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©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
Network Network LevelLevel Framing in INSTANCE Framing in INSTANCE
Pål Halvorsen, Thomas Plagemann, and Vera GoebelUniversity of Oslo, UniK- Center for Technology at Kjeller
Norway
Overview:• Application Scenario
• The INSTANCE project:– Zero-Copy-One-Copy Memory Architecture
– Integrated Error Management
– Network Level FramingNetwork Level Framing
• Conclusions
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
Media-on-Demand server:Applicable in applications like News- or Video-on-Demand provided by city-wide cable or pay-per-view companies
Application Scenario
Network Network
Multimedia Storage Server
Project goals:Optimize performance within a single server:• Reduce resource requirements • Maximize number of clients
Retrieval is the bottleneck:Some important factors:• Memory management• Error management• Communication protocol processing
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
Zero-Copy-One-Copy IZero-Copy Delay-Minimized Broadcast
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
Zero-Copy-One-Copy II
Integrated Zero-Copy and Delay-Minimized Broadcasting
Zero-Copy Delay-Minimized Broadcast
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
Traditional Error Management
Encoder Decoder
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
Integrated Error Management
Encoder Decoder
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
Traditional Storage
TRANSPORT
NETWORK
LINK
TRANSPORT
NETWORK
LINK
TRANSPORT
NETWORK
LINK
TRANSPORT
NETWORK
LINK
Upload to serverFrequency: low (1)
Download from serverFrequency: very high
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
Network Level Framing (NLF)
TRANSPORT
NETWORK
LINK
TRANSPORT
NETWORK
LINK
NETWORK
LINK
NETWORK
LINK
TRANSPORT TRANSPORTTRANSPORT TRANSPORT
Upload to serverFrequency: low (1)
Download from serverFrequency: very high
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
NLF:
When to Store Packets
IP
Transport Layer
Network Layer
Link Layer
IP
UDP
UDP
IP
TCP
IP
TCP
IP
UDP
IP
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
NLF:
Splitting the UDP Protocol
UDP
IP
UDP
Prepend UDP and IP headers
Prepare pseudo header for checksum
Calculate checksum
Fill in some other IP header fields
Hand over datagram to IP
udp_output()
Temporarily connect
Disconnect connectedsocket
udp_output()
Prepend UDP and IP headers
Prepare pseudo header for checksum, clear unknown fields
Prealculate checksum
udp_PreOut()
Update UDP and IP headers
Update checksum, i.e., only add checksum of prior unknown fields
Fill in other IP header fields
Hand over datagram to IP
udp_QuickOut()
UDP
IP
UDP
UDP
IP
UDP
UDP
IP
UDP
UDP
IP
UDP
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
NLF:
Checksum Operations I• The UDP checksum covers three fields:
– A 12 byte pseudo header containg fields from the IP header
– The 8 byte UDP header
– The UDP data
• Checksum calculation function (in_cksum):
u_16int_t *w;for each mbuf in packet {
w = mbuf->m_data;while data in mbuf {
checksum += w;w++;
}}
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
NLF:
Checksum Operations II• Traditional checksum operation:
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
NLF:
Checksum Operations III• NLF checksum operation:
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
FEC
FEC
Integrated Error Management and NLF
UDP - PreOut
Network
UDP - QuickOut
UDP - Input
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
Expected Performance Gain
• Traditionally, 60% of the UDP/IP processing is spent on checksum calculation [Kay et al. 93]
• Performance gain using NLF (packet size dependent):– The checksum operation is greatly reduced
• E.g., 4KB packet size checksum operation on only 0.2% of data
• Speed-up factor of about 2
– Throughput gain of about 10%
©2000 Pål HalvorsenMIS 2000, Chicago, October 2000
Conclusion
The INSTANCE project aims at optimizing the data retrieval in an MoD server:– Zero-Copy-One-Copy memory architecture– Integrated Error Management
– Network Level FramingNetwork Level Framing Saving time for checksum calculation where expected
performance gain is:– About 99% reduction of the checksum calculation time
(UDP/IP processing speed-up of 2)– About 10% increase in throughput
– Future work
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