B345 Internet Science and Technology 
Week 2 lecture 2

Prelude
- Lecture handouts
- Tutorial exercises and assessments

This lecture's Learning Objectives
- Understand what is the Architecture of the Internet.
- Current issues about the future of the Internet Architecture.

What is "Architecture"?
- A reminder from the last lecture.

Topologies
- LAN, MAN, WAN interconnections
- ISP, PoP and customers
- NSP and NAPs
- Direct-interconnections
- Peering

TCP/IP Protocol Suite
- Network access
- IPv4 and IPv6
- ICMP, ARP, RARP 
- TCP and UDP
- Application protocols
- DNS

Routing
- Internet as a collection of autonomous systems.
- Internal routing (IGPs)
    - RIP, EIGRP, OSPF, IS-IS
- Exterior routing (EGP)
    - BGP-4

Design Goals Again
- Design to Implementation, or the other way around?
- Design goals of the Internet Architecture

    - internetworking
    - robustness
    - heterogeneity
    - distributed management
    - cost effective
    - ease of attachment
    - accountability

Achieving the design goals
- Some features of the Internet Architecture to achieve the design goals
    - Datagrams and connectionless service.
    - State information and where to store them - Transport vs Network layers.
    - Need for unreliable service - TCP vs UDP.
    - Hierarchical scaling - DNS, subnets, CIDR, AS.

Failing the design goals
- Some features of the Internet Architecture that fails the design goals
    - Lack of ways to do distributed resource management.
    - Packet sizes.
    - Retransmission of lost packets.
    - Performance specifications.

Architectural Failings
- Clash between principles and actual operations.
    - IPSEC
    - Firewalls
    - NAT
    - MPLS

New Requirements
- Some examples for a new Internet Architecture.
    - Mobility
    - Policy-driven auto-configuration
    - Highly time-variable resources
    - Allocation of capacity and RT traffic control
    - Multi-protocol support
    - Security