February Posts

This past week I’ve been learning about the basics about Branch Connections. Early cable systems were one-way, but modern cable systems provide two-way communications that enable internet access, Cable TV, and telephone services. These connections require Hybrid Fiber coaxial. a cabling type that provides the infrastructure that allows cable operators to enable high speed transmission of data to cable modems located in small office/home office. Data over cable service interface specifications (DOCSIS) is the standard that is used to define the communications and support interface requirements for cable. The headend of a network, is the unmanned location where signals are first received, processed, formatted, and then distributed downstream to the cable network. Cable Modem Termination Systems (CMTS) and Cable Modems are required in order to send digital signals upstream and downstream on a cable system; the CMTS is at the head end of the cable operator while the Cable modem is at the subscriber/customer end. Nodes are used in order to convert optical signals to RF signals. DSL is used to provide high-speed connections over installed copper wires. ADSL provides higher downstream bandwidth to the user than upload bandwidth, while the SDSL provides the same capacity in both directions.

PPPoE is Point-to-point protocol over Ethernet, a network protocol for encapsulating PPP frames inside Ethernet frames. PPPoE has the ability to assign IP addresses to remote ends of a link, and ISP’s can use it to assign customers each 1 public address. Using Point to point allows for authentication because it supports CHAP, and this allows ISPs to check accounting records to determine when a customer's line has been paid for or not making use of the link management features. To configure a PPPoE you need to create a dialer interface, a type of a virtual interface, and then configure an ethernet interface to be linked to the dialer interface. In addition, a username and password must be configured matching what the ISP is expecting. Also, it is important to reconfigure the MTU to be 1492, to ensure that it can support transporting PPPoE headers. If issues arise the most likely points of failure are: no responses from the ISP, the LCP is not open, CHAP is misconfigured causing authentication errors, or an IPCP failure. Overall, PPPoE is a very cost-effective way to implement PPP between an ISP and a client without creating a brand new dedicated WAN line.

This past week I’ve been learning more about Access Control Lists. Access Control Lists are sequential lists of either permit or deny statements that apply to addresses or upper layer protocols to decide if a packet should be processed or dropped. Access Control Lists are in charge of limiting network traffic to increase network performance, provide traffic flow control, provide a basic level of security for network access, filter traffic based on traffic type, and control which areas a host can access on a network. Within Access Control Lists there are statements known as Access Control Entries that are used to either permit or deny traffic. To decide if a packet matches the Access Control Entry the Access Control List compares the subnet mask of the incoming/outgoing packet and the wildcard mask in the Access List Entry. If the Wildcard mask and Subnet mask match then the packet will be either permitted or denied depending on the Access Control Entry’s designation. There are 2 main types of Access Control Lists: Standard and Extended. Standard Access Control Lists focus on comparing the source IP address and their subnet masks with the wildcard mask; Extended Access Control Lists are more customizable. Using an Access Control Lists is an effective way to maximize the efficiency of a router and maximize the productivity of the router resources.

This past week I’ve been learning more about Extended Access Control Lists. Access Control Lists are sequential lists of either permit or deny statements that apply to addresses or upper layer protocols to decide if a packet should be processed or dropped. Extended Access Control Lists are in charge of limiting network traffic, based off of Protocol, Source, Destinations, TCP/UDP Ports, or other optional port information, to increase network performance, provide traffic flow control, provide a basic level of security for network access, filter traffic based on traffic type, and control which areas a host can access on a network. To decide if a packet matches the Extended Access Control List Access Control Entry the Extended Access Control List compares the subnet mask of the incoming/outgoing packet and the wildcard mask in the Access List Entry along with any other information listed(like Protocol, Source, Destinations, TCP/UDP Ports, or other optional port information) in the Access Control Entry. If the all the requirements are met then the packet will be either permitted or denied depending on the Access Control Entry’s designation. Extended Access Control Lists are more customizable than Standard Access Control Lists. Using an Extended Access Control Lists is an effective way to maximize the efficiency of a router and maximize the productivity of the router resources.