Using and Managing PPP: Help for Network Administrators

by Andrew Sun, Mike Loukides (Editor)

Overview

In the last decade, the Internet has grown from a network that connected a few universities and research centers to a network that links many businesses and households all over the country. That expansion occurred for many reasons, but the technological advance that facilitated this growth was an obscure protocol called PPP. PPP isn't talked about as much as TCP and IP, but it plays a crucial role in extending networks into remote locations. The Point-to-Point Protocol enables telephone lines and other point-to-point connections to carry Internet traffic. It's the protocol that establishes and maintains the connection between your home and an Internet service provider. This book provides in-depth coverage of PPP for network administrators and others who are involved in the care and maintenance of PPP connections. It provides a thorough introduction to how PPP works, which will help you diagnose and troubleshoot problems. It discusses in detail how to set up dial-in and dial-out PPP on the most important platforms, including Windows, Linux, and Solaris. Whether you're a sophisticated user responsible for your own connection or a network administrator providing dial-up services for hundreds of remote users, you'll find this book an essential addition to your library. Covers:

• PPP implementations in Windows 95/98/NT, Solaris, and Linux
• Authentication (CHAP, PAP, Microsoft variants, and other techniques)
• Virtual networks and tunnels, including PPTP
• Modems and serial lines
• Related technologies, including DNS and ARP
• Optimizing and customizing a connection
• Debugging techniques

Product Details

ISBN-13:	9781565923218
Publisher:	O'Reilly Media, Incorporated
Publication date:	01/28/1999
Pages:	444
Product dimensions:	7.00(w) x 9.19(h) x 0.93(d)

About the Author

Andrew Sun's experience with computers dates back to the early 1980s. He is an electrical engineer by training, with an MSEE degree from Stanford University. Andrew has many years of experience in the telecommunications industry and has performed engineering work for emerging broadband ISDN and ATM products. He currently engineers IT infrastructures, and his areas of expertise include networking, firewalls, email with SMTP, DNS, Usenet, Solaris administration, and of course, dial-up remote access.

Table of Contents

Preface

1. What Is PPP?
     Early Remote Access and Networking
     Serial Line Internet Protocol (SLIP)
     Point-to-Point Protocol (PPP)
     Open Systems Interconnect Model
     What You Need to Know

2. Serial Interfaces and Modems
     Serial Interfacing
     Modems

3. How PPP Works
     PPP Frame Format
     PPP Connection States
     Link Control Protocol
     Authentication in PPP
     Network Control Protocol
     Internet Protocol Control Protocol
     Compressed Datagram
     What PPP Doesn't Provide

4. TCP/IP
     The Internet Protocol
     Van Jacobson Compression
     IP Addresses
     Media Access Control Addresses
     Routing

5. Selecting Hardware, Software, and Services
     Selecting Serial Connections
     PPP Hardware
     PPP Software

6. Dial-out PPP Setup
     PPP Sign-on Procedures
     General PPP Setup Steps
     Linux PPP-2.3
     Solaris PPP
     Windows 3.1
     Windows 98 (and 95)
     Windows NT 4.0 Workstation

7. Dial-in PPP Setup
     Dial-in PPP Architecture for Internet Access
     Communication Servers
     Linux PPP-2.3
     Solaris PPP
     Windows NT 4.0 Server

8. Network Architectures Incorporating PPP
     Choosing Network Architectures
     Proxy ARP
     Split Subnet
     Unnumbered
     PPP in a Subnet
     Multipoint PPP in a Subnet

9. Routing to PPP Connections
     Routing Entries
     Using Default Routes
     Using Subnet Routes
     Using Host-Specific Routes
     Dynamic Routing Protocols

10. Domain Name System
     Domain Name System Hierarchy
     Using DNS
     DNS Records for PPP
     Setting up DNS Name Resolution
     DNS Servers

11. Customizing and Tuning PPP
     PPP Startup Options for Dial-in Servers
     PPP Startup Options for Dial-out Servers
     Adjustable LCP Options
     Authentication Policy
     Adjustable IPCP Options
     Setting IP Addresses
     Other Adjustable Settings

12. Authentication
     Password Authentication Protocol
     Challenge Handshake Authentication Protocol
     Microsoft CHAP
     Authenticating Outside PPP
     Call Back
     Security Tokens

