5 ms·

One of the ideas of ipv6 was to reduce routing tables, those tables that backbone providers have to keep in memory and look up for incoming traffic. With ipv4's

by est31 4y ago

One of the ideas of ipv6 was to reduce routing tables, those tables that backbone providers have to keep in memory and look up for incoming traffic. With ipv4's fragmented allocation scheme, these routing tables are huge. With ipv6, even huge companies like amazon only have a couple of global allocations. A "ipv4 with more octets" scheme would have kept that fragmentation around. That being said, Amazon currently has 2880 ipv4 allocations and 946 ipv6 allocations... not much gained I guess? :p https://asnlookup.com/asn/AS16509/ https://asnlookup.com/asn/AS16509/ Also, there are definitely some horrible ipv6 warts, like that the only standard for local ipv6 addresses forces you to adopt a scheme where your local address is horribly long, for the sake of global uniqueness, which is something that most people don't really need.

justsomehnguy 4y ago
> Amazon currently has 2880 ipv4 allocations and 946 ipv6 allocations... not much gained I guess? Whole IPv4 address space is 4294967296 addresses. A single /48 is 1,208,925,819,614,629,174,706,176. And 2804:800::/32 is 79,228,162,514,264,337,593,543,950,336.
- ipython 4y ago
  Gp comment refers to the number of routing table entries, not total number of addressable ips. Ideally the number of ipv6 allocations should be close to 1 rather than close to 1000.
tlb 4y ago
I'm not up to date, but when I knew about this stuff the cost of memory for routing tables was only a tiny, tiny fraction of the cost of a network. Most of the cost is burying and maintaining fiber. So unless something big has changed, it seems like a terrible choice to twist the whole system into uselessness to try to save a small amount of RAM cost.
- cranekam 4y ago
  According to this Stack Exchange post from last year a full IPv4 routing table requires on the order of a few hundred MBs of RAM. This is indeed a tiny fraction of the cost of maintaining the global internet infrastructure. https://networkengineering.stackexchange.com/questions/76562/how-much-ram-you-actually-need-to-keep-whole-global-bgp-routing-table https://networkengineering.stackexchange.com/questions/76562...
  - bauruine 4y ago
    The problem is that the routers that have to hold the routing table can only handle a limited number of routes. There is a good article from APNIC about the topic. https://blog.apnic.net/2021/03/03/what-will-happen-when-the-routing-table-hits-1024k/ https://blog.apnic.net/2021/03/03/what-will-happen-when-the-...
    - pifm_guy 4y ago
      Said routers could be redesigned... And besides, there is no need to keep the whole routing table in RAM. Instead all that's necessary is a single integer per route representing which port packets to each route needs to be sent down. So even for a large router with 64 ports, the whole routing table fits inside 1 megabyte.
      - bauruine 4y ago
        Sure they can create routers with more space for the routing table but you still have to replace all the old ones which isn't cheap. A single port of a router at an internet exchange can reach more than 1000 different routers. A router has to decide to which IP it should forward a packet not just the port.
- Dagger2 4y ago
  It's not "twisted into uselessness"... the reduction in routing table size comes from the large address space. No twisting was needed. Also, the routing tables we're talking about here need to be stored in TCAM. Content-addressed memory is a lot more expensive than regular DRAM.
viraptor 4y ago
> where your local address is horribly long, for the sake of global uniqueness, which is something that most people don't really need Apart from debugging where you can copy-paste anyway, does it matter? I've got a few services on the local network and over zerotier that all talk IPv6. In the last 3 years or so I've never used an ipv6 address directly. There's enough DNS and discovery protocols that I never needed to.
- zahllos 4y ago
  Plus if you're using enough IPv4 addresses it is going to be the same problem anyway. I can barely keep track of what I've assigned everything to in just a /24 so I have local DNS and I don't need to.
- chillfox 4y ago
  Any sysadmin for a medium sized company with their own servers are likely to end up having to type in IP address or get them off shitty management consoles that don't support copy paste in any way.
  - bert64 4y ago
    Using IP addresses directly is a bad practice in general, it introduced security risks in many scenarios. SSL - usually cannot verify the cert, defeating the point of SSL SMB - windows will fail over to less secure ntlm auth instead of kerberos If your using IP addresses instead of hostnames to reference machines, you're doing it wrong. Also IPv6 is easier to remember in general... We have a single large IPv6 allocation (eg 2001:db8::/32), and everything sits under that in a logical layout. For legacy IP, we have several different allocations in different class A blocks (104.x, 66.x, 62.x etc) plus all the RFC1918 space used internally
