Transcript ESI Extensions for Web

ESI Extensions for
Web-based Collaboration
Merlin W. Vincent
Master’s Thesis Defense
4/28/2004
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Outline
Characteristics of Collaboration Systems
 Edge-Side Includes Protocol
 ESI Extensions for Collaboration
 Extended Example ESIC Application
 Performance Evaluation
 Security Issues
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Motivation
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Provide an easy-to-use framework for developers
– collaboration becoming more popular
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Improve performance by offloading I/O
Decrease application complexity
– gain multicast distribution services
– gain collaboration-specific communications
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Utilize existing content delivery network (CDN)
Infrastructure
– Extend edge cache server function and Edge Side Includes
protocol for collaboration
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HTTP is ubiquitous and convenient
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General Collaboration Features
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Any framework should support:
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Authentication
Access Controls
Awareness
Transport Security
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Dynamic Interaction
Unrestricted doc types
Unrestricted app types
Unrestricted messaging
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Communications for Collaboration
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Collaboration application comm can be
– asynchronous
– synchronous
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Synchronous Real-time Communications
– operation propagation
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Replication of shared objects
– something must exist on user’s system
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Approaches to Object Replication
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Collaboration Awareness
– Lower bandwidth required
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model
view
Collaboration Transparency
– Higher bandwidth required
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widget
window
screen
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Edge Network Cache
Servers
Mirror Site
Fast Response
Clients
Cache
Server
PSINet
Client
Cache
Cache
Server
@Home
Host Server
UUnet
QWest
Server
Mind
Spring
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Cache
Server
Sprint
Cache
Server
Clients
Fewer Requests
Client
Side
Cache
Server
Gloobix
Edge
Network
Cache
Server
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Mirror Site
Clients
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Edge-Side Includes Protocol
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Used to generate dynamic web pages
– based on HTTP and HTML
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Involves only the proxy and server
– transparent to clients
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Controlled by HTTP headers
– proxy sends Surrogate-Capabilities header
– server sends Surrogate-Control header
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Implemented in markup
– in-message XML
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Edge-Side Includes Markup
<table>
<tr><td colspan=“2”>
<esi:try>
<esi:attempt>
<esi:include
src=http://www.myxyz.com/news/top.html
onerror=“continue” />
</esi:attempt>
<esi:except>
<!- -esi
This spot is reserved for your company’s
advertising. For more info <a
href=www.myxyz.com> click here </a>
-->
</esi:except>
</esi:try>
</td></tr>
</table>
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ESI for Collaboration (ESIC)
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Collaboration framework
–
–
–
–
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sessions
channels
users
addressable messaging
Extends existing ESI standard
– uses ESI extension processor
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Proxies act as surrogates
– DNS returns proxy address
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Origin Server
Homed
Channel
ESIC Architecture
Content Delivery
Network
Proxy A
Proxy C
Proxy B
Peer-to-peer
Channel
Clients
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Clients
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ESIC Protocol
Controlled by HTTP headers
 Control functions
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– create/update/remove sessions, &c.
– via in-message XML markup
– involves only proxy and server
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Messaging functions
– multiple channel types
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Sessions
An on-going collaboration instance
 Consist of:
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– a set of users
– a set of channels
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Attributes:
– session ID
– base path, e.g.,
http://www.collabr8.com/basePath
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Users
Collaborators
 Attributes:
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– client ID
– channels that may be used
– user roles
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define channel access rights (rw, ro, wo)
role names defined by the application
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Channels
A bi-directional communications link
 Accessed via URL
 Attributes:
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– access types for user roles
– activity timeout
– channel type
– URL is relative to session base path, e.g.,
http://www.collabr8.com/basePath/channelPath
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ESIC Channel Types
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Basic
– bi-directional link
– peer-to-peer, one-to-many
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Homed
– all requests forwarded to server
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Monitored
– copy of all requests sent to monitor
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Ordered
– all requests sent through single proxy
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Extended Example: drawboard
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Modified open source applet & server
– converted applet to application
 issue: couldn’t simulate DNS lookup
– added use of HTTP messages (non-ESIC version)
– added use of ESIC framework
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Initial Client Login
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DNS => proxy IP address
Client logs in to application
– proxy passes messages not
bound for channel URL
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Server response contains
markup creating the session
Proxy A broadcasts info on
new session
Server informs client of
collaboration channel URLs
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Initial Client Login Request
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Drawboard login consists of GET request
– the /drawServer URL is not a collaboration channel
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Msg 4: Proxy adds Surrogate-Capabilities header
GET/drawServer HTTP/1.1
User-Agent: DrawboardClient/1.0
Accept: text/xml,application/x.HttpDrawboard,application/xml...
