Comparison between SNA & TCP/IP

 TCP/IP versus SNA-- Part of the History!!

 TCP/IP and SNA were designed from diametrically opposite standpoints: SNA once was a centrally managed architecture with predefined static routing aimed at high bandwidth utilization and optimal response time, whereas TCP/IP is a decentralized network with dynamic routing aimed at easier connectivity.

 Although the number of TCP/IP installations is growing at an exponential rate (almost any PC-based communications package includes the IP stack), not too many of 50,000+ SNA installations migrated their mission-critical applications to IP.

 The developers and users realized that, unfortunately, the bandwidth of the WAN is not sufficient for LAN-based protocols. Most of the LAN protocols (AppleTalk, network basic input/output systems [NetBIOS], internetwork packet exchange [IPX]) are too chatty and may cause so-called broadcast storms.

 The next natural step was to utilize the least expensive and most available protocol for WAN communications. However, there was no magic with TCP/IP either:

 So, Why didn't SNA really take off like TCP/IP did?

 A vast majority of SNA shops are reluctant to convert their SNA backbones to TCP/IP, protecting performance of mission-critical applications.

 Many vendors realized the importance of consolidation of the network infrastructure and the potential savings and developed products allowing utilization of non-SNA networks for SNA traffic.

 Some solutions provide SNA based gateways and routers to allow utilization of SNA backbone for non-SNA traffic. This approach permits capitalization on investments that many corporations have already made in their SNA backbones.

 It also grants the users a better utilized and more cost-effective SNA network, supporting many new applications.

 TCP/IP is actually two protocols sandwiched one over other. IP deals exclusively with the routers and is primarily concerned with the speed of delivery rather than reliability. To combat this problem of unreliability, TCP was developed.

 The TCP/IP protocols were developed with public funding and are in the public domain. This was probably the sole reason for its popularity!!

 The TCP/IP protocol suite is a set of network standards originally developed for the Advanced Research Projects Agency (ARPA), of the US Department of Defense. This development led to the creation of the ARPANET which, in turn, led to the system of national and international networks known as the Internet.

 The formal network standards for the TCP/IP protocol suite are available as a set of documents known as Request for Comments (RFCs). The RFCs contain a wealth of material, and some RFCs are written specifically to provide tutorial information on the TCP/IP protocol suite.

 Some sites from where you can download the RFC's

  1. DS.INTERNIC.NET {Username: anonymous, Password: Email address}
  2. NIC.DDN.MIL {Username: anonymous, Password: guest}
  3. FTP.NISC.SRI.COM {Username: anonymous, Password: guest}
  4. NIS.NSF.NET {Username: anonymous, Password: guest}
  6. VENERA.ISI.EDU {Username: anonymous, Password: guest}
  8. FTP.CONCERT.NET {Username: anonymous, Password: Email address}
  9. SRC.DOC.IC.AC.UK {Username: anonymous, Password: Email address

 RFC Index search at <>

 Hard Copies of the RFC's can be obtained from

SRI International Network Information Systems Center - EJ291
333 Ravenswood Avenue
Menlo Park, CA 94025
Tel: (415) 859-6387
Fax: (415) 859-6028


I have listed some books, which I have found very useful and interesting.

Author & Publisher


Douglas E. Comer [Prentice Hall], 2nd ed. Internetworking with TCP/IP: Vol.1 [Principles, Protocols and Architecture]
Charles L. Hedrick [] Download File: = tcp-ip-intro.doc (or) Introduction to the Internet Protocols

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Maintained by Mohan Atreya , Last update April 8, 1999

First created on November 18, 1998