Serialization/Access-Rate is the physical clocking speed of the interface (ie 64-kbps/128-kbps etc), which determines the amount of data that can be encapsulated on to the wire.
Serialization Delay or Serialization Rate is a constant based on the access rate of the interface. It is the time needed to place data on the physical wire.
These values are set in hardware and cannot be changed.
A data frame can be sent onto the physical wire ONLY at the serialization rate of the interface. Thus serialization delay is the size of the frame in bits divided by the clocking speed of the interface.
Serialization Delay = Frame Size/Link Speed
For example, a 1500-byte frame (12000-bits/64000-bits) will take 187.5ms to serialize (put on the wire) on a 64-kbps circuit.
|Link-||Frame Size (Bytes)|
|64 kbps||8 ms||16 ms||32 ms||64 ms||128 ms||187 ms|
|128 kbps||4 ms||8 ms||16 ms||32 ms||64 ms||93 ms|
|256 kbps||2 ms||4 ms||8 ms||16 ms||32 ms||46 ms|
|512 kbps||1 ms||2 ms||4 ms||8 ms||16 ms||23 ms|
|768 kbps||0.640 ms||1.28 ms||2.56 ms||5.12 ms||10.4 ms||15 ms|
For low-speed WAN connections (those with a clocking speed of 768kbps or below), it might be necessary to provide a mechanism for Link Fragmentation and Interleaving (LFI) when running delay sensitive application like voice.