CSE 190: Internet E-Commerce
Lecture 16: Performance
Performance Parameters
• Four dimensions of performance
– CPU Usage
• Issue for app server, DB
– Disk I/O
• Issue for DB, video streaming
– Memory Usage
– Network Usage
• Reflected in cost
• Each may be a bottleneck depending on the
application
Network Speeds
(What do all these names mean?)
Connection Type
Speed
T-1
1.544 Mbps (24 voice channels) ~$1k/m
T-3
44.7 Mbps (30 T-1s) ~$20k/m
OC-1
51.8 Mbps (SONET standard)
OC-3
155 Mbps ~50k/mo
OC-192
9.95 Gbps
For comparison:
Connection Type
Speed
Analog POTS modem
300 bps – 56.7 kbps
Cable modem
Upstream: 320 Kbps – 10 Mbps
Downstream: 30 – 42 Mbps
ADSL (Asymmetric Digital Subscriber Line)
Upstream: 64 kbps – 1.5 Mbps
Downstream: 768 kbps – 9 Mbps ~$40-120/m
Ethernet 10-BaseT
10 Mbps
Ethernet 100BaseT
100 Mbps
Effect of Architecture
• Small # of servers (Concentrated)
– Availability under high load
– Vulnerability to attack
– Cost/unit performance is lower
• Distributed architecture
– DNS load balancing
– Application load balancing
– Capacity upgrades require smaller investment
DNS Load Balancing
• DNS Load Balancing
– When address of web server is resolved, it may return
any of N IP addresses associated with it
– Yahoo Example
• Reference: Figure 7.2, page 188, “Web Servers”
by Benay Dara et al.
• HTTP Requests distributed over a farm of
servers.
• Content mirrored at each server
• Server A gets first request, server B gets
second, server C gets third, etc.
Application Load Balancing
• HTTP Requests sent to the least busy
server
• NOT distributed in a linear fashion
• All servers kept equally busy
• Reference: Figure 7.3, page 189, “Web
Servers” by Benay Dara et al.
• Bridge acts as virtual server to requesting
browsers/clients.
• More complex monitoring => may go awry
State And Server Affinity
No Affinity
Client IP Affinity
Request Forwarding
Multiple Web Farms
Proxy Servers
• Proxy, cache, and mirror techniques: for
improving web performance
– reduce latency of access to most frequently accessed
web documents
– Reduce network bandwidth congestion
– Increase security of electronic services
• Proxies provide web gateway on private
networks
• Configurable within browser (e.g. in IE, Tools |
Options | Connections)
• Reference: Figure 7.4, page 189, “Web Servers”
by Benay Dara et al.
Proxy servers
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Proxy servers run on Firewalls.
Handle both incoming and outgoing web requests.
Hide IP addresses of requesting clients
Handle NAT – Network address translation
Advantages:
– Access control of web sites by employees of an organization.
– Selective blocking of protocols such ftp.
– Cache relayed responses for performance.
• Cache problem: how current is the data
• Products:
– Apache with proxy configuration
– MS ISA Server (previously MS Proxy Server)
Scalability
THE BIG CHOICE
Distributed (e.g., Yahoo!, Google, Yodlee) vs. Concentrated (many e-commerce
sites)
Pros
Cons
Lower initial cost
Complex deployment infrastructure
Gradual ramp in cost
Involved monitoring infrastructure
Highly redundant
3rd party hosting expensive
More amenable for LARGE systems
Managing state across systems
complex
Scalability
Stateless (vs Stateful systems)
Pros
Cons
Highly redundant
Lower performance
Easier implementation in distributed
Network level load balancers
Application Level Load Balancers (vs. Network level)
Pros
Cons
More closed loop load balancing
Lower performance
Can help manage stateful systems
Higher cost
Performance
Elements of Performance
 Throughput (affecting scalability)
 Response Time (affecting user experience)
Elements of Response Time
 HTML Rendering
 Network download speed
 Application processing time
 Database performance
 Queues (web server, application server, network level)
Elements of Throughput
 Application processing time
 Database performance