Port 1304: Boomerang — When DNS Became a Race

Service: Boomerang
Protocol: TCP and UDP
Port Range: Registered Port (1024-49151)
Status: End-of-life (2008)

Port 1304 is the registered port for Cisco's Boomerang protocol—a component of Cisco's Distributed Director product that solved content distribution through an elegant idea: turn DNS into a race and let the fastest server win.

What Boomerang Does

Boomerang was a dynamic server selection mechanism. When a client requested a hostname that was served by multiple redundant servers, instead of relying on static mappings or complex algorithms, Boomerang did something brilliant—it made all the servers answer at once.

Here's how it worked:

1. Client queries DNS — A local DNS server asks Distributed Director for the IP address of a hostname
2. Racing message sent — Distributed Director tells multiple DRP Server Agents (routers near different content servers) to respond directly to the client
3. All servers answer simultaneously — Each DRP sends back its DNS response at the same time
4. Fastest packet wins — The packet from the server closest to the client arrives first
5. Client uses first answer — Standard DNS behavior: take the first response, ignore the rest

The network itself decided which server was best. No centralized algorithm. No metrics to calculate. Just physics—the packet with the shortest path wins.

The DRP Protocol

The Director Response Protocol (DRP) was a simple UDP-based protocol that enabled Distributed Director to query routers for BGP and IGP routing metrics. But with Boomerang enabled, DRP did something different: it sent DNS responses directly to clients rather than back to Distributed Director.

This was "DNS racing." All candidates answer at once. The fastest one arrives first. The client doesn't know a race happened—it just got the best answer for its network position.

Why This Mattered

Before Boomerang, content distribution systems relied on static server selection or centralized decision-making. Distributed Director would query routers for routing metrics, calculate the best path, and return an answer. This worked, but it was slow and couldn't adapt to real-time network conditions.

Boomerang changed the model: let the network decide. If a link was congested or a route was failing, the packet from that direction would arrive late. The client would never use it. The system self-corrected based on actual network conditions, not predicted ones.

It was load balancing through competition.

The History

Boomerang was developed by Cisco Systems as part of the Distributed Director product line. The protocol was registered with IANA on port 1304 (both TCP and UDP) with Bruce Lueckenhoff listed as the contact at Cisco.

Distributed Director was designed in an era when content distribution networks were just emerging and companies needed ways to direct users to the nearest or fastest server. Boomerang represented a particularly elegant approach to this problem.

However, Distributed Director reached end-of-life in Cisco IOS Release 12.4(24)T (around 2008). All Distributed Director features—including Boomerang support—were removed from later IOS releases.¹ The technology has been superseded by more modern load balancing and content delivery solutions.

Port 1304 Today

Port 1304 remains officially registered to the Boomerang service in IANA's registry,² but the protocol itself is no longer in active use. Cisco has retired the Distributed Director product, and modern networks use different mechanisms for server selection and load balancing—Global Server Load Balancing (GSLB), anycast routing, and content delivery networks with their own proprietary selection algorithms.

If you see traffic on port 1304 today, it's likely either:

• Legacy equipment still running old Cisco IOS versions
• Misidentified traffic from another service
• Security scanning probing for old Cisco installations

Checking Port 1304

To see if anything is listening on port 1304 on your system:

Linux/Mac:

sudo lsof -i :1304
sudo netstat -tulpn | grep 1304

Windows:

netstat -ano | findstr :1304

Using nmap:

nmap -p 1304 <target-ip>

The Beautiful Idea

Boomerang is gone, but the idea remains beautiful: use the network as the oracle. Don't try to predict which path is fastest—run the race and find out.

Modern systems have largely moved away from this approach. They use sophisticated algorithms, real-time telemetry, and centralized control planes to make routing decisions. These work well, but they've lost something—the elegant simplicity of letting packets race and trusting the fastest one to win.

Port 1304 carried a protocol that understood something fundamental: the network already knows which path is best. Just ask all of them at once and listen for the first answer.