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The maximum number of combined external coupling links (active CE LR, ICA SR links) is 160 per z15 server. z15 servers support up to 384 coupling CHPIDs per CPC. A z15 coupling link support summary is shown in Figure 4-4 on page 197. Consider the following points: 

GLYPH<SM590000> The maximum supported links depends on the IBM Z model or capacity feature code and the numbers are marked with an asterisk (*). 

GLYPH<SM590000> z15 ICA SR maximum depends on the number of CPU drawers. A total of 12 PCIe+ fanouts are used per CPU drawer, which gives a maximum of 24 ICA SR ports. The z15 machine maximum ICA SR1.1 and ICA SR ports combined is 96. 

For more information about distance support for coupling links, see System z End-to-End Extended Distance Guide , SG24-8047 . 

## Internal Coupling link 

IC links are Licensed Internal Code-defined links to connect a CF to a z/OS logical partition in the same CPC. These links are available on all IBM Z platforms. The IC link is an IBM Z coupling connectivity option that enables high-speed, efficient communication between a CF partition and one or more z/OS logical partitions that are running on the same CPC. The IC is a linkless connection (implemented in LIC) and does not require any hardware or cabling. 

An IC link is a fast coupling link that uses memory-to-memory data transfers. IC links do not have PCHID numbers, but do require CHPIDs. 

IC links have the following attributes: 

GLYPH<SM590000> They provide the fastest connectivity that is significantly faster than external link alternatives. 

GLYPH<SM590000> They result in better coupling efficiency than with external links, effectively reducing the CPU cost that is associated with Parallel Sysplex. 

