Talk:Packet switching

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Redirects: Packet Switching, packet switching, packet mode, packet oriented, packet based

Contents

[edit] History of packet switching

Please refer to the Talk:Packet switching/OriginsArchive for the lengthy discussion that led to the baselining of the respective roles of Paul Baran, Donald Davies, and Leonard Kleinrock in the history of packet switching.

[edit] 3 Sept 2006 edit of initial sentence

I have made two changes to the initial sentence: a] "are individually routed" changed to "are routed" recognizes that some virtual-call networks such as TYMNET, RCP and IPSANET used fixed routing. b] changed "which might be shared by many other nodes" to "shared with other traffic". Nodes originate and receive little information. Most traffic is generated outside of nodes (perhaps by hosts or terminals which are attached to a node).Rdmoore6 16:14, 3 September 2006 (UTC)

[edit] Other networks (non-ARPANET/INTERNET)

The article has little mention of packet switching networks other than ARPANET/Internet. Possible examples include GTE TELENET, Tymnet, X.25/X.75, Systems Network Architecture, IPSANET. The external links are devoid of references to these non-mainstream networks.Rdmoore6 20:52, 21 February 2006 (UTC)

No one is stopping you from adding in these other networks... Cburnett 20:23, 14 March 2006 (UTC)
I'm taking over Packet switched network for just this purpose. It was a redirect here, but had no links to it. I'll add a see also at the top, just in case. Ewlyahoocom 08:02, 18 March 2006 (UTC)
Let me know if you need details on some of these. I was a network management architect for GTE TELENET and worked, at a detailed level, with Tymnet and SNA. Howard C. Berkowitz 19:44, 3 July 2007 (UTC)

[edit] Cleanup - Current Article Misses the Mark

The article is marked for cleanup. This strikes me as justified as the current article misses the mark in many respects. The first couple of sentences, for example, make it sound as if routing and delay are the distinguishing properties of a packet-switched network. In fact, the essential property is that there is no static division of the underlying transmission facility into fixed-bandwidth channels or "circuits". The division of the underlying bandwidth is dynamic, based on the division of payload into "packets" and the addition to the packets of some sort of control information. This control information, rather than the appearance of the data on a pre-determined circuit, is what allows the data to be directed to its proper destination. Characteristics such as statistical multiplexing, buffering delay, circuit emulation, etc. stem from this, but are not fundamental. Should the article be rewritten from this point of view? GrahamDavies 21:48, 5 July 2007 (UTC)

Historically (and I speak as an X.25 person before I was an IP person, with a brief period of OSI insanity), statistical multiplexing was indeed the first motivation, but close behind it came resiliency through some level of routing. Admittedly dating myself as a Neolithic networker, I do remember point-to-point statistical multiplexers (Timeplex, Codex, etc.) long before they had any alternate routing capability.
Telenet, ARPANET, and Tymnet, all with quite different underlying models, still distinguished themselves from oversubscription-based point-to-point products by their ability to do quasi-static alternate routing.
I agree that controlled delay, virtual circuit emulation, etc., did not seriously get considered until the semi-blind-alley of ATM. Statistical multiplexing and routing, however, are, to me, the distinguishing features of early packet switching. The routing, at first, was not always dynamic (yes, it was in ARPANET, but Telenet was quasi-static and Tymnet centralized with redundant centers). Howard C. Berkowitz 23:10, 5 July 2007 (UTC)
OK, that's a good explanation of the present point of view. The approach is "why should we do it this way" (because we can oversubscribe bandwidth and use statistical multiplexing and for that we'll accept some buffering delay) rather than "how does this aproach differ fundamentally from the alternatives" (which is where I was going). I suppose the issue is whether to lead with the technology itself or the motivation for the technology.
I'm still not sure that routing should appear so early in the article and I don't understand why the motivation for routing should be resiliency. I think circuit-switching incorporated pretty good resiliency mechanisms. I rather thought the point of routing was inter-networking and cost reduction, perhaps in conjunction with connection-less service, which isn't really possible with circuit switching.
Having argued this far, I now see clearly why I prefer to lead with a description of the technology rather than its motivation. It's easier to agree on what the technology is than how it got that way. I'm not about to push that point of view, however, so let's see what happens. 64.119.141.34 14:44, 6 July 2007 (UTC)

[edit] Packet mode verses packet switching

User:Hcberkowitz changed the following:

Packet switching is based on packet mode or packet oriented data link layer communication between the network nodes. This is a statistical multiplexing technique, where a physical communication channel is divided into an arbitrary number of logical variable bit-rate channels or data streams.

to

Packet switching is based on packet mode or packet oriented communication between the network nodes, which, depending on the implementation, can involve mechanism at the network layer, the data link layer, or both. Some legacy packet techniques, such as X.25, may have functions normally associated with other layers. This is a statistical multiplexing technique, where a physical communication channel is divided into an arbitrary number of logical variable bit-rate channels or data streams.

Thankyou for your contribution. However, it is not clear to me what you mean. The aim with this paragraph is to distinguish the definition of packet switching from packet-mode communication over point-to-point links and non-switched LAN, for example bus networks or ring networks. X.25 is packet switched, and not only packet oriented. Perhaps you mean LAPB. But that is a link layer protocol. Anyway, this is the article header, which should not deal with basic definitions rather than detail discussions. Please simplify this paragraph and move the detail discussions into the discussion page or the end of the article. Mange01 18:34, 17 July 2007 (UTC)

My concern, where I tried to make a minimal edit, was the previous comment that the data link layer was responsible for the statistical multiplexing. In X.25, that is flatly wrong; the LCN/LCGN field in the packet header, after call setup, is responsible for multiplexing multiple virtual circuits onto LAP-B. LAP-B is unaware of any multiplexing.
While one could argue that a polled SDLC channel shares bandwidth, I wouldn't call it statistical multiplexing given that it's strictly deterministic. In other words, I didn't accept that any form of packet switching exists at the data link layer.
I don't follow your point about distinguishing packet-mode communication relevant to point-to-point, nonswitched LANs, or any other medium. I've run X.25 over LANs (ISO 8880) and connectionless packets (ISO 8881 and IP) over point-to-point and switched media. Indeed, I would need to be convinced that there is any significant and contemporary distinction between packet mode and packet switching. Both terms are largely obsolete; it's arguable that this article should primarily be a redirect.
There are always exotic applications when one has to do strange things. I once had to run TCP/IP over slow and error-prone links in a third-world country. Turning on LAP-B retransmission alone wasn't sufficient, because IP's minimum packet length of 576 made retransmission extremely inefficient. By sliding in the X.25 packet level (i.e., between LAP-B and IP), I was able to negotiate a packet length of 128, which was optimal for retransmission. Howard C. Berkowitz 19:08, 17 July 2007 (UTC)
Well, packet mode/switching is not obsolete. See for example the discussion about GPRS, HSDPA, 4G versus 3G, etc. But X.25 is rather obsolete and should perhaps not be the first thing we mention here.
Your third world story was interesting.
I'm sorry, I know too little about X.25, LAP-B and SDLC to understand your point.
I have made an attempt to clarify the paragraph, but I think it can be further improved. I removed the layer issues. I must leave for now. Good night! Mange01 03:25, 18 July 2007 (UTC)