I am not sure what you are referring to by "broker[ing] peace." There is a very big desert between the more heavily inhabited areas of North Africa and the ancient-medieval empires of northern sub-Saharan Africa (Djenne in Sudan, Ghana, Mali, etc). Neither side had any real interest in conquering the other.

Around the fourth century (predating the birth of Islam), North African Berber merchants link sub-Saharan trading centers with the Mediterranean Sea trade in the north and east. With the rise of the gold-mining empires in West Africa starting with Ghana, North African and Western Saharan Muslims are basically the exclusive conveyers of gold across the Sahara.

Even before West Africa adopted Islam for itself, Muslim North Africans were able to set up their own small communities in the south to aid in the trade. (I believe this was a deliberate policy of the rulers of Ghana, at least--they wanted to benefit from the Muslims' presence, not let their religion filter out to the people). Literate Muslims also served as advisors to the sub-Saharan rulers. By the height of the Mali Empire in the thirteenth-fourteenth century, rulers have adopted Islam wholesale--Mansa Musa's pilgrimage to Mecca is noted even in European sources for its impact on the Mediterranean economy. Arab scholars like Ibn Battuta who traveled to West Africa and were warmly welcomed recorded some ways in which they were zealously Islamic (e.g. required memorization of the Qur'an) and customs that seemed odd to him (women walking around naked in front of the ruler). Meanwhile, Muslim merchants from North Africa and the Sahara continued as the primary means of transporting goods between sub-Saharan West Africa and the Mediterranean (Marrakesh, Algiers, Cairo.)

As far as conflict goes, when the Almoravids took over in Spain and North Africa, there was some fighting between their more conservative forces and some of the more Islamic-African acculturated communities in the southern Sahara.

Here is a nice online overview of how western Africa slowly adopted Islam. For printed materials, my favorite is probably the introduction to Medieval West Africa: Views from Arab Scholars and Merchants ed. Levtzion and Spaulding (a fantastic collection of excerpts from translated sources), but it is not organized chronologically very well. A good textbook-style description is in Collins and Burns, A History of Sub-Saharan Africa in chapter 6, "Empires of the Plains." ETA: I totally forgot Levtzion's History of Islam in Africa as /u/ghostofpennwast reminded me, despite it sitting on my desk.

(This is my first post in this sub--I hope my citation of sources is adequate.)

This is one of the best secondary texts on it. http://www.barnesandnoble.com/w/history-of-islam-in-africa-nehemia-levtzion/1101388751?ean=9780821412978&st=PLA&sid=BNB_DRS_Core+Shopping+Textbooks_00000000&2sid=Google_&sourceId=PLGoP210&k_clickid=3x210&kpid=9780821412978

Islamic traders from North Africa and the Sahara brought their culture as well as trade into the forrested part of Africa.

https://en.wikipedia.org/wiki/Dyula_people

They had brotherhoods which acted as gathering places for their people in diaspora, but they had a pretty progressive view code of conduct for their diaspora community.

Talking about West Africa in general from 1500-1900, there were some pretty frequent Jihads (Sokoto/Fulbe/Fula), but the Dyula were a big boon when it came to making transaharan trade possible. They had business and cultural contacts with North Africa (because they were related to and often relatives of North Africans), and they were able to bring a lot of wealth to the region. Levetzion talks about this extensively.

What sense do you mean about brokering peace?

The Fula Jihads essentially were the result of Islam moving south over time and eventually trying to usurp the Animist natives, but on the other hand different regions which were populated by the non-Muslims.

On the other hand, you have places like the Djula communities which were so well accepted that they were often tasked to be trade/financial aids by the rulers of their cities/states, which could be seen as pretty indicative of social acceptance.

Both of those sort of major issues could be seen as a whole. They traded and sometimes fought. Sometimes Islam was passive and very accomidationist, other times Islamic states were set up. Levetzion's book is a classic and highly regarded in the field.