Figure 49 Analyzing the IPX Header

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Table 4-6. The IPX Header (Packet or Datagram)

Field

Bits

Description

Checksum

16 bits

Not used when set to all 1s (FFFF).

Packet Length

1(5 bits

Number of bytes up to the MTUl*! size. No fragmentation.

Trans |aort Control

8 bi ts

Shows routers the packet has transited. The lim it is 16.

Packet Type

8 bits

Link to next layer (like IP protocol number). Examples include 0-unknown, 1-RIP, 5-SPX, and 17-NCP.

Destination Network:

322 bits

External (wire) network number.

Destination Node

"48t bits

MAC add re ss.

Destination Socket

16 bits

See source socket.

Source Network

32 bits

[External (wire) netw ork.

Source Node

"48 bits

MAC address.

Source Socket

16 bits

Pointer to upper layers (like a TCP/UDP port number). Examples include 0451-NCP, 0452-SAP, 0453-RIP, 0455-NetBIOS, and 0456-Diagnostics. 4000-6000 are ephemeral sockets for server and network communications.

Upper Layer Data

Varies

Information for upper-layer processes.

[*] MTU = Maximum Transmission Unit

[*] MTU = Maximum Transmission Unit

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