4 ms·

Seems to me that the real problem is the 1500 byte MTU that hasn't increased in practice in over 40 years.

_cenw 2y ago
That's on the list that right after we all migrate to IPv6.
p_l 2y ago
For all practical purposes, the internet MTU is lower than ethernet default MTU. Sometimes for ease of mind I end up clamping it to v6 minimum (1280) just in case .
j16sdiz 2y ago
The real problem is some so called "sysadmin" drop all ICMP, breaking path mtu discovery.
- icedchai 2y ago
  The most secure network is one that doesn't pass any traffic at all. ;)
- cryptonector 2y ago
  That's why PMTUD (P for Passive) exists.
throw0101c 2y ago
> Seems to me that the real problem is the 1500 byte MTU that hasn't increased in practice in over 40 years. As per a sibling comment, 1500 is just for Ethernet (the default, jumbo frames being able to go to (at least) 9000). But the Internet is more than just Ethernet. If you're on DSL, then RFC 2516 states that PPPoE's MTU is 1492 (and you probably want an MSS of 1452). The PPP, L2TP, and ATM AAL5 standards all have 16-bit length fields allowing for packets up 64k in length. GPON ONT MTU is 2000. The default MTU for LTE is 1428. If you're on an HPC cluster, there's a good chance you're using Infiniband, which goes to 4096. What are size do you suggest everyone on the planet go to? Who exactly is going to get everyone to switch to the new value?
- Hikikomori 2y ago
  The internet is mostly ethernet these days (ISP core/edge), last mile connections like DSL and cable already handle a smaller MTU so should be fine with a bigger one.
  - cesarb 2y ago
    > The internet is mostly ethernet these days (ISP core/edge), A lot of that ISP edge is CPEs with WiFi, which AFAIK limits the MTU to 2304 bytes.
  - throw0101c 2y ago
    > The internet is mostly ethernet these days […] Except for the bajillion mobile devices in people's pockets/purses.
- fallingsquirrel 2y ago
  > What are size do you suggest everyone on the planet go to? 65536 > Who exactly is going to get everyone to switch to the new value? The same people who got everyone to switch to IPv6. It's a missed opportunity that these migrations weren't done at the same time imho. It'll take a few decades, sure, but that's how big migrations go. What's the alternative? Making no improvements at all, forever?
  - 0xbadcafebee 2y ago
    > got everyone to switch to IPv6 I have some bad news... > What's the alternative? Making no improvements at all, forever? No, sadly. The alternative is what the entire tech world has been doing for the past 15 years: shove "improvements" inside whatever crap we already have because nobody wants to replace the crap. If IPv6 were made today, it would be tunneled inside an HTTP connection. All the new apps would adopt it, the legacy apps would be abandoned or have shims made, and the whole thing would be inefficient and buggy, but adopted. Since poking my head outside of the tech world and into the wider world, it turns out this is how most of the world works.

That's on the list that right after we all migrate to IPv6.

p_l 2y ago

For all practical purposes, the internet MTU is lower than ethernet default MTU. Sometimes for ease of mind I end up clamping it to v6 minimum (1280) just in case .

j16sdiz 2y ago

The real problem is some so called "sysadmin" drop all ICMP, breaking path mtu discovery.

icedchai 2y ago
The most secure network is one that doesn't pass any traffic at all. ;)
cryptonector 2y ago
That's why PMTUD (P for Passive) exists.

throw0101c 2y ago

> Seems to me that the real problem is the 1500 byte MTU that hasn't increased in practice in over 40 years. As per a sibling comment, 1500 is just for Ethernet (the default, jumbo frames being able to go to (at least) 9000). But the Internet is more than just Ethernet. If you're on DSL, then RFC 2516 states that PPPoE's MTU is 1492 (and you probably want an MSS of 1452). The PPP, L2TP, and ATM AAL5 standards all have 16-bit length fields allowing for packets up 64k in length. GPON ONT MTU is 2000. The default MTU for LTE is 1428. If you're on an HPC cluster, there's a good chance you're using Infiniband, which goes to 4096. What are size do you suggest everyone on the planet go to? Who exactly is going to get everyone to switch to the new value?

Hikikomori 2y ago
The internet is mostly ethernet these days (ISP core/edge), last mile connections like DSL and cable already handle a smaller MTU so should be fine with a bigger one.
- cesarb 2y ago
  > The internet is mostly ethernet these days (ISP core/edge), A lot of that ISP edge is CPEs with WiFi, which AFAIK limits the MTU to 2304 bytes.
- throw0101c 2y ago
  > The internet is mostly ethernet these days […] Except for the bajillion mobile devices in people's pockets/purses.
fallingsquirrel 2y ago
> What are size do you suggest everyone on the planet go to? 65536 > Who exactly is going to get everyone to switch to the new value? The same people who got everyone to switch to IPv6. It's a missed opportunity that these migrations weren't done at the same time imho. It'll take a few decades, sure, but that's how big migrations go. What's the alternative? Making no improvements at all, forever?
- 0xbadcafebee 2y ago
  > got everyone to switch to IPv6 I have some bad news... > What's the alternative? Making no improvements at all, forever? No, sadly. The alternative is what the entire tech world has been doing for the past 15 years: shove "improvements" inside whatever crap we already have because nobody wants to replace the crap. If IPv6 were made today, it would be tunneled inside an HTTP connection. All the new apps would adopt it, the legacy apps would be abandoned or have shims made, and the whole thing would be inefficient and buggy, but adopted. Since poking my head outside of the tech world and into the wider world, it turns out this is how most of the world works.