© Copyright 1997, The University of New Mexico D-1 Dialups Access for Remote Users via Telephone lines

© Copyright 1997, The University of New Mexico D-2 Dialups Uses a remote node - typically a PC Requires phone lines, modems, and terminal servers Phone lines are typically set up in ‘hunt groups’ (a.k.a. phone rotors)

© Copyright 1997, The University of New Mexico D-3 Analog Uses standard phone lines and modems Limited to < 53 Kbps Line quality often limits throughput

© Copyright 1997, The University of New Mexico D-4 Digital ISDN, ADSL, etc. Requires Digital Lines and Service Requires Digital Modems at both ends

© Copyright 1997, The University of New Mexico D-5 ASCII Dial-in Services The remote node acts like (emulates) a ‘dumb’ terminal. Requires the remote node to run terminal emulation software: –Kermit, ProComm, HyperTerminal, etc. The terminal server provides telnet or other capabilities

© Copyright 1997, The University of New Mexico D-6 Dialup Networking (PPP and SLIP) The remote node acts like a locally-attached network node. Requires the remote node to run a TCP/IP stack –Winsock for windows 3.1 and 3.11 –Windows 95 or NT Dialup Networking –MacPPP or Apple OpenTransport

© Copyright 1997, The University of New Mexico D-7 PPP Point to Point Protocol Preferable to SLIP –Requires less setup and scripting –Negotiates MTU, IP address, subnet mask, default gateway

© Copyright 1997, The University of New Mexico D-8 Winsock Windows Sockets Standardized Interface to TCP/IP services

© Copyright 1997, The University of New Mexico D-9 Windows 95 Dialup Networking is PPP Treats Modem like any other network interface Applications don’t know the difference

© Copyright 1997, The University of New Mexico D-10 MacPPP Implements PPP on MacOSs

© Copyright 1997, The University of New Mexico D-11 Unices May require recompiling kernel or kernel extensions

© Copyright 1997, The University of New Mexico D-12 Protocols IP IPX NetBEUI Appletalk

© Copyright 1997, The University of New Mexico D-13 TCP/IP Internet Standard Protocol End node requires an IP address, subnet mask, gateway address, MTU

© Copyright 1997, The University of New Mexico D-14 IPX Novell Netware typically uses IPX packets, not IP packets End node needs a network number and network ID

© Copyright 1997, The University of New Mexico D-15 Appletalk Appletalk is used to access AppleShare disks and/or printers End node requires an Appletalk Zone

© Copyright 1997, The University of New Mexico D-16 Virtual Private Tunneling Networks Creates a private, encrypted network within a public network Packets are encrypted, then passed over public networks Encryption reduces the risk of ‘packet sniffing’ Primarily used on NT

© Copyright 1997, The University of New Mexico D-17 Capacity Currently one of the fastest-growing services Typical ‘prime time’ hours are 8:00 am to midnight Average ASCII session lasts < 20 minutes Average PPP session lasts > 40 minutes

© Copyright 1997, The University of New Mexico D-18 Time Limits A necessity unless you have unlimited resources (phone lines, modems, terminal servers) They are never popular They should be imposed from the beginning They are easier to relax than to tighten, so start conservatively

© Copyright 1997, The University of New Mexico D-19 Time Limits Some lines for very short sessions (< 10 minutes) to check The vast majority of sessions are under 2 hours. A few lines for very long or unlimited sessions (downloads, etc.) You can roll lesser service levels over to greater service levels

© Copyright 1997, The University of New Mexico D-20 Security Authorization - who is connected to you network –RADIUS Access Controls - Where can they connect to and what can they do –by network or per host A ‘must’ for PPP and SLIP A good idea for ASCII users

© Copyright 1997, The University of New Mexico D-21 Problem Determination Who is on? Is the user actually connected? Where are they connected? What protocol are they using? How is the connection configured?

© Copyright 1997, The University of New Mexico D-22 Accounting Important as an audit trail Begin and end date and time, user, line, protocol

© Copyright 1997, The University of New Mexico D-23 Routing Controls Without a route to a given destination set on the terminal server, clients cannot send packets to that network or system. If ASCII dial-in users are not authenticated, then they should not have routes to any unsecured systems, services, or the Internet

© Copyright 1997, The University of New Mexico D-24 Throughput Modem protocols above 14.4 Kbps include data compression, so compressible data gets a bigger apparent boost

© Copyright 1997, The University of New Mexico D-25 Line Quality Modems test the line quality and will ‘throttle down’ to a reliable speed Line quality involves several segments –End user’s lines to local switch –Inter-office trunk lines –Service Provider’s lines to local switch

© Copyright 1997, The University of New Mexico D-26 Telephone Switching Capacity Inter-office services - ‘trunk lines’ between local switching centers - are the most common bottleneck. The typical telephone switching center is designed for each phone to be in use an average of 3 minutes per hour at peak load. Widespread Internet access via dialups may require as much as 15 times the telephone switching capacity currently in place