions Ansi — Corresponding to the ANSI standard T1.617 Annex D q933a — Corresponding to the ITU standard Q933 Annex A

LMI Frame Format 1 2 1 1 1 1 2 1 Flag Address Control PD CR MT LMI Message FCS Flag Frame Relay Characteristics: - Connection oriented protocol with a path defined between two end devices (PVC) - Basic Error Detection w / no Recovery (Relies on upper layer protocols) - Data Link Connection Identifier (DLCI) used to identify ‘conversations’ on link - Each DLCI has local significance determined by provisioning - LAPD packet encapsulation (ITU-T Q.922) - Contains data and addressing information Analogy: Phone cable has multiple pairs of wires (one for each conversation) a single Frame Relay interface can contain multiple ‘conversations’. Network Telephone switches cross-connect physical circuits until a complete connection is made through the network. Frame Relay is routed through the network based on the DLCI within each frame. The difference is multiple channels exist within a single physical circuit and the circuit is not tying up resources during idle times. (Unlike falling asleep on the phone..)

Stages of Inverse ARP and LMI Operation #1

Stages of Inverse ARP and LMI Operation #2