13. Private Networks
     Private Network Setup
     Application Layer Proxies
     Network Address Translation

14. Virtual Private Networking and Tunneling
     Virtual Private Network Architectures
     Tunneling Protocols
     Redirecting Serial Input/Output
     Setting up Outgoing PPP Tunnels
     Setting up Incoming PPP Tunnels
     Routing with Tunnels
     Network Security

15. Troubleshooting
     Troubleshooting Approaches
     Trace and Activity Logs
     Checking the Serial Connection
     Checking Modems
     Chat Script Problems
     PPP Failures
     Checking TCP/IP

16. What's New for PPP?
     Communication Services
     Network Layer Protocols
     PPP Extensions
     Developments Relating to PPP
     Product Obsolescence

A. PPP Assigned Numbers

B. Serial Interface Emulation Index:

A
ACCM (see asyncmap)
activity logs, 330
Address Resolution Protocol (see ARP)
admintool utility, configuring Solaris login service, 174
application layer proxies, 291-292
ARP (Address Resolution Protocol), 77-78
ARP tables
      listing contents of, 77
      Proxy ARP, 196
      Split Subnet, 199
arp utility
      checking DNS, 236
      editing ARP tables, 178
      listing ARP table contents, 77
ARPAnet, history of PPP and, 3-4
asppp program, 123-126, 177-178
asyncmap (async control character map), 32-34, 43, 98
      asyncmap default, 367
      setting options, 251-252
authentication, 114, 269
      CHAP, 276-277
      counters and timers, 259
      dial-in PPP, 157
            authentication servers, 160
            Windows NT, 183, 187
      DNS names, 237
      options offered by PPP software, 98-99
      outside PPP, 281-283
      PAP, 270-272
      policy, 257-260
      problems with, 356-359
      protocol option, 44
      protocols, 49-53
      security-token, 285-288
      supported by Windows 98, 135
      (see also individual authentication protocols)
autodetection, of PPP frames, 35

B
bandwidth-to-user ratios, 93
BAP (Bandwidth Allocation Protocol), 392
BIND (Berkeley Internet Name Domain), 240
B-ISDN (Broadband Integrated Services Digital Network), 385
bit timings, of TD line format, 14-16
breakout boxes, 13

C
Call Back Control Protocol (CBCP), 393
call-back systems, 392-394
      authentication, 284-285
      security, 284
carrier rate, 22
CBCP (Call Back Control Protocol), 393
CCP (Compression Control Protocol), 58, 135, 363-364
CD (Carrier Detect) control signal, 18
CHAP, 51-52, 260, 274-275
      authenticating clients, 276
      authenticators, 276-277
CHAP-80 (see MS-CHAP)
chap-secrets file, 276-277
chat
      configuration, 112-113
      dial-up process and, 115
      invoking with pppd, 112
chat scripts, 112
      authenticating with outside PPP, 283
      call-back systems, 285
      as feature of PPP software, 96-97
      problems with, 348-354
      UUCP, 120-122
CIDR tables, 79-216
classful routing tables, 80-82
classless interdomain routing (see CIDR tables)
code-reject LCP error packet, 46
communications servers, 158
      authenticating clients, PAP, 270
      CHAP authentication, 276
      dial-in PPP on, 156, 246
      LAN settings, 160
      PAP authentication, 271-272
      as PPP hardware platform, 89-90
      Proxy ARP, setting up, 195
      RIP options, 229
compiling PPP (see dial-in PPP; dial-out PPP)
compressed datagram, 28, 58-59, 66
Compressed SLIP (CSLIP), 5
compression, 389-390
      of fields in PPP frames, 250
      issues on Windows 98, 135
      (see also VJ compression)
Compression Control Protocol, 58, 135, 363
configure utility, compiling PPP, 108
connection states, 35-36
      network, 53-58
control packets, 35
CSLIP (Compressed SLIP), 5
CTS control signal, 17
cu utility
      checking serial interface, 333
      connecting to pseudo-terminal devices, 312
      testing chat scripts, 122

