3 ms·

Sure, but what is UDP bringing to the party then? The pseudoheader? A reasonable RPC layer could just layer on IP.

by cjsplat 4y ago

wmf 4y ago
The UDP header will give you proper ECMP hashing.
- cjsplat 4y ago
  Yup - this is the correct answer
roncesvalles 4y ago
IIRC, UDP just adds port numbers and a checksum to IP. It's about as bare bones as it can get, unless you want to get rid of the checksum too.
- rezonant 4y ago
  Some implementations do skip checksum (leaving it as zero), for instance you can configure a Linux UDP socket to skip it if you can't afford the time it would take to calculate them.
cryptonector 4y ago
> Sure, but what is UDP bringing to the party then? Interoperability. It's been how many years since SCTP was published? How's that going?
- noselasd 4y ago
  You're likely interacting with SCTP every time you use a mobile phone, as it's in heavy use in the control plane of telecom networks. Outside that, not so much though.
  - ithkuil 4y ago
    Yes but if my program on my laptop wants to talk to my program in my server somewhere out there, chances are the SCTP will be blocked by some piece of blinking furniture along the path.
  - monocasa 4y ago
    Also every Zoom/Google Meet call. WebRTC is on top of SCTP.
    - rezonant 4y ago
      Sort of. SCTP is used for data channels, the audio/video is RTP. Still an important piece though.
    - Jasper_ 4y ago
      WebRTC uses SCTP in a weird way: on top of DTLS, which is itself on top of UDP. When most people talk about using SCTP, they mean using it instead of UDP.
  - cryptonector 4y ago
    > Outside that, not so much though. Thanks for making my point.
kwantam 4y ago
Well, for one, UDP brings the U. It's called the User Datagram Protocol because (at least on UNIX-like systems) unprivileged programs can almost always send and receive UDP datagrams, but in general cannot send and receive raw IP datagrams.
themoonisachees 4y ago
UDP gives you port numbers supported by every networking equiment your datacenter already has, instead of having to deal with raw IP frames or somehow extending how your firewalls and servers handle your special boy packets. Especially useful considering you probably want port numbers anyway, and checksums are just a nice bonus. You'll probably reimplement part of TCP on top of it too.

Sure, but what is UDP bringing to the party then? The pseudoheader? A reasonable RPC layer could just layer on IP.

wmf 4y ago

The UDP header will give you proper ECMP hashing.

cjsplat 4y ago
Yup - this is the correct answer

roncesvalles 4y ago

IIRC, UDP just adds port numbers and a checksum to IP. It's about as bare bones as it can get, unless you want to get rid of the checksum too.

rezonant 4y ago
Some implementations do skip checksum (leaving it as zero), for instance you can configure a Linux UDP socket to skip it if you can't afford the time it would take to calculate them.

cryptonector 4y ago

> Sure, but what is UDP bringing to the party then? Interoperability. It's been how many years since SCTP was published? How's that going?

noselasd 4y ago
You're likely interacting with SCTP every time you use a mobile phone, as it's in heavy use in the control plane of telecom networks. Outside that, not so much though.
- ithkuil 4y ago
  Yes but if my program on my laptop wants to talk to my program in my server somewhere out there, chances are the SCTP will be blocked by some piece of blinking furniture along the path.
- monocasa 4y ago
  Also every Zoom/Google Meet call. WebRTC is on top of SCTP.
  - rezonant 4y ago
    Sort of. SCTP is used for data channels, the audio/video is RTP. Still an important piece though.
  - Jasper_ 4y ago
    WebRTC uses SCTP in a weird way: on top of DTLS, which is itself on top of UDP. When most people talk about using SCTP, they mean using it instead of UDP.
- cryptonector 4y ago
  > Outside that, not so much though. Thanks for making my point.

kwantam 4y ago

Well, for one, UDP brings the U. It's called the User Datagram Protocol because (at least on UNIX-like systems) unprivileged programs can almost always send and receive UDP datagrams, but in general cannot send and receive raw IP datagrams.

themoonisachees 4y ago

UDP gives you port numbers supported by every networking equiment your datacenter already has, instead of having to deal with raw IP frames or somehow extending how your firewalls and servers handle your special boy packets. Especially useful considering you probably want port numbers anyway, and checksums are just a nice bonus. You'll probably reimplement part of TCP on top of it too.