Ready to Wumbo: LND Enables More, Larger Bitcoin Transactions on Lightning

LND now supports Lightning Network wumbo channels. These channels have the capacity to hold more funds, and users can send larger bitcoin transactions.

AccessTimeIconAug 20, 2020 at 5:31 p.m. UTC
Updated Sep 14, 2021 at 9:46 a.m. UTC

Bitcoin's Lightning Network has reached a significant milestone. An important capacity limit meant to protect users of the nascent protocol is being tweaked, toppling a barrier to entry for companies looking to adopt the novel payment system. 

LND, a leading Lightning Network implementation from startup Lightning Labs, has announced it has adopted support for wumbo channels. Going forward, users can deposit more money into Lightning Network channels than before, as well as send larger transactions.

ACINQ's eclair and Blockstream's c-lightning both adopted a form of wumbo earlier this year. According to LND's fresh release notes, the node software now allows users to opt into "accepting" and "creating" wumbo channels.

What is wumbo?

The word "wumbo" comes from, believe it or not, SpongeBob SquarePants, a cartoon series about a talking sponge that works at a burger joint under the sea with an assortment of sea friends. In one scene, SpongeBob's starfish friend Patrick Star teaches him the word "wumbo." 

"You wumbo, I wumbo," Star says, pointing to Spongebob, then himself. Lightning's "wumbo" is similar in that two users have to agree to wumbo before they wumbo.

There are two parts to wumbo. The first part removes the limit to the total amount of bitcoin that can be held in a channel: This limit is currently capped at 0.16777215 BTC, worth about $1,988 at press time. The second strips away the limit to how large an individual payment can be: That limit has been 0.04294967 BTC, worth about $508 at press time.

Wumbo isn't technically difficult; in fact, it's very simple. With wumbo channel support, a user can signal he or she wants to go beyond the aforementioned limits and find other nodes to connect to that also support higher limits.

Developers added the limitation to protect users from pouring too much money into Lightning, as it's still a new and experimental technology. As such, one reason wumbo is a big deal is it is a sign that the payment technology is maturing.

"We view shipping wumbo in LND as a sign that the software has progressed to a certain point where advanced users, companies, and node operators can open larger channels. These larger wumbo channels enable a better user experience with larger transactions on the network and more efficient capital usage for startups and node operators," Lightning Labs CEO Elizabeth Stark told CoinDesk.

That's not to say they don't think people still need to be careful working with this new technology.

"That said, we do not encourage people to go all 'DeFi' on Lightning (looking at you, YAM), as we believe people should balance the risks of deploying capital on a new protocol that could have bugs with the benefits of larger channel sizes," Stark added.

Why wumbo?

Average Lightning users might not be impacted much by wumbo. If they're using the Lightning Network to send small amounts, then this lift on capacity won't make a difference to them. 

Larger entities such as business or exchanges, on the other hand, might want to take advantage of a larger capacity.

"Most users can likely get by without wumbo channels, but larger nodes or exchanges/services may really benefit from the ability to manage a smaller set of larger channels," LND developers explain in the release notes.

That's why some developers think wumbo will take the Lightning Network to the next level. They think it will attract wider adoption of the Lightning Network among larger entities, making it accessible to more bitcoin users.

"Most of the major node operators and startups run our LND implementation, so unless they’ve forked LND and added Wumbo themselves (which a few have, and this was riskier without official support), they would not have had this feature enabled," Stark said.

Still, some companies have already added support for wumbo without waiting for an official route to do so. As such, Acinq CEO Pierre-Marie Padiou is skeptical LND adding support for wumbo will make a huge difference.

"It can't hurt, but larger nodes [...] have already switched, so the improvement has probably already taken place," he told CoinDesk.

Are we ready to wumbo?

Channel and transaction limits were put in place to protect users from potentially losing large amounts of bitcoin by sending it over an experimental network. What makes developers think Lightning is now ready to live without these limits?

"I think we've gained experience, and with that comes confidence," said Blockstream engineer Rusty Russell, though he still expressed caution: "As always, it's best to think of Lightning as your petty cash, rather than your life savings."

People have a choice – they obviously don't have to use the ballooned capacity that wumbo channels allow. "With regard to security, with Eclair you can decide whether or not you decide to allow large channels and what the maximum channel size you accept [is]. We also scale the number of confirmations for the funding transaction depending on the amount of funds at stake," Padiou told CoinDesk.

Russell also pointed out that the payment limit of 0.16777215 BTC was far less valuable, equivalent to about $10 dollars, when it was originally proposed years ago. As bitcoin's price has increased over the last several years, this value limit has ballooned to almost $2,000. So, to a degree, the limit has naturally lifted over time.

"So we got wumboed already without having to even put our belt on," Russell said, referencing the belt SpongeBob wears in the wumbo scene.


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