Re: Serial links [7:28270]
Michael Williams wrote: For a device (or interface) operating in full-duplex, wouldn't total throughput = total full-duplex throughput?!?!??! I.E. Isn't it a correct statement to say: FastEthernet is capable of a total throughput of 200Mbps? I believe it is. Mike W. Mike, If you trully beleive this then I fear your are destined for that dark place which is marketing. Ok it is not incorrect but does not give the full picture. Getting back to the original question I beleive it is possible to run 2Mbps full duplex across a serial link. The restriction you quote I think may be something to do with the ISP SLA. OK two for and two against, who will swing the vote. RB. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28390t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Serial links [7:28270]
richard beddow wrote: If you trully beleive this then I fear your are destined for that dark place which is marketing. Ok it is not incorrect but does not give the full picture. I take exception to this comment. If there is one thing that is *preached* by Cisco is that the main advantage of utilizing switches over hubs is that your clients can now operate in full duplex mode, 200Mbps in the case of FastEthernet. If you read on Cisco's site about FastEtherchannel, it mentions that it is based on the 802.3 full-duplex standard, but then virtually everywhere else bandwidth is talked about they say bandwidth not full-duplex bandwidth. From one of many pages on FastEtherchannel: Fast Ethernets to provide 400+ Mbps between the wiring closet and the data center, while in the data center bandwidths of up to 800 Mbps can be provided between servers and the network backbone to provide large amounts of scalable incremental bandwidth So I do believe that my original statement was correct... Getting back to the original question I beleive it is possible to run 2Mbps full duplex across a serial link. The restriction you quote I think may be something to do with the ISP SLA. OK two for and two against, who will swing the vote. RB. My example I gave with the T1 to an ISP was probably misleading because of possible SLAs, etc. Let's change that to a point-to-point T1 link. I can only conclude that the total available bandwidth on such a link would be ~3Mbps (1.5Mbps possible throughtput in each direction). That's the only thing that makes sense given we know it's full-duplex. Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28400t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Serial links [7:28270]
Mike, I have three final comments then I think enough has been said. 1. Ethernet has always been a half duplex standard until recent times, FDX operation is always quoted therefore to make the distinction from the default. 2. Serial lines, however, since the late seventies-early eighties have been by default a full duplex offering. Therefore FDX is assumed unless otherwise stated. 3. My comments were not ment to offend but supposed to be funny. Humour on a forum such as this is often missread and I should have learnt my leason along time ago but I just can't help it. Charles do you have your answer??? RB Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28406t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Serial links [7:28270]
Yes I do. Thanks to all for your comments and help. It's always interesting to open a debate on a subject like this. Regards, Charles. richard beddow wrote: Mike, I have three final comments then I think enough has been said. 1. Ethernet has always been a half duplex standard until recent times, FDX operation is always quoted therefore to make the distinction from the default. 2. Serial lines, however, since the late seventies-early eighties have been by default a full duplex offering. Therefore FDX is assumed unless otherwise stated. 3. My comments were not ment to offend but supposed to be funny. Humour on a forum such as this is often missread and I should have learnt my leason along time ago but I just can't help it. Charles do you have your answer??? RB [GroupStudy.com removed an attachment of type text/x-vcard which had a name of cdowling.vcf] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28410t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Serial links [7:28270]
Richard, Sorry for the misread of your humor. You're correct, sometimes text doesn't convey your true spirit. Oh well not a thang =) Here's the damnest thing tho. I've asked many networking professionals, including two CCIEs (not candidates), and no could seem to know 100% about whether serial links were half or full duplex. Sad, eh? I'm tempted to setup a test with 2 PCs and 2 routers with a low bandwidth connection (128Kbps or so) and try to jam traffic through both ways and monitor the speeds and see what I get. But I've got that nagging in the back of my mind that you're correct and serial links are indeed full duplex. Having said that, what are your thoughts on my question about a point to point T1 link at 1.544 Mbps? Is that 768Kbps each way or 1.544each way? Mike W. richard beddow wrote: Mike, I have three final comments then I think enough has been said. 1. Ethernet has always been a half duplex standard until recent times, FDX operation is always quoted therefore to make the distinction from the default. 2. Serial lines, however, since the late seventies-early eighties have been by default a full duplex offering. Therefore FDX is assumed unless otherwise stated. 3. My comments were not ment to offend but supposed to be funny. Humour on a forum such as this is often missread and I should have learnt my leason along time ago but I just can't help it. Charles do you have your answer??? RB Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28409t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Serial links [7:28270]
