(a) lower throughput (performance) caused by additional overhead Some of the downsides of fragmentation are: What is a fragmentation and why do we want to avoid it?įragmentation is a process of splitting an IP packet into multiple fragments (which are also IP packets themselves) in case the data to be carried exceeds egress interface MTU. Additionally, MTU can be different (lower) along the whole connection path and introduce issues.
Why do we need to consider MTU size when we are talking about VPN solutions, such as GlobalProtect?Īll VPN solutions are adding certain overhead to our original data, thus effectively reducing MTU we are able to use (if we are to avoid fragmentation). Note: Though we are often calling different Protocol Data Units (PDUs) at different layers 'packet', the usual convention is that the PDUs are named as: Layer SDU received on a layer n is a PDU for a layer n+1. MTU (Maximum Transmission Unit) usually refers to a maximum amount of data (Bytes) that we can place as a payload into a L2 frame. In most of the cases, we are talking about Ethernet on Layer2 and IP on Layer3, where the previous statement translates to maximum IP packet size that can be carried over by Ethernet Frame. Formally, each OSI (Open Systems Interconnection) model layer has its own PDU (Protocol Data Unit) which encapsulates the data called SDU (Service Data Unit) as its payload.