D
data bits, number of, 15
data communications equipment (DCE), 12-13
Data Set Ready (DSR) control signal, 18
data terminal equipment (see DTE)
Data Terminal Ready (DTR) control signal, 18
datagrams (see IP datagrams)
DB serial interface connectors, 11
DCE (data communications equipment), 12-13
DDS (Digital Data Service), 85
default routes, 218-219
Devices and Dialers files, 120-122
DHCP (Dynamic Host Configuration Protocol), 179
      IP addresses, 267
      MS PPP extensions, 238
dial-in PPP, 156-157
      authentication, 157, 269-288
      configuration
            asppp, 177-178
            DNS IP addresses, 238
            LAN interface settings, 160
            ports, 161-165
            pppd, 169-171
            RAS, 144
            Solaris login service, 174
            Windows NT network interface, 179-180
      Linux, 167-169
      Proxy ARP, 193-194
      RAS, 178, 181-187
      security
            Linux, 160, 170
            Solaris, 177
      software features, 96
      Solaris, 174-176
      startup options, 245-248
      verification, 165
      Windows NT, 180, 183, 187, 189
dial-out PPP, 104
      compilation, Linux, 109-110
      configuration
            asppp, 123-124
            chat, 112-113, 120-122
            pppd, 113-114
            RAS, 144
            Windows 98, 133-137
      establishing connection
            Linux, 115-116
            Solaris, 125-127
            Windows 98, 137-140
            Windows NT, 150-152
      initiation, commands for, 105-106
      installation
            Linux, 107-109
            Solaris, 117-118
            Windows 98, 128-129
            Windows NT, 144-145
      setting up (general), 106
      software features, 96-97
      startup options, 249
      termination, 117
            Solaris, 127
dial-up adapter
      Windows 98, 129, 131-133
      Windows NT, 255
dial-up line connections, 87-88
dial-up networking (see DUN)
Digital Data Service (DDS), 85
DIN serial interface connector, 11
DNS, 232-235
      authentication, 237
      checking functioning of, 235-236
      dial-in PPP on Windows NT and, 180
      dial-out PPP on Windows 95/98 and, 136
      DNS servers, 243
      Linux and, 116
      missing records, 237
      name resolution on various platforms, 238-242
      operation of, 233
      registering PPP users, 236
      Solaris and, 127
      User Datagram Protocol (UDP) and, 64
Domain Name System (see DNS)
dongle (see security token)
DTE (data terminal equipment), 13, 22, 28
DUN (dial-up networking), 128
      Windows 95/98, 128, 140-142
      Windows NT, 152-154
Dynamic Host Configuration Protocol (DHCP), 179
      IP addresses, 267
      MS PPP extensions, 238
dynamic routes, 217
dynamic routing protocols, 226-231

E
EAP (Extensible Authentication Protocol), 273, 394
echo requests, 256
encryption, 389-390
      tunneling, 326-327
      Windows 98 and, 136
errors
      correction, 59
      detection, 116
      error packets, 46-47
Ethernet addresses, 76-77
eventvwr utility, viewing dial-in PPP connections, 187
Extensible Authentication Protocol (EAP), 273, 394
exterior gateway protocols, 226

F
FCS (frame check sequence), 31, 45, 59
File Transfer Protocol (FTP), 64
flow control, 16-17, 59
      checking, 335-337
      dial-in PPP, on communications servers, 161
fragmentation, 347
frame check sequence (FCS), 31, 45, 59
frame relay, 384-385
frames
      fields in, 30-35
            setting compression, 251
            VJ compression and, 66
      LCP packets and, 37
      unrecognizable, 352, 369
FTP, TCP and, 64
full duplex communications, 14

G
GND (ground reference), 14

H
hardware flow control, 17
host-specific routes, 223-226
Hyperterminal program, 23, 333