    - chillfox 4y ago
      Sure, but most places are not setup to using DHCP on servers or automated installs. So you will be typing in IP addresses through some kind of console to configure the machine in the first place and you will be typing in that IP address in the DNS system and when someone remotely fucks up the routing or IP config then you will be manually typing in lots of IP addresses to fix it.
Sesse__ 4y ago
> One of the ideas of ipv6 was to reduce routing tables That idea was abandoned about 20 years ago. One fairly quickly discovered that hierarchical routing does not work well in the real Internet, where redundancy is done on the IP level with everybody and their dog having provider-indepent IP space. > like that the only standard for local ipv6 addresses Which one is the only standard? Link-local, site-local, ULA, or using a non-routed netblock with or without DHCPv6 (or RA)?
- est31 4y ago
  site-local addresses are deprecated since RFC 3879. Link-local addresses are indeed another standard, but have the very same length problem. You have these horribly long ipv6 addresses... those can't reasonably be parsed by humans... There is no 192.168.* equivalent in ipv6. Why don't we have something like fd00::1 being the router and fd00::2, fd00::3, etc being the devices in the local network, assigned by DHCP. You can absolutely configure your router that way but it is violating a MUST requirement of RFC 4193. That's my point. There is no non-routed netblock where you can just use it for local purposes, outside of the one for SLAAC and the one for ULA, both creating these horribly long monsters of addresses. All the others have purposes attached that are not meant to be used for local networks.
  - keiyakins 4y ago
    Why do you care how long the addresses are? That's what DNS is for. Within a link - most home networks are only one, and those are the ones that need to be simplest - there's even mDNS.
    - est31 4y ago
      DNS is great but it is not available in all settings. Eventually you need to type in ip addresses, there are gazillions of workflows where you have to do that.
      - keiyakins 4y ago
        There's only a very few places where typing IP addresses actually makes sense. Configuring DNS is the main one. Trying to isolate problems is another - if you can ping 8.8.8.8 but not google.com you can reasonably infer that the problem is DNS. I really can't think of any others. That latter one is admittedly kind of a pain, but a wallet-sized cheat sheet can solve it for you. Might be a good idea to try to convince vendors to include a reliable entry or two in the hosts file for that purpose? You can always add it yourself for now, when you're on your own workstation.
error503 4y ago
Amazon is really not a great example, I don't think. The giant cloud providers are outliers with respect to DFZ announcements, as they have many, many POPs and also allow their customers to announce address space. They're more like transit networks at this point than what could be reasonably considered a representative end user. More reasonable to look at announcements per AS, where it's currently about half of IPv4, but trending upwards at a faster pace. v6: https://www.cidr-report.org/cgi-bin/plota?file=%2fvar%2fdata%2fbgp%2fv6%2fas2.0%2fbgp%2dentries%2das%2etxt&descr=Average%20entries%20per%20origin%20AS&ylabel=Average%20entries%20per%20origin%20AS&with=step https://www.cidr-report.org/cgi-bin/plota?file=%2fvar%2fdata... v4: https://www.cidr-report.org/cgi-bin/plota?file=%2fvar%2fdata%2fbgp%2fas2.0%2fbgp%2dentries%2das%2etxt&descr=Average%20entries%20per%20origin%20AS&ylabel=Average%20entries%20per%20origin%20AS&with=step https://www.cidr-report.org/cgi-bin/plota?file=%2fvar%2fdata...
- est31 4y ago
  So Amazon with its 3-fold ratio is in fact giving a better argument for ipv6 than the average, nice. Generally a factor of two doesn't say much about ipv6 creating less allocations at all, given how ipv6 is roughly within a factor of two in terms of adoption in general.
lmm 4y ago
> That being said, Amazon currently has 2880 ipv4 allocations and 946 ipv6 allocations... not much gained I guess? :p https://asnlookup.com/asn/AS16509/ https://asnlookup.com/asn/AS16509/ I remember the line being "the IPv4 routing table is 3x as big as it needs to be due to fragmentation", so that seems pretty in line with that.
throw0101a 4y ago
> That being said, Amazon currently has 2880 ipv4 allocations and 946 ipv6 allocations... not much gained I guess? :p https://asnlookup.com/asn/AS16509/ https://asnlookup.com/asn/AS16509/ How many clients can those IPv4 allocations serve? How many clients can those 946 serve? If Amazon had 2880 IPv6 allocations, how many clients could they serve? I'd say a lot was gained. Someone asking for a random PI IPv6 allocation gets, at minimum, a /48 for a "site". That's the equivalent of a Class A (16 bits for subnets). Are you saying everyone being able to get their own Class A equivalent is 'nothing gained'?

