網路TCP/IP軟體  NUCLEUS NET

Nucleus NET is a feature-rich TCP/IP stack for applications built on Nucleus real-time kernels. Every possible affordance for the performance, efficiency and security requirements of embedded systems is built into Nucleus NET.

The basic protocol stack is highly versatile, small in size, quick in execution and designed for multi-tasking environments. Extreme caution has been taken to avoid excessive operating system overhead, so tasks spend little time in the stack itself. Nucleus NET handles time-consuming processes like check summing and data copies very efficiently, so even slower processors can maintain high data rates. It supports many IP addresses and many MAC layer drivers, but is stingy on memory usage. It contains routing facilities and supports IP multicasting, IGMP and DHCP services. The result is a fast networking stack that can be scaled and configured to meet the needs of practically any embedded system, from the smallest connected device to network equipment like routers, switches and bridges.

Nucleus NET is delivered as C source code and implemented as a function library, so only the features you need are compiled into your system. The sources are well structured and easy to understand, and of course, complete tutorial and reference documentation is included. Going even further to help you get started on application development, demonstration applications are provided that illustrate how to create basic network clients and servers.

The protocols included with Nucleus NET are:

• TCP
• UDP
• IPv4
• ICMP
• IGMPv3
• ARP
• RARP
• BOOTP Client
• DNS Resolver
• DHCP Client
• RIP/RIP II
• TFTP Client

In addition to the standard TCP/IP package, Nucleus NET is the foundation for Nucleus network software that supports protocols and applications like Telnet, FTP, SNMP and e-mail. It also underlies Web-related applications like Nucleus WebServ and Nucleus SSL.

Some of Nucleus NET’s best features are described below.

Highly Portable

Nucleus NET is the most portable network stack available today. Porting the networking stack to any

particular hardware platform is very easy. No changes are required to the Nucleus NET source code, only a recompile with the required toolset is needed to make it work on a particular CPU architecture.

Standards Compliant

Providing a standards-compliant protocol stack can be a difficult task, especially one with as many features as Nucleus NET. Even more difficult is proving that the implementation is, in fact, standards compliant. To facilitate this, the Automated Network Validation Library (ANVL) from Ixia is applied to every revision of Nucleus NET, along with tests created by our in house experts. The testing is performed on a number of different hardware architectures such as ARM, Freescale, Renesas, x86 and with a number of different toolsets to ensure that not only is Nucleus NET standards compliant, but it is also stable and error free across any hardware/toolset combination.

Fully Configurable

Care has been taken to isolate configuration options and to modularize many features of the networking stack. If a protocol is not used by the application, it can be removed from the stack in order to lower the memory requirements. Timeout values, cache sizes, retry limits and many other options can be tuned for optimal performance in a particular network environment.

Simple Driver Interface

Due to the large number of potential platforms for Nucleus NET and the complexities of combining CPU and network controller options, the interface between Nucleus NET and the driver is as straightforward and simple as possible. A comprehensive template can be provided with Nucleus NET to minimize the effort required to port a new networking device to Nucleus NET.

Sockets API

The Nucleus NET interface is modeled after the BSD socket implementation. The interface is easy to use, implements the standard networking features of sockets and is very efficient.

Zero Copy API

The BSD style socket interface requires at least one copy of data for each packet that is sent or received. A data copy is an expensive operation and can negatively affect network throughput. For applications that require greater data throughput, the zero copy interface can be used instead of the normal BSD send and receive functions to avoid any copy operations on packet data below the application layer.

Enhanced TCP Support

Nucleus NET supports the following enhancements to TCP:

• Slow Start
• Congestion Avoidance
• Fast Retransmit
• Fast Recovery
• Keep-Alive
• Path MTU Discovery

TCP Security

In response to the vulnerabilities found in TCP by CERT Advisory TA04-111A, Nucleus NET supports draft 0 of the “Transmission Control Protocol Security Considerations” Internet Draft released on April 19, 2004 and will be updated as the draft is revised.

IP Multicasting

Nucleus NET supports multicast packet transmission and reception. An interface is provided that allows the application to join and leave multicast groups. Internet Group Management Protocol version 3 (IGMPv3) is used to notify routers of the request for multicast packets.

IPv6 Add-On

The next generation of the Internet Protocol, IPv6, is being deployed around the world. Vendors of network-enabled devices are making the transition to this replacement Internet protocol. Nucleus NET has been updated to support IPv6, available as an add-on package, to ensure its place in the development of these devices and support the vendors that are making this change. Nucleus IPv6 has been certified as “IPv6 Ready” by the IPv6 Forum, demonstrating its standards compliant and interoperable implementation.

Efficient Packet Buffering

Nucleus NET stores packets in a chain of memory buffers to minimize wasted memory space per packet. This buffering scheme also helps to lower the total amount of memory required to perform network communication.

Multiple Physical Interfaces

Nucleus NET supports multiple network interfaces at the same time. This means that Nucleus NET can be used in products like routers and switches, which by definition have more than one physical network interface.

Hardware Offloading

Many new Ethernet interfaces provide hardware offloading of costly operations formerly performed in software. Nucleus NET is capable of using checksum offloading for sending and receiving of the TCP, UDP and IP layer headers.

Ping Application

Nucleus NET includes a simple ping application that allows the network device to send an ICMP Echo Request and wait for a response. Ping has many uses such as basic network diagnostics. It is a simple tool yet very handy to application developers.

VLAN Support

Virtual LANs are used to create a simulated LAN of individual end nodes attached to real LANs. The overall intention is to reduce unwanted message traffic between members of the VLAN group, thus aiding in increasing overall network performance.

Sidebar: Nucleus NET Protocols and RFCs

Nucleus NET supports the following Internet Engineering Task Force (IETF) recommendations:

RFC 793: Transmission Control Protocol (TCP)
RFC 791: Internet Protocol (IP)
RFC 768: User Datagram Protocol (UDP)
RFC 792: Internet Control Message Protocol (ICMP)
RFC 894: Transmission of IP Datagrams over Ethernet Networks
RFC 1034: Domain Names – Concepts and Facilities (DNS)
RFC 1035: Domain Names – Implementation and Specification (DNS)
RFC 951: Bootstrap Protocol (BOOTP)
RFC 826: An Ethernet Address Resolution Protocols (ARP)
RFC 903: Reverse Address Resolution Protocol (RARP)
RFC 2131: Dynamic Host Configuration Protocol (DHCP)
RFC 2132: DHCP Options and BOOTP Vendor Extensions
RFC 1112: Host Extensions for IP Multicasting (IGMPv1 level 2)
RFC 1191: Path MTU Discovery
RFC 1350: Trivial File Transfer Protocol Rev. 2 (TFTP client implementation only)
RFC 2347: TFTP Option Extension
RFC 2348: TFTP Blocksize Option
RFC 2349: TFTP Timeout Interval and Transfer Size Options
RFC 2453: Routing Information Protocol Version 2 (RIPv2)
RFC 2474: Definition of the Differentiated Services Field in the IPv4 and IPv6 Headers
RFC 2988: Computing TCP’s Retransmission Timer
RFC 2581: TCP Congestion Control
RFC 2923: TCP Problems with Path MTU Discovery (except 2.2)
RFC 3376: Internet Group Management Protocol, Version 3 (host support only)
draft-ietf-tcpm-tcpsecure-00.txt: Transmission Control Protocol security considerations