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Capturing Xbox System Link Traffic while playing Halo

CAIA Technical report 020802A, August 2002

Mark Pozzobon
mpozzobon@groupwise.swin.edu.au

Introduction

This preliminary investigation of Xbox in-game network traffic aims to report upon the inter-packet arrival times, packet size distributions, packet per second rates and console data rates used by the game Halo and Microsoft's System Link networking interface. In doing so, a better understanding of Xbox networking traffic characteristics will be ascertained, that will aid further analysis into the possibilities of online Xbox games and their sensitivity to the effects of packet loss and delay.

Generating and Capturing Xbox Traffic

Results/Discussion

Summary and Further Analysis

Microsoft use UDP/IP over Ethernet for System Link games, with each console being differentiated by their Ethernet MAC address. The UDP/IP information is fixed and apparently identical for each participating console. The MAC addresses have vendor code 00:50:F2. The IP address used in-game is the invalid address of 0.0.0.1. Also, the broadcast address of 255.255.255.255 is used in polling available client consoles. The traffic uses UDP port 3074 which is assigned as the Xbox port (as per IANA). It is also interesting to note that Microsoft have also registered this port for TCP traffic - although no TCP traffic was observed.


Server to Client

Client to Server

Inter-packet Arrival Times

On average 40ms

On average 40ms

Packet Lengths

160 (2 players), 192 (3 players) or 216 bytes (4 players) 100% of time

72 bytes for 16.6% of time

112 bytes (1 player on client console)/136 bytes (2 players on client console) for the remaining period

Packets per second

25 packets per second

30 packets per second

Data Rate

32+ kbit/sec, depending on number of players

25+ kbit/sec, depending on number of players

The results clearly show the predictability of the inter-arrival packet time being 40ms for traffic flowing from the server and client consoles. It is interesting to note the low distribution of packets arriving between 0ms and 40ms for traffic flowing from the client to server consoles. This jittery behaviour appears to only occur in one direction and produces the "ramp-like" plots to 33% on the cumulative inter-arrival histograms prior to the sharp rise at 40ms to 100%. Whilst for the inter-arrival histograms, this appears cyclic and noise-like.

Our next steps involve analysing the effect of jitter, packet loss and link latency on game play. We plan to simulate the adversities of Internet game play in the lab, experiment with routing System Link traffic over public Internet paths, and explore the consequences of adding a third Xbox to our multiplayer LAN environment.

References



 

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