A

1
A segmentation exercise

• What changes to our segment.c device-driver
  module are needed for offloading of UDP
  Segmentation?

2
Ethernet Header
Destination MAC-address
Source MAC-address
TYPE / LENGTH
3
IP Header
VERS
Total Length
TOS
HLEN
Identification
fragment offset
FLAGS
IP Header Checksum
Protocol ID
TTL
Destination IP-address
Source IP-address
4
UDP Header
Source port-number
Destination port-number
UDP Segment Length
UDP Checksum
5
UDP Pseudo Header
Destination IP-address
Source IP-address
UDP Length
Protocol ID
ZERO
6
Partial pseudo-header
Destination IP-address
Source IP-address
ZERO
Protocol ID
ZERO
7
Context descriptor (type 0)
63 48
47 40 39 32 31
16 15
8 7 0
IPCSS
IPCSE
IPCSO
TUCSS
TUCSE
TUCSO
PAYLEN
DTYP 0
MSS
TUCMD
STA
HDRLEN
RSV
DEXT1 (Extended Descriptor)
Legend IPCSS (IP CheckSum Start) TUCSS
(TCP/UDP CheckSum Start) IPCSO (IP CheckSum
Offset) TUCSO (TCP/UDP CheckSum Offset) IPCSE
(IP CheckSum Ending) TUCSE (TCP/UDP CheckSum
Ending) PAYLEN (Payload Length) DTYP
(Descriptor Type) TUCMD (TCP/UCP Command) STA
(TCP/UDP Status) HDRLEN (Header Length) MSS
(Maximum Segment Size)
8
The TUCMD byte
7 6 5 4
3 2 1 0
IDE
SNAP
DEXT (1)
reserved (0)
RS
TSE
IP
TCP
Legend IDE (Interrupt Delay Enable) SNAP
(Sub-Network Access Protocol) DEXT (Descriptor
Extension) RS (Report Status) TSE
(TCP-Segmentation Enable) IP (Internet
Protocol) TCP (Transport Control Protocol)
always valid valid only when TSE1
9
Context descriptor (type 1)
63 48
47 40 39 32 31
16 15
8 7 0
BASE ADDRESS
DTALEN
DTYP 1
VLAN
DCMD
STA
POPTS
RSV
DEXT1 (Extended Descriptor)
Legend DTALEN (Data Length) DTYP (Descriptor
Type) DCMD (Descriptor Command) STA (Status)
RSV (Reserved) POPTS (Packet Options) VLAN
(VLAN tag)
10
The DCMD byte
7 6 5 4
3 2 1 0
IDE
VLE
DEXT (1)
reserved (0)
RS
TSE
IFCS
EOP
Legend IDE (Interrupt Delay Enable) VLE
(VLAN Enable) DEXT (Descriptor Extension) RS
(Report Status) TSE (TCP-Segmentation Enable)
IFCS (Insert Frame CheckSum) EOP (End Of
Packet))
always valid valid only when EOP1