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6 votes
Accepted

In IPv4 Fragmentation, should the first block be necessarily the closest smaller multiple to 8

The Fragment Offset field is three bits smaller than the Total Length field. 2^3 = 8 That means that you must use a multiple of eight. Typically you will use the largest multiple of eight that fits ...
Ron Maupin's user avatar
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5 votes
Accepted

How can a router know the MTU of the next router?

How does router B know that the MTU of router C is 1400 bytes? The MTU is a property of a network segment/subnet (more specifically of a link), not of a device/node which can have many interfaces ...
Zac67's user avatar
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4 votes

How can a router know the MTU of the next router?

To add to Zac67's answer: why router B pre-fragment packets to send before router C Fragmentation is expensive in terms of system ressources on routers, and should be avoided. Routers and Firewalls ...
Marc 'netztier' Luethi's user avatar
2 votes

In IPv4 Fragmentation, should the first block be necessarily the closest smaller multiple to 8

For IPv4, see RFC 791: To fragment a long internet datagram, an internet protocol module (for example, in a gateway), creates two new internet datagrams and copies the contents of the internet header ...
Zac67's user avatar
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2 votes

How does a router behave when some of the fragments of a packet is lost?

Routers typically do not care about fragmentation. They pass things on exactly as they receive them. (unless it's the source of the fragmentation.) As such, the router will be unaware of missing ...
Blue Flame's user avatar
2 votes
Accepted

Can MAC fragmentation improve throughput fairness in 802.11?

802.11 frame fragmentation isn't about bandwidth distribution, it's about getting a frame delivered in smaller fragments across a noisy channel.
Zac67's user avatar
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1 vote

IP fragmentation and PMTUD

The ICMP header is at the beginning of an IP packet. Since fragmentation doesn't change the IP packet itself, the header needs to be present in the first fragment. Whatever you think you've seen must'...
Zac67's user avatar
  • 85.8k

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