1.544 each way. Do some research on T-1. Hint - it originally was designed for voice. 24 channels of 64 kbs (1536) each plus framing. I think that the Larscom CSU/DSU manuals have a good tutorial. -Original Message- From: Michael Williams [mailto:[EMAIL PROTECTED]] Subject: Re: Serial links [7:28270] Having said that, what are your thoughts on my question about a point to point T1 link at 1.544 Mbps? Is that 768Kbps each way or 1.544each way? Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28423t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Serial links [7:28270]
I hope your joking. To go thru all that in order to find documnted information. T1's are nothing new nor is full duplex synchronous communications. BTW it's 1.5 in each direction so i spose that makes a T1 a 3M link ;) Dave Michael Williams wrote: Richard, Sorry for the misread of your humor. You're correct, sometimes text doesn't convey your true spirit. Oh well not a thang =) Here's the damnest thing tho. I've asked many networking professionals, including two CCIEs (not candidates), and no could seem to know 100% about whether serial links were half or full duplex. Sad, eh? I'm tempted to setup a test with 2 PCs and 2 routers with a low bandwidth connection (128Kbps or so) and try to jam traffic through both ways and monitor the speeds and see what I get. But I've got that nagging in the back of my mind that you're correct and serial links are indeed full duplex. Having said that, what are your thoughts on my question about a point to point T1 link at 1.544 Mbps? Is that 768Kbps each way or 1.544each way? Mike W. richard beddow wrote: Mike, I have three final comments then I think enough has been said. 1. Ethernet has always been a half duplex standard until recent times, FDX operation is always quoted therefore to make the distinction from the default. 2. Serial lines, however, since the late seventies-early eighties have been by default a full duplex offering. Therefore FDX is assumed unless otherwise stated. 3. My comments were not ment to offend but supposed to be funny. Humour on a forum such as this is often missread and I should have learnt my leason along time ago but I just can't help it. Charles do you have your answer??? RB -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 Emotion should reflect reason not guide it Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28418t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Serial links [7:28270]
At 10:54 AM 12/7/01, Michael Williams wrote: Richard, Here's the damnest thing tho. I've asked many networking professionals, including two CCIEs (not candidates), and no could seem to know 100% about whether serial links were half or full duplex. Sad, eh? It's not sad. Most serial, WAN technologies have been full duplex for so long that the question just doesn't come up. Each side has a dedicated transmit circuit (pair of wires), separate from the receive circuit. On a T1 link, to use your example, each side can transmit 1.544 Mbps. The two sides can do this simultaneously. Old style WAN links used a single cable, like the string between two cans in the game we played as kids. They were half duplex and required a station to send a Go Ahead message to tell the other side it was its turn. You sill see remnants of this in protocols used today. Telnet has a Go Ahead message for example. (It's not used anymore, though.) The LAN people stole the full duplex term to refer to Ethernet switched, point-to-point links, which are no longer really CSMA/CD. They aren't multiple access (MA) and since there's no chance of someone else using your transmit circuit, there's no need to do CS either. Each side has its own dedicated transmit pair. Big deal. That's been the case on WANs since like the 1940s or something. Well, maybe the 1970s. Old-style Ethernet used coax cable. There wasn't a separate transmit and receive pair. All devices shared the cable. Think about what a coax cable looks like: single, center copper core, surrounded by cladding. Bits sent by one station radiate outwards to all other stations who have no choice but to receive them. This isn't really half duplex and nobody called it half duplex until the time when the Ethernet people borrowed the term full duplex to refer to the point-to-point link between a device and its switch port. That's my take, anyway! Priscilla I'm tempted to setup a test with 2 PCs and 2 routers with a low bandwidth connection (128Kbps or so) and try to jam traffic through both ways and monitor the speeds and see what I get. But I've got that nagging in the back of my mind that you're correct and serial links are indeed full duplex. Having said that, what are your thoughts on my question about a point to point T1 link at 1.544 Mbps? Is that 768Kbps each way or 1.544each way? Mike W. richard beddow wrote: Mike, I have three final comments then I think enough has been said. 1. Ethernet has always been a half duplex standard until recent times, FDX operation is always quoted therefore to make the distinction from the default. 2. Serial lines, however, since the late seventies-early eighties have been by default a full duplex offering. Therefore FDX is assumed unless otherwise stated. 3. My comments were not ment to offend but supposed to be funny. Humour on a forum such as this is often missread and I should have learnt my leason along time ago but I just can't help it. Charles do you have your answer??? RB Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28458t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Serial links [7:28270]
