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SLIP and PPP: Remote access to PennNet

By Celeste Stewart and Tony Olejnik

If you haven't heard about PPP, it's time to update your network vocabulary. Data Communications and Computing Services (DCCS) recently announced support of PPP software for Windows. PPP, like MacSLIP (a Macintosh product supported at Penn for some time), allows you to access Internet resources such as World-Wide Web (WWW) and NetNews as well as PennInfo and the Library's many online services, using a high-speed modem and the same point-and-click suite of software already available to those with an Ethernet connection in their campus office or ResNet dorm room. You can, for example, use Mosaic rather than Lynx to access the WWW, or NewsWatcher or Trumpet, rather than the character-based tin newsreader, to read and post news.

SLIP vs PPP

Both SLIP (Serial Line Internet Protocol) and PPP (Point-to-Point Protocol), the underlying protocols on which MacSLIP and PPP are based, package Internet Protocol (IP) data for transmission over serial wires such as telephone lines. But that's where the similarity ends. Although SLIP is still widely used, it appears to have exhausted its potential and its development has stagnated. In contrast, PPP is under active development and is widely regarded as the eventual successor to SLIP. PPP has features lacking in SLIP, including error detection and mechanisms for negotiating IP parameters such as IP addresses. More importantly, the PPP specification supports protocols other than IP, such as AppleTalk and IPX (Novell's Netware). Thus, you will eventually be able to access IP services (FTP, Telnet, WWW, NetNews, etc.) as well as campus AppleTalk and Netware file servers from off-campus locations. The University has already begun to migrate from a mixed PPP/SLIP environment to a unified PPP environment.

Which one is for me?

Simple. If you use a Windows-based PC off campus, install the PPP software. If you use a Macintosh, install MacSLIP, the SLIP software.

Penn is migrating from SLIP to PPP in two phases. The first phase, implementing a PPP solution for Windows, has been completed. As a result, DCCS will no longer distribute or provide support for the PCSLIP tool included with Novell's LAN Workplace (LWP) software. Windows users of PCSLIP should migrate to PPP to remain current with supported software. PPP takes advantage of the currently-supported vendor software bundled with LWP, which includes the TCP/IP stack for on-campus access to IP services, as well as extensive vendor support, documentation, and online help. In addition, PPP resolves most of the scripting problems users encountered with LWP's PCSLIP.

PPP and PennNet

PPP, and not SLIP, will play an important role in the future architecture of PennNet. To complete the transition to PPP, DCCS must implement a PPP solution for the Macintosh and upgrade the University's terminal servers. Although PennNet itself "supports" both SLIP and PPP, the terminal servers (which enable modems to access PennNet and Internet services) currently only support the Internet Protocol. Therefore, feature-rich PPP services - assigning dynamic IP addresses, built-in authentication, and the much-awaited ability to access AppleTalk and Novell's IPX services via modem - will not be available until DCCS acquires advanced terminal servers that can support PPP's functionality. Solutions for both Macintosh PPP and advanced terminal servers will be announced in the Penn Printout as future phases of the project are completed.

Additional information

Check PennInfo for more information about MacSLIP (keyword "macslip") and PPP (keyword "ppp"), call the PennNet help desk at 898-8171, or send e-mail to help@dccs. Additionally, check the following newsgroups for information: upenn.net.ppp, comp.protocols.ppp, upenn.net.macslip, and comp.sys.mac.comm.

Sidebar: Where to get PPP and SLIP

Windows PC

PPP is available via ftp at ftp.upenn.edu/pc/ppp. For instructions on downloading and installing the software, see the README file in the /pc/ppp directory. Note that PPP is site-licensed software from Novell and is available via authenticated ftp only, so log on to the server using your PennNet ID and password.

PPP is also distributed on installation disks by the PennNet help desk, (Suite 221A, 3401 Walnut Street) Monday through Friday from 10 AM to noon. Bring two unformatted DS/HD (double-sided/high-density) disks. If these hours are not convenient, call the PennNet help desk (898-8171) to arrange a time to pick up the software.

Macintosh

MacSLIP, site-licensed software from Hyde Park Software, is distributed free of charge by the CRC, 3732 Locust Walk. The MacSLIP distribution disk includes MacSLIP, Apple's MacTCP, some sample networking software, and instructions on how to install the software. To obtain MacSLIP, bring one unformatted DS/DD (double-sided/double-density) disk or two unformatted DS/HD (double-sided/high-density) disks.

MacSLIP is also available on Penn's ApppleShare server, which is in the UPenn-ISC-DCCS AppleTalk zone. Log in as user "Penn" with password "Penn" and then select the Penn_Software volume. MacSLIP is in the network_drivers folder.