Frame Relay PVC Connection by Li, Sheng Wide-Area Network (WAN) Wide-Area Network (WAN)

Wide-area Network

WAN connection type  Leased lines  Circuit switched  Packet switched

WAN connection type Leased Lines—also known as a point-to-point or dedicated connection, provides a single preestablished WAN communications path from the customer premises through a service provider network to a remote network.This connection is reserved by the service provider for the client’s private use. Leased lines are very fast but they are also costly.

WAN connection type Circuit switched –circuit switched is a WAN switching method in which a dedicated circuit path must exist between sender and receiver for the duration of the call. Circuit-switched connection are commonly used in environments that require only sporadic WAN usage. For example, It is used by service provider network when providing ISDN, and it is cheap one.

WAN connection type Packet switched—Packet switched is a WAN switching method in which network devices share a single point to point link to transport packets from a source to a destination across a carrier network. Packet switching offers services similar to Those of leased lines, except the line is shared, and the cost of the service is lower. But the cost of the service is higher than circuit switched connection types.

WAN connection type

Wan layer2 encapsulation type

 Leased line : HDLC, PPP, SLIP  Circuit-Switched: HDLC, PPP, SLIP  Packet-Switched: X.25, Frame Relay,ATM

Frame Relay  is a data link layer protocol that handles multiple virtual circuits.  is an standard that defines the interconnection process between your router and service provider`s local access switching equipment.  is a connection-oriented data link technology that is streamline to provide high performance and efficiency.

Frame Relay overview Frame relay only works at User’s DTE ( means Data terminal equipment) and provider’s DCE( data circuit –terminating equipment) or frame relay switch.

Frame Relay components

PVC SVC  VC (Virtual Circuit) : Logical circuit created to ensure communication between two network devices. Include PVC (permanently VC) and SVC(switched VC);  DLCI (Data-link connection identifier): A number that identifies the logical circuit between the router and the frame relay switch.  Inverse ARP(Inverse Address Resolution Protocol): Method of dynamically associating a network layer address with a DLCI.

Frame Relay link initialization Each router thought a CSU/DSU connects to the Frame Relay switch.

Frame Relay link initialization(1)

Frame Relay link initialization (2)

Step 5: Frame Relay address mapping

Step 6: Send Inverse ARP again 6 Hello, I am Hello, I am

Step 7: Keepalive signaling

Frame Relay link initialization review  Step 1:  Step 2:  Step 3:  Step 4:  Step 5: Frame Relay map  Step 6:  Step 7: Keepalives message(every 10 seconds) csu/dsu Status inquiry Local DLCI number and status Inverse ARP Inverse ARP(every 60 seconds)

Connection Type Applications Leased Lines High control, full bandwidth, high-cost enterprise networks, and last-mile access Frame Relay Medium control, shared bandwidth, medium cost enterprise backbone; branch sites ISDN Low control, shared bandwidth, more bandwidth than dialup Asynchronou s Dialup Low control, shared bandwidth, variable cost- effectiveness for limited use connections like DDR X.25 Low control, shared bandwidth, variable cost- effectiveness for limited use connections, high reliability WAN Connection Considerations

References  Interconnecting Cisco network devices (Cisco press, Edited by Steve McQuerry)  Online version of the BCRAN (Cisco's e- learning )