Network Sales and Services Handbook (Cisco Press Networking Technology)

Customer site access to network services (from a NSP) requires a physical connection, often in the form of landline facilities (as opposed to wireless facilities) to the NSP CO or point-of-presence (POP). This local access, also known as the local loop or the last mile, can support both dedicated and switched services, including voice, data, fax, or video services. This local access can be either a copper or fiber-optic based facility, depending on the customer's requirements and the cost and expense of laying new facilities (if necessary).

There are two types of access circuits:

• Dedicated DS0, DS1/DS3, OC-x

• Switched POTS/PSTN, ISDN-BRI/PRI

Dedicated access circuits provide permanent connectivity to a network service provider, whereas switched access circuits provide on-demand connectivity. Switched access requires a call-setup procedure, often in the form of dialing a PIC/CIC from the user interface, unless otherwise programmed into the customer premise PBX or voice switch.

The following components are fundamental to a local access circuit:

• CSU/DSU or other signal termination device (for example, WAN interface card (WIC) in a Cisco Series Router

• RJ Jack

• (Extended) Demarc point

• Punch-down block (also known as 66-block)

• NIU/NTU

• Local Loop (Copper or Fiber)

• LEC CO

• LEC/IXC trunk between the LEC CO and the IXC CO (depending on the subscribed service; for example, long-distance voice or data service)

The following components are fundamental to a LEC/IXC CO:

• LTE Light termination equipment

• M13 Multiplexer DS1/DS3

• DACS (or DXC)

• Voice or data switch