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doc: remove excessive formatting in dgram.md #35234

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Sep 19, 2020
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doc: remove excessive formatting in dgram.md #35234

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18 changes: 9 additions & 9 deletions doc/api/dgram.md
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Expand Up @@ -520,25 +520,25 @@ 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
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