Sarah Richey
Introduction to Networks & Data Comm
Cynthia Thomas/James McGuffee
Internet Objectives

3. Describe how ISPs work together to create the Internet core.
Internet Service Providers (ISPs) work together to create the internet core by creating connections to each other. First, individual ISPs create their own points of presence (POP). These POP can be geographic or global depending on the ISP. Then the ISP creates connections to their own POP creating their own TCP/IP network. Finally the individual ISPs create connections between each other’s networks. The connections between the ISPs create the internet core. Peering agreements are made between the ISPs which allows packets to be sent to any host connected to the internet using any ISP.
4. Describe the Layer 1 and Layer 2 features used when connecting to an ISP using analog, DSL and cable modems.

Layer 1 & 2 using analog – A local loop is used between the telco central office and the customer (home, business, etc.). At each end of the local loop an analog modem is used. The modems covert the digital signal to analog to send across the loop, and once it arrives to the analog modem at the other end it is converted back into a digital signal. A unique phone number is assigned to a customer by the telco. When the internet is being accessed through an analog local loop you cannot make a phone call. Using analog means you can be on the phone or you can be on the internet, but you cannot do both at the same time. For the data link portion point-to-point protocol (PPP) is used for encapsulating and sending IP packets. PPP also assists in helping a host learn their own IP configurations by making requests.

Layer 1 & Layer 2 using DSL – Digital subscriber lines use the same local loop as analog, but utilize the frequencies outside of the frequencies in which humans speak and hear. DSL