diff --git a/doc/api/dgram.md b/doc/api/dgram.md index 7a3c110fbf2b66..fda68595a24eef 100644 --- a/doc/api/dgram.md +++ b/doc/api/dgram.md @@ -516,25 +516,25 @@ client.connect(41234, 'localhost', (err) => { #### Note about UDP datagram size -The maximum size of an `IPv4/v6` datagram depends on the `MTU` -(_Maximum Transmission Unit_) and on the `Payload Length` field size. +The maximum size of an IPv4/v6 datagram depends on the `MTU` +(Maximum Transmission Unit) and on the `Payload Length` field size. -* The `Payload Length` field is `16 bits` wide, which means that a normal - payload cannot exceed 64K octets _including_ the internet header and data +* The `Payload Length` field is 16 bits wide, which means that a normal + payload cannot exceed 64K octets including the internet header and data (65,507 bytes = 65,535 − 8 bytes UDP header − 20 bytes IP header); this is generally true for loopback interfaces, but such long datagram messages are impractical for most hosts and networks. * The `MTU` is the largest size a given link layer technology can support for - datagram messages. For any link, `IPv4` mandates a minimum `MTU` of `68` - octets, while the recommended `MTU` for IPv4 is `576` (typically recommended + datagram messages. For any link, IPv4 mandates a minimum `MTU` of 68 + octets, while the recommended `MTU` for IPv4 is 576 (typically recommended as the `MTU` for dial-up type applications), whether they arrive whole or in fragments. - For `IPv6`, the minimum `MTU` is `1280` octets, however, the mandatory minimum - fragment reassembly buffer size is `1500` octets. The value of `68` octets is + For IPv6, the minimum `MTU` is 1280 octets. However, the mandatory minimum + fragment reassembly buffer size is 1500 octets. The value of 68 octets is very small, since most current link layer technologies, like Ethernet, have a - minimum `MTU` of `1500`. + minimum `MTU` of 1500. It is impossible to know in advance the MTU of each link through which a packet might travel. Sending a datagram greater than the receiver `MTU` will