Back-channel communications are nothing new for White House Several previous administrations have used back channels.

 -- Jared Kushner and Russian ambassador Sergey Kislyak discussed the possibility of creating a back channel -- a secret communication channel -- between the Trump team and Russian officials, sources familiar with the matter told ABC News.

Kushner’s alleged request, first reported by the Washington Post on May 26, stirred controversy. But White House back-channel communications with foreign powers aren't unprecedented: Several other presidential administrations have used back-channel communication as a means of problem solving outside of traditional avenues.

“Back channels are a tool in the diplomatic tool box, and they can be a very effective tool,” said Richard Moss, author of the book “Nixon’s Back Channel to Moscow” and a professor at the U.S. Naval War College. “There’s a long tradition of it -- it goes back as long as diplomacy itself.”

Back channels can be a good way to achieve diplomatic breakthroughs, but they can also indicate something more sinister.

“They certainly have a varied history,” Moss said. “And it varies from nefarious and illegal to perfectly legitimate and effective.”

Whether back-channel diplomacy is legal depends on the context: There is a clear line between back channels and espionage, Moss said.

Here’s a rundown of past administrations that have used back-channel communications:

The Roosevelt administration

Back-channel lines of communication with Russia have not only been used before -- they were in some ways the birthplace of the two countries’ relationship. Back-channel negotiations were used to establish diplomatic relations under the Franklin D. Roosevelt presidency in 1933, Moss said.

During World War II, the Roosevelt administration and Winston Churchill used FDR’s associate Harry Hopkins as a non-official negotiator with the fledgling communist nation. Hopkins “transmitted diplomatic messages that bypassed the State Department with the Soviets,” Moss said.

The Kennedy administration

A series of documents related to Robert Kennedy’s role in his brother’s administration indicate that he had a significant role in foreign policy and particularly the Cuban missile crisis, despite his official role as U.S. Attorney General.

Robert Kennedy’s role as an intermediary between the White House and the Soviets eventually helped sidestep the two countries’ use of nuclear weapons through a public U.S. pledge not to invade Cuba if the Soviet Union pulled out their missiles along with a private promise to remove U.S. missiles in Italy and Turkey.

There is “some irony” in this scenario, Moss said, “because there were anti-nepotism laws enacted after that.”

The Nixon administration

The Nixon White House kept the State Department out of the loop on their negotiations with the Soviet Union throughout the Cold War because it “suited his idea of centralizing power in the White House,” Moss said.

Over the course of his presidency, Nixon worked to achieve détente -- the relaxing of tensions between the U.S. and the Soviet Union -- largely through a back-channel diplomatic relationship between Henry Kissinger and Soviet ambassador Anatoly Dobrynin because he was wary of press leaks and distrustful of traditional channels of diplomacy.

In 1971 Nixon said of his own White House: “There have been more back-channel games played in this administration than any in history because we couldn’t trust the goddamned State Department."

Nixon’s affinity for back-channel communications also contributed to several other major foreign policy achievements of his administration, Moss said.

He employed Kenneth Rush, one of his former law school professors and then-ambassador to West Germany, to synchronize negotiations on the Quadripartite Access Agreement on Berlin with the Kissinger-Dobrynin Channel, outside of the purview of the State Department.

The “opening of China” to the United States in 1972 following a historic presidential visit remains one of the Nixon administration’s claims to fame. Contacts with Chinese leadership -- and eventually the fostering of a diplomatic relationship with China -- were made possible with the help of Pakistan’s ruler and military dictator Yahya Khan, who delivered messages back and forth between the powers.

Even before coming into office, Nixon’s campaign staff secretly communicated with South Vietnam to sabotage President Lyndon Johnson’s 1968 peace talks. In his book “Richard Nixon: The Life,” John A. Farrell reported that notes from Nixon’s closest aide, H.R. Haldeman, indicated that the campaign staff encouraged South Vietnam not to come to the negotiating table.

The Obama administration

In March 2013, the Obama administration opened up a back channel with Iran, and subsequently held several secret meetings. When the Iran Nuclear deal was brokered, Obama said the back-channel conversations were instrumental in negotiating the deal, according to the Associated Press.

Obama also approved secret negotiations with Iran in 2014 that were used to negotiate for the freedom of Americans held captive there.

So, what’s different about Kushner’s back-channel request?

Moss said there is some clear context missing in Kushner’s alleged request, particularly because he asked to use the Russians’ secure facilities.

“I’m baffled about that kind of request,” Moss said, because it would require the administration to rely on the Russians to keep the information secret and would open it up to possible surveillance by U.S. intelligence.

Kislyak claimed Kusher requested opening a back-channel line of communication during a meeting at Trump Tower in December, while Trump was still president-elect. That has led some to wonder whether the request would constitute a violation of the Logan Act, a law that prohibits private citizens from trying to influence foreign governments dealing with the U.S.

Moss and other experts say it’s unlikely that Kushner broke the law under the Logan Act. Attempting to negotiate with foreign powers during the presidential transition period “is neither unique or anything to be concerned about in a legal sense,” citing Nixon’s use of aide Robert Ellsworth to kill a summit with the Soviets planned by Johnson.

Moss also added that it’s unlikely Kushner acted on his own.

“If earlier back channels are a guide, I believe there is no way [Kushner] would have done this without getting at least verbal approval from the president,” Moss said.