Questions and Answers on Networking and Internets From time to time, readers have sent questions to the netbook@cs.purdue.edu mailing list. The list below contains links to answers to these from Doug Comer. The Relationship between Protocol Layers and Modality Hardware Technologies Internet Standards Routing TCP Multi-homed host network bandwidth Analog modems, voice circuits and T1 circuits Packets, frames, datagrams and PDUs Distance limitations with 10Base-T wiring Mixing wiring schemes Octets and bytes Mixing thick Ethernet and 10Base-T Timing out a TCP connection Demultiplexing TCP connections Reserved ports in UNIX Sizes of IP headers and IP datagrams Queuing arriving UDP datagrams The definition of "mega" Identifying a DHCP client RTT - Round Trip Time Failure recovery in FDDI Identifying UNIX protocol family connections "Snoop"ing on network traffic Rebooting and TCP connections Types of Ethernet Operating systems with two network interfaces List of Ethernet frame types The origin of Ethernet addresses What is a "prototype implementation"? 100Base-T and 10Base-T cabling More questions about thicknet, thinnet and 10Base-T ICMP "Connection refused" message What is the audience for "Computer Networks and Internets" Using LEO satellites for universal wireless service Why the white cover? Routing updates Network byte ordering Differentiating between a single LAN and an internet Using UDP and TCP echo for checking the status of a computer Cheap routers Detecting and fixing routing problems New top-level domains (TLDs)? Dotted decimal notation confusion Switches and routers Port selection and coding questions for clients and servers 10BaseT Cabling 100Mbps Network Performance Dyanmic Assignment of IP Addresses Data Typing IP Addresses Router Statistics in HPOpenView The Difference Between Hardware and IP Addresses Broadcast and Loopback Addresses Physical Addresses on WAN Interfaces ARP and the TCP/IP Layering Model ARP Results and the TCP/IP Layering Model Which Hosts Respond to an ARP Request? Programming Languages for Applets Repeaters in Ethernet Networks Bridges in Ethernet Networks Link Layer Broadcast Broadcast mand Multicast 10BaseT Termination and Cabling Buying and Selling Domain Names Serial Data Transmission Physical and Protocol Layers TCP: Connection-oriented or connectionless? TCP and Path Selection The TCP/IP Layering Model RIP Heuristics for Routing Loops Delay for CSMA Carrier Sense DOS (Denial of Service) Attacks Computer Networks and Internets Glossary Ports and Sockets Data Link and Transport Protocols Error in Dijkstra's Algorithm Direct Socket Printing DNS Architecture DNS And Load Balancing Record Route Option Record Route Optino and Routing Information Manchester Encoding Attenuation in Ethernet Network Design Ethernet and Transmission Errors Ethernet and Carrier Frequency Minimum Frame Size for Ethernet Minimum Frame SIze for 802.3 Reasons for Limits on Ethernet Frame Size Reasons for Limits on Length of an Ethernet Segment Ethernet Types Code for Internetworking with TCP/IP, Volume 3 Fragmentation "Third-party" FTP TCP Connections with FTP Full Duplex Ethernet Problem with Terminal Server Implementation Exmaple of Poisoned Reverse and Split Horizon Homogeneous and heterogeneous Networks Protocol Stack Implementation Redirect Messages Correction on Number of Hosts Connected to the Internet Differences Between Editions U.S.-Centric Internet Architecture Peering Arrangements Distributed Private Networks All 1s Octet in a Class B Address "Net 0" IP Addresses "Routers" vs. "Gateways" Valid IP Addresses Statistics on Packet Length in the Internet TCP Segment Sizes Internet Security Mailboxes and Mail Systems Load Balancing Data Link Layer in OSI Loopback Adapter Load Balancing TCP Connections Additional Teaching Materials WinNT and Win95 Routing Tables Multicast Time Division Multiplexing Packet Switches Network Address Translation (NAT) E-Commerce with HTML NetBIOS and NETBEUI "nslookup" client QoS Packet Classification Nyquist's Theorem Transferring Packet Traces from CD-ROM Host and Protocol Port Lookup Packet Delivery in TELNET and rlogin ICMP Messages ARP and the ARP Cache IP routing Speed of the Internet traceroute "Routers" and "Gateways" CRCs in Data Link Protocols "Proxies", "cookies", Internet FAQ Choosing a Default Route "getservbyname" and byte ordering IP over ATM Routers vs. Switches Ports in IPC and Sockets Origin of Hardware Errors FTP and "Reverse Names" (Inverse Lookups) Determining the IP Address of a Router Notifying a Server when a Client Disconnects TCP FIN-WAIT -2 and CLOSE-WAIT states TCP Bandwidth Overhead Traceroute Traceroute and TTL field E-mail, Telephone and the Client-Server model Initialization in Routers for Vector-distance Routing Solution Manual and Additional Teaching Materials Effectiveness of CRC and Checksum ATM Cell Size, IP and SMDS Modulating Electromagnetic Signals Tracking Denial of Service Attacks through IP Source Addresses Security and ICMP Redirects Ethernet Standard and Repeaters Network Topologies RMON Port Number Packet Switches NAT (Network Address Translation) Endpoints for Sockets IP Address Prefixes and Suffixes Specification of a Subnet Mask TPC/IP Layering Model "Internetworking with TCP/IP, Volume 1" ARP Table Implementation Exercises in Computer Networks and Internets Ethernet Repeaters Network Standard Byte Order and User Data ARP and the TCP/IP Layering Model TCP and Bytestream Model Doug Speaks Out on Perl ADSL Data Rates over Copper Ethernet Payloads and Typing AT&T TLI vs. Berkeley Sockets Clients, Servers and Ports Advice on LAN Design Traceroute and ICMP Traffic Management and Congestion Control IP, UDP and Checksums Ethernet Voltae Levels Ethernet Connectors Blocking vs. Non-blocking Socket Calls Megabit vs. Megabyte Determining the Geographic Location of an IP Address Ethernet Address Space TCP/IP Between Hosts on a Single Network Wireless LAN Systems More on Wireless LANs WDM and DWDM IGMP and IGMP Snooping Automatic Virus Scanning Transport Layer, Network Layer and Fragmentation "Best Effort" Delivery Passing Sockets Between Processes "send" and Successful Delivery of Data IP Routing, PPP, DMZ, SNMP and VLANs IPv6 and Load Balancing Supernetting and CIDR IPv6 "anycast" CIDR and Subnet Masks VLAN and Host Addressing CIDR and the IETF TCP Sequence Numbers WLAN (Wireless LAN) Options for Home Internet Conneciton Why use VLANs? ARP and DNS SONET "Seamless data", "switching fabric" and IEEE 802.3x "Packets" and "Frames" Ethernet Cabling Mixed Ethernet Wiring Schemes "Octets" vs. "Bytes" TCP Timeout and Retransmission Multithreading and TCP Reserved Ports for TCP and UDP Sizes of IP Messages Modem Connections UDP Input Queues Precise Definition of "Mega" Definition and Use of RTT Failures in FDDI UNIX Pipes Tracing Packets with General-Purpose Computers Detecting Failure in a TCP Peer "Fast" Ethernet Ethernet Standards Ethernet Frame Types Ethernet Address Assignment What is a "Prototype Implementation" 100BaseT and 10BaseT Cabling Ethernet Transceivers and "10BaseT" "Connection Refused" Response to Attempted TCP Connection Audience for Computer Networks and Internets Satellite Technology for the Internet and Frequency Dividion Multiplexing Routing Table Updates and Routing Protocols Network Byte Ordering One LAN or Many LANs on a Campus ICMP and UDP "ping" Cheap Routers Repairing Problems with Routign Tables New Top-Level Domains for DNS Interpreting IP Addresses in Octal Switches vs. Routers Ports Available on a System Netweork Analyzer Software Minimum Packet Size for IP Writing a Network Analyzer Switches versus Routers Application Level Gateways Router Interfaces "Auto-negotiation" and "auto-sensing" Obtaining the IP Address of the Computer a Program is Running On Ethernet Standard Preamble Teoretical ANalysis of Router Systems Minimum Frame Size for 100BaseT Ethernet Current "Size of the Internet" IP Addresses versus Physical Addresses Redundant DNS Service Modem Not Answering Managing a Switch "Non-Blocking Architecture" Setting up a Backup Internet Connection TCP Segment Lengths Conversion of "Epoch Times" Reuse of UDP Ports and RPC "In-band" and "Out-of-band" Management Some Networking Jargon WAP and TCP CAT-5E Cable Speeds of 4-wire and Dialup Modems Rea;t-Time Transport Protocol (RTP) Gratuitous ARP Replies Finding the IP Address of the Computer at the Other End of a TCP Connection Anonymous Networks Setting up a Home Network Sharing Files on a Home Networks Pseudo-header in UDP and TCP checksum