cisco ccna home lab kit

cisco ccna home lab kit.PVC is similar to a leased line, which is why it is called a permanent VC. To send data using a PVC, you must configure it on the router and on the carrier switch. One disadvantage of PVCs is that a lot of manual configuration work needs to be done in advance to build the PVC. another disadvantage is that it is not very flexible: when a PVC fails, it cannot be rebuilt dynamically. However, after a PVC is configured, it will always be available unless there is a failure between the source and destination sites. One area where PVCs are superior to SVCs is that they must be established before sending data using an SVC, which introduces some delay to traffic.SVCSVC is similar to making a phone call. For example, when making a phone call in the United States, you need to dial a 7, 10, or 11-digit phone number. These numbers are handled by the carrier's telephone switch, which establishes a circuit to the destination telephone based on the telephone routing table. Once the circuit is established, the destination phone will ring, and the conversation can begin once the phone is taken off-hook. After the conversation is complete, the phone hangs up, causing the carrier switch to remove the corresponding circuit-switched connection.SVCs use a similar process. Each SVC device is assigned a unique address, similar to a telephone number. To connect to the target device using the SVC, its address needs to be known; in a WAN environment, this is typically configured manually on the SVC device. Once the address of the target device is known, the source device can communicate it to the operator SVC switch. The SVC switch finds a path to the target device and establishes a VC to the target device; once the VC is established, the source and target devices are notified and they can begin sending data over that VC. After sending the data, the source and target devices can send a signal to the operator switch to remove the connection. An example of such a VC is ATM, where the Layer 2 addresses are called Network Service Access Point (NSAP) addresses, which are similar to Ethernet MAC addresses and Frame Relay Data Link Connection Identifiers (DLCIs).One advantage of SVCs is that they are temporary. Because SVCs are used only occasionally, they are less expensive than PVCs, which remain on the carrier's network even when you are not sending data over them.However, the problem with SVCs is that the more you use them, the more they cost. It's like long-distance calling on a per-minute basis - the longer you talk, the more it costs. After a certain point of use, dynamic SVC costs more than fixed PVCo Part 7 Cisco Routers and WANsIn practice, SVCs are ideal for use as a backup connection: you can purchase both a primary PVC for a monthly fee and a backup SVC for a per-use fee (based on time of use or traffic sent); if the primary PVC goes down, use the SVC, and then stop using it when the primary PVC is restored.To determine whether to use SVC or PVC, several factors need to be weighed, such as usage and the cost of PVC and SVC at that usage level. Another advantage of SVC is the ability to adapt to network changes: if a physical link in the carrier's network fails, the SVC can be rebuilt over a redundant physical link in the carrier's network.The main disadvantage of SVC is that you are responsible for configuring and troubleshooting it, and it takes some time to set up. For example, to build an SVC, you need to manually create resolution tables for the network layer protocols used between the current router and the remote router. If IP, IPX, and AppleTalk are also used, you will need to configure entries in the resolution table for all of these protocols. The resolution table maps the remote router's network layer address to the SVC address; it can take a long time to create the resolution table, depending on the number of protocols running and the number of sites connected. Also, troubleshooting SVCs is more difficult because it involves additional configuration that you are responsible for, in addition to the Layer 2 routing table used by the carrier. PVCs are actually much easier to configure. Also, when there is no SVC to the remote site, the router must establish the SVC and wait for the carrier switch to complete the process before it can begin sending information to the remote site.While Frame Relay is a much more cost-effective solution than private circuits, it is increasingly being replaced by other solutions such as VPNs over the Internet using DSL and cable modems. however, private networks such as Frame Relay and ATM are still used for latency-sensitive traffic such as voice and video, but these two private network technologies are increasingly being used Ethernet or ATM in the carrier network for Multiprotocol Label Switching (MPLS).