Manual Summaries and the AS_PATH Path Attribute
As covered in the last several pages, a router can add entries to its BGP table using the network command and route redistribution. Additionally, BGP can use manual route summarization to advertise summary routes to neighboring routers, causing the neighboring routers to learn additional BGP routes. BGP manual summarization with the aggregate-address command differs significantly from using the auto-summary command. It can summarize based on any routes in the BGP table, creat..
Basic subnetting and variable-length subnets are often misunderstood. This section gives a brief introduction to how subnetting works, and the next section discusses variable-length subnet masks (VLSMs). A subnet, or subnetwork, is a subset of a Class A, B, or C network. To better understand subnetting, it helps to take a closer look at IP addresses that are not subnetted. As explained earlier, IP addresses are comprised of a network portion and a host portion, representing a..
If noise at the radio card is high, the radio card will have difficulty recovering the signal, which results in bits errors and retransmissions. An important signal measurement is the signal-to-noise ratio (SNR). The SNR (in dB) at a particular point in the network is simply the signal power (in dBm) minus the noise power (in dBm). A signal power of –65 dBm and noise power of –90 dBm yields an SNR of 25 dB. The noise power is anything other than signals corresponding to t..
The first approach utilizes a single CPU-controlled shared bus that connects a number of slave interface cards. This arrangement can be based on a general-purpose computer, such as a PC running UNIX or Windows NT. Various bus communication strategies (such as shared memory, DMA, and bus mastering), together with high-performance RISC CPUs, can result in a router of significant forwarding capabilities. A large number of dedicated-purpose centralized CPU router pl..
The Need for Queuing on Frame Relay Networks
Modern Frame Relay networks service a mixed variety of traffic types from users. Among the different types of traffic, mission-critical and delay-sensitive traffic are extremely susceptible to network latency. For example, delay-sensitive traffic, such as voice, is intolerant to network latency and delay largely because of the nature of the application. Network latency and delay could cause voice packets to be delayed, lost, or arrive out of order. This can severely impact th..
