Talk:DOCSIS

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Questions[edit]

Q: I am running a Linux image using VMWare and tried to bridge the VM to the LAN that the Cable Modem is connected to, not expecting it to work. But it did! Both the Windows host machine and the Linux VM now have public IP addresses ( verified using whatsmyip.org) and full internet connectivity. The only problem is I can't figure out why it works, seeing as how their is no router between the two IP addresses and the CMTS. Another oddity is that the first hop in traceroutes is a different IP address then the default gateway. Can anyone explain this, its driving me crazy! —Preceding unsigned comment added by 72.133.245.204 (talk) 06:39, 28 May 2010 (UTC)

Q: If a cable modem is DOCSIS 2.0 compatible, will it work with a DOCSIS 1.1 provider? Thanks!

A: Yes it will. DOCSIS 2.0 is backward-compatible with 1.1 and 1.0.

Q: Must a commercial company be named? as an employee of the competition, i'm offended ;)

One Answer: I don't see any problem with the mention of commercial names if it is relevant or unique information. However, I think the information about cable operator product transfer rates, and their service areas, may be difficult to verify and subject to change making it difficult to keep the article current. One thing I would avoid when mentioning commercial companies are adjectives like "fastest" as applied here to the Cablevision product. The term "fastest" sounds like a little too much marketing-speak for the article. Who knows if it's the fastest? Also - I assume these transfer rates are theoretical and not measured in a specific system installation. Despite the transfer rate spec, Cablevision might actually have slow actual system performance when compared to others.

Q: Should the MIBs that are cable related be referenced in the wiki page? See [1].

What does HFC stand for?[edit]

The article states Before a cable company can deploy DOCSIS 1.1 or above, it must upgrade its HFC network to support a return path for upstream traffic.. But what exactly is an HFC? BigE1977 03:54, 6 June 2006 (UTC)

  • Hybrid Fibre Coax. This needs to be added to the disambiguation page and linked in the article. Thanks Snafflekid 16:42, 6 June 2006 (UTC)

Update The use of HFC has now become dated, if it was not so when added to the article in the first place. The DOCSIS specification does not require optical fiber in the network (ergo the hybrid-fiber) in order to work. A DOCSIS network can be coaxial only. Further DOCSIS networks can be fiber only, by example of RF-over-Glass (RFoG) networks. The article should be revised relevant to the current DOCSIS 3.0 specification.Bsv109 (talk) 21:03, 22 November 2011 (UTC)

Zon gigabit[edit]

I can't find any indication anywhere (except from the article which I am commenting on) that Zon Multimedias 1gbps line should be based on DOCSIS. The product seems to be based on fibre optic cables. —Preceding unsigned comment added by 77.215.56.13 (talk) 22:38, 20 October 2009 (UTC)

I edited ZON's mention to 200Mbps which is in fact based on EuroDOCSIS3.0. The 1Gbps is based on FTTH GEPON and GPON. —Preceding unsigned comment added by 212.113.163.70 (talk) 11:30, 4 November 2009 (UTC)

Verizon[edit]

I removed the Verizon speeds from the page as FiOS is delivered over Optical Fibre, and not over coaxial. Janipewter 05:11, 7 September 2006 (UTC)

DOCSIS MAC Edit[edit]

I edited the section that discusses the DOCSIS MAC layer to make it clear that DOCSIS does use a mix of contention and deterministic mechanisms for bandwidth allocation, while, I hope, perserving the point made by the original article that collisions are much less of a problem than they would be with a pure contention MAC such as Ethernet uses. The use of contention regions for bandwidth requests in DOCSIS is actually quite important as it allows very fast and efficient accomodation of applications, such as web browsing, that have bursty traffic patterns. Also I added a brief mention of QoS. Given how much of the DOCSIS 1.1 RFI specification is devoted to managing QoS parameters, I thought it at least deserved a mention.

At some future point, when I have the time, I might do an entire article on the DOCSIS MAC. It is interesting from a nerdy computer science sort of perspective and given how common cable modems have become there might even be interest in it. Rusty Cashman 04:14, 7 September 2006 (UTC)

DOCSIS Speeds[edit]

I've just edited the DOCSIS speeds to CableLabs' official ones. I guess that no one is against that, if so... just write your suggestion here :-) Heffeque 22:07, 14 February 2007 (UTC)

What do the numbers in brackets stand for? Add a description or sth. 193.43.241.16 16:58, 15 February 2007 (UTC)

They are the usable bitrate. Heffeque 17:07, 15 February 2007 (UTC)

ipv6 in DOCSIS 3[edit]

I made a change to the statement that IPv6 support is included in DOCSIS 3. I wanted to clarify this as it implies that other versions of DOCSIS cannot support IPv6 at all.

Cable modems are, in most installations, layer 2 devices that pass Ethernet frames rather than IP packets. It's irrelevant what protocol stack is run on the hosts attached to them, since the cable modem doesn't examine the layer 3 information at all (where IPv6 lives). This isn't always the case, but it's perfectly possible to implement IPv6 over a DOCSIS 2 modem, provided the modem isn't doing the routing. What's not possible is to manage the cable modem over IPv6 which is largely unimportant since the management IPs are on reserved space anyway. Hence the change to the article...