I
IANA (Internet Assigned Numbers Authority), 65, 290, 397
ICMP (Internet Control Message Protocol), 64
IETF (Internet Engineering Task Force), 5
ifconfig utility
      commands establishing PPP, 123
      detecting errors at serial interface, 116
      installing Solaris dial-in PPP interfaces, 177
      MAC address reporting, 76
in.routed program, implementing RIP, 227-231
installation of PPP (see dial-in PPP or dial-out PPP)
Integrated Services Digital Network (ISDN), 385-386
interior gateway protocols, 226
International Standards Organization (ISO), 7
Internet
      history of, 4
      PPP software on, 94
      routing, 78, 82
            problems with, 381
      (see also tunneling protocols)
Internet Assigned Numbers Authority (IANA), 65, 290, 397
Internet Control Message Protocol (ICMP), 64
Internet Engineering Task Force (IETF), 5
Internet Protocol Control Protocol (see IPCP)
interrupt requests (IRQs), 92
      sharing, 111
IP addresses, 69-74, 79
      assigning, 265-267
            to private networks, 290
      conflicts with, 362
      depletion of, workarounds for, 73
      determining specific addresses for PPP, 264
      DHCP and, 267
      dial-in PPP, 156
            communications servers, 163
            Windows NT, 183-184
      DNS and, 234
      Ethernet, 76-77
      Gateway, 216-217
      MAC addresses, 75-78
      network architectures and, 194-210
      PPP gateways and, 290
      PPP in a Subnet, 205
      routing, 216
      settings, 261-263
      special-purpose, 74-75
      translating with NAT, 296-298
IP datagrams, 60-62
      format, 62-63
      forwarding, 375
      fragmentation, 347
      Linux, 167
      routing, 79, 213-217
      Solaris, 173
IPCP (Internet Protocol Control Protocol), 54-57
      counters and timers, 263
      IP addresses, 261-263
      MS PPP extensions, 238
      PPP software and, 99
      problems with, 360-363
      VJ compression, 69, 260
IRQs (interrupt requests), 92
      sharing, 111
ISDN (Integrated Services Digital Network), 385-386
ISO (International Standards Organization), 7
ITU V.42/LAPM modem correction standard, 27

L
LANs (local area networks)
      Linux and, 166-167
      PPP gateways and, 290
      routing, problems with, 378-381
      Solaris and, 118, 172-173
      subnet mask for, 160
      subnets and, 72
LCP (Link Control Protocol), 30, 35
      counters and timers, 255-256
      echo requests, 256
      extensions, 388-389
      packets, 37-48
            PPP options and, 42-45
      problems with, 355-356
leased line connections, 85-86
line formats, 14-16
Link Control Protocol (see LCP)
link termination, reasons for, 45
Linux
      capturing messages with syslog, 111-112
      CHAP authentication, 276
      configuration
            chat, 112-113
            network, 116
            pppd, 113-114
      dial-in PPP on, 167-169
      DNS and, 116, 240-241
      IP forwarding, 167, 375
      LANs, 166-167
      MS-CHAP, 279
      NAT setup on, 298-300
      PAP authentication, 270-272
      PPP, 94, 107-112
            dial-in, 247
            establishing connection, 115-116
            negotiation example, 40-42
      pseudo-terminal devices, 311-312
      routing, 217
      serial interface, checking, 333
      TCP/IP and, 167
      terminal programs for, 23
local area networks (see LANs)
longest match algorithm, 80

M
MAC (media access control) addresses, 75-78
magic number option, 44
magic numbers
      improper use of, 370
      setting, 251
maximum receive unit (MRU), 97, 347-348
      setting, 253-255
maximum transmission unit (MTU), 63, 97, 347-348
      setting, 253-255
media access control (MAC) addresses, 75-78
mgetty utility, 168-169
      enabling automatic PPP detection, 247-248
modems, 21, 23-25
      bandwidth, 93-94
      compression, 28
            Windows 98, 135
      connecting and configuring, 22-25
      control signals, 18-19
      dial-in PPP, 157
            communications servers, 161
            Windows NT, 181, 187
      error detection and correction, 27, 346
      modulation, 25-27
      number of users per, 92
      setting up
            Windows 98, 129-131, 133-134
            Windows NT, 146-150
      throughput, 93-94
      troubleshooting, 337, 343-348
MRU (maximum receive unit), 97, 347-348
      setting, 253-255
MRU option, 43
MS-CHAP, 183
      for PPP v2.3, 279-280
      Windows NT RAS, 279
MS DNS PPP extension, 239
MS-DOS 6.22, and PPP, 91
MTU (maximum transmission unit), 63, 97, 347-348
      setting, 253-255
multilink PPP, 391-392
multiplexing, 62
Multipoint PPP in a Subnet, 191, 209-212
musrmgr utility, creating Windows NT user accounts, 185

N
name services switch, 241
NAT (network address translation), 295-301
NCP (Network Control Protocol), 99
      packets, 36
      problems with, 359-360
      protocols, 54
            (see also IPCP)
negotiation process of PPP, 38
netconfig utility
      configuring networks with Slackware Linux, 110
      setting up files for DNS, 116
netmasks, 79-80
      in routing tables, 216
network adapter, for dial-in PPP on Windows NT, 179
network address translation (NAT), 295-301
network architectures
      choosing, 190-193
      (see also individual architectures)
network layer protocols, 387-388
none flow control option, 17
nslookup, checking DNS servers, 242
null modems, 13
      cables, 11
      Windows 98 and, 142
      Windows NT and, 154, 189

