Level of ISP Internet Access Redundancy
Murphy is out there, ready to make your life miserable. Whether because of bad weather, carrier problems, or just plain bad luck, an ISP's connection to a NAP, another provider, or another POP will become unavailable at some point, potentially resulting in the inability to reach all or a set of destinations. A redundant network enables traffic to utilize an alternative path to reach those destinations until the problem has been corrected. A well-designed ISP network has POPs ..
Figure 14-13 shows the format of RSVP messages, which consist of a header containing seven defined fields and one reserved field, followed by a main body containing a series of RSVP objects. Figure 14-13. RSVP Message s Each message begins with a 4-bit RSVP version number: the current version is 2. This is followed by a 4-bit flag field, which is currently unused. The type field indicates the message type: A 16-bit standard TCP/UDP checksum is used over the..
Layer 2 Virtual Private Networks
An L2VPN interconnects customer devices (such as a host, a router, or a Layer 2 switch) at multiple sites and allows them to communicate using Layer 2 frames.[13] An L2VPN service provider can offer several types of L2VPN services to its customers, such as point-to-point and point-to-multipoint. In any type of L2VPN service, a PE performs the following tasks: • Receives a Layer 2 frame from a CE over an attachment circuit (which could be an FR DLCI, an AT..
The value proposition of a network is that it ties together different entities and enables exchange of information. The network's value is also directly related to its size. The more entities that are connected and partake in the network, the higher the impact of the network is. For exchange and scaling to occur in a relevant and orderly manner, the connected entities must use the same language. As such, standards form an integral component of networks because they enforce or..
Manually Configuring STP Timers
Use one or more of the following global configuration commands to modify STP timers: Switch(config)# spanning-tree [vlan vlan-id] hello-time seconds Switch(config)# spanning-tree [vlan vlan-id] forward-time seconds Switch(config)# spanning-tree [vlan vlan-id] max-age seconds Notice that the timers can be changed for a single instance (VLAN) of STP on the switch by using the vlan vlan-id parameters. If you omit the vlan keyword, the timer values are configured for all in..
