WAN

• There are three types of Wan Connectivity :

– Dedicated Lines (Leased Lines)

– Circuit Switching

– Packet Switching

WAN Connection Types

– Permanent connection for the destination– Used for short or long distance– Bandwidth is fixed– Availability is 24/7– Charges are fixed whether used or not.– Uses analog circuits – Always same path is used for destination– Example is Leased Line

• Leased Line is of three types1) Short Leased Line

2) Medium Leased Line

3) Long Lease Line (IPLC)

Dedicated line

EXCHANGE

E0 10.1.1.1/8

LAN – 10.0.0.0/8HYDERABAD

OFFICE

E0 20.1.1.1/8

LAN – 20.0.0.0/8

KSAMUX

2 pair of Copper Wire

G.703 Modem

G.703Modem

HYDERABADMUX

KSA OFFICE

Fiber Optic Cable

V.35 Cable

V.35 Cable

V.35 Modem

• Advantages• Complete secure • High Bandwidth• High speed connection• Superior quality • Reliable

• Disadvantages• Expensive • Permanent physical connection

Advantages and Disadvantages of Leased Lines

– It is also used for short and medium distances.– Bandwidth is fixed– Charges depend on usage of line– Also called as line on demand.– Usually used for backup line– Connects at BRI port of router– ISDN and PSTN are the examples

Circuit switched Networks

– Used for medium or longer connections– Bandwidth is shared– Many virtual connections on one physical

connection– Example: - Frame Relay

Packet switched Networks

Frame Relay

• Frame Relay is a connection oriented, standard NBMA layer 2 WAN protocol

• Connections in Frame Relay are provided by Virtual circuits.

• Virtual circuits are multiple logical connections on same physical connection

• Frame Relay virtual connection types.a) PVC b) SVC

Frame Relay

• Advantages Of Frame-relay

– VC’s overcome the scalability problem of leased line by providing the 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

– Cheaper– Best quality– VC’s are full duplex

• 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 DLCI’s 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 DLCI’s in the range of 16

to 1007.

Frame Relay Terminology

• Frame-relay technology Uses Shared bandwidth

• Local Management interface(LMI):

– used between the Frame relay DTE (eg.Router) and the Frame

Relay DCE (e.g.. 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

Frame Relay Terminology

Congestion Notification

• 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.

Congestion Notification

• INSERT LAB steps