I started working on T-1s in 1969. Actually four wire circuits go way back to analog trunk lines. An amplifier works in one direction only. Two wire circuits went through a two wire to four wire coil at each end.(can't remember the terminology). The circuit was four wire for the long haul. Each transmit was amplified. N carrier circuits again used four wire. The channels were seperated by frequency. L carrier used coax. Can't remember if one or two cables as I didn't work on it. -Original Message- From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] m Subject: Re: Serial links [7:28270] Each side has its own dedicated transmit pair. Big deal. That's been the case on WANs since like the 1940s or something. Well, maybe the 1970s. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28467t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Serial links [7:28270]
But with voice it would be OK as long as only one person spoke at once :-) Gaz P.S. J for Joke. Daniel Cotts wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... 1.544 each way. Do some research on T-1. Hint - it originally was designed for voice. 24 channels of 64 kbs (1536) each plus framing. I think that the Larscom CSU/DSU manuals have a good tutorial. -Original Message- From: Michael Williams [mailto:[EMAIL PROTECTED]] Subject: Re: Serial links [7:28270] Having said that, what are your thoughts on my question about a point to point T1 link at 1.544 Mbps? Is that 768Kbps each way or 1.544each way? Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28471t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Serial links [7:28270]
Terminology - Hybrid. (maybe) Reminds me of the days when I used to understand things, or at least my memory's bad enough to have blurred the truth :-) Gaz Daniel Cotts wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... I started working on T-1s in 1969. Actually four wire circuits go way back to analog trunk lines. An amplifier works in one direction only. Two wire circuits went through a two wire to four wire coil at each end.(can't remember the terminology). The circuit was four wire for the long haul. Each transmit was amplified. N carrier circuits again used four wire. The channels were seperated by frequency. L carrier used coax. Can't remember if one or two cables as I didn't work on it. -Original Message- From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] m Subject: Re: Serial links [7:28270] Each side has its own dedicated transmit pair. Big deal. That's been the case on WANs since like the 1940s or something. Well, maybe the 1970s. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28474t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Serial links [7:28270]
Good point. I was thinking the 1970s might be too late, even if the 1940s was too early. ;-) The 4-wire to 2-wire connection is important to know about because it represents an impedance mismatch and may cause echo. It's called the hybrid. The change from 2 wire to 4 wire lets the network apply amplification in just one direction, from what I understand. For the various Cisco classes that cover voice, you need to know about the hybrid. I mostly work above the physical layer, as you can probably tell. ;-) But even a minimal understanding of the physical layer is helpful for understanding full duplex, half duplex, etc. Priscilla At 05:01 PM 12/7/01, Daniel Cotts wrote: I started working on T-1s in 1969. Actually four wire circuits go way back to analog trunk lines. An amplifier works in one direction only. Two wire circuits went through a two wire to four wire coil at each end.(can't remember the terminology). The circuit was four wire for the long haul. Each transmit was amplified. N carrier circuits again used four wire. The channels were seperated by frequency. L carrier used coax. Can't remember if one or two cables as I didn't work on it. -Original Message- From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] m Subject: Re: Serial links [7:28270] Each side has its own dedicated transmit pair. Big deal. That's been the case on WANs since like the 1940s or something. Well, maybe the 1970s. Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28477t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Serial links [7:28270]
Absolutely correct! At least in the case of radio. Quite a protocol to indicate that one is done speaking and the other is now free to speak. -Original Message- From: Gaz [mailto:[EMAIL PROTECTED]] Sent: Friday, December 07, 2001 4:16 PM To: [EMAIL PROTECTED] Subject: Re: Serial links [7:28270] But with voice it would be OK as long as only one person spoke at once :-) Gaz P.S. J for Joke. Daniel Cotts wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... 1.544 each way. Do some research on T-1. Hint - it originally was designed for voice. 24 channels of 64 kbs (1536) each plus framing. I think that the Larscom CSU/DSU manuals have a good tutorial. -Original Message- From: Michael Williams [mailto:[EMAIL PROTECTED]] Subject: Re: Serial links [7:28270] Having said that, what are your thoughts on my question about a point to point T1 link at 1.544 Mbps? Is that 768Kbps each way or 1.544each way? Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28484t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Serial links [7:28270]