That is mostly right. But, DOCSIS 3 introduces more than just management via IPv6. While DOCSIS modems are layer 2 forwarders (bridges), they are layer 3 & 4 aware, and can provide filtering and quality of service differentiation based on L3/L4 information. DOCSIS 1 & 2 modems do not support those features for IPv6 packets, while DOCSIS 3 modems will. Also, DOCSIS 1 & 2 modems are only required to bridge frames with EtherType 0x0800 (IPv4). While they might bridge IPv6 packets, there is no guarantee. DOCSIS 3 modems are required to bridge EtherTypes 0x0800 & 0x86DD (IPv6). 192.160.73.64 20:03, 12 July 2007 (UTC)

DOCSIS3 gets nothing extra out of the medium. To implement DOCSIS3 (for more per user speed) you need fibre to each side of the street, small segments on each CMTS. Typical cable segments are too big to give everyone 10mbps (possible on DOCSIS 2 or DOCSIS 1.1

The user can even have IP6 on DOCSIS 1.1. The Modem and CMTS won't care. The user's IP and Modem management IP are always different. Wattyirl 17:26, 10 November 2007 (UTC)

Not true. While DOCSIS 3 is no more bandwidth efficient than DOCSIS 2, it does allow the operator to combine together the bandwidth of multiple channels, hence increasing the total capacity of the DOCSIS link available to the pool of active subscribers on the segment. The capacity of a DOCSIS 2 channel is 40 Mbps, the capacity of a DOCSIS 3 channel is X*40 Mbps where X can be 2, 3, 4, 5, 6, etc. Also, DOCSIS 3 is completely deployable on existing cable systems without any changes to the amount of fiber deployed or the node (segment) size. Certainly, pushing fiber deeper (closer to the user) and decreasing node sizes improves things too, but that is true regardless of what version of DOCSIS is being used.
See above for the correct answer regarding IPv6. Unless you are talking about IPv6 tunneled over IPv4, it is not going to work with DOCSIS 1.0/1.1/2.0.
24.8.35.172 (talk) 21:21, 30 December 2007 (UTC)

Lack of technical information in article[edit]

Could we please get more technical information in this article? I'd like to see more details about the actual specification f.ex. the MAC and RFI. Currently it reads as a shopping list of internet connection speeds offered by different ISPs.

Along with the above user...[edit]

...I agree that there is FAR too much here about various ISPs, which is only tangentially related to DOCSIS. I'll wait for someone else's comment on this though... 68.39.174.238 21:04, 19 October 2007 (UTC)

The speed stuff for ISPs should be moved to a new article. Moreover, the speed list is related to cable modem than to DOCSIS. --Mircea.Vutcovici 16:30, 2 November 2007 (UTC)

Suggestion to divide the article[edit]

I think it's a bit mislead to list all the cable ISP's and speeds on an article which is titled to the underlying standard. Therefore I suggest the article to be divided from "Transfer rates offered by various cable operators" on to a new article named "Cable internet". 81.197.68.150 (talk) 22:46, 24 November 2007 (UTC)

Judging by the comments here as well as those on cable modem it looks like some reorganization would be helpful. I just moved the "Transfer rates offered by various cable operators" section to cable internet as you mentioned. I also moved the "cable internet access" section of cable modem there as well. I think this page looks much better and is now focussed on the DOCSIS standard. Cable internet can still use some help though. 24.8.35.172 21:44, 1 December 2007 (UTC)

Topography[edit]

What types of network topography are required to use DOCSIS? From my reading of the piece, a bus topography cable network couldn't use it, but this isn't explicitly stated. 203.33.3.2 (talk) 23:43, 3 June 2009 (UTC)

Definition of DOCSIS.[edit]

As an engineer, there is a great amount of technical information relating to DOCSIS usage, the technical implementations and practical applications. What is a bit light is the actual definition of what DOCSIS actually is and what it is intended to do. This could be added to provide a context for the rest of the discussion and improves the readability of the article. It is as if the bridge onto the rest of the article is missing because it is assumed that the reader already has a comprehensive understanding of DOCSIS. Andmark (talk) 22:42, 22 November 2009 (UTC)

Request to Add Technical Information and References[edit]

I would like to add a number of technical points to this article, especially related to D3.0 regarding MAC, IPv6, Channel Bonding, etc. A number of my adds will reference my blog @ bradyvolpe.com. I had originally added an external link to this blog indicating it was the only comprehensive tutorial on DOCSIS, however it was removed as "Spam". I am putting in this request because:

  • I don't want to edit the work of the original authors without collaboration / permission
  • I don't want to add back in references to my blog without approval - I encourage you review the blog tutorials, etc. This is not a money making blog. It is a technical reference used by most of the major MSOs as a training reference. — Preceding unsigned comment added by Bsv109 (talkcontribs) 15:50, 12 September 2011 (UTC)
According to our guideline on sourcing, blogs are not acceptable. Do you have alternate sources for the information? Where did you learn it originally? - MrOllie (talk) 15:54, 12 September 2011 (UTC)

New Information to be added[edit]

DOCSIS 3.1 specifications have come out now supporting 10Gbps Down and 1Gbps up.[1] Whiskytaxidriver (talk) 19:59, 30 October 2013 (UTC)

  1. ^ http://www.cablelabs.com/cablemodem/specifications/specifications31.html