Scalability l l HA HA Server HA Firewall

Scalability

การนำไปใชงาน l l HA อปกรณเครอขาย HA Server HA Firewall HA Data Center : การทำ Disaster Recovery Center

Load Balancing

Layer 4 -7 Switch

อลกอรทมในการกระจายภาระงาน l l l Round Robin Least Connection Weight Distribution Response Time Least Connection & Response Time Primary & Backup Server

การสงคำรองขอตางๆ ไปยงเซรฟเวอร l l l Server Load Balance Source NAT Direct Server Return

Server Load Balance l กระบวนการทำงานคลายกบการทำ Translation Network Address

Server Load Balance

Source NAT

Direct Server Return

ความสามารถอนๆ l l l ของ Load Balancer Application Level Health Check Content Management Session Persistence High Availability Load Balance Global Server Load Balance

How GSLB Works www. foo. com 162. 113. 25. 20 Rank 1 2 3 Site B C A %Traffic 70 20 10 C 1. Client’s DNS request for www. foo. com sent to local DNS 1 www. foo. com 172. 168. 13. 10 5 4 2. Local DNS queries upstream DNS 3. Switch at site C receives DNS request and determines that sites B and C are closest to user. Acting as Authoritative Name Server, switch selects the best site (B) and returns site B’s IP to client’s local DNS 4. Local DNS server responds to client with site B’s VIP 5. Client opens application session to 205. 178. 2. 2 (site B) NANOG L 4 Switching Presentation 2 DSSP Updates 3 DNS www. foo. com 205. 178. 2. 2 Rank 1 2 3 Site B C A B Traffic 75 15 5 A Rank 1 2 3 Site health, response time and throughput exchanged between switches on a periodic or event-driven basis using encoded DSSP Site B C A Traffic 80 20 10

Distributed Site State Protocol l l Lightweight, encoded protocol runs over HTTP Used to exchange health, load, throughput information Periodic Updates l Peer site performance behavior (one site’s view of all other sites) l Local site status information (server health, current connections, etc) l Periodic Updates result in each switch building an Ordered Handoff Table Triggered Updates l If a site observes that another site is unresponsive, it will Trigger all other sites to check the questionable site l If a site experiences a connection spike (reaching Max. Conns) it will trigger an update to all other sites to stop Site Handoff NANOG L 4 Switching Presentation

Web Caching l Caches can be installed and utilized with the Load balancers in the following ways l Forward proxy for client acceleration l Transparent proxy for client acceleration l Reverse proxy for server acceleration l Transparent reverse proxy for server acceleration

Web Caching l Transparent reverse proxy for server acceleration