Charles, Serial lines are full duplex, actual line speed is 2048Kbps. RB. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28277t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Serial links [7:28270]
Michael, Is this so?? If so then it is not full-duplex but half-duplex. So why then do cisco say this: The NM-4T serial network module has four synchronous serial interfaces. The network module supports a total full-duplex throughput of 8 megabits per second (Mbps), on this data sheet: http://www.cisco.com/warp/public/cc/pd/rt/3600/prodlit/seral_ds.htm RB. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28283t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Serial links [7:28270]
4T x Duplex x 1 Meg 4 x 2 x 1 richard beddow wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Michael, Is this so?? If so then it is not full-duplex but half-duplex. So why then do cisco say this: The NM-4T serial network module has four synchronous serial interfaces. The network module supports a total full-duplex throughput of 8 megabits per second (Mbps), on this data sheet: http://www.cisco.com/warp/public/cc/pd/rt/3600/prodlit/seral_ds.htm RB. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28285t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Serial links [7:28270]
So should the data sheet say total throughput and not total full-duplex throughput?? RB Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28286t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Serial links [7:28270]
Each port on the NM-4T is capable of supporting 2Mb full-duplex, 2Mb upstream and 2Mb downstream. The card has a total 8Mb Full-Duplex throughput. You can actually have 8Mb in one direction and 8 Mb in the other direction at the same time assuming all the channels are bonded together. HTH, Scott Riley Senior Network Engineer Firstnet Services Ltd W: http://www.firstnet.net.uk [This message subject to: http://www.firstnet.net.uk/disclaimer.html] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Thursday, 06 December 2001 14:48 To: [EMAIL PROTECTED] Subject: Re: Serial links [7:28270] So should the data sheet say total throughput and not total full-duplex throughput?? RB Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28290t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Serial links [7:28270]
RB, First, you can't simply look at a speed and say it's half or full duplex. Full duplex simply means it can send data while simultaneously receiving data. As far as that datasheet, you left out the rest of that sentence you quoted, which says, which can be realized over one port (at 8 Mbps) or across all four ports (at 2 Mbps on each port). Obviously they're discussing bandwidth limitations of the module itself. If you look closely at what that is saying, it's saying that MODULE can communicate at up to 8Mbps. I don't believe this is the same as what we're talking about when we talk about a serial link at 1.544Mbps or the like and whether that port is half/full duplex. Mike W. richard beddow wrote: Michael, Is this so?? If so then it is not full-duplex but half-duplex. So why then do cisco say this: The NM-4T serial network module has four synchronous serial interfaces. The network module supports a total full-duplex throughput of 8 megabits per second (Mbps), on this data sheet: http://www.cisco.com/warp/public/cc/pd/rt/3600/prodlit/seral_ds.htm RB. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28356t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Serial links [7:28270]
richard beddow wrote: So should the data sheet say total throughput and not total full-duplex throughput?? RB For a device (or interface) operating in full-duplex, wouldn't total throughput = total full-duplex throughput?!?!??! I.E. Isn't it a correct statement to say: FastEthernet is capable of a total throughput of 200Mbps? I believe it is. Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28358t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Serial links [7:28270]
One last thing from me, and I'll shut up. =) I have to yield the floor here to an authority. I'm sure that serial links can (and many times do) operate in full-duplex mode, but I cannot say that I know for a fact that when you have a 2Mbps serial line that it doesn't yield 4Mbps of total bandwidth (2Mbps each way). I can only speculate what I think I know. =) I've always been under the impression that when you have, for instance, a T1 to an ISP that you could utilize 1.544Mbps of bandwidth whether incoming or outgoing (i.e. if you were downloading at 1Mbps, then you had ~.5mbps left for uploads), but that seems to contradict my belief that the same T1 line operates in full-duplex mode (which would limit incoming to 768Kbps and outgoing to 768Kbps). So I'm more than willing to hear the true explanation of this situation... Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=28364t=28270 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