by est31 4y ago

justsomehnguy 4y ago

> Amazon currently has 2880 ipv4 allocations and 946 ipv6 allocations... not much gained I guess? Whole IPv4 address space is 4294967296 addresses. A single /48 is 1,208,925,819,614,629,174,706,176. And 2804:800::/32 is 79,228,162,514,264,337,593,543,950,336.

ipython 4y ago
Gp comment refers to the number of routing table entries, not total number of addressable ips. Ideally the number of ipv6 allocations should be close to 1 rather than close to 1000.

tlb 4y ago

I'm not up to date, but when I knew about this stuff the cost of memory for routing tables was only a tiny, tiny fraction of the cost of a network. Most of the cost is burying and maintaining fiber. So unless something big has changed, it seems like a terrible choice to twist the whole system into uselessness to try to save a small amount of RAM cost.

cranekam 4y ago
According to this Stack Exchange post from last year a full IPv4 routing table requires on the order of a few hundred MBs of RAM. This is indeed a tiny fraction of the cost of maintaining the global internet infrastructure. https://networkengineering.stackexchange.com/questions/76562/how-much-ram-you-actually-need-to-keep-whole-global-bgp-routing-table https://networkengineering.stackexchange.com/questions/76562...
- bauruine 4y ago
  The problem is that the routers that have to hold the routing table can only handle a limited number of routes. There is a good article from APNIC about the topic. https://blog.apnic.net/2021/03/03/what-will-happen-when-the-routing-table-hits-1024k/ https://blog.apnic.net/2021/03/03/what-will-happen-when-the-...
  - pifm_guy 4y ago
    Said routers could be redesigned... And besides, there is no need to keep the whole routing table in RAM. Instead all that's necessary is a single integer per route representing which port packets to each route needs to be sent down. So even for a large router with 64 ports, the whole routing table fits inside 1 megabyte.
    - bauruine 4y ago
      Sure they can create routers with more space for the routing table but you still have to replace all the old ones which isn't cheap. A single port of a router at an internet exchange can reach more than 1000 different routers. A router has to decide to which IP it should forward a packet not just the port.
Dagger2 4y ago
It's not "twisted into uselessness"... the reduction in routing table size comes from the large address space. No twisting was needed. Also, the routing tables we're talking about here need to be stored in TCAM. Content-addressed memory is a lot more expensive than regular DRAM.

viraptor 4y ago

> where your local address is horribly long, for the sake of global uniqueness, which is something that most people don't really need Apart from debugging where you can copy-paste anyway, does it matter? I've got a few services on the local network and over zerotier that all talk IPv6. In the last 3 years or so I've never used an ipv6 address directly. There's enough DNS and discovery protocols that I never needed to.

zahllos 4y ago
Plus if you're using enough IPv4 addresses it is going to be the same problem anyway. I can barely keep track of what I've assigned everything to in just a /24 so I have local DNS and I don't need to.
chillfox 4y ago
Any sysadmin for a medium sized company with their own servers are likely to end up having to type in IP address or get them off shitty management consoles that don't support copy paste in any way.
- bert64 4y ago
  Using IP addresses directly is a bad practice in general, it introduced security risks in many scenarios. SSL - usually cannot verify the cert, defeating the point of SSL SMB - windows will fail over to less secure ntlm auth instead of kerberos If your using IP addresses instead of hostnames to reference machines, you're doing it wrong. Also IPv6 is easier to remember in general... We have a single large IPv6 allocation (eg 2001:db8::/32), and everything sits under that in a logical layout. For legacy IP, we have several different allocations in different class A blocks (104.x, 66.x, 62.x etc) plus all the RFC1918 space used internally
  - chillfox 4y ago
    Sure, but most places are not setup to using DHCP on servers or automated installs. So you will be typing in IP addresses through some kind of console to configure the machine in the first place and you will be typing in that IP address in the DNS system and when someone remotely fucks up the routing or IP config then you will be manually typing in lots of IP addresses to fix it.