Accept-Language: en-us,en;q= 0.5
Accept-Encoding:
Accept-Charset: ISO-8859-1,utf-8;q= 0.7,* ;q= 0.7
Proxy-Connection: keep-alive
Host: blanca.uccs.edu:8064
Via: 1.1 sanluis
Surrogate-Capability: sanluis= "ESI/1.0 ESIC/0.1"
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Initial Client Login Response
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Server accepts login, assigns session & client ID
Msg 5: Initial server response creates session
HTTP/1.1 200 OK
Surrogate-Control: content= "ESIC/0.1"
Set-Cookie: esicClient= "client1"
Set-Cookie: esicSession= "draw1234"
Content-Type: application/x.drawboard.ConxStarter
Content-Length: 232
[ ...ESIC XML markup...]
[ ...serialized ConxStarter object... ]
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Proxy Control: XML Markup
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ESIC Proxy controlled by in-message XML
General structure of markup:
<esicSession id="abc123">
<sessionControl>
session control elements
</sessionControl>
<channelTraffic>
channel addressing elements
</channelTraffic>
</esicSession>
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< esic Session id= "draw1234">
< sessionControl ac tion= "c reate">
< basePath> /drawServer < /basePath>
< c lientList>
Server XML creating
< c lient ac tion= "c reate">
the session
< id> c lient1 < /id>
< ac c essList>
< c hannelAc c ess path= "/drawboard" role= "partic ipant"/>
< /ac c essList>
< /c lient>
< /c lientList>
< c hannelList>
< c hannel ac tion= "c reate">
< path> /drawboard < /path>
< type> homed < /type>
< ac c essControl>
< ac c ess role= "partic ipant"> readwrite < /ac c ess>
< /ac c essControl>
< /c hannel>
< /c hannelList>
< /sessionControl>
< /esic Session>
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Initial Client Channel Connection
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Client must connect to
collaboration channel
Msg 8 includes ID headers
GET/drawServer/drawboard HTTP/1.1
Cookie: esicSession= ”draw1234”
Cookie: esicClient= ”client1”
[ ...other headers... ]
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Msgs 10, 11 are
application specific
– Pinger
– Archive (latecomer support)
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Additional Client Logins
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New clients may login
via another proxy
Client login messaging
is identical
– server assigns client ID
and role
– response XML adds
client to session
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Proxy B broadcasts
update to session
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HTTP/1.1 200 OK
Surrogate-Control: c ontent= "ESIC/0.1"
Set-Cookie: esicClient= "client2"
Set-Cookie: esicSession= "draw1234"
Content-Type: application/x.drawboard.ConxStarter
Content-Length: 232
Server
response
with XML
updating
the session
< esic Session id= "draw1234">
< sessionControl ac tion= "update">
< c lientList>
< client ac tion= "c reate">
< id> c lient2 < /id>
< ac c essList>
< c hannelAcc ess path= "/drawboard" role= "partic ipant"/>
< /ac c essList>
< /client>
< /clientList>
< /sessionControl>
< /esicSession>
[ ...serialized ConxStarter object... ]
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Using a Channel
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Client receives assigned IDs
– Set-Cookie headers in initial response
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esicSession=“abc123”, esicClient=“def456”
Client receives channel URLs
– mechanism is application-specific (ConxStarter)
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Client connects to channels
Client may now send data to the channel
– via GET/POST/PUT requests
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Sender must provide address information
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Channel Addressing
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Sender provides an address
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recipient’s client ID, or ‘*’ for broadcast
homed channel: server is implied
monitored channel: monitor is implied in addition
mechanism differs for client & server
Client addresses in method or header
Cookie: esicToList=”def456,ghi789”
- or -
http://a.b.com/base/ch1?esicToList=def456,ghi789
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Server Channel Addressing
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Server addresses are in message XML
– message body contains address list
< esicSession id= "draw1234">
< channelTraffic>
< path> /drawboard < /path>
< toList>
< client id= "* "/>
< /toList>
< /channelTraffic>
< /sessionControl>
< /esicSession>
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Proxy Actions
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Upon receiving a request to a channel:
– ESIC proxy intercepts the message
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recognizes client requests to channel URLs
server responses will contain control header
– Routes messages appropriately
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verifies client role allows write access
extracts address list
channel type considered
forward to other proxies if necessary
– proxies comprise multicast group
– routing table maps client to proxy connection
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Sending Collaboration Data
10. Client2 issues POST request
Origin Server
11. Homed channel goes to server
with Surrogate-Capability header
12. Response with ‘*’ address in XML
and Surrogate-Control header
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Proxy A
Proxy B
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14
10
13. Forwarded to client1 proxy
14,15. Delivery to addressees
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Client2
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Client1
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POST request
POST/drawServer/drawboard HTTP/1.1
from client2
Cookie: esicClient= "client2"
Cookie: esicSession= "draw1234"
User-Agent: DrawboardClient/1.0)
Accept: text/xml,application/x.HttpDrawboard,application/xml...
