Novel Networks Theo Benson Cellular Networks Data Center

Novel Networks Theo Benson

• Cellular Networks • Data Center Networks • Current Class Grades

Mobile Traffic: Path Features Mobile Network Internet Google Network Think BGP 15

What Does a Mobile Network Look Like? Internet Gateway • One point of access to the internet: gateway – All traffic must use the same gateway • Each carrier has many mobile-networks

Canonical Mobile Network Architecture Courtesy: Q. Xu et al.

Location of Sprint’s Mobile gateways Seattle Omaha New York Chicago San Francisco Phoenix Washington Kansas City Los Angeles Atlanta Dallas Miami 12 or more gateways observed 30

Understanding the Structure of Mobile Networks • Requirements: – Billing of different users • Requires to be able to count all traffic • Even when users move between towns – Mobility • Users will use different towers • Must keep connections alive as user moves around – Optimize user performance • Change Video quality • Change image quality • Run a proxy

Understanding the Structure of Mobile Networks Internet • Gateway (GGSN) – A central point – Runs advanced proxies+transcoders • Allows for: – Billing • Because it sees all traffic – Seamless mobility • Runs a proxy

Implications of this Network

Background: DNS – How Load Balancing Works • Client Sends Request to DNS-server Server A Server B 44. 10/16 22. 55/16 32. 10/16 Server C • Server uses client-IP address to determine best server • For example – Client-IP: 32. 10. 08. 1 – DNS directs you to Server C • For example – Client-IP: 22. 55. 18. 11 – DNS directs you to Server A

Background: DNS Load balancing with Mobile networks Gateway Server A Server B 44. 10/16 22. 55/16 • Client Sends Request to DNS -server • Server uses client-IP address to determine best server • For example 32. 10/16 Server C – Client-IP: 32. 10. 08. 1 – DNS directs you to Server C – Indirect path • Things get worse when users drive around – 32. 10. 08. 1 can show up in different locations!

Mobile IP Addresses are hard to Geolocate • Hard to figure out where a users is – One Michigan’s cellular device’s IP is located to places far away Courtesy: Q. Xu et al.

Background BGP: How Internet Works ISP A ISP B ISPC Routing and network paths are limited to links exposed by BGP • To send traffic to someone in the same city as you may need to go to a different state

Background BGP: How Internet Works ISP A ISP B ISPC Routing and network paths are limited to links exposed by BGP • To send traffic to someone in your City, traffic may need to go to another city

Putting BGP and DNS Load-Balancing together Gateway Mobile Network Public Internet Google Server Location Google-Mobile Peering point • DNS gives you a server – Based on your IP address – So the server may be close to you physically • But your Mobile Network Gateway may be far away from the server • Also the peering point to the server’s ISP may be far away from your gateway 6

Gate. Way Mobile Network Public Internet Google Server Location Google-Mobile Peering point 6

Types of Path Inflation Four types of path inflation based on the path segment where inflation occurs Mobile Network Internet Google Network ● Mobile Network Inflation ● BGP Inflation 14

Mobile Network Inflation Mobile Gateway is in a different City But server is in your city Local City Mobile Network Remote City Internet Network Google Network 18

Case Study 1: Bad Gateway Placement AT&T New York traffic enters public Internet in Chicago area New York Chicago 1074 km extra distance 16 ms extra latency 24

BGP Inflation (Bad peering practices) Peering point to Google’s ISP (server ISP) is in a different city Local City Mobile Network Remote City Google Network Internet Network 17

Case Study 2: Lack of Peering AT&T Seattle traffic enters Google’s network in Bay area Seattle 1089 km extra distance 16 ms extra latency San Francisc o 25

• Cellular Networks • Data Center Networks • Current Class Grades

Mobile Traffic: Path Features Mobile Network Internet Google Network Think Data center 15

What is a Data Center? • Huge warehouse with racks of servers – All cloud services run on a data center • Challenges – Power/Energy: cooling – Performance: network throughput + latency

Canonical Data Center Architecture Core Aggregation Edge Top-of. Rack Application servers

How should the network be setup? Which will provide best performance? • Layer 2: Ethernet? ATM? • Layer 3: Distance-vector? Link-state?

Layer 2: Ethernet Network -Uses Flooding to know where a host is -- uses a lot of bandwidth (doesn’t scale) ++ automatically learn addresses ++ enables mobility of a hosts -Flat addressing no aggregatioin: --very large table (doesn’t scale) -Each host comes with MAC-Address: . ++ No need to configure addresses -Build a spanning tree ++ No loops in the Network -- links unused -- uneven loads -- only uses one path 27

Layer 3: IP Networks -Routing done though OSPF + Efficient use of links + No loops - easy to reconfigure -IP-addresses are hierarchical aggregation - Must configure address for each host - hosts can’t easily move hosts around (must re-assign IP-address and netmask) +Small forwarding tables (scales) 29

Comparison of L 2 and L 3 Architectures Features Ease of configuration Optimality in addressing Host mobility Path efficiency Load distribution (Layer-2) Ethernet Bridging (Layer 3) IP Routing

Data Centers Today • Use Layer 3 for the performance benefits • Enhance Layer 3 to allow for Mobility – e. g. Microsoft’s VL 2, VMWare’s NVP – Each server has two IP addresses: • Physical-Address: routing uses this address • Logical-Address: servers identify each other using this address – Adds a bit more complexity to the system

How does it work? Src: Alice Dst: Bob Logical: Alice Physical: H 1 • • Logical: Bob Physical: H 2 Physical-Address: routing uses this address Logical-Address: servers identify each other using this address Alice wants to send to Bob: Alice uses Bob’s Logical-Address The first device in the network rewrites all addresses from logicaladdresses to physical addresses.

How does it work? Src: H 1 Dst: H 2 Logical: Alice Physical: H 1 • • Logical: Bob Physical: H 2 Physical-Address: routing uses this address Logical-Address: servers identify each other using this address Alice wants to send to Bob: Alice uses Bob’s Logical-Address The first device in the network rewrites all addresses from logicaladdresses to physical addresses.

How does it work? Src: H 1 Dst: H 2 Logical: Alice Physical: H 1 • • Logical: Bob Physical: H 2 Physical-Address: routing uses this address Logical-Address: servers identify each other using this address Alice wants to send to Bob: Alice uses Bob’s Logical-Address The first device in the network rewrites all addresses from logicaladdresses to physical addresses.

How does it work? Src: Alice Dst: Bob Logical: Alice Physical: H 1 Logical: Bob Physical: H 2 Physical-Address: routing uses this address Logical-Address: servers identify each other using this address Alice wants to send to Bob: Alice uses Bob’s Logical-Address The first device in the network rewrites all addresses from logicaladdresses to physical addresses. • Now you can move around: when you move your Physical address changes but not your logical address • •

• Cellular Networks • Data Center Networks • Current Class Grades

Assignment 2 & 3 • Grades have been put up. – If you have a ‘ 0’ on assignment 2 then your code does not run with auto-graded – Please send an email to see the TA • Assign 3: avg 100/110, std: 24 • Assign 2: avg 70/100, std: 43

Current Class Grades • Avg: 78 • Std: 14 • How to Calculate your grade: Your grade = (Assign*50+ HW*10 + midterm *15)/75 Ignore extra-credit for now