4 ms·

Does anyone have a clear explanation for why QUIC exists when SCTP (which can be run over UDP) existed? What does QUIC bring over it?

wmf 11y ago
QUIC is supposed to be quicker than SCTP+TLS or SCTP+IPSec by using some "rampant layering violations" to combine security and transport into one layer and eliminate a lot of round trips.
waqf 11y ago
Your question is answered in the design doc at https://docs.google.com/document/d/1RNHkx_VvKWyWg6Lr8SZ-saqsQx7rFV-ev2jRFUoVD34/edit?pli=1#heading=h.nvk2biis6bpk https://docs.google.com/document/d/1RNHkx_VvKWyWg6Lr8SZ-saqs... tl;dr minimizing latency, particularly in establishing a connection, is an important design objective.
dragontamer 11y ago
SCTP isn't implemented on most routers, firewalls. UDP is.
- imglorp 11y ago
  SCTP is in Cisco IOS[1], but regardless, it sits at the IP layer so all routers need to do is pass it as IP, unless you want to do more. It's also in plenty of OS kernels already, such as solaris and linux, and can be written as userspace libraries. 1: http://www.cisco.com/c/en/us/td/docs/ios/12_4t/12_4t15/htsctp.html http://www.cisco.com/c/en/us/td/docs/ios/12_4t/12_4t15/htsct...
  - dragontamer 11y ago
    I'm talking about your typical Netgear router / firewall application. > it sits at the IP layer so all routers need to do is pass it as IP Erm... no. The vast majority of consumer electronics are built up from NAT. You are NOT getting past your Verizon/Comcast router with IP alone. It's getting interpreted as TCP, and then getting NATted over to something else. As far as i can tell, UDP has a similar process. But its a major problem with SCTP and consumer routers. Have you ever tried to send an SCTP connection across your typical consumer Verizon router?
    - wtallis 11y ago
      > You are NOT getting past your Verizon/Comcast router with IP alone. ... on IPv4. On IPv6 you don't have to worry about NAT, and IPv6 usage is growing: the percentage of Google traffic conducted over IPv6 has doubled in the past year and is significantly higher on weekends, which means consumers are driving a lot of that traffic. It's now over 7% on weekends and growing by about one percentage point every 3-4 months. That seems to me like a sufficiently large pool of potential testers. The NAT problem is really finally going away. What we need to be worrying about is dumb firewalls, but I'd bet that there will be just as many consumer routers that fail to make any of their firewall rules apply to IPv6 as there will be routers that can pass TCP over IPv6 but not arbitrary protocols.
  - acdha 11y ago
    The catch is that most NAT devices don't support it, which is a deal-breaker for something to be deployed on the public internet, and many firewalls either don't support it or would require firmware updates / policy changes to support it. There's a wicked chicken-and-egg problem deploying SCTP: a popular service would be a good reason to push vendors, enterprise firewall admins, etc. to support SCTP but it'd be financial suicide to build a general service which depends on it now.
- stormbrew 11y ago
  There is a UDP form of SCTP [1], which should traverse consumer routers just fine. You may note that I actually mentioned this in my post. [1] https://tools.ietf.org/html/rfc6951 https://tools.ietf.org/html/rfc6951
- detaro 11y ago
  which works against pure SCTP, but SCTP over UDP shouldn't be hindered any more than QUIC
- deleted 11y ago
  [deleted]
- lttlrck 11y ago
  SCTP can be run over UDP.
pthatcherg 11y ago
I know that one big deal is fewer round trips. DTLS+SCTP requires several round trips to establish a secure connection (around 4 I think). DTLS 1.3 should improve that on the DTLS side of things, but QUIC is designed from the beginning to have 0 round trips for many cases, and 1 round trip in the worst case. For high RTT scenarios, that can make a big difference.

wmf 11y ago

QUIC is supposed to be quicker than SCTP+TLS or SCTP+IPSec by using some "rampant layering violations" to combine security and transport into one layer and eliminate a lot of round trips.

waqf 11y ago

Your question is answered in the design doc at https://docs.google.com/document/d/1RNHkx_VvKWyWg6Lr8SZ-saqsQx7rFV-ev2jRFUoVD34/edit?pli=1#heading=h.nvk2biis6bpk https://docs.google.com/document/d/1RNHkx_VvKWyWg6Lr8SZ-saqs... tl;dr minimizing latency, particularly in establishing a connection, is an important design objective.

dragontamer 11y ago

SCTP isn't implemented on most routers, firewalls. UDP is.

imglorp 11y ago
SCTP is in Cisco IOS[1], but regardless, it sits at the IP layer so all routers need to do is pass it as IP, unless you want to do more. It's also in plenty of OS kernels already, such as solaris and linux, and can be written as userspace libraries. 1: http://www.cisco.com/c/en/us/td/docs/ios/12_4t/12_4t15/htsctp.html http://www.cisco.com/c/en/us/td/docs/ios/12_4t/12_4t15/htsct...
- dragontamer 11y ago
  I'm talking about your typical Netgear router / firewall application. > it sits at the IP layer so all routers need to do is pass it as IP Erm... no. The vast majority of consumer electronics are built up from NAT. You are NOT getting past your Verizon/Comcast router with IP alone. It's getting interpreted as TCP, and then getting NATted over to something else. As far as i can tell, UDP has a similar process. But its a major problem with SCTP and consumer routers. Have you ever tried to send an SCTP connection across your typical consumer Verizon router?
  - wtallis 11y ago
    > You are NOT getting past your Verizon/Comcast router with IP alone. ... on IPv4. On IPv6 you don't have to worry about NAT, and IPv6 usage is growing: the percentage of Google traffic conducted over IPv6 has doubled in the past year and is significantly higher on weekends, which means consumers are driving a lot of that traffic. It's now over 7% on weekends and growing by about one percentage point every 3-4 months. That seems to me like a sufficiently large pool of potential testers. The NAT problem is really finally going away. What we need to be worrying about is dumb firewalls, but I'd bet that there will be just as many consumer routers that fail to make any of their firewall rules apply to IPv6 as there will be routers that can pass TCP over IPv6 but not arbitrary protocols.
- acdha 11y ago
  The catch is that most NAT devices don't support it, which is a deal-breaker for something to be deployed on the public internet, and many firewalls either don't support it or would require firmware updates / policy changes to support it. There's a wicked chicken-and-egg problem deploying SCTP: a popular service would be a good reason to push vendors, enterprise firewall admins, etc. to support SCTP but it'd be financial suicide to build a general service which depends on it now.
stormbrew 11y ago
There is a UDP form of SCTP [1], which should traverse consumer routers just fine. You may note that I actually mentioned this in my post. [1] https://tools.ietf.org/html/rfc6951 https://tools.ietf.org/html/rfc6951
detaro 11y ago
which works against pure SCTP, but SCTP over UDP shouldn't be hindered any more than QUIC
deleted 11y ago
[deleted]
lttlrck 11y ago
SCTP can be run over UDP.

pthatcherg 11y ago

I know that one big deal is fewer round trips. DTLS+SCTP requires several round trips to establish a secure connection (around 4 I think). DTLS 1.3 should improve that on the DTLS side of things, but QUIC is designed from the beginning to have 0 round trips for many cases, and 1 round trip in the worst case. For high RTT scenarios, that can make a big difference.