Backbone Network Architectures Identifies the way backbone interconnects LANs Defines how it manages packets moving through BB Fundamental architectures –Bridged Backbones –Routed Backbones –Collapsed Backbones Rack-based Chassis-based –Virtual LANs Single-switch VLAN Multiswitch VLAN

Bridged Backbone bus topology Entire network is just one subnet

Bridged Backbones Move packets between networks based on their data link layer addresses Cheaper (since bridges are cheaper than routers) and easier to install (configure) –Just one subnet to worry –Change in one part may effect the whole network Performs well for small networks –For large networks broadcast messages (e.g., address request, printer shutting down) can lower performance Formerly common in the distribution layer –Declining due to performance problems

Routed Backbone Usually a bus topology Example of a routed BB at the Distribution layer Each LAN is a separate subnet

Routed Backbones Move packets using network layer addresses Commonly used at the core layer –Connecting LANs in different buildings in the campus –Can be used at the distribution layer as well LANs can use different data link layer protocols Main advantage: LAN segmentation –Each message stays in one LAN; unless addressed outside the LAN –Easier to manage Main disadvantages –Tend to impose time delays compared to bridging –Require more management than bridges & switches

Star topology Collapsed Backbone A connection to the switch is a separate point-to-point circuit Most common type BB mainly used in distribution layer

Collapsed Backbones Replaces the many routers or bridges of the previous designs –Backbone has more cables, but fewer devices –No backbone cable used; switch is the backbone. Advantages: –Improved performance ( % higher) Simultaneous access; :switched” operations –A simpler more easily managed network – less devices Two minor disadvantages –Use more and longer cables –Reliability: If the central switch fails, the network goes down.

Virtual LANs (VLANs) A new type of LAN-BN architecture –Made possible by high-speed intelligent switches –Computers assigned to LAN segments by software Often faster and provide more flexible network management –Much easier to assign computers to different segments More complex and so far usually used for larger networks Basic VLAN designs: –Single switch VLANs –Multi-switch VLANs

Single Switch VLAN Collapsed Backbone Switch acting as a large physical switch Computers assigned to different LANs by software

VLAN Operating Characteristics Advantages of VLANs –Faster performance Precise management of traffic flow Ability to allocate resources to different type of applications –Traffic prioritization (via 802.1q VLAN tag) Include in the tag: a priority code based on 802.1p Can have QoS capability at MAC level –Similar to RSVP and QoS capabilities at network and transport layers Drawbacks –Cost –Management complexity

Basic Internet Architecture

Internet’s Access Points Network Access Points (NAPs) –Connect National ISPs together –Sometimes large regional and local ISPs also have access directly to NAPs Indiana University, for example, which provides services to about 40,000 individuals, connects directly to the Chicago NAP –About a dozen NAPs in the U.S. –Run by common carriers such as Sprint and AT&T Metropolitan Area Exchanges (MAEs) –Connect Regional ISPs together –About 50 such MAEs in the U.S. today

Packet Exchange Charges Peering –ISPs at the same level usually do not charge each other for exchanging messages Higher level ISPs charge lower level ones –National ISPs charge regional ISPs which in turn charge local ISPs Local ISPs charge individuals and corporate users for access

Connecting to an ISP Done by through ISP’s Point of Presence (POP) –A place ISP provides service to its customers Individual users –Typically through a dial-up line using the PPP protocol Handled by the ISP’s modem pool –Userid and password checked by Remote Access Server (RAS) Once logged in, the user can send packets over the phone line Corporate users –Typically access the POP using a T-1, T-3 or ATM OC-3 connections provided by a common carrier Cost = ISP charges + circuit charges

ISP Point-of Presence Modem Pool Individual Dial-up Customers Corporate T1 Customer T1 CSU/DSU Corporate T3 Customer T3 CSU/DSU Corporate OC-3 Customer ATM Switch Layer-2 Switch ISP POP NAP/MAE Remote Access Server ATM Switch Inside an ISP POP

Internet Governance No one operates the Internet Closest thing: Internet Society (ISOC) –Open membership professional society –Over 175 organizational and 8000 individual members in over 100 countries –Mission: “Open development, evolution and use of the Internet for the benefit of the people in the world.” –ISOC work areas Public policy: –Involves in debates in copyright, censorship, privacy Education –Training and education programs Standards

ISOC Standard Bodies Internet Engineering Task Force (IETF) –Concerned with evolution of Internet architecture and smooth operation of Internet –Work through groups (organized by topics) –Request For Comments (RFC): basis of Internet standards Internet Engineering Steering Group (IESG) –Responsible for management of the standard process –Establishes and administers rules in creating standards Internet Architecture Board (IAB) –Provides strategic architectural oversight, guidance Internet Research Task Force (IRTF) –Focus on long-term specific issues

Internet 2 Many new projects designing new technologies to evolve Internet Primary North American projects –Next Generation Internet (NGI) funded by NSF Developed very high performance Backbone Network Service (vBNS) –Run by WorldCom –University Corporation for Advanced Internet Development (UCAID) with 34 universities Developed Abilene network (also called Internet 2) –Advanced Research and Development Network Operations Center (ARDNOC) funded by Canadian government Developed CA*Net

Internet2 Backbone Networks Donna Cox, Robert Patterson, NCSA

Features of Future Internet Access via Gigapops, similar to NAPs –Operate at very high speeds (622 Mbps to 2.4 Gbps) using SONET, ATM and IPv6 protocols IPv6 not IPv4 New protocol development focuses on issues like –Quality of Service –Multicasting New applications include –Tele-immersion –Videoconferencing

Tele-immersion Shared virtual reality University of Illinois at Chicago Images courtesy Univ. of Illinois- Chicago