The Need for Bandwidth Management
Since almost all network links are shared by multiple users and applications, the available bandwidth must be shared. Bandwidth management tools enable you to manage how the bandwidth is shared.
If a network link is continuously congested, the link must be upgraded to provide greater capacity. In many cases, however, the average load on a link is within the link capacity, and the link is only congested temporarily. Temporary congestion is sometimes predictable; for example, there are typically peaks in network use at particular time of the day or following a particular event. Other causes of temporary congestion, such as the transferring a large file, are not predictable.
The Solaris Bandwidth Manager software enables you to manage the bandwidth used by IP traffic. It does this by:
Allocating traffic to a class based on the application type, source and destination IP address, URL group, or a combination
Assigning individual limits for each class. For example:
Traffic to engineering must have at least 50 percent of the link.
HTTP traffic cannot exceed 10 percent of the link.
Prioritizing traffic. Some types of traffic, for example interactive traffic generated when using telnet or rlogin, need a quick response time. Solaris Bandwidth Manager lets you assign a higher priority to that traffic. Traffic that does not require a quick response time, such as a file transfer using FTP, can be assigned a lower priority.
By balancing the bandwidth allocated to different types of network traffic and the relative priorities, you can optimize your network performance. Solaris Bandwidth Manager also allows you to monitor the achieved performance of your network, and has interfaces for third party billing applications.
The current version of the product as of this writing is Solaris Bandwidth Manager 1.5; the previous version of the product was known as Sun Bandwidth Allocator 1.0.
Examples of When to Use Bandwidth Management
You are the owner of a LAN, leasing a network connection from a service provider. You can use the Solaris Bandwidth Manager software to make sure you make the most efficient use of the capacity you lease. Bandwidth allocation ensures that your higher-priority traffic is sent first and that you always get the maximum use of the capacity you are paying for. It will no longer be necessary to over-specify your requirements just to guarantee that priority traffic can be sent. You might even be able to reduce the capacity you lease.
You are the owner of a WAN, providing network services to many clients. The Solaris Bandwidth Manager software enables you to regulate the traffic in your network. You can provide a guaranteed minimum bandwidth to a client, and as a bonus, provide additional bandwidth from time to time when it is not required by other clients. Since you know the level of guaranteed bandwidth, capacity planning will be both easier and more accurate.
You are a web service provider, hosting several web sites on behalf of commercial companies. The Solaris Bandwidth Manager software enables you to guarantee your client companies that a given bandwidth is available to the customers visiting their web sites. Today, many web providers charge based on either disk space used or on the number of times a site is visited. Disk space used is not a good indication of the cost to a provider, since a small site that is visited frequently can be as expensive to provide as a large site that is visited less frequently. Using the number of visits to a site is a better indicator of the cost to a provider, but is potentially an unbounded cost for the client. With Solaris Bandwidth Manager you can charge clients for a guaranteed bandwidth for their web site. Additionally, you can provide extra functionality such as providing a higher priority to network traffic originating from web site visitors who are paying for online shopping goods as opposed to visitors who are just looking around.
You are an ISP providing services to many customers. The Solaris Bandwidth Manager software enables you to provide different classes of service to different customers. For example, you could offer Premium and Standard services, with different guaranteed minimum access levels, to suit the needs and budgets of your customers. This will also allow you to start consolidating many services from many small machines onto fewer larger servers. Optional Resource Management products such as Solaris Resource Manager (covered in Chapter 7) can be used on these servers to guarantee processing power as well as networking bandwidth to your customers, while at the same time reducing the total cost of administration and cost of ownership.
End-to-End Quality of Service
To manage network resources, it is not sufficient to manage and control only the network segment close to the computer systems that supply the services in question. Clients can be anywhere on the network, and the whole network path from client to server needs to be considered. This is what is meant by end-to-end QoS, and in general, it can be very difficult to achieve. If congestion takes place anywhere on the network, it will affect the overall QoS. Therefore, routers need to help supply QoS. In the Internet Engineering Task Force (IETF), several working groups have been working on this problem, notably the Integrated Services working group (Int-Serv) and the Differentiated Services working group (Diff-Serv).
Integrated Services
In recent years, several developments in the IETF have attempted to make end-to-end QoS to the Enterprise and the Internet a reality. To guarantee a certain bandwidth to an application, each hop in the network from client to server must guarantee the resources that are required.
The Internet Integrated Services framework (Int-Serv) was developed by the IETF to provide applications the ability to have multiple levels of QoS to deliver data across the network. It consists of two components:
Network components along the path must support multiple levels of service.
Applications must have a way to communicate their desired level of service to the network components.
The RSVP protocol was developed for the latter. It requires each hop from end to end be RSVP-enabled, including the application itself (through an API). Bandwidth will be reserved at each hop along the way before transmitting begins, guaranteeing that enough resources will be available for the duration of this connection.
For the internet backbone, RSVP never received widespread acceptance. One reason is that backbone routers handle the forwarding and routing of very large amounts of concurrent flows (connections). Deploying RSVP means that routers need to keep state on each connection. This puts a very high load on these routers, which leads inevitably to performance, scalability, and management problems.
Still, RSVP could be the right solution for certain applications, especially on better contained networks (such as corporate). The Solaris Bandwidth Manager software does not use RSVP to manage bandwidth. However, Sun offers a separate product called Solstice™ Bandwidth Reservation Protocol 1.0 that does exactly that. It can be downloaded from http://www.sun.com/solstice/telecom/bandwidth.
Differentiated Services
More recent developments in the IETF's Diff-Serv working group are attempting to resolve the concern of overloaded backbone routers. Instead of requiring per-flow resource reservation at each hop, it moves the complexity of this to the network edge, to keep the packet-forwarding mechanisms in the network core relatively simple.
The IPv4 packet header includes a field called ToS (Type of Service) which can be used to mark a packet for different levels of quality. In the Diff-Serv context, this IP header is renamed the DS header byte. The IPv6 header has a similar field. At the edge of the network, packets and flows are classified and shaped (scheduled). The DS field in the IP header is marked for a corresponding level of service, and the network core routers inspect the DS field and give the type of service that was requested. In the Diff-Serv specification, care was taken to supply as much backwards compatibility with the original meaning of the Type of Service header, as defined in RFC 791 (the original IP specification) and RFC 1349 which refines these definitions.
For more information regarding Diff-Serv, see RFC 2474 and RFC 2475.
The Solaris Bandwidth Manager software is Diff-Serv compliant. The software can classify, filter and mark network packets based on the DS field contents. This allows the software to be deployed in a Diff-Serv environment together with networking equipment (such as routers and switches) from other vendors that are Diff-Serv compliant.