Sesse__ 4y ago

> One of the ideas of ipv6 was to reduce routing tables That idea was abandoned about 20 years ago. One fairly quickly discovered that hierarchical routing does not work well in the real Internet, where redundancy is done on the IP level with everybody and their dog having provider-indepent IP space. > like that the only standard for local ipv6 addresses Which one is the only standard? Link-local, site-local, ULA, or using a non-routed netblock with or without DHCPv6 (or RA)?

est31 4y ago
site-local addresses are deprecated since RFC 3879. Link-local addresses are indeed another standard, but have the very same length problem. You have these horribly long ipv6 addresses... those can't reasonably be parsed by humans... There is no 192.168.* equivalent in ipv6. Why don't we have something like fd00::1 being the router and fd00::2, fd00::3, etc being the devices in the local network, assigned by DHCP. You can absolutely configure your router that way but it is violating a MUST requirement of RFC 4193. That's my point. There is no non-routed netblock where you can just use it for local purposes, outside of the one for SLAAC and the one for ULA, both creating these horribly long monsters of addresses. All the others have purposes attached that are not meant to be used for local networks.
- keiyakins 4y ago
  Why do you care how long the addresses are? That's what DNS is for. Within a link - most home networks are only one, and those are the ones that need to be simplest - there's even mDNS.
  - est31 4y ago
    DNS is great but it is not available in all settings. Eventually you need to type in ip addresses, there are gazillions of workflows where you have to do that.
    - keiyakins 4y ago
      There's only a very few places where typing IP addresses actually makes sense. Configuring DNS is the main one. Trying to isolate problems is another - if you can ping 8.8.8.8 but not google.com you can reasonably infer that the problem is DNS. I really can't think of any others. That latter one is admittedly kind of a pain, but a wallet-sized cheat sheet can solve it for you. Might be a good idea to try to convince vendors to include a reliable entry or two in the hosts file for that purpose? You can always add it yourself for now, when you're on your own workstation.

error503 4y ago

Amazon is really not a great example, I don't think. The giant cloud providers are outliers with respect to DFZ announcements, as they have many, many POPs and also allow their customers to announce address space. They're more like transit networks at this point than what could be reasonably considered a representative end user. More reasonable to look at announcements per AS, where it's currently about half of IPv4, but trending upwards at a faster pace. v6: https://www.cidr-report.org/cgi-bin/plota?file=%2fvar%2fdata%2fbgp%2fv6%2fas2.0%2fbgp%2dentries%2das%2etxt&descr=Average%20entries%20per%20origin%20AS&ylabel=Average%20entries%20per%20origin%20AS&with=step https://www.cidr-report.org/cgi-bin/plota?file=%2fvar%2fdata... v4: https://www.cidr-report.org/cgi-bin/plota?file=%2fvar%2fdata%2fbgp%2fas2.0%2fbgp%2dentries%2das%2etxt&descr=Average%20entries%20per%20origin%20AS&ylabel=Average%20entries%20per%20origin%20AS&with=step https://www.cidr-report.org/cgi-bin/plota?file=%2fvar%2fdata...

est31 4y ago
So Amazon with its 3-fold ratio is in fact giving a better argument for ipv6 than the average, nice. Generally a factor of two doesn't say much about ipv6 creating less allocations at all, given how ipv6 is roughly within a factor of two in terms of adoption in general.

lmm 4y ago

> That being said, Amazon currently has 2880 ipv4 allocations and 946 ipv6 allocations... not much gained I guess? :p https://asnlookup.com/asn/AS16509/ https://asnlookup.com/asn/AS16509/ I remember the line being "the IPv4 routing table is 3x as big as it needs to be due to fragmentation", so that seems pretty in line with that.

throw0101a 4y ago

> That being said, Amazon currently has 2880 ipv4 allocations and 946 ipv6 allocations... not much gained I guess? :p https://asnlookup.com/asn/AS16509/ https://asnlookup.com/asn/AS16509/ How many clients can those IPv4 allocations serve? How many clients can those 946 serve? If Amazon had 2880 IPv6 allocations, how many clients could they serve? I'd say a lot was gained. Someone asking for a random PI IPv6 allocation gets, at minimum, a /48 for a "site". That's the equivalent of a Class A (16 bits for subnets). Are you saying everyone being able to get their own Class A equivalent is 'nothing gained'?