Wide-Area Network
(WAN)
Frame Relay PVC Connection
by
Li , Sheng
104419
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
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
Frame Relay components
 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
Hello, I am 172.168.5.5
6
Hello, I am 172.168.5.7
6
Step 7:Keepalive signaling
Frame Relay link initialization
review
 Step 1:
csu/dsu
 Step 2: Status inquiry
 Step 3: Local DLCI number and status




Step 4: Inverse ARP
Step 5: Frame Relay map
Step 6: Inverse ARP(every 60 seconds)
Step 7: Keepalives message(every 10 seconds)
WAN Connection Considerations
Connection Type
Applications
Leased Lines High control, full bandwidth, high-cost
Frame Relay
ISDN
Asynchronou
s Dialup
X.25
enterprise networks, and last-mile access
Medium control, shared bandwidth, medium
cost enterprise backbone; branch sites
Low control, shared bandwidth, more
bandwidth than dialup
Low control, shared bandwidth, variable costeffectiveness for limited use connections like
DDR
Low control, shared bandwidth, variable costeffectiveness 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 )