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Wannabe Geek


Topic # 60661 29-Apr-2010 20:49
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Hi, anybody know where on the web I can find a comparison of WAN transmission technologies.?

Comparing features such as throughput, media, implementation costs plus other features for technologies such as:

SONet, DSL, DUN/PSTN, x.25/Frame Relay, ISDN, T-Carriers, DSL, Cable, ATM



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  Reply # 325679 1-May-2010 22:45
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Hmm, I would look at Wikipedia but remember its written by people who have interpreted the standards for you themselves. Actually, SDH is the international version of SONET but very expensive compared to Ethernet. MPLS is a layer-2 routing technology that runs over Ethernet or ATM that is kind of equivalent to IS-IS or OSPF, although ATM is falling out of favour.  Border Gateway Protocol is used for public internet peering as opposed to WAN, which is a network that may be "wide" but is still internal for a telco/carrier.

PSTN is not WAN at all, being public by nature (and name) and only ever switching telephony circuits ie. phone calls. Have a look at 10GBase Ethernet as an alternative to SDH/SONET though. VLAN stacking is another way that Ethernet is moving into the WAN space.

"T-Carrier" is part of the PDH structure, although E-carrier such as E1 is generally used in NZ. Quite expensive compared to SHDSL, so generally used for equipment like old DSLAMs and cell sites that are designed for it.




Qualified in business, certified in fibre, stuck in copper, have to keep going  ^_^

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  Reply # 325708 2-May-2010 07:31
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SaturnV: Hi, anybody know where on the web I can find a comparison of WAN transmission technologies.?

Comparing features such as throughput, media, implementation costs plus other features for technologies such as:

SONet, DSL, DUN/PSTN, x.25/Frame Relay, ISDN, T-Carriers, DSL, Cable, ATM

What are you actually trying to achieve?  These are not really comparable technologies as they serve different needs and markets.  Broadly you could categories them into "packet switched" vs "circuit switched" but that's about it.  These are also a mix of OSI layer technologies so not easy to give you a single answer (e.g. ISDN can run on SDH delivered T-carriers; Dial-Up-Networking could run over ISDN; etc).

Very high level view follows; but if you're more specific I can try to give you a better answer:

SONET/SDH is a multiplexing technology for circuit switching.  This can carry your "T-Carrier" or "E-Carrier" transport over high-order bearers (up to STM64/OC-192).  It's an older, but very mature, technology which supports protection mechanisms and a variety of interface types.  It is very transparent to other protocols so it can be used for carrying e.g. Ethernet, ATM, or just straight packet-over-SONET.  Extremely widely deployed, but not really growing due to high cost and relatively low bandwidth (although in some ways it can be considered quite cheap, especially when considering the cost of an ADM instead of a PWE device!).

DSL is a technology family for providing transmission over copper.  There's a variety of bitrates and encoding mechanisms to support low-speed and high-speed services.  It then uses other encapsulations (e.g. ATM or PTM) for providing packet-switched services on top of the link layer.

Dial-up-Networking tends to refer to the use of modems to transfer data over analog voice circuits.  PSTN is, well, voice networking - how much detail do you want here?  This is an almost infinitely deep topic.

X.25 and Frame-Relay are both legacy packet switched networks that provide p2p and p2mp services, within the context of a "cloud".  X.25 is fairly deprecated these days and rarely used.  Frame-relay is still around as it supports low-speed services that are often still found in bank networks or airlines, as well as interworking quite nicely with ATM.  Most frame-relay networks now are actually just FRF.8 interfaces on ATM switches; or in some cases circuit-emulation interfaces on IP/MPLS networks.  Frame-relay supports low-speed (e.g. down to 2.4Kbps) and high-speed (E3-34Mbps/T3-45Mbps) and is still sometimes used on POS interfaces as well.

ISDN is a digital telephony service that supports data/voice circuit switching on the PSTN.  It's still in fairly common use for BRIs (2x64K B-Channels) and PRIs (up to 30x64K B-Channels on an E1, or 24 on a T1) for PBXs.  Not so common for data services these days except older video conferencing kit.

T-Carriers: to quote Wikipedia: "In telecommunications, T-carrier, sometimes abbreviated as T-CXR, is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America, Japan, and Korea.".  Fairly valid and to the point.  Effectively it is any type of "T" service (T1, T2, T3, T4, T5) made up of DS0s (64K circuits), in many cases specifying framing, encoding, and error-correction.  These can be delivered off a number of technologies including PDH and SDH.

Cable: I assume you refer to Hybrid Fiber Coaxial (HFC) networks, which is a network technology for delivering services (TV, Internet, etc) over coaxial cables using digital RF signals.  The hybrid bit refers to carrying the RF signal over fibre to the RF node.

ATM: A fairly legacy technology these days that supports both circuit-switching and packet-switching.  It uses the concept of cells rather than packets or frames, and specifies a number of signalling, encoding, and service modes.  A fairly deep topic to discuss.  It's used on top of many other technologies (ADSL, SDH, etc) and supports a number of fairly neat tricks including fairly comprehensive Quality of Service and service multiplexing.

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