O
octet stuffing, 32-33
on-demand PPP, 126-127
      Windows 98 and, 140
      Windows NT and, 151-152
One PPP Link per Subnet, 191
OSI (Open Systems Interconnect), 6-8

P
packet switching, 3
packet switching service, 85
PAP (Password Authentication Protocol), 49-51, 270-272
pap-secrets file, 270-272
parity bits, 16
PCs
      CHAP authentication, 276
      dial-in PPP on, 248
      DNS name resolution, 238-240
      modem control signals and, 19
      PAP authentication, 270-272
      PPP
            dial-in, 156
            hardware platforms, 89, 91-92
            history of, 2-3
      resource conflicts and, 92
      routing, 218
      RS-232 interface, 11-12
      Solaris for, 119
      TCP/IP and, 99
Phonebook (Windows NT), 146-150
ping
      Internet Control Message Protocol (ICMP) and, 64
      troubleshooting PPP, 373-374
Plain Old Telephone Service (POTS), 87
pmadm utility, servicing incoming connections, 248
point-to-multipoint interfaces
      Multipoint PPP in a Subnet, 211-212
      routing, 225-226
      Solaris, 211
point-to-point interfaces, Multipoint PPP in a Subnet, 210-211
point-to-point protocol (see PPP)
point-to-point serial connections, 1, 4
Point-to-Point Tunneling Protocol (see PPTP)
ports, 11
      configuration, example of, 161-165
      port numbers, 64-65
      translating port pairs with NAT, 297-298
POTS (Plain Old Telephone Service), 87
PPP, 6, 35
      assigned numbers, 397-409
      compatibility problems, 364-367
      compression, Windows 98, 135
            (see also VJ compression)
      connection states, 35-36
            authentication, 49-53
            network, 53-58
      dial-in/dial-out (see dial-in PPP; dial-out PPP)
      dial-up services, 88
      DNS, 236, 238, 243
      extensions, 388-394
      features lacking, 59
      frames, 30-35, 37
      gateways to private LANs, 290
      hardware platforms for, 89-92
      history of, 2-5
      leased line serial connection and, 86
      MS-DOS 6.22 and, 91
      MTU and, 63
      Multilink PPP, 87
      negotiation, 38, 40-42
      octet stuffing, 32-33
      options, 43-45
      OSI reference model and, 7-8
      product obsolescence, 396
      RIP-1, problems with, 229
      software, 94-102
      subnets and, 73-74
      terminal emulators, contention with, 282-283
      termination, transaction example, 46
      Unix software and, 90
      v2.3
            authentication, 257-260, 270-272, 276-280, 285
            on the Internet, 107
            IP addresses, 262-263
            IPCP options, 261-264
            LCP options, 250-257
            logging, 330
            manual pages, 268
            MS-CHAP, 279-280
            on-demand PPP settings, 249
            Proxy ARP, 195
      VJ compression and (see VJ compression)
      VPNs and, 395
      Windows 3.x and, 91, 128
      (see also dial-in PPP or dial-out PPP)
PPP in a Subnet, 205-209
pppd program, 112-117
      authentication and, 271-272
      configuration, 169-171
      verification, 171-172
ppplog.txt file, 140
pppstat utility, 116
PPTP (Point-to-Point Tunneling Protocol), 306-307
      incoming tunnels, 318-320
      outgoing tunnels, 313-314
Progressive Systems PPP
      incoming tunnels, 320-321
      outgoing tunnels, 315-316
protocol field compression option, 44
protocol field of PPP frames, 30-32, 35
protocol-reject LCP error packet, 46
Proxy ARP, 157, 178, 191, 193
      configuration, 195-196
            Split Subnet, 199-200
      IP addresses and subnets, 194-195
proxy servers, 291-295
pseudo-terminal devices, 311-312
PSN (packet-switching nodes), 3
ptysh utility
      managing pseudo-terminal devices, 311-312, 411-412
      for Unix System V, 412-413

