It's now high summer, and many migrants who live and work in Europe are traveling home for their annual holiday. For Spanish and other European authorities, it's a mammoth logistical and security challenge, to cope with the mass movement. All this week we're bringing you stories about the increasing traffic and trade links between Europe and North Africa. In today's episode, Al Goodman takes you to the port of Algeciras, a focal point of the operations.

Loaded up and waiting to board a ferry in southern Spain. Heading for Morocco, to spend vacations there with family. A great summer migration, that starts with a huge movement south from Europe. Three million travelers and seven hundred thousand vehicles, the Spanish government says. The busiest port of all is here at Algeciras.

AL GOODMAN ALGECIRAS, SPAIN "There's so much attention now on African migrants trying to get into Europe on clandestine boats. But every summer there's a different migration going in the other direction. People in Europe, going home to see family in Africa, especially in Morocco."

Mohamed and son, Karim, have gone from Paris to Morocco for decades. Years ago, they waited up to two days to board a ferry. Now, they say it's much faster. This retired Michelin tire factory worker from France has made the trip to Morocco for 45 years.

BEN BOUGRINE LAHCEN MOROCCAN-BORN FRENCH CITIZEN "The roads used to be awful when we made this trip. Now, there are modern highways, and plenty of gas stations and rest areas."

Spanish highways leading to the ports are marked with signs in Arabic. And ferry tickets can be bought well in advance of the port. He says there's still some waiting at the port, but he understands many people are traveling. Keeping a close watch on them is the Algeciras port control room. The director of port security has been working at this for three decades.

MANUEL ALCAZAR DIRECTOR OF SECURITY, ALGECIRAS PORT "Twenty years ago, the cars arrived and stayed a long time in the roads of the city. That has changed."

Now, entire sections of the port used for cargo in winter are set aside for the human migration in summer. But police must juggle the free flow of people, with security against potential terrorism.

JOSE ANTONIO RIOS DOMINGUEZ SPANISH CIVIL GUARD LIEUTENANT "With that many people and vehicles moving, evidently the possibilities of an attack increases. So, we can't lower our guard."

Police from other European nations are also stationed at Algeciras, to fight illegal immigration. They'll be especially busy later when the vacationers return north to Europe. But for now, it's time to head south. A huge annual migration, that keeps Europe and Africa in close contact. Al Goodman, CGTN, Algeciras, Spain.