| A | B |
|---|
| Frame Relay | switched data-link layer protocol that handles multiple virtual circuits using HDLC encapsulation between connected devices |
| Virtual Circuits | What Frame Relay uses to establish connections across the WAN |
| A connection-oriented service | Where the complete path to the destination is established prior to the sending of the first frame |
| DLCIs | used to identify Virtual Circuits |
| Frame Relay provides a means for multiplexing many logical data conversations (referred to as virtual circuits) | by assigning each pair of DTEs connection identifiers |
| Frame Relay can divide a single Physical WAN Interface into | multiple Subinterfaces |
| Physical and Data Link Layers | Layer of the OSI model at which Frame Relay operates |
| Customer Premises Equipment | CPE |
| data terminal equipment | DTE |
| Frame Relay defines the interconnection process between | the Customer Premises Equipment (CPE) (also known as data terminal equipment - DTE), such as a router, and the service provider’s local access switching equipment (known as data communications equipment - DCE) |
| data communications equipment | DCE |
| Access speed of Frame Relay | 56 kbps, 64 kbps, or 1.544 Mbps |
| VC (Virtual circuit) | Logical circuit created to ensure reliable communication between two network devices. |
| PVC (Permanent Virtual Circuit) | Virtual circuits that save bandwidth associated with circuit establishment and tear down in situations where certain virtual circuits must exist all the time |
| SVC (Switched Virtual Circuit) | Virtual circuit that is dynamically established on demand and is torn down when transmission is complete |
| Data-Link Connection Identifier (DLCI) | A 'local identifier' between the DTE and the DCE, it identifies the logical connection that is multiplexed into the physical channel |
| LMI (Local Management Interface) | A signaling standard between the CPE device and the FR Switch that is responsible for managing the connection and maintaining "status" between the devices. |
| keepalive mechanism | LMI supported mechanism which verifies that data is flowing |
| multicast mechanism | LMI supported mechanism which provides the network server with its local DLCI and the multicast DLCI |
| global addressing | LMI supported mechanism which gives DLCIs global rather than local significance in Frame Relay networks |
| status mechanism | LMI supported mechanism which provides an on-going status report on the DLCIs known to the FR Switch. |
| The main purpose for the LMI process is | management of the connection |
| Transmission of 'keepalive' packets | Insure that the PVC stays up and does not shut down due to inactivity |
| Types of LMIs | Cisco, ansi, q933a |
| LMI encapsulation types | IETF and Cisco |
| CIR (Committed Information Rate) | The rate at which a Frame Relay network agrees to transfer information under normal conditions, averaged over a minimum increment of time, measured in bits per second, and is one of the key negotiated tariff metrics. |
| Local access rate | The clock speed (port speed) of the connection (local loop) to the Frame Relay cloud. It is the rate at which data travels into or out of the network. |
| Committed Burst (Bc) | The maximum number of bits that the switch agrees to transfer during any Committed Rate Measurement Interval |
| Tc | Committed Rate Measurement Interval |
| Excess Burst | The maximum number of uncommitted bits that the Frame Relay switch will attempt to transfer beyond the CIR. |
| Excess Burst is dependent on the service offerings available by your vendor, but is typically limited | to the port speed of the local access loop |
| FECN (Forward explicit congestion notification) | A packet sent by the Frame Relay switch to the destination device indicating that congestion has occurred. |
| BECN (Backward explicit congestion notification) | When a Frame Relay switch recognizes congestion in the network, it sends this packet to the source router instructing the router to reduce the rate at which it is sending packets. |
| DE (Discard Eligibility indicator) | When the router detects network congestion, the FR switch will drop packets with this bit set, first. |