Q
quality protocol option, 44

R
RADIUS (remote authentication dial in user), 395
RAS (remote access service), 143-146, 186-187
      dial-in PPP, 178, 181-187
rasadmin utility
      administering RAS, 186
      Windows NT RAS registry keys, 268
RD (received data) signals, 14
remote access servers (see communications servers)
remote access service (see RAS)
remote authentication dial in user service (RADIUS), 395
resequencing, PPP and, 59
resource conflicts, PCs and, 92
RFCs
      accessing, xii
      FCS computational algorithm, 31
      FCS standards, 45
      IP address options, 56
      IPCP standards, 54
      LCP counters and timers standards, 255
      MS PPP extensions, 238
      multilink PPP, 391
      PAP and CHAP standards, 49
      PPP standards, 5, 29, 35
      RADIUS, 395
      SLIP standards, 5
      VJ compression standards, 66
Ring Indicator (RI) control signal, 18
RIP (Routing Information Protocol), 180
RIP-1 (Routing Information Protocol v1), 227-229
rlogin, as a tunneling protocol, 309-310
route command, editing routing tables, 217
routers, as PPP hardware platform, 89-90
routing, 78, 82, 224, 229
      default routes, 116, 124, 126, 218-219
      host-specific routes, 223
      for point-to-multipoint, 225-226
      problems with, 376-381
      protocols, 226-231
            (see also individual protocols)
      Solaris, 173
routing (continued)
      static routes, 218
            Split Subnet, 200-201
      subnet routes, 220-223
      tables, 213-217
            (see also CIDR tables)
      with tunnels, 322-326
      Windows NT, 188
Routing and Remote Access Upgrade, 188
Routing Information Protocol (RIP), 180
Routing Information Protocol v1 (RIP-1), 227-229
RS-232 interface, 11-13, 22, 84
      Linux and, 111
      octet stuffing and, 35
      PPP drivers, 109
RTS control signal, 17

S
SAC (Service Access Controller), 174
security
      call-back systems, 284-285
      dial-in PPP
            Linux, 160, 170
            Solaris, 177
      dial-up services and, 88
      routing, 229
      tunneling, 326-327
security token, 285-288
serial connections, 85-88
      checking, 331, 338-342
serial interface, 10-11
      checking, 331-334
      detecting errors at, 116
      dial-in PPP, 157, 174
            Windows NT, 181
      emulation, 410
      Solaris, 119
      Windows 98, 129-131
serial I/O, redirecting, 310-312
Serial Line Internet Protocol (SLIP), 4-5
Service Access Controller (SAC), 174
set up/shut down PPP (see dial-in PPP or dial-out PPP)
single octet code field in PPP frames, 37
Slackware v3.4 Linux (see Linux)
SLIP (Serial Line Internet Protocol), 4-5
software flow control, 17
Solaris
      authentication, 257-260
      chat scripts, 350
      configuration
            asppp, 123-124
            IP addresses, 263
      IP forwarding, enabling, 375
      IPCP options, 261-264
      LANs, 118, 172-173
      LCP options, 250-257
      LCP protocol-reject example, 47
      logging, 330
      point-to-multipoint interfaces, 211
      PPP
            configuring OS for, 118-120
            dial-in, 174-176, 247-248
            dial-out, 249
            establishing connection, 125-127
            installing, 117-118
            manual pages, 268
            termination, 127
      Proxy ARP, setting up, 196
      routing, 173
      serial interface devices, 119
      tunneling, 321-322
      (see also Unix)
Split Subnet, 191, 197, 201
      configuration, 199-201
      IP addresses and subnets, 197-199
start bits and stop bits, 14
static address pool, 183-184
static routes, 217-218
straight-through cables, 11
stty utility, setting Unix serial I/O options, 20
subnet masks, 71, 210
      fixed, 221
      for LAN interface, 160
      Proxy ARP, 195
      Split Subnet, 199
      variable length subnet masks (VLSM), 72
subnet routes, 220-224
subnets, 70-74, 79
      network architectures and, 194-210
SunOS 4.1.x, DNS name resolution, 242
switched services, 87-88
syslog, capturing messages on Linux, 111-112
Systems file, 120-122, 124
sys-unconfig utility, configuring LANs, 173