Accept-Language: en-us,en;q= 0.5
Accept-Encoding:
Accept-Charset: ISO-8859-1,utf-8;q= 0.7,*;q= 0.7
Proxy-Connection: keep-alive
Content-Type: application/x.drawboard.Freehand
Content-Length: 1160
Host: blanca.uccs.edu:8064
Via: 1.1 sanluis
Surrogate-Capability: sanluis= "ESI/1.0 ESIC/0.1"
[ ...serialized Freehand object... ]
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Server Broadcasts Data to Users
HTTP/1.1 200 OK
Surrogate-Control: c ontent= "ESIC/0.1"
Content-Type: applic ation/x.drawboard.Freehand
Content-Length: 1160
< esic Session id= "draw1234">
< c hannelTraffic >
< path> /drawboard < /path>
< toList>
< c lient id= "* "/>
< /toList>
< /c hannelTraffic >
< /sessionControl>
< /esic Session>
[ ...serialized FreeHand objec t... ]
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Performance Evaluation
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Test configuration
– drawboard server on blanca
– two ESIC proxies, sanluis & crestone
– multiple drawboard instances
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running on Windows workstations
evenly distributed between the proxies
repeat the last generated drawing object
at rate of 1 msg/sec
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Non-ESIC Test Rig
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blanca: dual 933MHz PIII,
1.5GB RAM, Redhat 9, Java
1.4.1
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Windows PCs: one
Blanca
933MHz PIII, 512MB RAM,
Java 1.4.1
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n clients => n2+n msg/sec
– 1640 msg/sec maximum
From 2 to 40 c lients
Odd-numbered clients
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Even-numbered clients
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ESIC Test Rig
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Crestone: same as
Blanca
Blanca
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Sanluis: same except
has dual 1.64GHz PIII
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n clients => 2n msg/sec
Crestone
Sanluis
– 80 msg/sec maximum
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JDOM XML adds a lot of
overhead
– turnaround time: 4.415
mSec to 11.578 mSec
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From 2 to 40 clients
Odd-numbered clients
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Even-numbered clients
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CPU Utilization
100
90
80
70
60
50
40
30
20
10
0
2
4
6
8
10
12
14
16
18
20
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26
28
30
32
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38
40
Number of Clients (each sending 1 msg/sec)
Non-ESIC Results
ESIC Results
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Message Latency
260
240
220
200
180
160
140
120
100
80
60
40
20
0
2
4
6
8
10
12
14
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18
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26
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30
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Number of Clients
Non-ESIC Latency
ESIC Latency
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ESIC Security
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Complex issue
– proxy must have access to msg contents
– server response messages
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ESI is still allowed
markup may be anywhere within the message
markup controls the proxy
– client request messages
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addresses are in the HTTP headers
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ESIC Security, cont.
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Proxy is a surrogate for the server
– tightly integrated
– server is client of Content Delivery Network
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Proxy/Server Connection
– SSL, with client authentication
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Client/Proxy Connection
– SSL, proxy uses subscriber’s certificate
– similar approach used for virtual hosting
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Future Work

Improve efficiency
– connection pooling to origin server
– extend multicast group to clients
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Experiment with virtual clusters
– avoid the Java applet security issue
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Address caching issues
– optional channel attribute
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Conclusion
Presented a design based on analysis of
collaboration requirements
 Implemented a prototype to
demonstrate usability
 Evaluated performance
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