 ncherryPremium
join:2003-07-13
Monroe Township, NJ | reply to RARPSL
Re: 2^128 Addresses Claim is inaccurate/misleading said by RARPSL  ...
The standard code in all the operating systems reserve the low order 64 bits for the host address. Thus they assume (require?) that the user's prefix is no longer than a /64. My comment about not giving everyone a /48 but supplying a longer prefix allows the ISP (Comcast) to support more users by dividing each /48 into a number of separate user prefixes.
The loop back address (equivelent to 127.0.0.1) is ::1 [which is 127 0's and a 1 : a reserved address - see the Wikipedia address. Also, your point-to-point uses only two of your assigned addresses since each device will have a host address. If on separate networks (ie: Different prefixes) your end acts as a router gateway. Also, remember that a NIC/Port can have multiple addresses. I understand your point on the /64, neighbor discovery, auto-configuration, mobility etc. all pretty much depend on it. Every host will support it.
Sorry, the "loopbacks" I'm referring to are on the router (specifically Cisco) and are really not a loopback interface (i.e. associated with 127.0.0.1 or ::1). They're more of a virtual LAN (but not a VLAN) associated with no physical interface but useful for things like management and tunnel termination for routers that might have multiple interface. Generally you can set these interfaces to a /128 (IPv6) or /32 (IPv4).
Okay, the next comments are "my general practice" type comments. Engineering always depends on the constraints. Understand that my general work is done on the WAN portion of networks and that different practices apply to the LAN (and even the internet).
On the point-to-point (things like DSL, T1s, Frame Relay, ATM, etc.) we build a network using /30 (IPv4) though Cisco does support a /31 (IPv4). Often using things like RFC1918 addresses. What you are suggesting sounds more like bridging than routing and for most WAN networks is not the preferred method (bridge interfaces eat up router resources more than routed interface). Bridging doesn't scale well across the WAN.
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Neil Cherry
Linux Home Automation
Linux HA Blog
Author: Linux Smart Homes For Dummies
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 RARPSL
join:1999-12-08
Suffern, NY | Thank you for your reply (and the mention in your web page of my input).
I have quickly scanned it but do not right now have time to read all of it for critiquing.
We have drifted from my original point that (due to the use of the low order 64 bits for the interface address) the number of IPv6/64 prefixes (2^64) is the equivelent of the number of possible IPv4 addresses (2^32) NOT 2^128.
I am currently not at home but once I get back I plan to pull out my O'Reilly IPv6 book to check on a number of areas.
Due to aggregation, the size of the backbone routing tables do not need to be larger than needed to get to the ISP. The ISP's tables only route over their LAN. If the ISP has 128 distribution points, each only needs to have 128 entries for LAN routing as well as Gateway entries to the backbone (I am assuming the each distribution point has it own unique prefix). The customer's prefix is only listed in the router that it is connected to so that router's table only needs to be large enough to handle the prefixes that are serviced by it as well as those of the routers it talks to. |
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ncherryPremium
join:2003-07-13
Monroe Township, NJ | RARPSL, you are quite correct, I'm moving this quite off-topic. I'll stop here and if you ever want to discuss this privately just use my contact information here or the email address on my web page (top right). I want to thank you for the information it's given me quite a few things to think about. I've already started to make changes to my notes web page and I've got quite a few more to make. 
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Neil Cherry
Linux Home Automation
Linux HA Blog
Author: Linux Smart Homes For Dummies
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RARPSL
join:1999-12-08
Suffern, NY | said by ncherry:RARPSL, you are quite correct, I'm moving this quite off-topic. I'll stop here and if you ever want to discuss this privately just use my contact information here or the email address on my web page (top right). I want to thank you for the information it's given me quite a few things to think about. I've already started to make changes to my notes web page and I've got quite a few more to make. No problem about getting off topic. I do not see it as such. I made the statement that the correct number to compare to 2^32 was 2^64 NOT 2^128 and needed to explain/defend my comment.
I can recommend the O'Reilly book for IPv6 information.
Once I get home and have time to look at and review your page, I might contimue our discussion. |
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ncherryPremium
join:2003-07-13
Monroe Township, NJ | said by RARPSL:No problem about getting off topic. I do not see it as such. I made the statement that the correct number to compare to 2^32 was 2^64 NOT 2^128 and needed to explain/defend my comment. I can recommend the O'Reilly book for IPv6 information. Ah, I'm kind of glad you didn't say it that way to begin with. It would have been a shorter conversation.
I have the book around here somewhere but I can't find it (just graduated with a BS, now working on an MS).
Had an interesting discussion at work with one of the engineers (he's signing up for the trial too) and we came to the conclusion that if left up to the end user they'll only use 1 subnet.
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Neil Cherry
Linux Home Automation
Linux HA Blog
Author: Linux Smart Homes For Dummies
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RARPSL
join:1999-12-08
Suffern, NY | said by ncherry:Had an interesting discussion at work with one of the engineers (he's signing up for the trial too) and we came to the conclusion that if left up to the end user they'll only use 1 subnet. I tend to agree so long as you say AVERAGE user. Most do not even have a router so the number of subnets is not an issue for them (they use the supplied IPv4/32 single address as is). Those who do have a router will not have enough devices to need a second subnet. I have seen people with both Wired and Wireless LANs who separate the two into different subnetworks for control purposes. As I said, the ISP giving out /56s (in lieu of a /48) will allow them to get 4096 times the number of prefixes to assign to their customers while still allowing the customer to have the same number of subnetworks that the current IPv4/32 + Class-C LAN NATing provides.
Given the size of the block the ISP is being given, this 4096 fold increase in prefixes should be a large enough supply of prefixes. |
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ncherryPremium
join:2003-07-13
Monroe Township, NJ | Yes, forgive me I definitely meant to say average user. Fortunately the engineer I was talking to is an above average Lab-ie. |
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