T
TCP (Transmission Control Protocol), 64
      incoming tunnels, 320-321
      outgoing tunnels, 315-318
TCP/IP, 73, 99
      datagrams and, 5
      diagnostic tools, 372-374
      dial-up PPP and, 160
      Ethernet addresses, 76-77
      history of PPP and, 3
      IP addresses, 69-75
      Linux, 110
      MAC addresses (see MAC addresses)
      network architectures (see network architectures)
      port numbers and, 64-65
      protocols, family of, 63-64
      routing, 78, 119, 213
            protocols, 82, 167
            Split Subnet and, 197
      Solaris, 117, 119
      Unix software and, 90
      VJ compression and (see VJ compression)
      Windows 98, 129, 136-137
TD (transmitted data) signals, 14-16
Telnet, 307-309
      checking DNS, 235-236
      incoming tunnels, 320-322
      outgoing tunnels, 315-318
      troubleshooting PPP, 374
terminal emulators, 281-285
terminal servers (see communications servers)
trace logs, 330
traceroute utility, sending UDP packet probes, 373
Transmission Control Protocol (see TCP)
transmission line formats (see line formats)
transmitted data (TD) signals, 14-16
transparency, 338-342
troubleshooting PPP, 328-382
      Solaris, 178
      Windows 98, 132
ttymon utility, servicing incoming connections, 248
tunneling, 305
      custom tunnels, 310
      incoming PPP, 318-322
      outgoing PPP, 313-318
            Progressive Systems PPP, 315-316
      protocols, 100, 306-310
            (see also individual protocols)
      routing and, 322-326
      security, 326-327

U
UART (Universal Asynchronous Receiver/Transmitter), 19-20
UDP (User Datagram Protocol), 63-64
      troubleshooting PPP, 373
Unix
      authenticating clients, PAP, 270
      CHAP authentication, 276
      checking DNS servers with nslookup, 242
      dial-in PPP on, 247-248
      DNS name resolution, 240-241
      MAC addresses and, 76
      MS-CHAP, 279
      PAP authentication, 271-272
      port numbers, 65
      proxy servers and, 294
      pseudo-terminal devices, 311-312, 411
      RIP-1 and, 229
      routing, 217
      serial device driver settings, 20-21
      serial interface, checking, 333
      servers, as PPP hardware platform, 89-91
      setting serial I/O options, 20
      terminal devices, 411
Unnumbered (network architecture), 191, 201
      IP addresses, 204
User Datagram Protocol (UDP), 63-64
      troubleshooting PPP, 373
user-to-modem ratios, 92

V
V.42bis modem compression standard, 28
virtual private networking (see VPNs)
VJ compression, 66-69, 260
      problems with, 365-367
      Windows 98 and, 137
VLSM (variable length subnet masks), 72
VPNs (virtual private networking)
      architectures, 303-305
      capabilities in PPP software, 100
      PPP and, 395

W
Web, 64, 94
Well Known Ports and Registered Ports, 65
Windows 3.x, 91, 128
Windows 95, 91
      DNS and, 136
      DUN, 128
      PPP software and, 94
      tunneling, outgoing, 313-314
Windows 98, 23, 91
      authentication, 135, 271, 273
      determining UART type, 19
      dial-out PPP, on-demand PPP settings, 249
      DNS and, 136
      DUN, 128-129
      encryption, 136
      establishing PPP connection, 137-140
      installing PPP, 128-129
      IP addresses, 263
      IPCP options, 261-264
      LCP options, 250-257
      logging, 330
      port numbers, 65
      redirecting serial I/O on, 312
      setting up
            clients for MS DNS PPP extension, 239
            null modems, 142-143
            PPP, 133-137
            serial interface and modems, 129-131, 133-134
      TCP/IP, 129, 136-137
      troubleshooting PPP, 132
      tunneling, outgoing, 313-314
Windows NT, 65
      authentication, 257-260
      client for MS DNS PPP extension, 239
      dial-in PPP on, 179-181, 248
      dial-out PPP, on-demand PPP settings, 249
      DUN scripts, 152-154
      establishing PPP connection, 150-152
      installation, of PPP, 144-145
      IP addresses, 263
      IPCP options, 261-264
      LCP options, 250-257
      logging, 330
      network adapter for, 179
      null modems, 154
      on-demand PPP, 151-152
      PAP authentication, 271-272
      Phonebook, 146-150
      PPP software and, 94
      RAS, 187, 263
            CHAP, 277
            MS-CHAP, 279
            Proxy ARP, 195
            setting up servers for MS DNS PPP extension, 239
      redirecting serial I/O on, 312
      routing, 188
      terminal program for, 23
Windows NT Server
      IP forwarding, enabling, 375
      tunneling, incoming, 318-320
winipcfg utility, listing addresses and gateways on Windows 98, 140
Winsock API, 128
wireless technology, 387
World Wide Web (see Web)

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