TCP/IP Features

To design an effective TCP/IP solution, you must understand the features of TCP/IP and how these features solve the connectivity requirements of your organization. The following diagram describes the seven crucial features that you must remember while making design decisions.

1. Security: TCP/IP allows enhanced data and connection security by supporting a number of IETF-proposed standards for data encryption, authentication and filtering. The Windows 2000 implementation of TCP/IP supports Internet Protocol Security (IPSec) and TCP/IP filtering for packet-level authentication and data encryption, as well as for filtering data. IPSec is new in Windows 2000 and provides end-to-end data authentication and encryption, which has never before been available in Windows network operating systems.
2. Bandwidth Management: Time-sensitive IP traffic streams such as streaming multimedia require connection protocols that provide bandwidth reservation within a network. TCP/IP supports bandwidth reservation by using Quality of Service (QoS) mechanisms, which allow IP traffic to be prioritized. QoS is especially important when an organization requires "real-time" delivery of TCP/IP packets, as would be required with various IP Telephony applications
3. Automatic Private IP Addressing: Automatic Private IP Addressing (APIPA) automates TCP/IP address configuration for hosts on a single-subnet network that has no DHCP server. APIPA eliminates IP address configuration for simple networks not connected to the Internet. The IP addresses for APIPA are allocated from 169.254.0.0/16, which is reserved by the Internet Assigned Numbers Authority (IANA) and represents a private network address class.
4. ICMP Router Discovery: Windows 2000-based computers running RRAS support Internet Control Message Protocol (ICMP) router discovery (RFC 1256). This allows a host to discover the router automatically, although a default gateway is not configured for the host. ICMP router discovery is disabled by default on TCP/IP for Windows 2000 hosts, and is managed by using DHCP.
5. Disabling NetBIOS over TCP/IP: Windows 2000 allows you to disable network basic input/output system (NetBIOS) over TCP/IP (NetBT) for computers that use only DNS name registration and resolution. These computers can browse resources only on those computers that:
   1. Have NetBT disabled.
   2. Use Client for Microsoft Networks, and File and Print Sharing for Microsoft Networks components.
   The ability to disable the NetBIOS interface, which is part of the TCP/IP protocol stack is a new feature available only with Windows 2000.
6. Large TCP Windows: When there are many active TCP connection endpoints (sockets) on a system, such as a popular Web or file server, then a large TCP window size will lead to high consumption of system (kernel) memory. This can have a number of negative consequences. The system may run out of buffer space so that no new connections can be opened, or the high occupation of kernel memory (which typically must reside in actual RAM and cannot be "paged out" to disk) can "starve" other processes of access to fast memory (cache and RAM)
7. TCP Selective Acknowledgement:TCP selective acknowledgment is used only when multiple packets are dropped within one TCP window. There is no performance impact when the feature is enabled but not used. Use the ip tcp selective-ack command in global configuration mode to enable TCP selective acknowledgment.

Protocols are formal rules of behavior. In international relations, protocols minimize the problems caused by cultural differences when various nations work together. By agreeing to a common set of rules that are widely known and independent of any nation's customs, diplomatic protocols minimize misunderstandings. Similarly, when computers communicate, it is necessary to define a set of rules to govern their communications. In data communications, these sets of rules are also called protocols. In homogeneous networks, a single computer vendor specifies a set of communications rules designed to use the strengths of the vendor’s operating system and hardware architecture. But homogeneous networks are like the culture of a single country, only the natives are truly at home in it. TCP/IP creates a heterogeneous network with open protocols that are independent of operating system and architectural differences. TCP/IP protocols are available to everyone and are developed and changed by consensus, not by the fiat of one manufacturer. Everyone is free to develop products to meet these open protocol specifications.
The open nature of TCP/IP protocols requires an open standards development process and publicly available standards documents. Internet standards are developed by the Internet Engineering Task Force (IETF) in open, public meetings. The protocols developed in this process are published as Requests for Comments (RFCs).* As the title “Request for Comments” implies, the style and content of these documents are much less rigid than in most standards documents. RFCs contain a wide range of interesting and useful information, and are not limited to the formal specification of data communications protocols. There are three basic types of RFCs: standards (STD), best current practices (BCP), and informational (FYI).

The Internet Control Message Protocol (ICMP) is a network layer protocol that serves as an auxiliary protocol to the Internet Protocol (IP). It is used by network devices, including routers, to communicate important information related to network connectivity and status. ICMP is designed to work with both IPv4 and IPv6. The primary purpose of the Internet Control Message Protocol is to provide error reporting and diagnostic functions to help network administrators and devices detect and resolve network issues. For example, if a data packet is not able to reach its intended destination due to various reasons such as a link being down, a router being unable to forward it, or the destination address not existing, the device that detects the error can use ICMP to send a message back to the source, informing it about the issue.
Additionally, ICMP is used for network testing and debugging. The "ping" and "traceroute" commands are common tools that utilize ICMP to test the connectivity and measure the round-trip time between two network devices. These tools help in diagnosing network issues and determining the best route for data transmission. In summary, the purpose of the Internet Control Message Protocol (ICMP) is to facilitate error reporting, network diagnostics, and network testing, helping to maintain the stability and performance of IP networks.

Click the Exercise link below to apply what you know about IP configuration strategies in a Problem Solver exercise.
IP Configuration Strategies - Exercise