frame relay

mattau

when they say frame relay is considered packet switching how does this work with a permanent virtual connection.

doesnt pvc more or less act like a leased line ? and therefore the packets that you send should only go through one path to get to the destination vs going through several interconnected paths within the cloud ?

how can it for example go through DLCI x and get to the DLCI on the other side by each packet taking different paths. When you buy a path from a service provider dont they set it up so it acts like a leased line and just the 1 path to your other destination (obviously you dont see the traceroute to within the cloud you only see that you have a direct route from A to B straight through. )

hope someone can clear this up for me. Unless what i am thinking is correct then just clarify for me

mattau

I think i found my answer on the microsoft site

In a connection-oriented service, the communications link is made before any packets are transmitted. Because the link is established before transmission begins, the packets comprising a message all follow the same route to their destination. In establishing the link between sender and recipient, a connection-oriented service can make use of either switched virtual circuits (SVCs) or permanent virtual circuits (PVCs):

Using a switched virtual circuit is comparable to calling someone on the telephone. The caller connects to the called computer, they exchange information, and then they terminate the connection.

Using a permanent virtual circuit, on the other hand, is more like relying on a leased line. The line remains available for use at all times, even when no transmissions are passing through it.

so i think i am correct in saying it is like a leased line that always has one path although the path is unknown as the service provider constructs that path through their network

greenerek

PVC provides permanent connection for DLCI during subscribe time even if session is finished, whiles SVC is provides link only when connection is active.

What Cisco says....

permanent virtual circuit (PVC)—A Frame Relay logical link whose endpoints and class of service are defined by network management. Analogous to an X.25 permanent virtual circuit, a PVC consists of the originating Frame Relay network element address, originating data-link control identifier, terminating Frame Relay network element address, and termination data-link control identifier. “Originating” refers to the access interface from which the PVC is initiated. “Terminating” refers to the access interface at which the PVC stops. Many data network customers require a PVC between two points. DTE that needs continuous communication uses PVCs.